Add InMon's sFlow Agent library to the build system.

The C source and header files added in this commit is covered under the
InMon sFlow license at http://www.inmon.com/technology/sflowlicense.txt

The library requires -Wno-unused to compile without warnings, so this
commit adds that for building the sFlow code only.  Automake can only
change compiler flags on a per-library or per-program basis, so sFlow
is built as a separate library.

The library will be used in upcoming commits.

10 files changed, 2565 insertions, 0 deletions

diff --git a/COPYING b/COPYING
index 134f02b0f..375efecae 100644
--- a/COPYING
+++ b/COPYING
@@ -22,3 +22,7 @@ Public License, version 2.
 Files under the xenserver directory are licensed on a file-by-file
 basis.  Some files are under an uncertain license that may not be
 DFSG-compliant or GPL-compatible.  Refer to each file for details.
+
+Files lib/sflow*.[ch] are licensed under the terms of the InMon sFlow
+licence that is available at:
+        http://www.inmon.com/technology/sflowlicense.txt
diff --git a/acinclude.m4 b/acinclude.m4
index e37a316df..e074c7d47 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -235,4 +235,14 @@ dnl Example: OVS_ENABLE_OPTION([-Wdeclaration-after-statement])
 AC_DEFUN([OVS_ENABLE_OPTION], 
   [OVS_CHECK_CC_OPTION([$1], [WARNING_FLAGS="$WARNING_FLAGS $1"])
    AC_SUBST([WARNING_FLAGS])])
+
+dnl OVS_CONDITIONAL_CC_OPTION([OPTION], [CONDITIONAL])
+dnl Check whether the given C compiler OPTION is accepted.
+dnl If so, enable the given Automake CONDITIONAL.
+
+dnl Example: OVS_CONDITIONAL_CC_OPTION([-Wno-unused], [HAVE_WNO_UNUSED])
+AC_DEFUN([OVS_CONDITIONAL_CC_OPTION],
+  [OVS_CHECK_CC_OPTION(
+    [$1], [ovs_have_cc_option=yes], [ovs_have_cc_option=no])
+   AM_CONDITIONAL([$2], [test $ovs_have_cc_option = yes])])
 dnl ----------------------------------------------------------------------
diff --git a/configure.ac b/configure.ac
index 300b21e2c..f901f96a9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -75,6 +75,7 @@ OVS_ENABLE_OPTION([-Wold-style-definition])
 OVS_ENABLE_OPTION([-Wmissing-prototypes])
 OVS_ENABLE_OPTION([-Wmissing-field-initializers])
 OVS_ENABLE_OPTION([-Wno-override-init])
+OVS_CONDITIONAL_CC_OPTION([-Wno-unused], [HAVE_WNO_UNUSED])
 
 AC_ARG_VAR(KARCH, [Kernel Architecture String])
 AC_SUBST(KARCH)
diff --git a/lib/automake.mk b/lib/automake.mk
index 9ba513acb..252abdf15 100644
--- a/lib/automake.mk
+++ b/lib/automake.mk
@@ -125,6 +125,19 @@ nodist_lib_libopenvswitch_a_SOURCES = \
 	lib/dirs.c
 CLEANFILES += $(nodist_lib_libopenvswitch_a_SOURCES)
 
+noinst_LIBRARIES += lib/libsflow.a
+lib_libsflow_a_SOURCES = \
+	lib/sflow_api.h \
+	lib/sflow.h \
+	lib/sflow_agent.c \
+	lib/sflow_sampler.c \
+	lib/sflow_poller.c \
+	lib/sflow_receiver.c
+lib_libsflow_a_CFLAGS = $(AM_CFLAGS)
+if HAVE_WNO_UNUSED
+lib_libsflow_a_CFLAGS += -Wno-unused
+endif
+
 if HAVE_NETLINK
 lib_libopenvswitch_a_SOURCES += \
 	lib/netlink-protocol.h \
diff --git a/lib/sflow.h b/lib/sflow.h
new file mode 100644
index 000000000..397ae2dae
--- /dev/null
+++ b/lib/sflow.h
@@ -0,0 +1,548 @@
+/* Copyright (c) 2002-2009 InMon Corp. Licensed under the terms of the InMon sFlow licence: */
+/* http://www.inmon.com/technology/sflowlicense.txt */
+
+#ifndef SFLOW_H
+#define SFLOW_H 1
+
+enum SFLAddress_type {
+    SFLADDRESSTYPE_IP_V4 = 1,
+    SFLADDRESSTYPE_IP_V6 = 2
+};
+
+typedef struct {
+    u_int32_t addr;
+} SFLIPv4;
+
+typedef struct {
+    u_char addr[16];
+} SFLIPv6;
+
+typedef union _SFLAddress_value {
+    SFLIPv4 ip_v4;
+    SFLIPv6 ip_v6;
+} SFLAddress_value;
+
+typedef struct _SFLAddress {
+    u_int32_t type;           /* enum SFLAddress_type */
+    SFLAddress_value address;
+} SFLAddress;
+
+/* Packet header data */
+
+#define SFL_DEFAULT_HEADER_SIZE 128
+#define SFL_DEFAULT_COLLECTOR_PORT 6343
+#define SFL_DEFAULT_SAMPLING_RATE 400
+#define SFL_DEFAULT_POLLING_INTERVAL 30
+
+/* The header protocol describes the format of the sampled header */
+enum SFLHeader_protocol {
+    SFLHEADER_ETHERNET_ISO8023     = 1,
+    SFLHEADER_ISO88024_TOKENBUS    = 2,
+    SFLHEADER_ISO88025_TOKENRING   = 3,
+    SFLHEADER_FDDI                 = 4,
+    SFLHEADER_FRAME_RELAY          = 5,
+    SFLHEADER_X25                  = 6,
+    SFLHEADER_PPP                  = 7,
+    SFLHEADER_SMDS                 = 8,
+    SFLHEADER_AAL5                 = 9,
+    SFLHEADER_AAL5_IP              = 10, /* e.g. Cisco AAL5 mux */
+    SFLHEADER_IPv4                 = 11,
+    SFLHEADER_IPv6                 = 12,
+    SFLHEADER_MPLS                 = 13
+};
+
+/* raw sampled header */
+
+typedef struct _SFLSampled_header {
+    u_int32_t header_protocol;            /* (enum SFLHeader_protocol) */
+    u_int32_t frame_length;               /* Original length of packet before sampling */
+    u_int32_t stripped;                   /* header/trailer bytes stripped by sender */
+    u_int32_t header_length;              /* length of sampled header bytes to follow */
+    u_int8_t *header_bytes;               /* Header bytes */
+} SFLSampled_header;
+
+/* decoded ethernet header */
+
+typedef struct _SFLSampled_ethernet {
+    u_int32_t eth_len;       /* The length of the MAC packet excluding 
+				lower layer encapsulations */
+    u_int8_t src_mac[8];    /* 6 bytes + 2 pad */
+    u_int8_t dst_mac[8];
+    u_int32_t eth_type;
+} SFLSampled_ethernet;
+
+/* decoded IP version 4 header */
+
+typedef struct _SFLSampled_ipv4 {
+    u_int32_t length;      /* The length of the IP packet
+			      excluding lower layer encapsulations */
+    u_int32_t protocol;    /* IP Protocol type (for example, TCP = 6, UDP = 17) */
+    SFLIPv4   src_ip;      /* Source IP Address */
+    SFLIPv4   dst_ip;      /* Destination IP Address */
+    u_int32_t src_port;    /* TCP/UDP source port number or equivalent */
+    u_int32_t dst_port;    /* TCP/UDP destination port number or equivalent */
+    u_int32_t tcp_flags;   /* TCP flags */
+    u_int32_t tos;         /* IP type of service */
+} SFLSampled_ipv4;
+
+/* decoded IP version 6 data */
+
+typedef struct _SFLSampled_ipv6 {
+    u_int32_t length;       /* The length of the IP packet
+			       excluding lower layer encapsulations */
+    u_int32_t protocol;     /* IP Protocol type (for example, TCP = 6, UDP = 17) */
+    SFLIPv6   src_ip;       /* Source IP Address */
+    SFLIPv6   dst_ip;       /* Destination IP Address */
+    u_int32_t src_port;     /* TCP/UDP source port number or equivalent */
+    u_int32_t dst_port;     /* TCP/UDP destination port number or equivalent */
+    u_int32_t tcp_flags;    /* TCP flags */
+    u_int32_t priority;     /* IP priority */
+} SFLSampled_ipv6;
+
+/* Extended data types */
+
+/* Extended switch data */
+
+typedef struct _SFLExtended_switch {
+    u_int32_t src_vlan;       /* The 802.1Q VLAN id of incomming frame */
+    u_int32_t src_priority;   /* The 802.1p priority */
+    u_int32_t dst_vlan;       /* The 802.1Q VLAN id of outgoing frame */
+    u_int32_t dst_priority;   /* The 802.1p priority */
+} SFLExtended_switch;
+
+/* Extended router data */
+
+typedef struct _SFLExtended_router {
+    SFLAddress nexthop;               /* IP address of next hop router */
+    u_int32_t src_mask;               /* Source address prefix mask bits */
+    u_int32_t dst_mask;               /* Destination address prefix mask bits */
+} SFLExtended_router;
+
+/* Extended gateway data */
+enum SFLExtended_as_path_segment_type {
+    SFLEXTENDED_AS_SET = 1,      /* Unordered set of ASs */
+    SFLEXTENDED_AS_SEQUENCE = 2  /* Ordered sequence of ASs */
+};
+  
+typedef struct _SFLExtended_as_path_segment {
+    u_int32_t type;   /* enum SFLExtended_as_path_segment_type */
+    u_int32_t length; /* number of AS numbers in set/sequence */
+    union {
+	u_int32_t *set;
+	u_int32_t *seq;
+    } as;
+} SFLExtended_as_path_segment;
+
+typedef struct _SFLExtended_gateway {
+    SFLAddress nexthop;                       /* Address of the border router that should
+						 be used for the destination network */
+    u_int32_t as;                             /* AS number for this gateway */
+    u_int32_t src_as;                         /* AS number of source (origin) */
+    u_int32_t src_peer_as;                    /* AS number of source peer */
+    u_int32_t dst_as_path_segments;           /* number of segments in path */
+    SFLExtended_as_path_segment *dst_as_path; /* list of seqs or sets */
+    u_int32_t communities_length;             /* number of communities */
+    u_int32_t *communities;                   /* set of communities */
+    u_int32_t localpref;                      /* LocalPref associated with this route */
+} SFLExtended_gateway;
+
+typedef struct _SFLString {
+    u_int32_t len;
+    char *str;
+} SFLString;
+
+/* Extended user data */
+
+typedef struct _SFLExtended_user {
+    u_int32_t src_charset;  /* MIBEnum value of character set used to encode a string - See RFC 2978
+			       Where possible UTF-8 encoding (MIBEnum=106) should be used. A value
+			       of zero indicates an unknown encoding. */
+    SFLString src_user;
+    u_int32_t dst_charset;
+    SFLString dst_user;
+} SFLExtended_user;
+
+/* Extended URL data */
+
+enum SFLExtended_url_direction {
+    SFLEXTENDED_URL_SRC = 1, /* URL is associated with source address */
+    SFLEXTENDED_URL_DST = 2  /* URL is associated with destination address */
+};
+
+typedef struct _SFLExtended_url {
+    u_int32_t direction;   /* enum SFLExtended_url_direction */
+    SFLString url;         /* URL associated with the packet flow.
+			      Must be URL encoded */
+    SFLString host;        /* The host field from the HTTP header */
+} SFLExtended_url;
+
+/* Extended MPLS data */
+
+typedef struct _SFLLabelStack {
+    u_int32_t depth;
+    u_int32_t *stack; /* first entry is top of stack - see RFC 3032 for encoding */
+} SFLLabelStack;
+
+typedef struct _SFLExtended_mpls {
+    SFLAddress nextHop;        /* Address of the next hop */ 
+    SFLLabelStack in_stack;
+    SFLLabelStack out_stack;
+} SFLExtended_mpls;
+
+/* Extended NAT data
+   Packet header records report addresses as seen at the sFlowDataSource.
+   The extended_nat structure reports on translated source and/or destination
+   addesses for this packet. If an address was not translated it should 
+   be equal to that reported for the header. */
+
+typedef struct _SFLExtended_nat {
+    SFLAddress src;    /* Source address */
+    SFLAddress dst;    /* Destination address */
+} SFLExtended_nat;
+
+/* additional Extended MPLS stucts */
+
+typedef struct _SFLExtended_mpls_tunnel {
+    SFLString tunnel_lsp_name;  /* Tunnel name */
+    u_int32_t tunnel_id;        /* Tunnel ID */
+    u_int32_t tunnel_cos;       /* Tunnel COS value */
+} SFLExtended_mpls_tunnel;
+
+typedef struct _SFLExtended_mpls_vc {
+    SFLString vc_instance_name; /* VC instance name */
+    u_int32_t vll_vc_id;        /* VLL/VC instance ID */
+    u_int32_t vc_label_cos;     /* VC Label COS value */
+} SFLExtended_mpls_vc;
+
+/* Extended MPLS FEC
+   - Definitions from MPLS-FTN-STD-MIB mplsFTNTable */
+
+typedef struct _SFLExtended_mpls_FTN {
+    SFLString mplsFTNDescr;
+    u_int32_t mplsFTNMask;
+} SFLExtended_mpls_FTN;
+
+/* Extended MPLS LVP FEC
+   - Definition from MPLS-LDP-STD-MIB mplsFecTable
+   Note: mplsFecAddrType, mplsFecAddr information available
+   from packet header */
+
+typedef struct _SFLExtended_mpls_LDP_FEC {
+    u_int32_t mplsFecAddrPrefixLength;
+} SFLExtended_mpls_LDP_FEC;
+
+/* Extended VLAN tunnel information 
+   Record outer VLAN encapsulations that have 
+   been stripped. extended_vlantunnel information 
+   should only be reported if all the following conditions are satisfied: 
+   1. The packet has nested vlan tags, AND 
+   2. The reporting device is VLAN aware, AND 
+   3. One or more VLAN tags have been stripped, either 
+   because they represent proprietary encapsulations, or 
+   because switch hardware automatically strips the outer VLAN 
+   encapsulation. 
