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IuUP->AMR: do not patch payload type a second time 

When converting IuUP to AMR/RTP, bridge_iuup_to_rtp_peer() sets the AMR
side's payload type number and then calls mgcp_send(). In mgcp_send(),
do not attempt to patch the payload type number a second time.

In mgcp_send(), skip patching payload type numbers if the source side is
IuUP. This matches exactly the case of converting IuUP to AMR/RTP.

There already is a check for IuUP, but for the wrong side. Drop that one
and explain in a comment why.

Move the comment about transcoding into the failure branch, where it is
relevant and doesn't clutter the new explanation of payload type
patching conditions.

Related: OS#5720
Related: SYS#5092
Change-Id: I7c722cd959f76bd104ae4941d182c77e5c025867
This commit is contained in:
Neels Hofmeyr 2022-10-24 01:00:26 +02:00
parent 24763eaa73
commit c1468ef7a5
1 changed files with 13 additions and 9 deletions
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22
src/libosmo-mgcp/mgcp_network.c
View File

@ -1160,17 +1160,21 @@ int mgcp_send(struct mgcp_endpoint *endp, int is_rtp, struct osmo_sockaddr *addr
else
LOGPENDP(endp, DRTP, LOGL_DEBUG, "delivering RTCP packet...\n");
/* 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. */
if (is_rtp && !mgcp_conn_rtp_is_iuup(conn_dst)) {
/* Patch the payload type number: translate from conn_src to conn_dst.
* Do not patch for IuUP, where the correct payload type number is already set in bridge_iuup_to_rtp_peer():
* 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_src, 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");
}