From a1efdf6b20f52312e2db8eabfd7f5f7b87d6a461 Mon Sep 17 00:00:00 2001
From: Richard Fuchs <rfuchs@sipwise.com>
Date: Wed, 5 Dec 2018 10:46:00 -0500
Subject: [PATCH] TT#45472 support generating a=mid lines if not present

closes #641

Change-Id: I849f0c73c5fdd575417a37a41d6701ea4454374b
---
 README.md                 |  4 ++++
 daemon/call.c             | 26 +++++++++++++++++---------
 daemon/call_interfaces.c  |  2 ++
 include/call_interfaces.h |  1 +
 utils/rtpengine-ng-client |  3 ++-
 5 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/README.md b/README.md
index d8db1b2b5..332473743 100644
--- a/README.md
+++ b/README.md
@@ -1247,6 +1247,10 @@ Optionally included keys are:
 		`=` characters used for padding should be omitted. With this flag set, these padding
 		characters will be left in place.
 
+	- `generate mid`
+
+		Add `a=mid` attributes to the outgoing SDP if they were not already present.
+
 * `replace`
 
 	Similar to the `flags` list. Controls which parts of the SDP body should be rewritten.
diff --git a/daemon/call.c b/daemon/call.c
index df3e4712d..0811222db 100644
--- a/daemon/call.c
+++ b/daemon/call.c
@@ -1674,15 +1674,23 @@ static void __update_media_id(struct call_media *media, struct call_media *other
 {
 	struct call *call = media->call;
 
-	if (!other_media->media_id.s) {
-		// incoming side: we copy what we received
-		if (sp->media_id.s)
-			call_str_cpy(call, &other_media->media_id, &sp->media_id);
-	}
-	if (!media->media_id.s) {
-		// outgoing side: we copy from the other side
-		if (other_media->media_id.s)
-			call_str_cpy(call, &media->media_id, &other_media->media_id);
+	if (flags && flags->opmode == OP_OFFER) {
+		if (!other_media->media_id.s) {
+			// incoming side: we copy what we received
+			if (sp->media_id.s)
+				call_str_cpy(call, &other_media->media_id, &sp->media_id);
+		}
+		if (!media->media_id.s) {
+			// outgoing side: we copy from the other side
+			if (other_media->media_id.s)
+				call_str_cpy(call, &media->media_id, &other_media->media_id);
+			else if (flags->generate_mid) {
+				// or generate one
+				char buf[64];
+				snprintf(buf, sizeof(buf), "%u", other_media->index);
+				call_str_cpy_c(call, &media->media_id, buf);
+			}
+		}
 	}
 }
 
diff --git a/daemon/call_interfaces.c b/daemon/call_interfaces.c
index 9cf023b65..da2fde0ed 100644
--- a/daemon/call_interfaces.c
+++ b/daemon/call_interfaces.c
@@ -611,6 +611,8 @@ static void call_ng_flags_flags(struct sdp_ng_flags *out, str *s, void *dummy) {
 		out->all = 1;
 	else if (!str_cmp(s, "port-latching"))
 		out->port_latching = 1;
+	else if (!str_cmp(s, "generate-mid"))
+		out->generate_mid = 1;
 	else if (!str_cmp(s, "record-call"))
 		out->record_call = 1;
 	else if (!str_cmp(s, "no-rtcp-attribute"))
diff --git a/include/call_interfaces.h b/include/call_interfaces.h
index e87318a4b..b39a6e012 100644
--- a/include/call_interfaces.h
+++ b/include/call_interfaces.h
@@ -53,6 +53,7 @@ struct sdp_ng_flags {
 	    rtcp_mux_accept:1,
 	    rtcp_mux_reject:1,
 	    no_rtcp_attr:1,
+	    generate_mid:1,
 	    strict_source:1,
 	    media_handover:1,
 	    dtls_passive:1,
diff --git a/utils/rtpengine-ng-client b/utils/rtpengine-ng-client
index 92d191528..f5dfb7f48 100755
--- a/utils/rtpengine-ng-client
+++ b/utils/rtpengine-ng-client
@@ -61,6 +61,7 @@ GetOptions(
 	'all'				=> \$options{'all'},
 	'address=s'			=> \$options{'address'},
 	'pad-crypto'			=> \$options{'pad crypto'},
+	'generate-mid'			=> \$options{'generate mid'},
 ) or die;
 
 my $cmd = shift(@ARGV) or die;
@@ -73,7 +74,7 @@ for my $x (split(/,/, 'from-tag,to-tag,call-id,transport protocol,media address,
 for my $x (split(/,/, 'TOS,delete-delay')) {
 	defined($options{$x}) and $packet{$x} = $options{$x};
 }
-for my $x (split(/,/, 'trust address,symmetric,asymmetric,force,strict source,media handover,sip source address,reset,port latching,no rtcp attribute,loop protect,record call,always transcode,all,pad crypto')) {
+for my $x (split(/,/, 'trust address,symmetric,asymmetric,force,strict source,media handover,sip source address,reset,port latching,no rtcp attribute,loop protect,record call,always transcode,all,pad crypto,generate mid')) {
 	defined($options{$x}) and push(@{$packet{flags}}, $x);
 }
 for my $x (split(/,/, 'origin,session connection')) {