+   Reporting extended_vlantunnel information is not a substitute for 
+   reporting extended_switch information. extended_switch data must 
+   always be reported to describe the ingress/egress VLAN information 
+   for the packet. The extended_vlantunnel information only applies to 
+   nested VLAN tags, and then only when one or more tags has been 
+   stripped. */ 
+
+typedef SFLLabelStack SFLVlanStack;
+typedef struct _SFLExtended_vlan_tunnel { 
+    SFLVlanStack stack;  /* List of stripped 802.1Q TPID/TCI layers. Each 
+			    TPID,TCI pair is represented as a single 32 bit 
+			    integer. Layers listed from outermost to 
+			    innermost. */ 
+} SFLExtended_vlan_tunnel;
+
+enum SFLFlow_type_tag {
+    /* enterprise = 0, format = ... */
+    SFLFLOW_HEADER    = 1,      /* Packet headers are sampled */
+    SFLFLOW_ETHERNET  = 2,      /* MAC layer information */
+    SFLFLOW_IPV4      = 3,      /* IP version 4 data */
+    SFLFLOW_IPV6      = 4,      /* IP version 6 data */
+    SFLFLOW_EX_SWITCH    = 1001,      /* Extended switch information */
+    SFLFLOW_EX_ROUTER    = 1002,      /* Extended router information */
+    SFLFLOW_EX_GATEWAY   = 1003,      /* Extended gateway router information */
+    SFLFLOW_EX_USER      = 1004,      /* Extended TACAS/RADIUS user information */
+    SFLFLOW_EX_URL       = 1005,      /* Extended URL information */
+    SFLFLOW_EX_MPLS      = 1006,      /* Extended MPLS information */
+    SFLFLOW_EX_NAT       = 1007,      /* Extended NAT information */
+    SFLFLOW_EX_MPLS_TUNNEL  = 1008,   /* additional MPLS information */
+    SFLFLOW_EX_MPLS_VC      = 1009,
+    SFLFLOW_EX_MPLS_FTN     = 1010,
+    SFLFLOW_EX_MPLS_LDP_FEC = 1011,
+    SFLFLOW_EX_VLAN_TUNNEL  = 1012,   /* VLAN stack */
+};
+
+typedef union _SFLFlow_type {
+    SFLSampled_header header;
+    SFLSampled_ethernet ethernet;
+    SFLSampled_ipv4 ipv4;
+    SFLSampled_ipv6 ipv6;
+    SFLExtended_switch sw;
+    SFLExtended_router router;
+    SFLExtended_gateway gateway;
+    SFLExtended_user user;
+    SFLExtended_url url;
+    SFLExtended_mpls mpls;
+    SFLExtended_nat nat;
+    SFLExtended_mpls_tunnel mpls_tunnel;
+    SFLExtended_mpls_vc mpls_vc;
+    SFLExtended_mpls_FTN mpls_ftn;
+    SFLExtended_mpls_LDP_FEC mpls_ldp_fec;
+    SFLExtended_vlan_tunnel vlan_tunnel;
+} SFLFlow_type;
+
+typedef struct _SFLFlow_sample_element {
+    struct _SFLFlow_sample_element *nxt;
+    u_int32_t tag;  /* SFLFlow_type_tag */
+    u_int32_t length;
+    SFLFlow_type flowType;
+} SFLFlow_sample_element;
+
+enum SFL_sample_tag {
+    SFLFLOW_SAMPLE = 1,              /* enterprise = 0 : format = 1 */
+    SFLCOUNTERS_SAMPLE = 2,          /* enterprise = 0 : format = 2 */
+    SFLFLOW_SAMPLE_EXPANDED = 3,     /* enterprise = 0 : format = 3 */
+    SFLCOUNTERS_SAMPLE_EXPANDED = 4  /* enterprise = 0 : format = 4 */
+};
+  
+/* Format of a single flow sample */
+
+typedef struct _SFLFlow_sample {
+    /* u_int32_t tag;    */         /* SFL_sample_tag -- enterprise = 0 : format = 1 */
+    /* u_int32_t length; */
+    u_int32_t sequence_number;      /* Incremented with each flow sample
+				       generated */
+    u_int32_t source_id;            /* fsSourceId */
+    u_int32_t sampling_rate;        /* fsPacketSamplingRate */
+    u_int32_t sample_pool;          /* Total number of packets that could have been
+				       sampled (i.e. packets skipped by sampling
+				       process + total number of samples) */
+    u_int32_t drops;                /* Number of times a packet was dropped due to
+				       lack of resources */
+    u_int32_t input;                /* SNMP ifIndex of input interface.
+				       0 if interface is not known. */
+    u_int32_t output;               /* SNMP ifIndex of output interface,
+				       0 if interface is not known.
+				       Set most significant bit to indicate
+				       multiple destination interfaces
+				       (i.e. in case of broadcast or multicast)
+				       and set lower order bits to indicate
+				       number of destination interfaces.
+				       Examples:
+				       0x00000002  indicates ifIndex = 2
+				       0x00000000  ifIndex unknown.
+				       0x80000007  indicates a packet sent
+				       to 7 interfaces.
+				       0x80000000  indicates a packet sent to
+				       an unknown number of
+				       interfaces greater than 1.*/
+    u_int32_t num_elements;
+    SFLFlow_sample_element *elements;
+} SFLFlow_sample;
+
+/* same thing, but the expanded version (for full 32-bit ifIndex numbers) */
+
+typedef struct _SFLFlow_sample_expanded {
+    /* u_int32_t tag;    */         /* SFL_sample_tag -- enterprise = 0 : format = 1 */
+    /* u_int32_t length; */
+    u_int32_t sequence_number;      /* Incremented with each flow sample
+				       generated */
+    u_int32_t ds_class;             /* EXPANDED */
+    u_int32_t ds_index;             /* EXPANDED */
+    u_int32_t sampling_rate;        /* fsPacketSamplingRate */
+    u_int32_t sample_pool;          /* Total number of packets that could have been
+				       sampled (i.e. packets skipped by sampling
+				       process + total number of samples) */
+    u_int32_t drops;                /* Number of times a packet was dropped due to
+				       lack of resources */
+    u_int32_t inputFormat;          /* EXPANDED */
+    u_int32_t input;                /* SNMP ifIndex of input interface.
+				       0 if interface is not known. */
+    u_int32_t outputFormat;         /* EXPANDED */
+    u_int32_t output;               /* SNMP ifIndex of output interface,
+				       0 if interface is not known. */
+    u_int32_t num_elements;
+    SFLFlow_sample_element *elements;
+} SFLFlow_sample_expanded;
+
+/* Counter types */
+
+/* Generic interface counters - see RFC 1573, 2233 */
+
+typedef struct _SFLIf_counters {
+    u_int32_t ifIndex;
+    u_int32_t ifType;
+    u_int64_t ifSpeed;
+    u_int32_t ifDirection;        /* Derived from MAU MIB (RFC 2668)
+				     0 = unknown, 1 = full-duplex,
+				     2 = half-duplex, 3 = in, 4 = out */
+    u_int32_t ifStatus;           /* bit field with the following bits assigned:
+				     bit 0 = ifAdminStatus (0 = down, 1 = up)
+				     bit 1 = ifOperStatus (0 = down, 1 = up) */
+    u_int64_t ifInOctets;
+    u_int32_t ifInUcastPkts;
+    u_int32_t ifInMulticastPkts;
+    u_int32_t ifInBroadcastPkts;
+    u_int32_t ifInDiscards;
+    u_int32_t ifInErrors;
+    u_int32_t ifInUnknownProtos;
+    u_int64_t ifOutOctets;
+    u_int32_t ifOutUcastPkts;
+    u_int32_t ifOutMulticastPkts;
+    u_int32_t ifOutBroadcastPkts;
+    u_int32_t ifOutDiscards;
+    u_int32_t ifOutErrors;
+    u_int32_t ifPromiscuousMode;
+} SFLIf_counters;
+
+/* Ethernet interface counters - see RFC 2358 */
+typedef struct _SFLEthernet_counters {
+    u_int32_t dot3StatsAlignmentErrors;
+    u_int32_t dot3StatsFCSErrors;
+    u_int32_t dot3StatsSingleCollisionFrames;
+    u_int32_t dot3StatsMultipleCollisionFrames;
+    u_int32_t dot3StatsSQETestErrors;
+    u_int32_t dot3StatsDeferredTransmissions;
+    u_int32_t dot3StatsLateCollisions;
+    u_int32_t dot3StatsExcessiveCollisions;
+    u_int32_t dot3StatsInternalMacTransmitErrors;
+    u_int32_t dot3StatsCarrierSenseErrors;
+    u_int32_t dot3StatsFrameTooLongs;
+    u_int32_t dot3StatsInternalMacReceiveErrors;
+    u_int32_t dot3StatsSymbolErrors;
+} SFLEthernet_counters;
+
+/* Token ring counters - see RFC 1748 */
+
+typedef struct _SFLTokenring_counters {
+    u_int32_t dot5StatsLineErrors;
+    u_int32_t dot5StatsBurstErrors;
+    u_int32_t dot5StatsACErrors;
+    u_int32_t dot5StatsAbortTransErrors;
+    u_int32_t dot5StatsInternalErrors;
+    u_int32_t dot5StatsLostFrameErrors;
+    u_int32_t dot5StatsReceiveCongestions;
+    u_int32_t dot5StatsFrameCopiedErrors;
+    u_int32_t dot5StatsTokenErrors;
+    u_int32_t dot5StatsSoftErrors;
+    u_int32_t dot5StatsHardErrors;
+    u_int32_t dot5StatsSignalLoss;
+    u_int32_t dot5StatsTransmitBeacons;
+    u_int32_t dot5StatsRecoverys;
+    u_int32_t dot5StatsLobeWires;
+    u_int32_t dot5StatsRemoves;
+    u_int32_t dot5StatsSingles;
+    u_int32_t dot5StatsFreqErrors;
+} SFLTokenring_counters;
+
+/* 100 BaseVG interface counters - see RFC 2020 */
+
+typedef struct _SFLVg_counters {
+    u_int32_t dot12InHighPriorityFrames;
+    u_int64_t dot12InHighPriorityOctets;
+    u_int32_t dot12InNormPriorityFrames;
+    u_int64_t dot12InNormPriorityOctets;
+    u_int32_t dot12InIPMErrors;
+    u_int32_t dot12InOversizeFrameErrors;
+    u_int32_t dot12InDataErrors;
+    u_int32_t dot12InNullAddressedFrames;
+    u_int32_t dot12OutHighPriorityFrames;
+    u_int64_t dot12OutHighPriorityOctets;
+    u_int32_t dot12TransitionIntoTrainings;
+    u_int64_t dot12HCInHighPriorityOctets;
+    u_int64_t dot12HCInNormPriorityOctets;
+    u_int64_t dot12HCOutHighPriorityOctets;
+} SFLVg_counters;
+
+typedef struct _SFLVlan_counters {
+    u_int32_t vlan_id;
+    u_int64_t octets;
+    u_int32_t ucastPkts;
+    u_int32_t multicastPkts;
+    u_int32_t broadcastPkts;
+    u_int32_t discards;
+} SFLVlan_counters;
+
+/* Counters data */
+
+enum SFLCounters_type_tag {
+    /* enterprise = 0, format = ... */
+    SFLCOUNTERS_GENERIC      = 1,
+    SFLCOUNTERS_ETHERNET     = 2,
+    SFLCOUNTERS_TOKENRING    = 3,
+    SFLCOUNTERS_VG           = 4,
+    SFLCOUNTERS_VLAN         = 5
+};
+
+typedef union _SFLCounters_type {
+    SFLIf_counters generic;
+    SFLEthernet_counters ethernet;
+    SFLTokenring_counters tokenring;
+    SFLVg_counters vg;
+    SFLVlan_counters vlan;
+} SFLCounters_type;
+
+typedef struct _SFLCounters_sample_element {
+    struct _SFLCounters_sample_element *nxt; /* linked list */
+    u_int32_t tag; /* SFLCounters_type_tag */
+    u_int32_t length;
+    SFLCounters_type counterBlock;
+} SFLCounters_sample_element;
+
+typedef struct _SFLCounters_sample {
+    /* u_int32_t tag;    */       /* SFL_sample_tag -- enterprise = 0 : format = 2 */
+    /* u_int32_t length; */
+    u_int32_t sequence_number;    /* Incremented with each counters sample
+				     generated by this source_id */
+    u_int32_t source_id;          /* fsSourceId */
+    u_int32_t num_elements;
+    SFLCounters_sample_element *elements;
+} SFLCounters_sample;
+
+/* same thing, but the expanded version, so ds_index can be a full 32 bits */
+typedef struct _SFLCounters_sample_expanded {
+    /* u_int32_t tag;    */       /* SFL_sample_tag -- enterprise = 0 : format = 2 */
+    /* u_int32_t length; */
+    u_int32_t sequence_number;    /* Incremented with each counters sample
+				     generated by this source_id */
+    u_int32_t ds_class;           /* EXPANDED */
+    u_int32_t ds_index;           /* EXPANDED */
+    u_int32_t num_elements;
+    SFLCounters_sample_element *elements;
+} SFLCounters_sample_expanded;
+
+#define SFLADD_ELEMENT(_sm, _el) do { (_el)->nxt = (_sm)->elements; (_sm)->elements = (_el); } while(0)
+
+/* Format of a sample datagram */
+
+enum SFLDatagram_version {
+    SFLDATAGRAM_VERSION2 = 2,
+    SFLDATAGRAM_VERSION4 = 4,
+    SFLDATAGRAM_VERSION5 = 5
+};
+
+typedef struct _SFLSample_datagram_hdr {
+    u_int32_t datagram_version;      /* (enum SFLDatagram_version) = VERSION5 = 5 */
+    SFLAddress agent_address;        /* IP address of sampling agent */
+    u_int32_t sub_agent_id;          /* Used to distinguishing between datagram
+					streams from separate agent sub entities
+					within an device. */
+    u_int32_t sequence_number;       /* Incremented with each sample datagram
+					generated */
+    u_int32_t uptime;                /* Current time (in milliseconds since device
+					last booted). Should be set as close to
+					datagram transmission time as possible.*/
+    u_int32_t num_records;           /* Number of tag-len-val flow/counter records to follow */
+} SFLSample_datagram_hdr;
+
+#define SFL_MAX_DATAGRAM_SIZE 1500
+#define SFL_MIN_DATAGRAM_SIZE 200
