Fix bug 9021: 'RTP not decoded inside the conversation in v.1.10.1'

The behavior for SIP/SDP handling of RTP conversation tracking
changed in v1.10, with some unintended consequences.  The bugs did not
show up at the time because wireshark makes 2 passes of the packet list,
and so the problems auto-corrected themselves in most cases.  Unfortunately,
a change in r53641 modified how UDP behaves, making it always create
conversations for UDP packets, and that exposed the bugs inherent in the
SIP/SDP code changes.

This commit reverts the behavior of SIP/SDP to its pre-1.10 model, but
creates a new preference setting for "Delay SDP changes for tracking media",
which if enabled, will turn on the new (but buggy) model introduced in 1.10.
This preference is *disabled* by default, since for a majority of cases the
new behavior is worse than the previous behavior.

The preference, and this commit's fix, is not intended to last long. I intend
to re-write the SIP/SDP/RTP interaction model for release 1.11 - I think it's
too big a change for 1.10, however, which is why I submitted this commit.

Change-Id: Ic5601749d6c2344e952ced8206dd9296bfdc4b90
Reviewed-on: https://code.wireshark.org/review/543
Reviewed-by: Evan Huus <eapache@gmail.com>

1 files changed, 17 insertions, 4 deletions

diff --git a/epan/dissectors/packet-sdp.c b/epan/dissectors/packet-sdp.c
index 939b356ce1..d7cbaa62b2 100644
--- a/epan/dissectors/packet-sdp.c
+++ b/epan/dissectors/packet-sdp.c
@@ -1684,7 +1684,8 @@ convert_disposable_media(transport_info_t* transport_info, disposable_media_info
 }
 
 void
-setup_sdp_transport(tvbuff_t *tvb, packet_info *pinfo, enum sdp_exchange_type exchange_type, int request_frame)
+setup_sdp_transport(tvbuff_t *tvb, packet_info *pinfo, enum sdp_exchange_type exchange_type,
+    int request_frame, const gboolean delay)
 {
     gint        offset = 0, next_offset, n;
     int         linelen;
@@ -1736,6 +1737,18 @@ setup_sdp_transport(tvbuff_t *tvb, packet_info *pinfo, enum sdp_exchange_type ex
     if (transport_info->media_count > 0)
         start_transport_info_count = transport_info->media_count;
 
+    /* if we don't delay, and this is an answer after a previous offer, then
+       we free'd the unused media rtp_dyn_payload last time while processing
+       the offer, so we need to re-create them this time in case we need them.
+       If they don't get used they'll get free'd again later */
+    if (!delay && (exchange_type == SDP_EXCHANGE_ANSWER_ACCEPT) &&
+        (transport_info->sdp_status == SDP_EXCHANGE_OFFER)) {
+        for (n = start_transport_info_count; n < SDP_MAX_RTP_CHANNELS; n++) {
+            if (!transport_info->media[n].rtp_dyn_payload)
+                transport_info->media[n].rtp_dyn_payload = g_hash_table_new(g_int_hash, g_int_equal);
+        }
+    }
+
     /*
      * Show the SDP message a line at a time.
      */
@@ -1815,8 +1828,8 @@ setup_sdp_transport(tvbuff_t *tvb, packet_info *pinfo, enum sdp_exchange_type ex
     convert_disposable_media(transport_info, &media_info, start_transport_info_count);
 
     /* We have a successful negotiation, apply data to their respective protocols */
-    if ((exchange_type == SDP_EXCHANGE_ANSWER_ACCEPT) &&
-        (transport_info->sdp_status == SDP_EXCHANGE_OFFER)) {
+    if (!delay || ((exchange_type == SDP_EXCHANGE_ANSWER_ACCEPT) &&
+        (transport_info->sdp_status == SDP_EXCHANGE_OFFER))) {
 
         for (n = 0; n <= transport_info->media_count; n++) {
           guint32 current_rtp_port = 0;
@@ -1920,7 +1933,7 @@ setup_sdp_transport(tvbuff_t *tvb, packet_info *pinfo, enum sdp_exchange_type ex
                 }
             }
         }
-        transport_info->sdp_status = SDP_EXCHANGE_ANSWER_ACCEPT;
+        transport_info->sdp_status = exchange_type;
 
     } else if ((exchange_type == SDP_EXCHANGE_ANSWER_REJECT) &&
                (transport_info->sdp_status != SDP_EXCHANGE_ANSWER_REJECT)) {