utilities: Add another GDB macro for ovs-vswitchd.

This commit adds a basic packet metadata macro to the already existing
macros in ovs_gdb.py, ovs_dump_packets will print out information about
one or more packets. It feeds packets into tcpdump, and the user can
pass in tcpdump options to modify how packets are parsed or even write
out packets to a pcap file.

Example usage:
(gdb) break fast_path_processing
(gdb) commands
 ovs_dump_packets packets_
 continue
 end
(gdb) continue

Thread 1 "ovs-vswitchd" hit Breakpoint 2, fast_path_processing ...
12:01:05.962485 ARP, Ethernet (len 6), IPv4 (len 4), Request who-has
    10.1.1.1 tell 10.1.1.2, length 28

Thread 1 "ovs-vswitchd" hit Breakpoint 1, fast_path_processing ...
12:01:05.981214 ARP, Ethernet (len 6), IPv4 (len 4), Reply 10.1.1.1
    is-at a6:0f:c3:f0:5f:bd (oui Unknown), length 28

Signed-off-by: Mike Pattrick <mkp@redhat.com>
Acked-by: Eelco Chaudron <echaudro@redhat.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

2 files changed, 171 insertions, 41 deletions

diff --git a/utilities/automake.mk b/utilities/automake.mk
index e2e22c39a..7808c0ead 100644
--- a/utilities/automake.mk
+++ b/utilities/automake.mk
@@ -126,6 +126,7 @@ endif
 
 FLAKE8_PYFILES += utilities/ovs-pcap.in \
 	utilities/checkpatch.py utilities/ovs-dev.py \
+	utilities/gdb/ovs_gdb.py \
 	utilities/ovs-check-dead-ifs.in \
 	utilities/ovs-tcpdump.in \
 	utilities/ovs-pipegen.py
diff --git a/utilities/gdb/ovs_gdb.py b/utilities/gdb/ovs_gdb.py
index 0b2ecb81b..62928d50f 100644
--- a/utilities/gdb/ovs_gdb.py
+++ b/utilities/gdb/ovs_gdb.py
@@ -29,6 +29,7 @@
 #    - ovs_dump_netdev
 #    - ovs_dump_netdev_provider
 #    - ovs_dump_ovs_list <struct ovs_list *> {[<structure>] [<member>] {dump}]}
+#    - ovs_dump_packets <struct dp_packet_batch|dp_packet> [tcpdump options]
 #    - ovs_dump_simap <struct simap *>
 #    - ovs_dump_smap <struct smap *>
 #    - ovs_dump_udpif_keys {<udpif_name>|<udpif_address>} {short}
@@ -56,8 +57,15 @@
 #    ...
 #
 import gdb
+import struct
 import sys
 import uuid
+try:
+    from scapy.layers.l2 import Ether
+    from scapy.utils import tcpdump
+except ModuleNotFoundError:
+    Ether = None
+    tcpdump = None
 
 
 #
@@ -81,7 +89,7 @@ N_UMAPS = 512
 # #
 # # This work is licensed under the terms of the GNU GPL version 2.
 #
-class CachedType:
+class CachedType(object):
     def __init__(self, name):
         self._type = None
         self._name = name
@@ -138,7 +146,7 @@ def get_time_msec():
 
 def get_time_now():
     # See get_time_msec() above
-    return int(get_global_variable("coverage_run_time"))/1000, -5
+    return int(get_global_variable("coverage_run_time")) / 1000, -5
 
 
 def eth_addr_to_string(eth_addr):
@@ -156,7 +164,7 @@ def eth_addr_to_string(eth_addr):
 #
 class ProgressIndicator(object):
     def __init__(self, message=None):
-        self.spinner = "/-\|"
+        self.spinner = "/-\\|"
         self.spinner_index = 0
         self.message = message
 