+#define SFL_DEFAULT_DATAGRAM_SIZE 1400
+
+#define SFL_DATA_PAD 400
+
+#endif /* SFLOW_H */
diff --git a/lib/sflow_agent.c b/lib/sflow_agent.c
new file mode 100644
index 000000000..4b25c25a9
--- /dev/null
+++ b/lib/sflow_agent.c
@@ -0,0 +1,492 @@
+/* Copyright (c) 2002-2009 InMon Corp. Licensed under the terms of the InMon sFlow licence: */
+/* http://www.inmon.com/technology/sflowlicense.txt */
+
+#include "sflow_api.h"
+
+static void * sflAlloc(SFLAgent *agent, size_t bytes);
+static void sflFree(SFLAgent *agent, void *obj);
+static void sfl_agent_jumpTableAdd(SFLAgent *agent, SFLSampler *sampler);
+static void sfl_agent_jumpTableRemove(SFLAgent *agent, SFLSampler *sampler);
+
+/*________________--------------------------__________________
+  ________________    sfl_agent_init        __________________
+  ----------------__________________________------------------
+*/
+
+void sfl_agent_init(SFLAgent *agent,
+		    SFLAddress *myIP, /* IP address of this agent in net byte order */
+		    u_int32_t subId,  /* agent_sub_id */
+		    time_t bootTime,  /* agent boot time */
+		    time_t now,       /* time now */
+		    void *magic,      /* ptr to pass back in logging and alloc fns */
+		    allocFn_t allocFn,
+		    freeFn_t freeFn,
+		    errorFn_t errorFn,
+		    sendFn_t sendFn)
+{
+    /* first clear everything */
+    memset(agent, 0, sizeof(*agent));
+    /* now copy in the parameters */
+    agent->myIP = *myIP; /* structure copy */
+    agent->subId = subId;
+    agent->bootTime = bootTime;
+    agent->now = now;
+    agent->magic = magic;
+    agent->allocFn = allocFn;
+    agent->freeFn = freeFn;
+    agent->errorFn = errorFn;
+    agent->sendFn = sendFn;
+
+#ifdef SFLOW_DO_SOCKET  
+    if(sendFn == NULL) {
+	/* open the socket - really need one for v4 and another for v6? */
+	if((agent->receiverSocket4 = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1)
+	    sfl_agent_sysError(agent, "agent", "IPv4 socket open failed");
+	if((agent->receiverSocket6 = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP)) == -1)
+	    sfl_agent_sysError(agent, "agent", "IPv6 socket open failed");
+    }
+#endif
+}
+
+/*_________________---------------------------__________________
+  _________________   sfl_agent_release       __________________
+  -----------------___________________________------------------
+*/
+
+void sfl_agent_release(SFLAgent *agent)
+{
+    /* release and free the samplers, pollers and receivers */
+    SFLSampler *sm = agent->samplers;
+    SFLPoller *pl = agent->pollers;
+    SFLReceiver *rcv = agent->receivers;
+
+    for(; sm != NULL; ) {
+	SFLSampler *nextSm = sm->nxt;
+	sflFree(agent, sm);
+	sm = nextSm;
+    }
+    agent->samplers = NULL;
+
+    for(; pl != NULL; ) {
+	SFLPoller *nextPl = pl->nxt;
+	sflFree(agent, pl);
+	pl = nextPl;
+    }
+    agent->pollers = NULL;
+
+    for(; rcv != NULL; ) {
+	SFLReceiver *nextRcv = rcv->nxt;
+	sflFree(agent, rcv);
+	rcv = nextRcv;
+    }
+    agent->receivers = NULL;
+
+#ifdef SFLOW_DO_SOCKET
+    /* close the sockets */
+    if(agent->receiverSocket4 > 0) close(agent->receiverSocket4);
+    if(agent->receiverSocket6 > 0) close(agent->receiverSocket6);
+#endif
+}
+
+
+/*_________________---------------------------__________________
+  _________________   sfl_agent_set_*         __________________
+  -----------------___________________________------------------
+*/
+
+void sfl_agent_set_agentAddress(SFLAgent *agent, SFLAddress *addr)
+{
+    if(addr && memcmp(addr, &agent->myIP, sizeof(agent->myIP)) != 0) {
+	/* change of address */
+	agent->myIP = *addr; /* structure copy */
+	/* reset sequence numbers here? */
+    }
+}
+
+void sfl_agent_set_agentSubId(SFLAgent *agent, u_int32_t subId)
+{
+    if(subId != agent->subId) {
+	/* change of subId */
+	agent->subId = subId;
+	/* reset sequence numbers here? */
+    }
+}
+
+/*_________________---------------------------__________________
+  _________________   sfl_agent_tick          __________________
+  -----------------___________________________------------------
+*/
+
+void sfl_agent_tick(SFLAgent *agent, time_t now)
+{
+    SFLReceiver *rcv = agent->receivers;
+    SFLSampler *sm = agent->samplers;
+    SFLPoller *pl = agent->pollers;
+    agent->now = now;
+    /* receivers use ticks to flush send data */
+    for(; rcv != NULL; rcv = rcv->nxt) sfl_receiver_tick(rcv, now);
+    /* samplers use ticks to decide when they are sampling too fast */
+    for(; sm != NULL; sm = sm->nxt) sfl_sampler_tick(sm, now);
+    /* pollers use ticks to decide when to ask for counters */
+    for(; pl != NULL; pl = pl->nxt) sfl_poller_tick(pl, now);
+}
+
+/*_________________---------------------------__________________
+  _________________   sfl_agent_addReceiver   __________________
+  -----------------___________________________------------------
+*/
+
+SFLReceiver *sfl_agent_addReceiver(SFLAgent *agent)
+{
+    SFLReceiver *rcv = (SFLReceiver *)sflAlloc(agent, sizeof(SFLReceiver));
+    sfl_receiver_init(rcv, agent);
+    /* add to end of list - to preserve the receiver index numbers for existing receivers */
+    {
+	SFLReceiver *r, *prev = NULL;
+	for(r = agent->receivers; r != NULL; prev = r, r = r->nxt);
+	if(prev) prev->nxt = rcv;
+	else agent->receivers = rcv;
+	rcv->nxt = NULL;
+    }
+    return rcv;
+}
+
+/*_________________---------------------------__________________
+  _________________     sfl_dsi_compare       __________________
+  -----------------___________________________------------------
+
+  Note that if there is a mixture of ds_classes for this agent, then
+  the simple numeric comparison may not be correct - the sort order (for
+  the purposes of the SNMP MIB) should really be determined by the OID
+  that these numeric ds_class numbers are a shorthand for.  For example,
+  ds_class == 0 means ifIndex, which is the oid "1.3.6.1.2.1.2.2.1"
+*/
+
+static inline int sfl_dsi_compare(SFLDataSource_instance *pdsi1, SFLDataSource_instance *pdsi2) {
+    /* could have used just memcmp(),  but not sure if that would
+       give the right answer on little-endian platforms. Safer to be explicit... */
+    int cmp = pdsi2->ds_class - pdsi1->ds_class;
+    if(cmp == 0) cmp = pdsi2->ds_index - pdsi1->ds_index;
+    if(cmp == 0) cmp = pdsi2->ds_instance - pdsi1->ds_instance;
+    return cmp;
+}
+
+/*_________________---------------------------__________________
+  _________________   sfl_agent_addSampler    __________________
+  -----------------___________________________------------------
+*/
+
+SFLSampler *sfl_agent_addSampler(SFLAgent *agent, SFLDataSource_instance *pdsi)
+{
+    /* Keep the list sorted. */
+    SFLSampler *prev = NULL, *sm = agent->samplers;
+    for(; sm != NULL; prev = sm, sm = sm->nxt) {
+	int64_t cmp = sfl_dsi_compare(pdsi, &sm->dsi);
+	if(cmp == 0) return sm;  /* found - return existing one */
+	if(cmp < 0) break;       /* insert here */
+    }
+    /* either we found the insert point, or reached the end of the list...*/
+    
+    {
+	SFLSampler *newsm = (SFLSampler *)sflAlloc(agent, sizeof(SFLSampler));
+	sfl_sampler_init(newsm, agent, pdsi);
+	if(prev) prev->nxt = newsm;
+	else agent->samplers = newsm;
+	newsm->nxt = sm;
+	
+	/* see if we should go in the ifIndex jumpTable */
+	if(SFL_DS_CLASS(newsm->dsi) == 0) {
+	    SFLSampler *test = sfl_agent_getSamplerByIfIndex(agent, SFL_DS_INDEX(newsm->dsi));
+	    if(test && (SFL_DS_INSTANCE(newsm->dsi) < SFL_DS_INSTANCE(test->dsi))) {
+		/* replace with this new one because it has a lower ds_instance number */
+		sfl_agent_jumpTableRemove(agent, test);
+		test = NULL;
+	    }
+	    if(test == NULL) sfl_agent_jumpTableAdd(agent, newsm);
+	}
+	return newsm;
+    }
+}
+
+/*_________________---------------------------__________________
+  _________________   sfl_agent_addPoller     __________________
+  -----------------___________________________------------------
+*/
+
+SFLPoller *sfl_agent_addPoller(SFLAgent *agent,
+			       SFLDataSource_instance *pdsi,
+			       void *magic,         /* ptr to pass back in getCountersFn() */
+			       getCountersFn_t getCountersFn)
+{
+    /* keep the list sorted */
+    SFLPoller *prev = NULL, *pl = agent->pollers;
+    for(; pl != NULL; prev = pl, pl = pl->nxt) {
+	int64_t cmp = sfl_dsi_compare(pdsi, &pl->dsi);
+	if(cmp == 0) return pl;  /* found - return existing one */
+	if(cmp < 0) break;       /* insert here */
+    }
+    /* either we found the insert point, or reached the end of the list... */
+    {
+	SFLPoller *newpl = (SFLPoller *)sflAlloc(agent, sizeof(SFLPoller));
+	sfl_poller_init(newpl, agent, pdsi, magic, getCountersFn);
+	if(prev) prev->nxt = newpl;
+	else agent->pollers = newpl;
+	newpl->nxt = pl;
+	return newpl;
+    }
+}
+
+/*_________________---------------------------__________________
+  _________________  sfl_agent_removeSampler  __________________
+  -----------------___________________________------------------
+*/
+
+int sfl_agent_removeSampler(SFLAgent *agent, SFLDataSource_instance *pdsi)
+{
+    /* find it, unlink it and free it */
+    SFLSampler *prev = NULL, *sm = agent->samplers;
+    for(; sm != NULL; prev = sm, sm = sm->nxt) {
+	if(sfl_dsi_compare(pdsi, &sm->dsi) == 0) {
+	    if(prev == NULL) agent->samplers = sm->nxt;
+	    else prev->nxt = sm->nxt;
+	    sfl_agent_jumpTableRemove(agent, sm);
+	    sflFree(agent, sm);
+	    return 1;
+	}
+    }
+    /* not found */
+    return 0;
+}
+
+/*_________________---------------------------__________________
+  _________________  sfl_agent_removePoller   __________________
+  -----------------___________________________------------------
+*/
+
+int sfl_agent_removePoller(SFLAgent *agent, SFLDataSource_instance *pdsi)
+{
+    /* find it, unlink it and free it */
+    SFLPoller *prev = NULL, *pl = agent->pollers;
+    for(; pl != NULL; prev = pl, pl = pl->nxt) {
+	if(sfl_dsi_compare(pdsi, &pl->dsi) == 0) {
+	    if(prev == NULL) agent->pollers = pl->nxt;
+	    else prev->nxt = pl->nxt;
+	    sflFree(agent, pl);
+	    return 1;
+	}
+    }
+    /* not found */
+    return 0;
+}
+
+/*_________________--------------------------------__________________
+  _________________  sfl_agent_jumpTableAdd        __________________
+  -----------------________________________________------------------
+*/
+
+static void sfl_agent_jumpTableAdd(SFLAgent *agent, SFLSampler *sampler)
+{
+    u_int32_t hashIndex = SFL_DS_INDEX(sampler->dsi) % SFL_HASHTABLE_SIZ;
+    sampler->hash_nxt = agent->jumpTable[hashIndex];
+    agent->jumpTable[hashIndex] = sampler;
+}
+
+/*_________________--------------------------------__________________
+  _________________  sfl_agent_jumpTableRemove     __________________
+  -----------------________________________________------------------
+*/
+
+static void sfl_agent_jumpTableRemove(SFLAgent *agent, SFLSampler *sampler)
+{
+    u_int32_t hashIndex = SFL_DS_INDEX(sampler->dsi) % SFL_HASHTABLE_SIZ;
+    SFLSampler *search = agent->jumpTable[hashIndex], *prev = NULL;
+    for( ; search != NULL; prev = search, search = search->hash_nxt) if(search == sampler) break;
+    if(search) {
+	// found - unlink
+	if(prev) prev->hash_nxt = search->hash_nxt;
+	else agent->jumpTable[hashIndex] = search->hash_nxt;
+	search->hash_nxt = NULL;
+    }
+}
+
+/*_________________--------------------------------__________________
+  _________________  sfl_agent_getSamplerByIfIndex __________________
+  -----------------________________________________------------------
+  fast lookup (pointers cached in hash table).  If there are multiple
+  sampler instances for a given ifIndex, then this fn will return
+  the one with the lowest instance number.  Since the samplers
+  list is sorted, this means the other instances will be accesible
+  by following the sampler->nxt pointer (until the ds_class
+  or ds_index changes).  This is helpful if you need to offer
+  the same flowSample to multiple samplers.
