Add force strip extmap flag

daemon/call.c

@@ -2762,6 +2762,8 @@ static void __call_monologue_init_from_flags(struct call_monologue *ml, struct c
 
 	call->last_signal_us = rtpe_now;
 	call->deleted_us = 0;
+	if (flags->force_strip_extmap)
+		CALL_SET(call, FORCE_STRIP_EXTMAP);
 	call->media_rec_slots = (flags->media_rec_slots > 0 && call->media_rec_slots == 0)
 								? flags->media_rec_slots
 								: call->media_rec_slots;

daemon/call_flags.c

@@ -970,6 +970,10 @@ const char *call_ng_flags_flags(str *s, unsigned int idx, helper_arg arg) {
 		case CSH_LOOKUP("strip-extmap"):
 		case CSH_LOOKUP("strip extmap"):
 			return call_ng_flags_str_ht(STR_PTR("all"), 0, &out->rtpext_strip);
+		case CSH_LOOKUP("force-strip-extmap"):
+		case CSH_LOOKUP("force strip extmap"):
+			out->force_strip_extmap = true;
+			break;
 		case CSH_LOOKUP("symmetric-codecs"):
 		case CSH_LOOKUP("symmetric codecs"):
 			ilog(LOG_INFO, "Ignoring obsolete flag `symmetric-codecs`");

daemon/media_socket.c

@@ -2545,7 +2545,10 @@ static void __determine_rtpext_handler(struct call_media *in, struct call_media
 	if (!sh || !out)
 		return;
 
-	if (in->extmap.length || out->extmap.length)
+	/* With `force strip extmap` set on the call, use the extmap printer even
+	 * if no header extensions were negotiated, so that unannounced header
+	 * extensions are removed from forwarded RTP. */
+	if (in->extmap.length || out->extmap.length || CALL_ISSET(out->call, FORCE_STRIP_EXTMAP))
 		sh->rtpext = &rtpext_printer_extmap;
 	else
 		sh->rtpext = &rtpext_printer_copy;

docs/ng_control_protocol.md

@@ -1361,6 +1361,15 @@ Spaces in each string may be replaced by hyphens.
     Legacy alias for `extmap=[strip=[all]]` to remove all `a=rtpmap` attributes
     from the outgoing SDP.
 
+* `force strip extmap`
+
+    Process RTP header extensions of forwarded media even if no header
+    extensions were negotiated in the SDP. Normally, RTP header extensions
+    are passed through untouched if neither side included any `a=extmap`
+    attributes. With this flag set, header extensions that were not
+    negotiated are removed from forwarded RTP. Once set, the flag remains
+    in effect for the lifetime of the call.
+
 * `strict source`
 
 	Normally, *rtpengine* attempts to learn the correct endpoint address for every stream during

include/call.h

@@ -255,6 +255,7 @@ enum {
 #define CALL_FLAG_BLOCK_MEDIA			(1LL << 28)
 #define CALL_FLAG_SILENCE_MEDIA			(1LL << 29)
 #define CALL_FLAG_NO_REC_DB			(1LL << 30)
+#define CALL_FLAG_FORCE_STRIP_EXTMAP		(1LL << 31)
 
 /* access macros */
 #define SP_ISSET(p, f)		bf_isset(&(p)->sp_flags, SP_FLAG_ ## f)

include/call_flags.h

@@ -323,7 +323,9 @@ RTPE_NG_FLAGS_STR_CASE_HT_PARAMS
 		     moh_sendrecv:1,
 		     moh_reflect:1,
 		     /* prevents double MoH holds */
-		     moh_double_hold:1;
+		     moh_double_hold:1,
+		     /* process RTP header extensions even if none were negotiated */
+		     force_strip_extmap:1;
 };
 
 

t/auto-daemon-tests-rtp-ext.pl

@@ -4026,5 +4026,62 @@
 
 
 
+# force strip extmap: header extensions removed even though none were negotiated
+
+($sock_a, $sock_ax, $sock_b, $sock_bx) = new_call(
+	[qw(198.51.100.1 7690)],
+	[qw(198.51.100.1 7691)],
+	[qw(198.51.100.3 7692)],
+	[qw(198.51.100.3 7693)],
+);
+
+($port_a, $port_ax) = offer('force strip extmap', { flags => ['force strip extmap'] }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+m=audio 7690 RTP/AVP 8
+c=IN IP4 198.51.100.1
+a=sendrecv
+----------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+m=audio PORT RTP/AVP 8
+c=IN IP4 203.0.113.1
+a=rtpmap:8 PCMA/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+($port_b, $port_bx) = answer('force strip extmap', { }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=audio 7692 RTP/AVP 8
+c=IN IP4 198.51.100.3
+a=rtpmap:8 PCMA/8000
+a=sendrecv
+--------------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=audio PORT RTP/AVP 8
+c=IN IP4 203.0.113.1
+a=rtpmap:8 PCMA/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+snd($sock_a, $port_b, rtp( 8, 1000, 3000+160*0, 0x1234, "\x10" . ("\x00" x 158) . "\x50", [[1, "foo"]]));
+rcv($sock_b, $port_a, rtpm(8, 1000, 3000+160*0, 0x1234, "\x10" . ("\x00" x 158) . "\x50"));
+snd($sock_b, $port_a, rtp( 8, 8000, 7000+160*0, 0x6543, "\x10" . ("\x00" x 158) . "\x50", [[2, "blah"]]));
+rcv($sock_a, $port_b, rtpm(8, 8000, 7000+160*0, 0x6543, "\x10" . ("\x00" x 158) . "\x50"));
+snd($sock_a, $port_b, rtp( 8, 1001, 3000+160*1, 0x1234, "\x10" . ("\x00" x 158) . "\x50"));
+rcv($sock_b, $port_a, rtpm(8, 1001, 3000+160*1, 0x1234, "\x10" . ("\x00" x 158) . "\x50"));
+
 #done_testing;NGCP::Rtpengine::AutoTest::terminate('f00');exit;
 done_testing();