@@ -295,7 +303,7 @@ class ForEachHMAP(object):
 #
 # Class that will provide an iterator over an Netlink attributes
 #
-class ForEachNL():
+class ForEachNL(object):
     def __init__(self, nlattrs, nlattrs_len):
         self.attr = nlattrs.cast(gdb.lookup_type('struct nlattr').pointer())
         self.attr_len = int(nlattrs_len)
@@ -386,7 +394,7 @@ class ForEachSMAP(ForEachHMAP):
 #
 # Class that will provide an iterator over an OVS list.
 #
-class ForEachLIST():
+class ForEachLIST(object):
     def __init__(self, list, typeobj=None, member='node'):
         self.list = list
         self.node = list
@@ -416,7 +424,7 @@ class ForEachLIST():
 #
 # Class that will provide an iterator over an OFPACTS.
 #
-class ForEachOFPACTS():
+class ForEachOFPACTS(object):
     def __init__(self, ofpacts, ofpacts_len):
         self.ofpact = ofpacts.cast(gdb.lookup_type('struct ofpact').pointer())
         self.length = int(ofpacts_len)
@@ -451,7 +459,8 @@ class ForEachOFPACTS():
 #
 class CmdDumpBridge(gdb.Command):
     """Dump all configured bridges.
-    Usage: ovs_dump_bridge {ports|wanted}
+    Usage:
+      ovs_dump_bridge {ports|wanted}
     """
     def __init__(self):
         super(CmdDumpBridge, self).__init__("ovs_dump_bridge",
@@ -500,7 +509,8 @@ class CmdDumpBridge(gdb.Command):
 #
 class CmdDumpBridgePorts(gdb.Command):
     """Dump all ports added to a specific struct bridge*.
-    Usage: ovs_dump_bridge_ports <struct bridge *>
+    Usage:
+      ovs_dump_bridge_ports <struct bridge *>
     """
     def __init__(self):
         super(CmdDumpBridgePorts, self).__init__("ovs_dump_bridge_ports",
@@ -538,7 +548,8 @@ class CmdDumpBridgePorts(gdb.Command):
 #
 class CmdDumpDpNetdev(gdb.Command):
     """Dump all registered dp_netdev structures.
-    Usage: ovs_dump_dp_netdev [ports]
+    Usage:
+      ovs_dump_dp_netdev [ports]
     """
     def __init__(self):
         super(CmdDumpDpNetdev, self).__init__("ovs_dump_dp_netdev",
@@ -575,7 +586,8 @@ class CmdDumpDpNetdev(gdb.Command):
 #
 class CmdDumpDpNetdevPollThreads(gdb.Command):
     """Dump all poll_thread info added to a specific struct dp_netdev*.
-    Usage: ovs_dump_dp_netdev_poll_threads <struct dp_netdev *>
+    Usage:
+      ovs_dump_dp_netdev_poll_threads <struct dp_netdev *>
     """
     def __init__(self):
         super(CmdDumpDpNetdevPollThreads, self).__init__(
@@ -608,7 +620,8 @@ class CmdDumpDpNetdevPollThreads(gdb.Command):
 #
 class CmdDumpDpNetdevPorts(gdb.Command):
     """Dump all ports added to a specific struct dp_netdev*.
-    Usage: ovs_dump_dp_netdev_ports <struct dp_netdev *>
+    Usage:
+      ovs_dump_dp_netdev_ports <struct dp_netdev *>
     """
     def __init__(self):
         super(CmdDumpDpNetdevPorts, self).__init__("ovs_dump_dp_netdev_ports",
@@ -646,7 +659,8 @@ class CmdDumpDpNetdevPorts(gdb.Command):
 #
 class CmdDumpDpProvider(gdb.Command):
     """Dump all registered registered_dpif_class structures.
-    Usage: ovs_dump_dp_provider
+    Usage:
+      ovs_dump_dp_provider
     """
     def __init__(self):
         super(CmdDumpDpProvider, self).__init__("ovs_dump_dp_provider",
@@ -674,7 +688,8 @@ class CmdDumpDpProvider(gdb.Command):
 #
 class CmdDumpNetdev(gdb.Command):
     """Dump all registered netdev structures.
-    Usage: ovs_dump_netdev
+    Usage:
+      ovs_dump_netdev
     """
     def __init__(self):
         super(CmdDumpNetdev, self).__init__("ovs_dump_netdev",
@@ -702,7 +717,8 @@ class CmdDumpNetdev(gdb.Command):
 #
 class CmdDumpNetdevProvider(gdb.Command):
     """Dump all registered netdev providers.
-    Usage: ovs_dump_netdev_provider
+    Usage:
+      ovs_dump_netdev_provider
     """
     def __init__(self):
         super(CmdDumpNetdevProvider, self).__init__("ovs_dump_netdev_provider",
@@ -762,34 +778,36 @@ class CmdDumpNetdevProvider(gdb.Command):
 #
 class CmdDumpOvsList(gdb.Command):
     """Dump all nodes of an ovs_list give
-    Usage: ovs_dump_ovs_list <struct ovs_list *> {[<structure>] [<member>] {dump}]}
+    Usage:
+      ovs_dump_ovs_list <struct ovs_list *> {[<structure>] [<member>] {dump}]}
 