+*/
+
+SFLSampler *sfl_agent_getSamplerByIfIndex(SFLAgent *agent, u_int32_t ifIndex)
+{
+    SFLSampler *search = agent->jumpTable[ifIndex % SFL_HASHTABLE_SIZ];
+    for( ; search != NULL; search = search->hash_nxt) if(SFL_DS_INDEX(search->dsi) == ifIndex) break;
+    return search;
+}
+
+/*_________________---------------------------__________________
+  _________________  sfl_agent_getSampler     __________________
+  -----------------___________________________------------------
+*/
+
+SFLSampler *sfl_agent_getSampler(SFLAgent *agent, SFLDataSource_instance *pdsi)
+{
+    /* find it and return it */
+    SFLSampler *sm = agent->samplers;
+    for(; sm != NULL; sm = sm->nxt)
+	if(sfl_dsi_compare(pdsi, &sm->dsi) == 0) return sm;
+    /* not found */
+    return NULL;
+}
+
+/*_________________---------------------------__________________
+  _________________  sfl_agent_getPoller      __________________
+  -----------------___________________________------------------
+*/
+
+SFLPoller *sfl_agent_getPoller(SFLAgent *agent, SFLDataSource_instance *pdsi)
+{
+    /* find it and return it */
+    SFLPoller *pl = agent->pollers;
+    for(; pl != NULL; pl = pl->nxt)
+	if(sfl_dsi_compare(pdsi, &pl->dsi) == 0) return pl;
+    /* not found */
+    return NULL;
+}
+
+/*_________________---------------------------__________________
+  _________________  sfl_agent_getReceiver    __________________
+  -----------------___________________________------------------
+*/
+
+SFLReceiver *sfl_agent_getReceiver(SFLAgent *agent, u_int32_t receiverIndex)
+{
+    u_int32_t rcvIdx = 0;
+    SFLReceiver *rcv = agent->receivers;
+    for(;  rcv != NULL; rcv = rcv->nxt)
+	if(receiverIndex == ++rcvIdx) return rcv;
+
+    /* not found - ran off the end of the table */
+    return NULL;
+}
+
+/*_________________---------------------------__________________
+  _________________ sfl_agent_getNextSampler  __________________
+  -----------------___________________________------------------
+*/
+
+SFLSampler *sfl_agent_getNextSampler(SFLAgent *agent, SFLDataSource_instance *pdsi)
+{
+    /* return the one lexograpically just after it - assume they are sorted
+       correctly according to the lexographical ordering of the object ids */
+    SFLSampler *sm = sfl_agent_getSampler(agent, pdsi);
+    return sm ? sm->nxt : NULL;
+}
+
+/*_________________---------------------------__________________
+  _________________ sfl_agent_getNextPoller   __________________
+  -----------------___________________________------------------
+*/
+
+SFLPoller *sfl_agent_getNextPoller(SFLAgent *agent, SFLDataSource_instance *pdsi)
+{
+    /* return the one lexograpically just after it - assume they are sorted
+       correctly according to the lexographical ordering of the object ids */
+    SFLPoller *pl = sfl_agent_getPoller(agent, pdsi);
+    return pl ? pl->nxt : NULL;
+}
+
+/*_________________---------------------------__________________
+  _________________ sfl_agent_getNextReceiver __________________
+  -----------------___________________________------------------
+*/
+
+SFLReceiver *sfl_agent_getNextReceiver(SFLAgent *agent, u_int32_t receiverIndex)
+{
+    return sfl_agent_getReceiver(agent, receiverIndex + 1);
+}
+
+
+/*_________________---------------------------__________________
+  _________________ sfl_agent_resetReceiver   __________________
+  -----------------___________________________------------------
+*/
+
+void sfl_agent_resetReceiver(SFLAgent *agent, SFLReceiver *receiver)
+{
+    /* tell samplers and pollers to stop sending to this receiver */
+    /* first get his receiverIndex */
+    u_int32_t rcvIdx = 0;
+    SFLReceiver *rcv = agent->receivers;
+    for(; rcv != NULL; rcv = rcv->nxt) {
+	rcvIdx++; /* thanks to Diego Valverde for pointing out this bugfix */
+	if(rcv == receiver) {
+	    /* now tell anyone that is using it to stop */
+	    SFLSampler *sm = agent->samplers;
+	    SFLPoller *pl = agent->pollers;
+
+	    for(; sm != NULL; sm = sm->nxt)
+		if(sfl_sampler_get_sFlowFsReceiver(sm) == rcvIdx) sfl_sampler_set_sFlowFsReceiver(sm, 0);
+      
+	    for(; pl != NULL; pl = pl->nxt)
+		if(sfl_poller_get_sFlowCpReceiver(pl) == rcvIdx) sfl_poller_set_sFlowCpReceiver(pl, 0);
+
+	    break;
+	}
+    }
+}
+  
+/*_________________---------------------------__________________
+  _________________     sfl_agent_error       __________________
+  -----------------___________________________------------------
+*/
+#define MAX_ERRMSG_LEN 1000
+
+void sfl_agent_error(SFLAgent *agent, char *modName, char *msg)
+{
+    char errm[MAX_ERRMSG_LEN];
+    sprintf(errm, "sfl_agent_error: %s: %s\n", modName, msg);
+    if(agent->errorFn) (*agent->errorFn)(agent->magic, agent, errm);
+    else {
+	fprintf(stderr, "%s\n", errm);
+	fflush(stderr);
+    }
+}
+
+/*_________________---------------------------__________________
+  _________________     sfl_agent_sysError    __________________
+  -----------------___________________________------------------
+*/
+
+void sfl_agent_sysError(SFLAgent *agent, char *modName, char *msg)
+{
+    char errm[MAX_ERRMSG_LEN];
+    sprintf(errm, "sfl_agent_sysError: %s: %s (errno = %d - %s)\n", modName, msg, errno, strerror(errno));
+    if(agent->errorFn) (*agent->errorFn)(agent->magic, agent, errm);
+    else {
+	fprintf(stderr, "%s\n", errm);
+	fflush(stderr);
+    }
+}
+
+
+/*_________________---------------------------__________________
+  _________________       alloc and free      __________________
+  -----------------___________________________------------------
+*/
+
+static void * sflAlloc(SFLAgent *agent, size_t bytes)
+{
+    if(agent->allocFn) return (*agent->allocFn)(agent->magic, agent, bytes);
+    else return SFL_ALLOC(bytes);
+}
+
+static void sflFree(SFLAgent *agent, void *obj)
+{
+    if(agent->freeFn) (*agent->freeFn)(agent->magic, agent, obj);
+    else SFL_FREE(obj);
+}
diff --git a/lib/sflow_api.h b/lib/sflow_api.h
new file mode 100644
index 000000000..be8d99773
--- /dev/null
+++ b/lib/sflow_api.h
@@ -0,0 +1,340 @@
+/* Copyright (c) 2002-2009 InMon Corp. Licensed under the terms of the InMon sFlow licence: */
+/* http://www.inmon.com/technology/sflowlicense.txt */
+
+#ifndef SFLOW_API_H
+#define SFLOW_API_H 1
+
+/* define SFLOW_DO_SOCKET to 1 if you want the agent
+   to send the packets itself, otherwise set the sendFn
+   callback in sfl_agent_init.*/
+/* #define SFLOW_DO_SOCKET */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/types.h>
+#include <arpa/inet.h> /* for htonl */
+
+#ifdef SFLOW_DO_SOCKET
+#include <sys/socket.h>
+#include <netinet/in_systm.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#endif
+
+#include "sflow.h"
+  
+/* define SFLOW_SOFTWARE_SAMPLING to 1 if you need to use the
+   sfl_sampler_takeSample routine and give it every packet */
+/* #define SFLOW_SOFTWARE_SAMPLING */
+
+/*
+  uncomment this preprocessor flag  (or compile with -DSFL_USE_32BIT_INDEX)
+  if your ds_index numbers can ever be >= 2^30-1 (i.e. >= 0x3FFFFFFF)
+*/
+/* #define SFL_USE_32BIT_INDEX */
+
+
+/* Used to combine ds_class, ds_index and instance into
+   a single 64-bit number like this:
+   __________________________________
+   | cls|  index     |   instance     |
+   ----------------------------------
+ 
+   but now is opened up to a 12-byte struct to ensure
+   that ds_index has a full 32-bit field, and to make
+   accessing the components simpler. The macros have
+   the same behavior as before, so this change should
+   be transparent.  The only difference is that these
+   objects are now passed around by reference instead
+   of by value, and the comparison is done using a fn.
+*/
+
+typedef struct _SFLDataSource_instance {
+    u_int32_t ds_class;
+    u_int32_t ds_index;
+    u_int32_t ds_instance;
+} SFLDataSource_instance;
+
+#ifdef SFL_USE_32BIT_INDEX
+#define SFL_FLOW_SAMPLE_TYPE SFLFlow_sample_expanded
+#define SFL_COUNTERS_SAMPLE_TYPE SFLCounters_sample_expanded
+#else
+#define SFL_FLOW_SAMPLE_TYPE SFLFlow_sample
+#define SFL_COUNTERS_SAMPLE_TYPE SFLCounters_sample
+/* if index numbers are not going to use all 32 bits, then we can use
+   the more compact encoding, with the dataSource class and index merged */
+#define SFL_DS_DATASOURCE(dsi) (((dsi).ds_class << 24) + (dsi).ds_index)
+#endif
+
+#define SFL_DS_INSTANCE(dsi) (dsi).ds_instance
+#define SFL_DS_CLASS(dsi) (dsi).ds_class
+#define SFL_DS_INDEX(dsi) (dsi).ds_index
+#define SFL_DS_SET(dsi,clss,indx,inst)		\
+    do {					\
+	(dsi).ds_class = (clss);		\
+	(dsi).ds_index = (indx);		\
+	(dsi).ds_instance = (inst);		\
+    } while(0)
+
+typedef struct _SFLSampleCollector {
+    u_int32_t data[(SFL_MAX_DATAGRAM_SIZE + SFL_DATA_PAD) / sizeof(u_int32_t)];
+    u_int32_t *datap; /* packet fill pointer */
+    u_int32_t pktlen; /* accumulated size */
+    u_int32_t packetSeqNo;
+    u_int32_t numSamples;
+} SFLSampleCollector;
+
+struct _SFLAgent;  /* forward decl */
+
+typedef struct _SFLReceiver {
+    struct _SFLReceiver *nxt;
+    /* MIB fields */
+    char *sFlowRcvrOwner;
+    time_t sFlowRcvrTimeout;
+    u_int32_t sFlowRcvrMaximumDatagramSize;
+    SFLAddress sFlowRcvrAddress;
+    u_int32_t sFlowRcvrPort;
+    u_int32_t sFlowRcvrDatagramVersion;
+    /* public fields */
+    struct _SFLAgent *agent;    /* pointer to my agent */
+    /* private fields */
+    SFLSampleCollector sampleCollector;
+#ifdef SFLOW_DO_SOCKET
+    struct sockaddr_in receiver4;
+    struct sockaddr_in6 receiver6;
+#endif
+} SFLReceiver;
+
+typedef struct _SFLSampler {
+    /* for linked list */
+    struct _SFLSampler *nxt;
+    /* for hash lookup table */
+    struct _SFLSampler *hash_nxt;
+    /* MIB fields */
+    SFLDataSource_instance dsi;
+    u_int32_t sFlowFsReceiver;
+    u_int32_t sFlowFsPacketSamplingRate;
+    u_int32_t sFlowFsMaximumHeaderSize;
+    /* public fields */
+    struct _SFLAgent *agent; /* pointer to my agent */
+    /* private fields */
+    SFLReceiver *myReceiver;
+    u_int32_t skip;
+    u_int32_t samplePool;
+    u_int32_t flowSampleSeqNo;
+    /* rate checking */
+    u_int32_t samplesThisTick;
+    u_int32_t samplesLastTick;
+    u_int32_t backoffThreshold;
+} SFLSampler;
+
+/* declare */
+struct _SFLPoller;
+
+typedef void (*getCountersFn_t)(void *magic,                   /* callback to get counters */
+				struct _SFLPoller *sampler,    /* called with self */
+				SFL_COUNTERS_SAMPLE_TYPE *cs); /* struct to fill in */
+
+typedef struct _SFLPoller {
+    /* for linked list */
+    struct _SFLPoller *nxt;
+    /* MIB fields */
+    SFLDataSource_instance dsi;
+    u_int32_t sFlowCpReceiver;
+    time_t sFlowCpInterval;
+    /* public fields */
+    struct _SFLAgent *agent; /* pointer to my agent */
+    void *magic;             /* ptr to pass back in getCountersFn() */
+    getCountersFn_t getCountersFn;
+    u_int32_t bridgePort; /* port number local to bridge */
+    /* private fields */
+    SFLReceiver *myReceiver;
+    time_t countersCountdown;
+    u_int32_t countersSampleSeqNo;
+} SFLPoller;
+
+typedef void *(*allocFn_t)(void *magic,               /* callback to allocate space on heap */
+			   struct _SFLAgent *agent,   /* called with self */
+			   size_t bytes);             /* bytes requested */
+
+typedef int (*freeFn_t)(void *magic,                  /* callback to free space on heap */
+			struct _SFLAgent *agent,      /* called with self */
+			void *obj);                   /* obj to free */
+
+typedef void (*errorFn_t)(void *magic,                /* callback to log error message */
+			  struct _SFLAgent *agent,    /* called with self */
+			  char *msg);                 /* error message */
+
+typedef void (*sendFn_t)(void *magic,                 /* optional override fn to send packet */
+			 struct _SFLAgent *agent,
+			 SFLReceiver *receiver,
+			 u_char *pkt,
+			 u_int32_t pktLen);
+
+
+/* prime numbers are good for hash tables */
+#define SFL_HASHTABLE_SIZ 199
+
+typedef struct _SFLAgent {
+    SFLSampler *jumpTable[SFL_HASHTABLE_SIZ]; /* fast lookup table for samplers (by ifIndex) */
+    SFLSampler *samplers;   /* the list of samplers */
+    SFLPoller  *pollers;    /* the list of samplers */
+    SFLReceiver *receivers; /* the array of receivers */
+    time_t bootTime;        /* time when we booted or started */
+    time_t now;             /* time now */
+    SFLAddress myIP;        /* IP address of this node */
+    u_int32_t subId;        /* sub_agent_id */
+    void *magic;            /* ptr to pass back in logging and alloc fns */
+    allocFn_t allocFn;
+    freeFn_t freeFn;
+    errorFn_t errorFn;
+    sendFn_t sendFn;
