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mgcp_network: do not deliver RTP packets with unpatched PT 

When a call leg is set up, then the call agent (e.g. BSC, MSC, etc.)
will also negotiate a codec along with a payload type number. When
sending RTP packets, each RTP packet must also contain the negotiated
payload type number. To prevent the emission of RTP packets with an
incorrect payload type number, ensure that no packet is sent when
mgcp_patch_pt() fails.

Change-Id: I013a24c1e0f853557257368cfab9192d4611aafa
Related: OS#5461
This commit is contained in:
Philipp Maier 2023-04-26 15:47:51 +02:00
parent 4c4d227624
commit 3d0676a791
1 changed files with 3 additions and 12 deletions
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15
src/libosmo-mgcp/mgcp_network.c
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@ -1164,18 +1164,9 @@ int mgcp_send(struct mgcp_endpoint *endp, int is_rtp, struct osmo_sockaddr *addr
* IuUP -> AMR: calls this function, skip patching if conn_src is IuUP.
* {AMR or IuUP} -> IuUP: calls mgcp_udp_send() directly, skipping this function: No need to examine dst. */
if (is_rtp && !mgcp_conn_rtp_is_iuup(conn_src)) {
rc = mgcp_patch_pt(conn_dst, msg);
if (rc < 0) {
/* FIXME: It is legal that the payload type on the egress connection is
* different from the payload type that has been negotiated on the
* ingress connection. Essentially the codecs are the same so we can
* match them and patch the payload type. However, if we can not find
* the codec pendant (everything ist equal except the PT), we are of
* course unable to patch the payload type. A situation like this
* should not occur if transcoding is consequently avoided. Until
* we have transcoding support in osmo-mgw we can not resolve this. */
LOGPENDP(endp, DRTP, LOGL_DEBUG,
"can not patch PT because no suitable egress codec was found.\n");
if (mgcp_patch_pt(conn_dst, msg) < 0) {
LOGPENDP(endp, DRTP, LOGL_NOTICE, "unable to patch payload type RTP packet, discarding...\n");
return -EINVAL;
}
}