     For example dump all the none quiescent OvS RCU threads:
 
       (gdb) ovs_dump_ovs_list &ovsrcu_threads
-      (struct ovs_list *) 0x7f2a14000900
-      (struct ovs_list *) 0x7f2acc000900
-      (struct ovs_list *) 0x7f2a680668d0
+      (struct ovs_list *) 0x1400
+      (struct ovs_list *) 0xcc00
+      (struct ovs_list *) 0x6806
 
     This is not very useful, so please use this with the container_of mode:
 
-      (gdb) ovs_dump_ovs_list &ovsrcu_threads 'struct ovsrcu_perthread' list_node
-      (struct ovsrcu_perthread *) 0x7f2a14000900
-      (struct ovsrcu_perthread *) 0x7f2acc000900
-      (struct ovsrcu_perthread *) 0x7f2a680668d0
+      (gdb) set $threads = &ovsrcu_threads
+      (gdb) ovs_dump_ovs_list $threads 'struct ovsrcu_perthread' list_node
+      (struct ovsrcu_perthread *) 0x1400
+      (struct ovsrcu_perthread *) 0xcc00
+      (struct ovsrcu_perthread *) 0x6806
 
     Now you can manually use the print command to show the content, or use the
     dump option to dump the structure for all nodes:
 
-      (gdb) ovs_dump_ovs_list &ovsrcu_threads 'struct ovsrcu_perthread' list_node dump
-      (struct ovsrcu_perthread *) 0x7f2a14000900 =
-        {list_node = {prev = 0xf48e80 <ovsrcu_threads>, next = 0x7f2acc000900}, mutex...
+      (gdb) ovs_dump_ovs_list $threads 'struct ovsrcu_perthread' list_node dump
+      (struct ovsrcu_perthread *) 0x1400 =
+        {list_node = {prev = 0x48e80 <ovsrcu_threads>, next = 0xcc00}, mutex...
 
-      (struct ovsrcu_perthread *) 0x7f2acc000900 =
-        {list_node = {prev = 0x7f2a14000900, next = 0x7f2a680668d0}, mutex ...
+      (struct ovsrcu_perthread *) 0xcc00 =
+        {list_node = {prev = 0x1400, next = 0x6806}, mutex ...
 
-      (struct ovsrcu_perthread *) 0x7f2a680668d0 =
-        {list_node = {prev = 0x7f2acc000900, next = 0xf48e80 <ovsrcu_threads>}, ...
+      (struct ovsrcu_perthread *) 0x6806 =
+        {list_node = {prev = 0xcc00, next = 0x48e80 <ovsrcu_threads>}, ...
     """
     def __init__(self):
         super(CmdDumpOvsList, self).__init__("ovs_dump_ovs_list",
@@ -836,7 +854,8 @@ class CmdDumpOvsList(gdb.Command):
 #
 class CmdDumpSimap(gdb.Command):
     """Dump all key, value entries of a simap
-    Usage: ovs_dump_simap <struct simap *>
+    Usage:
+      ovs_dump_simap <struct simap *>
     """
 