+#ifdef SFLOW_DO_SOCKET
+    int receiverSocket4;
+    int receiverSocket6;
+#endif
+} SFLAgent;
+
+/* call this at the start with a newly created agent */
+void sfl_agent_init(SFLAgent *agent,
+		    SFLAddress *myIP, /* IP address of this agent */
+		    u_int32_t subId,  /* agent_sub_id */
+		    time_t bootTime,  /* agent boot time */
+		    time_t now,       /* time now */
+		    void *magic,      /* ptr to pass back in logging and alloc fns */
+		    allocFn_t allocFn,
+		    freeFn_t freeFn,
+		    errorFn_t errorFn,
+		    sendFn_t sendFn);
+
+/* call this to create samplers */
+SFLSampler *sfl_agent_addSampler(SFLAgent *agent, SFLDataSource_instance *pdsi);
+
+/* call this to create pollers */
+SFLPoller *sfl_agent_addPoller(SFLAgent *agent,
+			       SFLDataSource_instance *pdsi,
+			       void *magic, /* ptr to pass back in getCountersFn() */
+			       getCountersFn_t getCountersFn);
+
+/* call this to create receivers */
+SFLReceiver *sfl_agent_addReceiver(SFLAgent *agent);
+
+/* call this to remove samplers */
+int sfl_agent_removeSampler(SFLAgent *agent, SFLDataSource_instance *pdsi);
+
+/* call this to remove pollers */
+int sfl_agent_removePoller(SFLAgent *agent, SFLDataSource_instance *pdsi);
+
+/* note: receivers should not be removed. Typically the receivers
+   list will be created at init time and never changed */
+
+/* call these fns to retrieve sampler, poller or receiver (e.g. for SNMP GET or GETNEXT operation) */
+SFLSampler  *sfl_agent_getSampler(SFLAgent *agent, SFLDataSource_instance *pdsi);
+SFLSampler  *sfl_agent_getNextSampler(SFLAgent *agent, SFLDataSource_instance *pdsi);
+SFLPoller   *sfl_agent_getPoller(SFLAgent *agent, SFLDataSource_instance *pdsi);
+SFLPoller   *sfl_agent_getNextPoller(SFLAgent *agent, SFLDataSource_instance *pdsi);
+SFLReceiver *sfl_agent_getReceiver(SFLAgent *agent, u_int32_t receiverIndex);
+SFLReceiver *sfl_agent_getNextReceiver(SFLAgent *agent, u_int32_t receiverIndex);
+
+/* jump table access - for performance */
+SFLSampler *sfl_agent_getSamplerByIfIndex(SFLAgent *agent, u_int32_t ifIndex);
+
+/* call these functions to GET and SET MIB values */
+
+/* receiver */
+char *      sfl_receiver_get_sFlowRcvrOwner(SFLReceiver *receiver);
+void        sfl_receiver_set_sFlowRcvrOwner(SFLReceiver *receiver, char *sFlowRcvrOwner);
+time_t      sfl_receiver_get_sFlowRcvrTimeout(SFLReceiver *receiver);
+void        sfl_receiver_set_sFlowRcvrTimeout(SFLReceiver *receiver, time_t sFlowRcvrTimeout);
+u_int32_t   sfl_receiver_get_sFlowRcvrMaximumDatagramSize(SFLReceiver *receiver);
+void        sfl_receiver_set_sFlowRcvrMaximumDatagramSize(SFLReceiver *receiver, u_int32_t sFlowRcvrMaximumDatagramSize);
+SFLAddress *sfl_receiver_get_sFlowRcvrAddress(SFLReceiver *receiver);
+void        sfl_receiver_set_sFlowRcvrAddress(SFLReceiver *receiver, SFLAddress *sFlowRcvrAddress);
+u_int32_t   sfl_receiver_get_sFlowRcvrPort(SFLReceiver *receiver);
+void        sfl_receiver_set_sFlowRcvrPort(SFLReceiver *receiver, u_int32_t sFlowRcvrPort);
+/* sampler */
+u_int32_t sfl_sampler_get_sFlowFsReceiver(SFLSampler *sampler);
+void      sfl_sampler_set_sFlowFsReceiver(SFLSampler *sampler, u_int32_t sFlowFsReceiver);
+u_int32_t sfl_sampler_get_sFlowFsPacketSamplingRate(SFLSampler *sampler);
+void      sfl_sampler_set_sFlowFsPacketSamplingRate(SFLSampler *sampler, u_int32_t sFlowFsPacketSamplingRate);
+u_int32_t sfl_sampler_get_sFlowFsMaximumHeaderSize(SFLSampler *sampler);
+void      sfl_sampler_set_sFlowFsMaximumHeaderSize(SFLSampler *sampler, u_int32_t sFlowFsMaximumHeaderSize);
+u_int32_t sfl_sampler_get_samplesLastTick(SFLSampler *sampler);
+/* poller */
+u_int32_t sfl_poller_get_sFlowCpReceiver(SFLPoller *poller);
+void      sfl_poller_set_sFlowCpReceiver(SFLPoller *poller, u_int32_t sFlowCpReceiver);
+u_int32_t sfl_poller_get_sFlowCpInterval(SFLPoller *poller);
+void      sfl_poller_set_sFlowCpInterval(SFLPoller *poller, u_int32_t sFlowCpInterval);
+
+/* fns to set the sflow agent address or sub-id */
+void sfl_agent_set_agentAddress(SFLAgent *agent, SFLAddress *addr);
+void sfl_agent_set_agentSubId(SFLAgent *agent, u_int32_t subId);
+
+/* The poller may need a separate number to reference the local bridge port
+   to get counters if it is not the same as the global ifIndex */
+void sfl_poller_set_bridgePort(SFLPoller *poller, u_int32_t port_no);
+u_int32_t sfl_poller_get_bridgePort(SFLPoller *poller);
+
+/* call this to indicate a discontinuity with a counter like samplePool so that the
+   sflow collector will ignore the next delta */
+void sfl_sampler_resetFlowSeqNo(SFLSampler *sampler);
+
+/* call this to indicate a discontinuity with one or more of the counters so that the
+   sflow collector will ignore the next delta */
+void sfl_poller_resetCountersSeqNo(SFLPoller *poller);
+
+#ifdef SFLOW_SOFTWARE_SAMLING
+/* software sampling: call this with every packet - returns non-zero if the packet
+   should be sampled (in which case you then call sfl_sampler_writeFlowSample()) */
+int sfl_sampler_takeSample(SFLSampler *sampler);
+#endif
+
+/* call this to set a maximum samples-per-second threshold. If the sampler reaches this
+   threshold it will automatically back off the sampling rate. A value of 0 disables the
+   mechanism */
+void sfl_sampler_set_backoffThreshold(SFLSampler *sampler, u_int32_t samplesPerSecond);
+u_int32_t sfl_sampler_get_backoffThreshold(SFLSampler *sampler);
+
+/* call this once per second (N.B. not on interrupt stack i.e. not hard real-time) */
+void sfl_agent_tick(SFLAgent *agent, time_t now);
+
+/* call this with each flow sample */
+void sfl_sampler_writeFlowSample(SFLSampler *sampler, SFL_FLOW_SAMPLE_TYPE *fs);
+
+/* call this to push counters samples (usually done in the getCountersFn callback) */
+void sfl_poller_writeCountersSample(SFLPoller *poller, SFL_COUNTERS_SAMPLE_TYPE *cs);
+
+/* call this to deallocate resources */
+void sfl_agent_release(SFLAgent *agent);
+
+
+/* internal fns */
+
+void sfl_receiver_init(SFLReceiver *receiver, SFLAgent *agent);
+void sfl_sampler_init(SFLSampler *sampler, SFLAgent *agent, SFLDataSource_instance *pdsi);
+void sfl_poller_init(SFLPoller *poller, SFLAgent *agent, SFLDataSource_instance *pdsi, void *magic, getCountersFn_t getCountersFn);
+
+
+void sfl_receiver_tick(SFLReceiver *receiver, time_t now);
+void sfl_poller_tick(SFLPoller *poller, time_t now);
+void sfl_sampler_tick(SFLSampler *sampler, time_t now);
+
+int sfl_receiver_writeFlowSample(SFLReceiver *receiver, SFL_FLOW_SAMPLE_TYPE *fs);
+int sfl_receiver_writeCountersSample(SFLReceiver *receiver, SFL_COUNTERS_SAMPLE_TYPE *cs);
+
+void sfl_agent_resetReceiver(SFLAgent *agent, SFLReceiver *receiver);
+
+void sfl_agent_error(SFLAgent *agent, char *modName, char *msg);
+void sfl_agent_sysError(SFLAgent *agent, char *modName, char *msg);
+
+u_int32_t sfl_receiver_samplePacketsSent(SFLReceiver *receiver);
+
+#define SFL_ALLOC malloc
+#define SFL_FREE free
+
+#endif /* SFLOW_API_H */
+
+
diff --git a/lib/sflow_poller.c b/lib/sflow_poller.c
new file mode 100644
index 000000000..ffd09d3c2
--- /dev/null
+++ b/lib/sflow_poller.c
@@ -0,0 +1,142 @@
+/* Copyright (c) 2002-2009 InMon Corp. Licensed under the terms of the InMon sFlow licence: */
+/* http://www.inmon.com/technology/sflowlicense.txt */
+
+#include "sflow_api.h"
+
+/*_________________--------------------------__________________
+  _________________    sfl_poller_init       __________________
+  -----------------__________________________------------------
+*/
+
+void sfl_poller_init(SFLPoller *poller,
+		     SFLAgent *agent,
+		     SFLDataSource_instance *pdsi,
+		     void *magic,         /* ptr to pass back in getCountersFn() */
+		     getCountersFn_t getCountersFn)
+{
+    /* copy the dsi in case it points to poller->dsi, which we are about to clear */
+    SFLDataSource_instance dsi = *pdsi;
+
+    /* preserve the *nxt pointer too, in case we are resetting this poller and it is
+       already part of the agent's linked list (thanks to Matt Woodly for pointing this out) */
+    SFLPoller *nxtPtr = poller->nxt;
+
+    /* clear everything */
+    memset(poller, 0, sizeof(*poller));
+  
+    /* restore the linked list ptr */
+    poller->nxt = nxtPtr;
+  
+    /* now copy in the parameters */
+    poller->agent = agent;
+    poller->dsi = dsi; /* structure copy */
+    poller->magic = magic;
+    poller->getCountersFn = getCountersFn;
+}
+
+/*_________________--------------------------__________________
+  _________________       reset              __________________
+  -----------------__________________________------------------
+*/
+
+static void reset(SFLPoller *poller)
+{
+    SFLDataSource_instance dsi = poller->dsi;
+    sfl_poller_init(poller, poller->agent, &dsi, poller->magic, poller->getCountersFn);
+}
+
+/*_________________---------------------------__________________
+  _________________      MIB access           __________________
+  -----------------___________________________------------------
+*/
+u_int32_t sfl_poller_get_sFlowCpReceiver(SFLPoller *poller) {
+    return poller->sFlowCpReceiver;
+}
+
+void sfl_poller_set_sFlowCpReceiver(SFLPoller *poller, u_int32_t sFlowCpReceiver) {
+    poller->sFlowCpReceiver = sFlowCpReceiver;
+    if(sFlowCpReceiver == 0) reset(poller);
+    else {
+	/* retrieve and cache a direct pointer to my receiver */
+	poller->myReceiver = sfl_agent_getReceiver(poller->agent, poller->sFlowCpReceiver);
+    }
+}
+
+u_int32_t sfl_poller_get_sFlowCpInterval(SFLPoller *poller) {
+    return poller->sFlowCpInterval;
+}
+
+void sfl_poller_set_sFlowCpInterval(SFLPoller *poller, u_int32_t sFlowCpInterval) {
+    poller->sFlowCpInterval = sFlowCpInterval;
+    /* Set the countersCountdown to be a randomly selected value between 1 and
+       sFlowCpInterval. That way the counter polling would be desynchronised
+       (on a 200-port switch, polling all the counters in one second could be harmful). */
+    poller->countersCountdown = 1 + (random() % sFlowCpInterval);
+}
+
+/*_________________---------------------------------__________________
+  _________________          bridge port            __________________
+  -----------------_________________________________------------------
+  May need a separate number to reference the local bridge port
+  to get counters if it is not the same as the global ifIndex.
+*/
+
+void sfl_poller_set_bridgePort(SFLPoller *poller, u_int32_t port_no) {
+    poller->bridgePort = port_no;
+}
+
+u_int32_t sfl_poller_get_bridgePort(SFLPoller *poller) {
+    return poller->bridgePort;
+}
+
+/*_________________---------------------------------__________________
+  _________________   sequence number reset         __________________
+  -----------------_________________________________------------------
+  Used to indicate a counter discontinuity
+  so that the sflow collector will know to ignore the next delta.
+*/
+void sfl_poller_resetCountersSeqNo(SFLPoller *poller) {  poller->countersSampleSeqNo = 0; }
+
+/*_________________---------------------------__________________
+  _________________    sfl_poller_tick        __________________
+  -----------------___________________________------------------
+*/
+
+void sfl_poller_tick(SFLPoller *poller, time_t now)
+{
+    if(poller->countersCountdown == 0) return; /* counters retrieval was not enabled */
+    if(poller->sFlowCpReceiver == 0) return;
+
+    if(--poller->countersCountdown == 0) {
+	if(poller->getCountersFn != NULL) {
+	    /* call out for counters */
+	    SFL_COUNTERS_SAMPLE_TYPE cs;
+	    memset(&cs, 0, sizeof(cs));
+	    poller->getCountersFn(poller->magic, poller, &cs);
+	    /* this countersFn is expected to fill in some counter block elements
+	       and then call sfl_poller_writeCountersSample(poller, &cs); */
+	}
+	/* reset the countdown */
+	poller->countersCountdown = poller->sFlowCpInterval;
+    }
+}
+
+/*_________________---------------------------------__________________
+  _________________ sfl_poller_writeCountersSample  __________________
+  -----------------_________________________________------------------
+*/
+
+void sfl_poller_writeCountersSample(SFLPoller *poller, SFL_COUNTERS_SAMPLE_TYPE *cs)
+{
+    /* fill in the rest of the header fields, and send to the receiver */
+    cs->sequence_number = ++poller->countersSampleSeqNo;
+#ifdef SFL_USE_32BIT_INDEX
+    cs->ds_class = SFL_DS_CLASS(poller->dsi);
+    cs->ds_index = SFL_DS_INDEX(poller->dsi);
+#else
+    cs->source_id = SFL_DS_DATASOURCE(poller->dsi);
+#endif
+    /* sent to my receiver */
+    if(poller->myReceiver) sfl_receiver_writeCountersSample(poller->myReceiver, cs);
