Changeset 1602

Timestamp:

07/15/10 16:53:37 (3 years ago)

Author:

salcock

Message:

• Set the value of remaining to the minimum of the wire and capture lengths when calling trace_get_packet_buffer()

File:

• trunk/lib/trace.c (modified) (1 diff)

trunk/lib/trace.c

@@ -817 +817 @@
 DLLEXPORT void *trace_get_packet_buffer(const libtrace_packet_t *packet,
                 libtrace_linktype_t *linktype, uint32_t *remaining) {
+        int cap_len;
+        int wire_len;
+
         assert(packet != NULL);
         if (linktype) *linktype = trace_get_link_type(packet);
-        if (remaining) *remaining = trace_get_capture_length(packet);
+        if (remaining) {
+                /* I think we should choose the minimum of the capture and
+                 * wire lengths to be the "remaining" value. If the packet has
+                 * been padded to increase the capture length, we don't want
+                 * to allow subsequent protocol decoders to consider the 
+                 * padding as part of the packet.
+                 *
+                 * For example, in Auck 4 there is a trace where the IP header
+                 * length is incorrect (24 bytes) followed by a 20 byte TCP
+                 * header. Total IP length is 40 bytes. As a result, the
+                 * legacyatm padding gets treated as the "missing" bytes of
+                 * the TCP header, which isn't the greatest. We're probably
+                 * better off returning an incomplete TCP header in that case.
+                 */
+                
+                cap_len = trace_get_capture_length(packet);
+                wire_len = trace_get_wire_length(packet);
+
+                assert(cap_len >= 0 && wire_len >= 0);
+                if (wire_len < cap_len)
+                        *remaining = wire_len;
+                else
+                        *remaining = cap_len;
+                /* *remaining = trace_get_capture_length(packet); */
+        }
         return (void *) packet->payload;
 }