     def __init__(self):
@@ -871,7 +890,8 @@ class CmdDumpSimap(gdb.Command):
 #
 class CmdDumpSmap(gdb.Command):
     """Dump all key, value pairs of a smap
-    Usage: ovs_dump_smap <struct smap *>
+    Usage:
+      ovs_dump_smap <struct smap *>
     """
 
     def __init__(self):
@@ -906,7 +926,8 @@ class CmdDumpSmap(gdb.Command):
 #
 class CmdDumpUdpifKeys(gdb.Command):
     """Dump all nodes of an ovs_list give
-    Usage: ovs_dump_udpif_keys {<udpif_name>|<udpif_address>} {short}
+    Usage:
+      ovs_dump_udpif_keys {<udpif_name>|<udpif_address>} {short}
 
       <udpif_name>    : Full name of the udpif's dpif to dump
       <udpif_address> : Address of the udpif structure to dump. If both the
@@ -1033,7 +1054,8 @@ class CmdDumpUdpifKeys(gdb.Command):
 #
 class CmdShowFDB(gdb.Command):
     """Show FDB information
-    Usage: ovs_show_fdb {<bridge_name> {dbg} {hash}}
+    Usage:
+      ovs_show_fdb {<bridge_name> {dbg} {hash}}
 
        <bridge_name> : Optional bridge name, if not supplied FDB summary
                        information is displayed for all bridges.
@@ -1199,7 +1221,8 @@ class CmdShowFDB(gdb.Command):
 #
 class CmdShowUpcall(gdb.Command):
     """Show upcall information
-    Usage: ovs_show_upcall {dbg}
+    Usage:
+      ovs_show_upcall {dbg}
 
       dbg  : Will show structure address information
     """
@@ -1271,7 +1294,8 @@ class CmdShowUpcall(gdb.Command):
 #
 class CmdDumpOfpacts(gdb.Command):
     """Dump all actions in an ofpacts set
-    Usage: ovs_dump_ofpacts <struct ofpact *> <ofpacts_len>
+    Usage:
+      ovs_dump_ofpacts <struct ofpact *> <ofpacts_len>
 
        <struct ofpact *> : Pointer to set of ofpact structures.
        <ofpacts_len>     : Total length of the set.
@@ -1279,12 +1303,12 @@ class CmdDumpOfpacts(gdb.Command):
     Example dumping all actions when in the clone_xlate_actions() function:
 
     (gdb) ovs_dump_ofpacts actions actions_len
-    (struct ofpact *) 0x561c7be487c8: {type = OFPACT_SET_FIELD, raw = 255 '', len = 24}
-    (struct ofpact *) 0x561c7be487e0: {type = OFPACT_SET_FIELD, raw = 255 '', len = 24}
-    (struct ofpact *) 0x561c7be487f8: {type = OFPACT_SET_FIELD, raw = 255 '', len = 24}
-    (struct ofpact *) 0x561c7be48810: {type = OFPACT_SET_FIELD, raw = 255 '', len = 32}
-    (struct ofpact *) 0x561c7be48830: {type = OFPACT_SET_FIELD, raw = 255 '', len = 24}
-    (struct ofpact *) 0x561c7be48848: {type = OFPACT_RESUBMIT, raw = 38 '&', len = 16}
+    (struct ofpact *) 0x87c8: {type = OFPACT_SET_FIELD, raw = 255 '', len = 24}
+    (struct ofpact *) 0x87e0: {type = OFPACT_SET_FIELD, raw = 255 '', len = 24}
+    (struct ofpact *) 0x87f8: {type = OFPACT_SET_FIELD, raw = 255 '', len = 24}
+    (struct ofpact *) 0x8810: {type = OFPACT_SET_FIELD, raw = 255 '', len = 32}
+    (struct ofpact *) 0x8830: {type = OFPACT_SET_FIELD, raw = 255 '', len = 24}
+    (struct ofpact *) 0x8848: {type = OFPACT_RESUBMIT, raw = 38 '&', len = 16}
     """
     def __init__(self):
         super(CmdDumpOfpacts, self).__init__("ovs_dump_ofpacts",
@@ -1307,6 +1331,110 @@ class CmdDumpOfpacts(gdb.Command):
 