+}
+
diff --git a/lib/sflow_receiver.c b/lib/sflow_receiver.c
new file mode 100644
index 000000000..7fccab30f
--- /dev/null
+++ b/lib/sflow_receiver.c
@@ -0,0 +1,832 @@
+/* Copyright (c) 2002-2009 InMon Corp. Licensed under the terms of the InMon sFlow licence: */
+/* http://www.inmon.com/technology/sflowlicense.txt */
+
+#include <assert.h>
+#include "sflow_api.h"
+
+static void resetSampleCollector(SFLReceiver *receiver);
+static void sendSample(SFLReceiver *receiver);
+static void sflError(SFLReceiver *receiver, char *errm);
+inline static void putNet32(SFLReceiver *receiver, u_int32_t val);
+inline static void putAddress(SFLReceiver *receiver, SFLAddress *addr);
+#ifdef SFLOW_DO_SOCKET
+static void initSocket(SFLReceiver *receiver);
+#endif
+
+/*_________________--------------------------__________________
+  _________________    sfl_receiver_init     __________________
+  -----------------__________________________------------------
+*/
+
+void sfl_receiver_init(SFLReceiver *receiver, SFLAgent *agent)
+{
+    /* first clear everything */
+    memset(receiver, 0, sizeof(*receiver));
+
+    /* now copy in the parameters */
+    receiver->agent = agent;
+
+    /* set defaults */
+    receiver->sFlowRcvrMaximumDatagramSize = SFL_DEFAULT_DATAGRAM_SIZE;
+    receiver->sFlowRcvrPort = SFL_DEFAULT_COLLECTOR_PORT;
+
+#ifdef SFLOW_DO_SOCKET
+    /* initialize the socket address */
+    initSocket(receiver);
+#endif
+
+    /* preset some of the header fields */
+    receiver->sampleCollector.datap = receiver->sampleCollector.data;
+    putNet32(receiver, SFLDATAGRAM_VERSION5);
+    putAddress(receiver, &agent->myIP);
+    putNet32(receiver, agent->subId);
+
+    /* prepare to receive the first sample */
+    resetSampleCollector(receiver);
+}
+
+/*_________________---------------------------__________________
+  _________________      reset                __________________
+  -----------------___________________________------------------
+
+  called on timeout, or when owner string is cleared
+*/
+
+static void reset(SFLReceiver *receiver) {
+    // ask agent to tell samplers and pollers to stop sending samples
+    sfl_agent_resetReceiver(receiver->agent, receiver);
+    // reinitialize
+    sfl_receiver_init(receiver, receiver->agent);
+}
+
+#ifdef SFLOW_DO_SOCKET
+/*_________________---------------------------__________________
+  _________________      initSocket           __________________
+  -----------------___________________________------------------
+*/
+
+static void initSocket(SFLReceiver *receiver) {
+    if(receiver->sFlowRcvrAddress.type == SFLADDRESSTYPE_IP_V6) {
+	struct sockaddr_in6 *sa6 = &receiver->receiver6;
+	sa6->sin6_port = htons((u_int16_t)receiver->sFlowRcvrPort);
+	sa6->sin6_family = AF_INET6;
+	sa6->sin6_addr = receiver->sFlowRcvrAddress.address.ip_v6;
+    }
+    else {
+	struct sockaddr_in *sa4 = &receiver->receiver4;
+	sa4->sin_port = htons((u_int16_t)receiver->sFlowRcvrPort);
+	sa4->sin_family = AF_INET;
+	sa4->sin_addr = receiver->sFlowRcvrAddress.address.ip_v4;
+    }
+}
+#endif
+
+/*_________________----------------------------------------_____________
+  _________________          MIB Vars                      _____________
+  -----------------________________________________________-------------
+*/
+
+char * sfl_receiver_get_sFlowRcvrOwner(SFLReceiver *receiver) {
+    return receiver->sFlowRcvrOwner;
+}
+void sfl_receiver_set_sFlowRcvrOwner(SFLReceiver *receiver, char *sFlowRcvrOwner) {
+    receiver->sFlowRcvrOwner = sFlowRcvrOwner;
+    if(sFlowRcvrOwner == NULL || sFlowRcvrOwner[0] == '\0') {
+	// reset condition! owner string was cleared
+	reset(receiver);
+    }
+}
+time_t sfl_receiver_get_sFlowRcvrTimeout(SFLReceiver *receiver) {
+    return receiver->sFlowRcvrTimeout;
+}
+void sfl_receiver_set_sFlowRcvrTimeout(SFLReceiver *receiver, time_t sFlowRcvrTimeout) {
+    receiver->sFlowRcvrTimeout =sFlowRcvrTimeout;
+} 
+u_int32_t sfl_receiver_get_sFlowRcvrMaximumDatagramSize(SFLReceiver *receiver) {
+    return receiver->sFlowRcvrMaximumDatagramSize;
+}
+void sfl_receiver_set_sFlowRcvrMaximumDatagramSize(SFLReceiver *receiver, u_int32_t sFlowRcvrMaximumDatagramSize) {
+    u_int32_t mdz = sFlowRcvrMaximumDatagramSize;
+    if(mdz < SFL_MIN_DATAGRAM_SIZE) mdz = SFL_MIN_DATAGRAM_SIZE;
+    receiver->sFlowRcvrMaximumDatagramSize = mdz;
+}
+SFLAddress *sfl_receiver_get_sFlowRcvrAddress(SFLReceiver *receiver) {
+    return &receiver->sFlowRcvrAddress;
+}
+void sfl_receiver_set_sFlowRcvrAddress(SFLReceiver *receiver, SFLAddress *sFlowRcvrAddress) {
+    if(sFlowRcvrAddress) receiver->sFlowRcvrAddress = *sFlowRcvrAddress; // structure copy
+#ifdef SFLOW_DO_SOCKET
+    initSocket(receiver);
+#endif
+}
+u_int32_t sfl_receiver_get_sFlowRcvrPort(SFLReceiver *receiver) {
+    return receiver->sFlowRcvrPort;
+}
+void sfl_receiver_set_sFlowRcvrPort(SFLReceiver *receiver, u_int32_t sFlowRcvrPort) {
+    receiver->sFlowRcvrPort = sFlowRcvrPort;
+    // update the socket structure
+#ifdef SFLOW_DO_SOCKET
+    initSocket(receiver);
+#endif
+}
+
+/*_________________---------------------------__________________
+  _________________   sfl_receiver_tick       __________________
+  -----------------___________________________------------------
+*/
+
+void sfl_receiver_tick(SFLReceiver *receiver, time_t now)
+{
+    // if there are any samples to send, flush them now
+    if(receiver->sampleCollector.numSamples > 0) sendSample(receiver);
+    // check the timeout
+    if(receiver->sFlowRcvrTimeout && (u_int32_t)receiver->sFlowRcvrTimeout != 0xFFFFFFFF) {
+	// count down one tick and reset if we reach 0
+	if(--receiver->sFlowRcvrTimeout == 0) reset(receiver);
+    }
+}
+
+/*_________________-----------------------------__________________
+  _________________   receiver write utilities  __________________
+  -----------------_____________________________------------------
+*/
+ 
+inline static void put32(SFLReceiver *receiver, u_int32_t val)
+{
+    *receiver->sampleCollector.datap++ = val;
+}
+
+inline static void putNet32(SFLReceiver *receiver, u_int32_t val)
+{
+    *receiver->sampleCollector.datap++ = htonl(val);
+}
+
+inline static void putNet32_run(SFLReceiver *receiver, void *obj, size_t quads)
+{
+    u_int32_t *from = (u_int32_t *)obj;
+    while(quads--) putNet32(receiver, *from++);
+}
+
+inline static void putNet64(SFLReceiver *receiver, u_int64_t val64)
+{
+    u_int32_t *firstQuadPtr = receiver->sampleCollector.datap;
+    // first copy the bytes in
+    memcpy((u_char *)firstQuadPtr, &val64, 8);
+    if(htonl(1) != 1) {
+	// swap the bytes, and reverse the quads too
+	u_int32_t tmp = *receiver->sampleCollector.datap++;
+	*firstQuadPtr = htonl(*receiver->sampleCollector.datap);
+	*receiver->sampleCollector.datap++ = htonl(tmp);
+    }
+    else receiver->sampleCollector.datap += 2;
+}
+
+inline static void put128(SFLReceiver *receiver, u_char *val)
+{
+    memcpy(receiver->sampleCollector.datap, val, 16);
+    receiver->sampleCollector.datap += 4;
+}
+
+inline static void putString(SFLReceiver *receiver, SFLString *s)
+{
+    putNet32(receiver, s->len);
+    memcpy(receiver->sampleCollector.datap, s->str, s->len);
+    receiver->sampleCollector.datap += (s->len + 3) / 4; /* pad to 4-byte boundary */
+}
+
+inline static u_int32_t stringEncodingLength(SFLString *s) {
+    // answer in bytes,  so remember to mulitply by 4 after rounding up to nearest 4-byte boundary
+    return 4 + (((s->len + 3) / 4) * 4);
+}
+
+inline static void putAddress(SFLReceiver *receiver, SFLAddress *addr)
+{
+    // encode unspecified addresses as IPV4:0.0.0.0 - or should we flag this as an error?
+    if(addr->type == 0) {
+	putNet32(receiver, SFLADDRESSTYPE_IP_V4);
+	put32(receiver, 0);
+    }
+    else {
+	putNet32(receiver, addr->type);
+	if(addr->type == SFLADDRESSTYPE_IP_V4) put32(receiver, addr->address.ip_v4.addr);
+	else put128(receiver, addr->address.ip_v6.addr);
+    }
+}
+
+inline static u_int32_t addressEncodingLength(SFLAddress *addr) {
+    return (addr->type == SFLADDRESSTYPE_IP_V6) ? 20 : 8;  // type + address (unspecified == IPV4)
+}
+
+inline static void putMACAddress(SFLReceiver *receiver, u_int8_t *mac)
+{
+    memcpy(receiver->sampleCollector.datap, mac, 6);
+    receiver->sampleCollector.datap += 2;
+}
+
+inline static void putSwitch(SFLReceiver *receiver, SFLExtended_switch *sw)
+{
+    putNet32(receiver, sw->src_vlan);
+    putNet32(receiver, sw->src_priority);
+    putNet32(receiver, sw->dst_vlan);
+    putNet32(receiver, sw->dst_priority);
+}
+
+inline static void putRouter(SFLReceiver *receiver, SFLExtended_router *router)
+{
+    putAddress(receiver, &router->nexthop);
+    putNet32(receiver, router->src_mask);
+    putNet32(receiver, router->dst_mask);
+}
+
+inline static u_int32_t routerEncodingLength(SFLExtended_router *router) {
+    return addressEncodingLength(&router->nexthop) + 8;
+}
+
+inline static void putGateway(SFLReceiver *receiver, SFLExtended_gateway *gw)
+{
+    putAddress(receiver, &gw->nexthop);
+    putNet32(receiver, gw->as);
+    putNet32(receiver, gw->src_as);
+    putNet32(receiver, gw->src_peer_as);
+    putNet32(receiver, gw->dst_as_path_segments);
+    {
+	u_int32_t seg = 0;
+	for(; seg < gw->dst_as_path_segments; seg++) {
+	    putNet32(receiver, gw->dst_as_path[seg].type);
+	    putNet32(receiver, gw->dst_as_path[seg].length);
+	    putNet32_run(receiver, gw->dst_as_path[seg].as.seq, gw->dst_as_path[seg].length);
+	}
+    }
+    putNet32(receiver, gw->communities_length);
+    putNet32_run(receiver, gw->communities, gw->communities_length);
+    putNet32(receiver, gw->localpref);
+}
+
+inline static u_int32_t gatewayEncodingLength(SFLExtended_gateway *gw) {
+    u_int32_t elemSiz = addressEncodingLength(&gw->nexthop);
+    u_int32_t seg = 0;
+    elemSiz += 16; // as, src_as, src_peer_as, dst_as_path_segments 
+    for(; seg < gw->dst_as_path_segments; seg++) {
+	elemSiz += 8; // type, length 
+	elemSiz += 4 * gw->dst_as_path[seg].length; // set/seq bytes
+    }
+    elemSiz += 4; // communities_length
+    elemSiz += 4 * gw->communities_length; // communities
+    elemSiz += 4; // localpref
+    return elemSiz;
+}
+
+inline static void putUser(SFLReceiver *receiver, SFLExtended_user *user)
+{
+    putNet32(receiver, user->src_charset);
+    putString(receiver, &user->src_user);
+    putNet32(receiver, user->dst_charset);
+    putString(receiver, &user->dst_user);
+}
+
+inline static u_int32_t userEncodingLength(SFLExtended_user *user) {
+    return 4
+	+ stringEncodingLength(&user->src_user)
+	+ 4
+	+ stringEncodingLength(&user->dst_user);
+}
+
+inline static void putUrl(SFLReceiver *receiver, SFLExtended_url *url)
+{
+    putNet32(receiver, url->direction);
+    putString(receiver, &url->url);
+    putString(receiver, &url->host);
+}
+
+inline static u_int32_t urlEncodingLength(SFLExtended_url *url) {
+    return 4
+	+ stringEncodingLength(&url->url)
+	+ stringEncodingLength(&url->host);
+}
+
+inline static void putLabelStack(SFLReceiver *receiver, SFLLabelStack *labelStack)
+{
+    putNet32(receiver, labelStack->depth);
+    putNet32_run(receiver, labelStack->stack, labelStack->depth);
+}
+
+inline static u_int32_t labelStackEncodingLength(SFLLabelStack *labelStack) {
+    return 4 + (4 * labelStack->depth);
+}
+
+inline static void putMpls(SFLReceiver *receiver, SFLExtended_mpls *mpls)
+{
+    putAddress(receiver, &mpls->nextHop);
+    putLabelStack(receiver, &mpls->in_stack);
+    putLabelStack(receiver, &mpls->out_stack);
+}
+
+inline static u_int32_t mplsEncodingLength(SFLExtended_mpls *mpls) {
+    return addressEncodingLength(&mpls->nextHop)
+	+ labelStackEncodingLength(&mpls->in_stack)
+	+ labelStackEncodingLength(&mpls->out_stack);
+}
+
+inline static void putNat(SFLReceiver *receiver, SFLExtended_nat *nat)
+{
+    putAddress(receiver, &nat->src);
+    putAddress(receiver, &nat->dst);
+}
+
+inline static u_int32_t natEncodingLength(SFLExtended_nat *nat) {
+    return addressEncodingLength(&nat->src)
+	+ addressEncodingLength(&nat->dst);
+}
+
+inline static void putMplsTunnel(SFLReceiver *receiver, SFLExtended_mpls_tunnel *tunnel)
+{
+    putString(receiver, &tunnel->tunnel_lsp_name);
+    putNet32(receiver, tunnel->tunnel_id);
+    putNet32(receiver, tunnel->tunnel_cos);
+}
+
+inline static u_int32_t mplsTunnelEncodingLength(SFLExtended_mpls_tunnel *tunnel) {
+    return stringEncodingLength(&tunnel->tunnel_lsp_name) + 8;
+}
+
+inline static void putMplsVc(SFLReceiver *receiver, SFLExtended_mpls_vc *vc)
+{
+    putString(receiver, &vc->vc_instance_name);
