Merge branch 'ip_offset-patch' into v1.1.2.1-forkv1.1.2.1-fork

2 files changed, 16 insertions, 4 deletions

diff --git a/libnet/include/libnet/libnet-functions.h b/libnet/include/libnet/libnet-functions.h
index c4fe599..99b1139 100644
--- a/libnet/include/libnet/libnet-functions.h
+++ b/libnet/include/libnet/libnet-functions.h
@@ -794,6 +794,7 @@ u_int8_t *payload, u_int32_t payload_s, libnet_t *l, libnet_ptag_t ptag);
 /**
  * Builds a version 4 RFC 791 Internet Protocol (IP) header.
  * @param len total length of the IP packet including all subsequent data
+ *   FIXME There is no reason this can't be calculated if zero is passed.
  * @param tos type of service bits
  * @param id IP identification number
  * @param frag fragmentation bits and offset
@@ -2080,10 +2081,10 @@ u_int8_t type);
   * Function updates referer used to compute the checksum. All
   * pblock need to know where is their referer (ie IP header).
   * So, this function is called each time a new IP header is inserted.
-  * It updates the ip_pos field (referer) of each subsequent pblock.
+  * It updates the ip_offset field (referer) of each previous pblock.
   */
 void
-libnet_pblock_record_ip_offset(libnet_t *l, u_int32_t offset);
+libnet_pblock_record_ip_offset(libnet_t *l, libnet_pblock_t *p);
 
 /*
  * [Internal] 
diff --git a/libnet/include/libnet/libnet-structures.h b/libnet/include/libnet/libnet-structures.h
index 38aff5d..eb7de76 100644
--- a/libnet/include/libnet/libnet-structures.h
+++ b/libnet/include/libnet/libnet-structures.h
@@ -79,8 +79,19 @@ struct libnet_protocol_block
     u_int8_t *buf;                      /* protocol buffer */
     u_int32_t b_len;                    /* length of buf */
     u_int16_t h_len;                    /* header length (for checksumming) */
-    u_int32_t ip_offset;                /* offset to IP header for csums */
-    u_int32_t copied;                   /* bytes copied */
+       /* Unused for IPV4_H block types.
+        * For protocols that sit on top of IP, it should be the the amount of
+        * buf that is the header, and will be included in the checksum.
+        */
+    u_int32_t ip_offset;                /* offset from end of pkt to beginning of IP header for csums */
+       /* Unused for IPV4_H block types.
+        * For protocols that sit on top of IP (UDP, ICMP, ...), they often
+        * include some information from the IP header (in the form of a "pseudo
+        * header") in their own checksum calculation. To build that
+        * pseudo-header, thet need to find the real header.
+        */
+    u_int32_t copied;                   /* bytes copied - the amount of data copied into buf */
+       /* Used and updated by libnet_pblock_append(). */
     u_int8_t type;                      /* type of pblock */
 /* this needs to be updated every time a new packet builder is added */
 #define LIBNET_PBLOCK_ARP_H             0x01    /* ARP header */