 
 #
+# Implements the GDB "ovs_dump_packets" command
+#
+class CmdDumpPackets(gdb.Command):
+    """Dump metadata about dp_packets
+    Usage:
+      ovs_dump_packets <struct dp_packet_batch|dp_packet> [tcpdump options]
+
+    This command can take either a dp_packet_batch struct and print out
+    metadata about all packets in this batch, or a single dp_packet struct and
+    print out metadata about a single packet.
+
+    Everything after the struct reference is passed into tcpdump. If nothing
+    is passed in as a tcpdump option, the default is "-n".
+
+    (gdb) ovs_dump_packets packets_
+    12:01:05.981214 ARP, Ethernet (len 6), IPv4 (len 4), Reply 10.1.1.1 is-at
+        a6:0f:c3:f0:5f:bd (oui Unknown), length 28
+    """
+    def __init__(self):
+        super().__init__("ovs_dump_packets", gdb.COMMAND_DATA)
+
+    def invoke(self, arg, from_tty):
+        if Ether is None:
+            print("ERROR: This command requires scapy to be installed.")
+            return
+
+        arg_list = gdb.string_to_argv(arg)
+        if len(arg_list) == 0:
+            print("Usage: ovs_dump_packets <struct dp_packet_batch|"
+                  "dp_packet> [tcpdump options]")
+            return
+
+        symb_name = arg_list[0]
+        tcpdump_args = arg_list[1:]
+
+        if not tcpdump_args:
+            # Add a sane default
+            tcpdump_args = ["-n"]
+
+        val = gdb.parse_and_eval(symb_name)
+        while val.type.code == gdb.TYPE_CODE_PTR:
+            val = val.dereference()
+
+        pkt_list = []
+        if str(val.type).startswith("struct dp_packet_batch"):
+            for idx in range(val['count']):
+                pkt_struct = val['packets'][idx].dereference()
+                pkt = self.extract_pkt(pkt_struct)
+                if pkt is None:
+                    continue
+                pkt_list.append(pkt)
+        elif str(val.type) == "struct dp_packet":
+            pkt = self.extract_pkt(val)
+            if pkt is None:
+                return
+            pkt_list.append(pkt)
+        else:
+            print("Error, unsupported argument type: {}".format(str(val.type)))
+            return
+
+        tcpdump(pkt_list, args=tcpdump_args)
+
+    def extract_pkt(self, pkt):
+        pkt_fields = pkt.type.keys()
+        if pkt['packet_type'] != 0:
+            return
+        if pkt['l3_ofs'] == 0xFFFF:
+            return
+
+        if "mbuf" in pkt_fields:
+            if pkt['mbuf']['data_off'] == 0xFFFF:
+                return
+            eth_ptr = pkt['mbuf']['buf_addr']
+            eth_off = int(pkt['mbuf']['data_off'])
+            eth_len = int(pkt['mbuf']['pkt_len'])
+        else:
+            if pkt['data_ofs'] == 0xFFFF:
+                return
+            eth_ptr = pkt['base_']
+            eth_off = int(pkt['data_ofs'])
+            eth_len = int(pkt['size_'])
+
+        if eth_ptr == 0 or eth_len < 1:
+            return
+
+        # Extract packet
+        pkt_ptr = eth_ptr.cast(
+                gdb.lookup_type('uint8_t').pointer()
+            )
+        pkt_ptr += eth_off
+
+        pkt_data = []
+        for idx in range(eth_len):
+            pkt_data.append(int(pkt_ptr[idx]))
+
+        pkt_data = struct.pack("{}B".format(eth_len), *pkt_data)
+
+        packet = Ether(pkt_data)
+        packet.len = int(eth_len)
+
+        return packet
+
+
+#
 # Initialize all GDB commands
 #
 CmdDumpBridge()
@@ -1319,6 +1447,7 @@ CmdDumpNetdev()
 CmdDumpNetdevProvider()
 CmdDumpOfpacts()
 CmdDumpOvsList()
+CmdDumpPackets()
 CmdDumpSimap()
 CmdDumpSmap()
 CmdDumpUdpifKeys()