+    putNet32(receiver, vc->vll_vc_id);
+    putNet32(receiver, vc->vc_label_cos);
+}
+
+inline static u_int32_t mplsVcEncodingLength(SFLExtended_mpls_vc *vc) {
+    return stringEncodingLength( &vc->vc_instance_name) + 8;
+}
+
+inline static void putMplsFtn(SFLReceiver *receiver, SFLExtended_mpls_FTN *ftn)
+{
+    putString(receiver, &ftn->mplsFTNDescr);
+    putNet32(receiver, ftn->mplsFTNMask);
+}
+
+inline static u_int32_t mplsFtnEncodingLength(SFLExtended_mpls_FTN *ftn) {
+    return stringEncodingLength( &ftn->mplsFTNDescr) + 4;
+}
+
+inline static void putMplsLdpFec(SFLReceiver *receiver, SFLExtended_mpls_LDP_FEC *ldpfec)
+{
+    putNet32(receiver, ldpfec->mplsFecAddrPrefixLength);
+}
+
+inline static u_int32_t mplsLdpFecEncodingLength(SFLExtended_mpls_LDP_FEC *ldpfec) {
+    return 4;
+}
+
+inline static void putVlanTunnel(SFLReceiver *receiver, SFLExtended_vlan_tunnel *vlanTunnel)
+{
+    putLabelStack(receiver, &vlanTunnel->stack);
+}
+
+inline static u_int32_t vlanTunnelEncodingLength(SFLExtended_vlan_tunnel *vlanTunnel) {
+    return labelStackEncodingLength(&vlanTunnel->stack);
+}
+
+
+inline static void putGenericCounters(SFLReceiver *receiver, SFLIf_counters *counters)
+{
+    putNet32(receiver, counters->ifIndex);
+    putNet32(receiver, counters->ifType);
+    putNet64(receiver, counters->ifSpeed);
+    putNet32(receiver, counters->ifDirection);
+    putNet32(receiver, counters->ifStatus);
+    putNet64(receiver, counters->ifInOctets);
+    putNet32(receiver, counters->ifInUcastPkts);
+    putNet32(receiver, counters->ifInMulticastPkts);
+    putNet32(receiver, counters->ifInBroadcastPkts);
+    putNet32(receiver, counters->ifInDiscards);
+    putNet32(receiver, counters->ifInErrors);
+    putNet32(receiver, counters->ifInUnknownProtos);
+    putNet64(receiver, counters->ifOutOctets);
+    putNet32(receiver, counters->ifOutUcastPkts);
+    putNet32(receiver, counters->ifOutMulticastPkts);
+    putNet32(receiver, counters->ifOutBroadcastPkts);
+    putNet32(receiver, counters->ifOutDiscards);
+    putNet32(receiver, counters->ifOutErrors);
+    putNet32(receiver, counters->ifPromiscuousMode);
+}
+
+
+/*_________________-----------------------------__________________
+  _________________      computeFlowSampleSize  __________________
+  -----------------_____________________________------------------
+*/
+
+static int computeFlowSampleSize(SFLReceiver *receiver, SFL_FLOW_SAMPLE_TYPE *fs)
+{
+    SFLFlow_sample_element *elem = fs->elements;
+#ifdef SFL_USE_32BIT_INDEX
+    u_int siz = 52; /* tag, length, sequence_number, ds_class, ds_index, sampling_rate,
+		       sample_pool, drops, inputFormat, input, outputFormat, output, number of elements */
+#else
+    u_int siz = 40; /* tag, length, sequence_number, source_id, sampling_rate,
+		       sample_pool, drops, input, output, number of elements */
+#endif
+
+    fs->num_elements = 0; /* we're going to count them again even if this was set by the client */
+    for(; elem != NULL; elem = elem->nxt) {
+	u_int elemSiz = 0;
+	fs->num_elements++;
+	siz += 8; /* tag, length */
+	switch(elem->tag) {
+	case SFLFLOW_HEADER:
+	    elemSiz = 16; /* header_protocol, frame_length, stripped, header_length */
+	    elemSiz += ((elem->flowType.header.header_length + 3) / 4) * 4; /* header, rounded up to nearest 4 bytes */
+	    break;
+	case SFLFLOW_ETHERNET: elemSiz = sizeof(SFLSampled_ethernet); break;
+	case SFLFLOW_IPV4: elemSiz = sizeof(SFLSampled_ipv4); break;
+	case SFLFLOW_IPV6: elemSiz = sizeof(SFLSampled_ipv6); break;
+	case SFLFLOW_EX_SWITCH: elemSiz = sizeof(SFLExtended_switch); break;
+	case SFLFLOW_EX_ROUTER: elemSiz = routerEncodingLength(&elem->flowType.router); break;
+	case SFLFLOW_EX_GATEWAY: elemSiz = gatewayEncodingLength(&elem->flowType.gateway); break;
+	case SFLFLOW_EX_USER: elemSiz = userEncodingLength(&elem->flowType.user); break;
+	case SFLFLOW_EX_URL: elemSiz = urlEncodingLength(&elem->flowType.url); break;
+	case SFLFLOW_EX_MPLS: elemSiz = mplsEncodingLength(&elem->flowType.mpls); break;
+	case SFLFLOW_EX_NAT: elemSiz = natEncodingLength(&elem->flowType.nat); break;
+	case SFLFLOW_EX_MPLS_TUNNEL: elemSiz = mplsTunnelEncodingLength(&elem->flowType.mpls_tunnel); break;
+	case SFLFLOW_EX_MPLS_VC: elemSiz = mplsVcEncodingLength(&elem->flowType.mpls_vc); break;
+	case SFLFLOW_EX_MPLS_FTN: elemSiz = mplsFtnEncodingLength(&elem->flowType.mpls_ftn); break;
+	case SFLFLOW_EX_MPLS_LDP_FEC: elemSiz = mplsLdpFecEncodingLength(&elem->flowType.mpls_ldp_fec); break;
+	case SFLFLOW_EX_VLAN_TUNNEL: elemSiz = vlanTunnelEncodingLength(&elem->flowType.vlan_tunnel); break;
+	default:
+	    sflError(receiver, "unexpected packet_data_tag");
+	    return -1;
+	    break;
+	}
+	// cache the element size, and accumulate it into the overall FlowSample size
+	elem->length = elemSiz;
+	siz += elemSiz;
+    }
+
+    return siz;
+}
+
+/*_________________-------------------------------__________________
+  _________________ sfl_receiver_writeFlowSample  __________________
+  -----------------_______________________________------------------
+*/
+
+int sfl_receiver_writeFlowSample(SFLReceiver *receiver, SFL_FLOW_SAMPLE_TYPE *fs)
+{
+    int packedSize;
+    if(fs == NULL) return -1;
+    if((packedSize = computeFlowSampleSize(receiver, fs)) == -1) return -1;
+
+    // check in case this one sample alone is too big for the datagram
+    // in fact - if it is even half as big then we should ditch it. Very
+    // important to avoid overruning the packet buffer.
+    if(packedSize > (int)(receiver->sFlowRcvrMaximumDatagramSize / 2)) {
+	sflError(receiver, "flow sample too big for datagram");
+	return -1;
+    }
+
+    // if the sample pkt is full enough so that this sample might put
+    // it over the limit, then we should send it now before going on.
+    if((receiver->sampleCollector.pktlen + packedSize) >= receiver->sFlowRcvrMaximumDatagramSize)
+	sendSample(receiver);
+    
+    receiver->sampleCollector.numSamples++;
+
+#ifdef SFL_USE_32BIT_INDEX
+    putNet32(receiver, SFLFLOW_SAMPLE_EXPANDED);
+#else
+    putNet32(receiver, SFLFLOW_SAMPLE);
+#endif
+
+    putNet32(receiver, packedSize - 8); // don't include tag and len
+    putNet32(receiver, fs->sequence_number);
+
+#ifdef SFL_USE_32BIT_INDEX
+    putNet32(receiver, fs->ds_class);
+    putNet32(receiver, fs->ds_index);
+#else
+    putNet32(receiver, fs->source_id);
+#endif
+
+    putNet32(receiver, fs->sampling_rate);
+    putNet32(receiver, fs->sample_pool);
+    putNet32(receiver, fs->drops);
+
+#ifdef SFL_USE_32BIT_INDEX
+    putNet32(receiver, fs->inputFormat);
+    putNet32(receiver, fs->input);
+    putNet32(receiver, fs->outputFormat);
+    putNet32(receiver, fs->output);
+#else
+    putNet32(receiver, fs->input);
+    putNet32(receiver, fs->output);
+#endif
+
+    putNet32(receiver, fs->num_elements);
+
+    {
+	SFLFlow_sample_element *elem = fs->elements;
+	for(; elem != NULL; elem = elem->nxt) {
+	    
+	    putNet32(receiver, elem->tag);
+	    putNet32(receiver, elem->length); // length cached in computeFlowSampleSize()
+	    
+	    switch(elem->tag) {
+	    case SFLFLOW_HEADER:
+		putNet32(receiver, elem->flowType.header.header_protocol);
+		putNet32(receiver, elem->flowType.header.frame_length);
+		putNet32(receiver, elem->flowType.header.stripped);
+		putNet32(receiver, elem->flowType.header.header_length);
+		/* the header */
+		memcpy(receiver->sampleCollector.datap, elem->flowType.header.header_bytes, elem->flowType.header.header_length);
+		/* round up to multiple of 4 to preserve alignment */
+		receiver->sampleCollector.datap += ((elem->flowType.header.header_length + 3) / 4);
+		break;
+	    case SFLFLOW_ETHERNET:
+		putNet32(receiver, elem->flowType.ethernet.eth_len);
+		putMACAddress(receiver, elem->flowType.ethernet.src_mac);
+		putMACAddress(receiver, elem->flowType.ethernet.dst_mac);
+		putNet32(receiver, elem->flowType.ethernet.eth_type);
+		break;
+	    case SFLFLOW_IPV4:
+		putNet32(receiver, elem->flowType.ipv4.length);
+		putNet32(receiver, elem->flowType.ipv4.protocol);
+		put32(receiver, elem->flowType.ipv4.src_ip.addr);
+		put32(receiver, elem->flowType.ipv4.dst_ip.addr);
+		putNet32(receiver, elem->flowType.ipv4.src_port);
+		putNet32(receiver, elem->flowType.ipv4.dst_port);
+		putNet32(receiver, elem->flowType.ipv4.tcp_flags);
+		putNet32(receiver, elem->flowType.ipv4.tos);
+		break;
+	    case SFLFLOW_IPV6:
+		putNet32(receiver, elem->flowType.ipv6.length);
+		putNet32(receiver, elem->flowType.ipv6.protocol);
+		put128(receiver, elem->flowType.ipv6.src_ip.addr);
+		put128(receiver, elem->flowType.ipv6.dst_ip.addr);
+		putNet32(receiver, elem->flowType.ipv6.src_port);
+		putNet32(receiver, elem->flowType.ipv6.dst_port);
+		putNet32(receiver, elem->flowType.ipv6.tcp_flags);
+		putNet32(receiver, elem->flowType.ipv6.priority);
+		break;
+	    case SFLFLOW_EX_SWITCH: putSwitch(receiver, &elem->flowType.sw); break;
+	    case SFLFLOW_EX_ROUTER: putRouter(receiver, &elem->flowType.router); break;
+	    case SFLFLOW_EX_GATEWAY: putGateway(receiver, &elem->flowType.gateway); break;
+	    case SFLFLOW_EX_USER: putUser(receiver, &elem->flowType.user); break;
+	    case SFLFLOW_EX_URL: putUrl(receiver, &elem->flowType.url); break;
+	    case SFLFLOW_EX_MPLS: putMpls(receiver, &elem->flowType.mpls); break;
+	    case SFLFLOW_EX_NAT: putNat(receiver, &elem->flowType.nat); break;
+	    case SFLFLOW_EX_MPLS_TUNNEL: putMplsTunnel(receiver, &elem->flowType.mpls_tunnel); break;
+	    case SFLFLOW_EX_MPLS_VC: putMplsVc(receiver, &elem->flowType.mpls_vc); break;
+	    case SFLFLOW_EX_MPLS_FTN: putMplsFtn(receiver, &elem->flowType.mpls_ftn); break;
+	    case SFLFLOW_EX_MPLS_LDP_FEC: putMplsLdpFec(receiver, &elem->flowType.mpls_ldp_fec); break;
+	    case SFLFLOW_EX_VLAN_TUNNEL: putVlanTunnel(receiver, &elem->flowType.vlan_tunnel); break;
+	    default:
+		sflError(receiver, "unexpected packet_data_tag");
+		return -1;
+		break;
+	    }
+	}
+    }
+
+    // sanity check
+    assert(((u_char *)receiver->sampleCollector.datap
+	    - (u_char *)receiver->sampleCollector.data
+	    - receiver->sampleCollector.pktlen)  == (u_int32_t)packedSize);
+
+    // update the pktlen
+    receiver->sampleCollector.pktlen = (u_char *)receiver->sampleCollector.datap - (u_char *)receiver->sampleCollector.data;
+    return packedSize;
+}
+
+/*_________________-----------------------------__________________
+  _________________ computeCountersSampleSize   __________________
+  -----------------_____________________________------------------
+*/
+
+static int computeCountersSampleSize(SFLReceiver *receiver, SFL_COUNTERS_SAMPLE_TYPE *cs)
+{
+    SFLCounters_sample_element *elem = cs->elements;
+#ifdef SFL_USE_32BIT_INDEX
+    u_int siz = 24; /* tag, length, sequence_number, ds_class, ds_index, number of elements */
+#else
+    u_int siz = 20; /* tag, length, sequence_number, source_id, number of elements */
+#endif
+
+    cs->num_elements = 0; /* we're going to count them again even if this was set by the client */
+    for(; elem != NULL; elem = elem->nxt) {
+	u_int elemSiz = 0;
+	cs->num_elements++;
+	siz += 8; /* tag, length */
+	switch(elem->tag) {
+	case SFLCOUNTERS_GENERIC:  elemSiz = sizeof(elem->counterBlock.generic); break;
+	case SFLCOUNTERS_ETHERNET: elemSiz = sizeof(elem->counterBlock.ethernet); break;
+	case SFLCOUNTERS_TOKENRING: elemSiz = sizeof(elem->counterBlock.tokenring); break;
+	case SFLCOUNTERS_VG: elemSiz = sizeof(elem->counterBlock.vg); break;
+	case SFLCOUNTERS_VLAN: elemSiz = sizeof(elem->counterBlock.vlan); break;
+	default:
+	    sflError(receiver, "unexpected counters_tag");
+	    return -1;
+	    break;
+	}
+	// cache the element size, and accumulate it into the overall FlowSample size
+	elem->length = elemSiz;
+	siz += elemSiz;
+    }
+    return siz;
+}
+
+/*_________________----------------------------------__________________
+  _________________ sfl_receiver_writeCountersSample __________________
+  -----------------__________________________________------------------
+*/
+
+int sfl_receiver_writeCountersSample(SFLReceiver *receiver, SFL_COUNTERS_SAMPLE_TYPE *cs)
+{
+    int packedSize;
+    if(cs == NULL) return -1;
+    // if the sample pkt is full enough so that this sample might put
+    // it over the limit, then we should send it now.
+    if((packedSize = computeCountersSampleSize(receiver, cs)) == -1) return -1;
+  
+    // check in case this one sample alone is too big for the datagram
+    // in fact - if it is even half as big then we should ditch it. Very
+    // important to avoid overruning the packet buffer.
+    if(packedSize > (int)(receiver->sFlowRcvrMaximumDatagramSize / 2)) {
+	sflError(receiver, "counters sample too big for datagram");
+	return -1;
+    }
+  
+    if((receiver->sampleCollector.pktlen + packedSize) >= receiver->sFlowRcvrMaximumDatagramSize)
+	sendSample(receiver);
+  
+    receiver->sampleCollector.numSamples++;
+  
+#ifdef SFL_USE_32BIT_INDEX
+    putNet32(receiver, SFLCOUNTERS_SAMPLE_EXPANDED);
+#else
+    putNet32(receiver, SFLCOUNTERS_SAMPLE);
+#endif
+
+    putNet32(receiver, packedSize - 8); // tag and length not included
+    putNet32(receiver, cs->sequence_number);
+
+#ifdef SFL_USE_32BIT_INDEX
+    putNet32(receiver, cs->ds_class);
+    putNet32(receiver, cs->ds_index);
+#else
+    putNet32(receiver, cs->source_id);
+#endif
+
+    putNet32(receiver, cs->num_elements);
+  
+    {
+	SFLCounters_sample_element *elem = cs->elements;
+	for(; elem != NULL; elem = elem->nxt) {
+	    
+	    putNet32(receiver, elem->tag);
+	    putNet32(receiver, elem->length); // length cached in computeCountersSampleSize()
+	    
+	    switch(elem->tag) {
+	    case SFLCOUNTERS_GENERIC:
+		putGenericCounters(receiver, &(elem->counterBlock.generic));
+		break;
+	    case SFLCOUNTERS_ETHERNET:
+		// all these counters are 32-bit
+		putNet32_run(receiver, &elem->counterBlock.ethernet, sizeof(elem->counterBlock.ethernet) / 4);
+		break;
+	    case SFLCOUNTERS_TOKENRING:
+		// all these counters are 32-bit
+		putNet32_run(receiver, &elem->counterBlock.tokenring, sizeof(elem->counterBlock.tokenring) / 4);
+		break;
+	    case SFLCOUNTERS_VG:
+		// mixed sizes
+		putNet32(receiver, elem->counterBlock.vg.dot12InHighPriorityFrames);
+		putNet64(receiver, elem->counterBlock.vg.dot12InHighPriorityOctets);
+		putNet32(receiver, elem->counterBlock.vg.dot12InNormPriorityFrames);
+		putNet64(receiver, elem->counterBlock.vg.dot12InNormPriorityOctets);
+		putNet32(receiver, elem->counterBlock.vg.dot12InIPMErrors);
+		putNet32(receiver, elem->counterBlock.vg.dot12InOversizeFrameErrors);
+		putNet32(receiver, elem->counterBlock.vg.dot12InDataErrors);
+		putNet32(receiver, elem->counterBlock.vg.dot12InNullAddressedFrames);
+		putNet32(receiver, elem->counterBlock.vg.dot12OutHighPriorityFrames);
+		putNet64(receiver, elem->counterBlock.vg.dot12OutHighPriorityOctets);
+		putNet32(receiver, elem->counterBlock.vg.dot12TransitionIntoTrainings);
+		putNet64(receiver, elem->counterBlock.vg.dot12HCInHighPriorityOctets);
+		putNet64(receiver, elem->counterBlock.vg.dot12HCInNormPriorityOctets);
+		putNet64(receiver, elem->counterBlock.vg.dot12HCOutHighPriorityOctets);
+		break;
+	    case SFLCOUNTERS_VLAN:
+		// mixed sizes
+		putNet32(receiver, elem->counterBlock.vlan.vlan_id);
+		putNet64(receiver, elem->counterBlock.vlan.octets);
+		putNet32(receiver, elem->counterBlock.vlan.ucastPkts);
+		putNet32(receiver, elem->counterBlock.vlan.multicastPkts);
+		putNet32(receiver, elem->counterBlock.vlan.broadcastPkts);
+		putNet32(receiver, elem->counterBlock.vlan.discards);
+		break;
+	    default:
+		sflError(receiver, "unexpected counters_tag");
+		return -1;
+		break;
+	    }
+	}
+    }
+    // sanity check
+    assert(((u_char *)receiver->sampleCollector.datap
+	    - (u_char *)receiver->sampleCollector.data
+	    - receiver->sampleCollector.pktlen)  == (u_int32_t)packedSize);
+
+    // update the pktlen
+    receiver->sampleCollector.pktlen = (u_char *)receiver->sampleCollector.datap - (u_char *)receiver->sampleCollector.data;
+    return packedSize;
+}
+
+/*_________________---------------------------------__________________
+  _________________ sfl_receiver_samplePacketsSent  __________________
+  -----------------_________________________________------------------
+*/
+
+u_int32_t sfl_receiver_samplePacketsSent(SFLReceiver *receiver)
+{
+    return receiver->sampleCollector.packetSeqNo;
+}
+
+/*_________________---------------------------__________________
+  _________________     sendSample            __________________
+  -----------------___________________________------------------
+*/
+
+static void sendSample(SFLReceiver *receiver)
+{  
+    /* construct and send out the sample, then reset for the next one... */
+    /* first fill in the header with the latest values */
+    /* version, agent_address and sub_agent_id were pre-set. */
+    u_int32_t hdrIdx = (receiver->agent->myIP.type == SFLADDRESSTYPE_IP_V6) ? 7 : 4;
+    receiver->sampleCollector.data[hdrIdx++] = htonl(++receiver->sampleCollector.packetSeqNo); /* seq no */
+    receiver->sampleCollector.data[hdrIdx++] = htonl((receiver->agent->now - receiver->agent->bootTime) * 1000); /* uptime */
+    receiver->sampleCollector.data[hdrIdx++] = htonl(receiver->sampleCollector.numSamples); /* num samples */
+    /* send */
+    if(receiver->agent->sendFn) (*receiver->agent->sendFn)(receiver->agent->magic,
+							   receiver->agent,
+							   receiver,
+							   (u_char *)receiver->sampleCollector.data, 
+							   receiver->sampleCollector.pktlen);
+    else {
+#ifdef SFLOW_DO_SOCKET
+	/* send it myself */
+	if (receiver->sFlowRcvrAddress.type == SFLADDRESSTYPE_IP_V6) {
+	    u_int32_t soclen = sizeof(struct sockaddr_in6);
+	    int result = sendto(receiver->agent->receiverSocket6,
+				receiver->sampleCollector.data,
+				receiver->sampleCollector.pktlen,
+				0,
+				(struct sockaddr *)&receiver->receiver6,
+				soclen);
+	    if(result == -1 && errno != EINTR) sfl_agent_sysError(receiver->agent, "receiver", "IPv6 socket sendto error");
+	    if(result == 0) sfl_agent_error(receiver->agent, "receiver", "IPv6 socket sendto returned 0");
+	}
+	else {
+	    u_int32_t soclen = sizeof(struct sockaddr_in);
+	    int result = sendto(receiver->agent->receiverSocket4,
+				receiver->sampleCollector.data,
+				receiver->sampleCollector.pktlen,
+				0,
+				(struct sockaddr *)&receiver->receiver4,
+				soclen);
+	    if(result == -1 && errno != EINTR) sfl_agent_sysError(receiver->agent, "receiver", "socket sendto error");
+	    if(result == 0) sfl_agent_error(receiver->agent, "receiver", "socket sendto returned 0");
+	}
+#endif
+    }
+
+    /* reset for the next time */
+    resetSampleCollector(receiver);
+}
+
+/*_________________---------------------------__________________
+  _________________   resetSampleCollector    __________________
+  -----------------___________________________------------------
+*/
+
+static void resetSampleCollector(SFLReceiver *receiver)
+{
+    receiver->sampleCollector.pktlen = 0;
+    receiver->sampleCollector.numSamples = 0;
+    /* point the datap to just after the header */
+    receiver->sampleCollector.datap = (receiver->agent->myIP.type == SFLADDRESSTYPE_IP_V6) ?
+	(receiver->sampleCollector.data + 10) :  (receiver->sampleCollector.data + 7);
+
+    receiver->sampleCollector.pktlen = (u_char *)receiver->sampleCollector.datap - (u_char *)receiver->sampleCollector.data;
+}
+
+/*_________________---------------------------__________________
+  _________________         sflError          __________________
+  -----------------___________________________------------------
+*/
+
+static void sflError(SFLReceiver *receiver, char *msg)
+{
+    sfl_agent_error(receiver->agent, "receiver", msg);
+    resetSampleCollector(receiver);
+}
diff --git a/lib/sflow_sampler.c b/lib/sflow_sampler.c
new file mode 100644
index 000000000..759b5a22c
--- /dev/null
+++ b/lib/sflow_sampler.c
@@ -0,0 +1,183 @@
+/* Copyright (c) 2002-2009 InMon Corp. Licensed under the terms of the InMon sFlow licence: */
+/* http://www.inmon.com/technology/sflowlicense.txt */
+
+#include "sflow_api.h"
+
+
+/*_________________--------------------------__________________
+  _________________   sfl_sampler_init       __________________
+  -----------------__________________________------------------
+*/
+
+void sfl_sampler_init(SFLSampler *sampler, SFLAgent *agent, SFLDataSource_instance *pdsi)
+{
+    /* copy the dsi in case it points to sampler->dsi, which we are about to clear.
+       (Thanks to Jagjit Choudray of Force 10 Networks for pointing out this bug) */
+    SFLDataSource_instance dsi = *pdsi;
+
+    /* preserve the *nxt pointer too, in case we are resetting this poller and it is
+       already part of the agent's linked list (thanks to Matt Woodly for pointing this out) */
+    SFLSampler *nxtPtr = sampler->nxt;
+  
+    /* clear everything */
+    memset(sampler, 0, sizeof(*sampler));
+  
+    /* restore the linked list ptr */
+    sampler->nxt = nxtPtr;
+  
+    /* now copy in the parameters */
+    sampler->agent = agent;
+    sampler->dsi = dsi;
+  
+    /* set defaults */
+    sampler->sFlowFsMaximumHeaderSize = SFL_DEFAULT_HEADER_SIZE;
+    sampler->sFlowFsPacketSamplingRate = SFL_DEFAULT_SAMPLING_RATE;
+}
+
+/*_________________--------------------------__________________
+  _________________       reset              __________________
+  -----------------__________________________------------------
+*/
+
+static void reset(SFLSampler *sampler)
+{
+    SFLDataSource_instance dsi = sampler->dsi;
+    sfl_sampler_init(sampler, sampler->agent, &dsi);
+}
+
+/*_________________---------------------------__________________
+  _________________      MIB access           __________________
+  -----------------___________________________------------------
+*/
+u_int32_t sfl_sampler_get_sFlowFsReceiver(SFLSampler *sampler) {
+    return sampler->sFlowFsReceiver;
+}
+void sfl_sampler_set_sFlowFsReceiver(SFLSampler *sampler, u_int32_t sFlowFsReceiver) {
+    sampler->sFlowFsReceiver = sFlowFsReceiver;
+    if(sFlowFsReceiver == 0) reset(sampler);
+    else {
+	/* retrieve and cache a direct pointer to my receiver */
+	sampler->myReceiver = sfl_agent_getReceiver(sampler->agent, sampler->sFlowFsReceiver);
+    }
+}
+u_int32_t sfl_sampler_get_sFlowFsPacketSamplingRate(SFLSampler *sampler) {
+    return sampler->sFlowFsPacketSamplingRate;
+}
+void sfl_sampler_set_sFlowFsPacketSamplingRate(SFLSampler *sampler, u_int32_t sFlowFsPacketSamplingRate) {
+    sampler->sFlowFsPacketSamplingRate = sFlowFsPacketSamplingRate;
+}
+u_int32_t sfl_sampler_get_sFlowFsMaximumHeaderSize(SFLSampler *sampler) {
+    return sampler->sFlowFsMaximumHeaderSize;
+}
+void sfl_sampler_set_sFlowFsMaximumHeaderSize(SFLSampler *sampler, u_int32_t sFlowFsMaximumHeaderSize) {
+    sampler->sFlowFsMaximumHeaderSize = sFlowFsMaximumHeaderSize;
+}
+
+/* call this to set a maximum samples-per-second threshold. If the sampler reaches this
+   threshold it will automatically back off the sampling rate. A value of 0 disables the
+   mechanism */
+void sfl_sampler_set_backoffThreshold(SFLSampler *sampler, u_int32_t samplesPerSecond) {
+    sampler->backoffThreshold = samplesPerSecond;
+}
+u_int32_t sfl_sampler_get_backoffThreshold(SFLSampler *sampler) {
+    return sampler->backoffThreshold;
+}
+u_int32_t sfl_sampler_get_samplesLastTick(SFLSampler *sampler) {
+    return sampler->samplesLastTick;
+}
+
+/*_________________---------------------------------__________________
+  _________________   sequence number reset         __________________
+  -----------------_________________________________------------------
+  Used by the agent to indicate a samplePool discontinuity
+  so that the sflow collector will know to ignore the next delta.
+*/
+void sfl_sampler_resetFlowSeqNo(SFLSampler *sampler) { sampler->flowSampleSeqNo = 0; }
+
+
+/*_________________---------------------------__________________
+  _________________    sfl_sampler_tick       __________________
+  -----------------___________________________------------------
+*/
+
+void sfl_sampler_tick(SFLSampler *sampler, time_t now)
+{
+    if(sampler->backoffThreshold && sampler->samplesThisTick > sampler->backoffThreshold) {
+	/* automatic backoff.  If using hardware sampling then this is where you have to
+	 * call out to change the sampling rate and make sure that any other registers/variables
+	 * that hold this value are updated.
+	 */
+	sampler->sFlowFsPacketSamplingRate *= 2;
+    }
+    sampler->samplesLastTick = sampler->samplesThisTick;
+    sampler->samplesThisTick = 0;
+}
+
+
+
+/*_________________------------------------------__________________
+  _________________ sfl_sampler_writeFlowSample  __________________
+  -----------------______________________________------------------
+*/
+
+void sfl_sampler_writeFlowSample(SFLSampler *sampler, SFL_FLOW_SAMPLE_TYPE *fs)
+{
+    if(fs == NULL) return;
+    sampler->samplesThisTick++;
+    /* increment the sequence number */
+    fs->sequence_number = ++sampler->flowSampleSeqNo;
+    /* copy the other header fields in */
+#ifdef SFL_USE_32BIT_INDEX
+    fs->ds_class = SFL_DS_CLASS(sampler->dsi);
+    fs->ds_index = SFL_DS_INDEX(sampler->dsi);
+#else
+    fs->source_id = SFL_DS_DATASOURCE(sampler->dsi);
+#endif
+    /* the sampling rate may have been set already. */
+    if(fs->sampling_rate == 0) fs->sampling_rate = sampler->sFlowFsPacketSamplingRate;
+    /* the samplePool may be maintained upstream too. */
+    if( fs->sample_pool == 0) fs->sample_pool = sampler->samplePool;
+    /* sent to my receiver */
+    if(sampler->myReceiver) sfl_receiver_writeFlowSample(sampler->myReceiver, fs);
+}
+
+#ifdef SFLOW_SOFTWARE_SAMPLING
+
+/* ================== software sampling ========================*/
+
+/*_________________---------------------------__________________
+  _________________     nextRandomSkip        __________________
+  -----------------___________________________------------------
+*/
+
+inline static u_int32_t nextRandomSkip(u_int32_t mean)
+{
+    if(mean == 0 || mean == 1) return 1;
+    return ((random() % ((2 * mean) - 1)) + 1);
+} 
+
+/*_________________---------------------------__________________
+  _________________  sfl_sampler_takeSample   __________________
+  -----------------___________________________------------------
+*/
+
+int sfl_sampler_takeSample(SFLSampler *sampler)
+{
+    if(sampler->skip == 0) {
+	/* first time - seed the random number generator */
+	srandom(SFL_DS_INDEX(sampler->dsi));
+	sampler->skip = nextRandomSkip(sampler->sFlowFsPacketSamplingRate);
+    }
+
+    /* increment the samplePool */
+    sampler->samplePool++;
+
+    if(--sampler->skip == 0) {
+	/* reached zero. Set the next skip and return true. */
+	sampler->skip = nextRandomSkip(sampler->sFlowFsPacketSamplingRate);
+	return 1;
+    }
+    return 0;
+}
+
+#endif /* SFLOW_SOFTWARE_SAMPLING */