Do not allow native RTP bridging if packetization of media streams differs.

The RTP engine will no longer allow for local and remote native RTP bridges
if packetization of streams differs. Allowing native bridging in this scenario
has been known to cause FAX failures.

(closes ASTERISK-20650)
Reported by: Maciej Krajewski
Patches:
	ASTERISK-20659.patch uploaded by Mark Michelson (License #5049)

Review: https://reviewboard.asterisk.org/r/2319
........

Merged revisions 381281 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@381306 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/rtp_engine.c

@@ -1460,6 +1460,7 @@ enum ast_bridge_result ast_rtp_instance_bridge(struct ast_channel *c0, struct as
 	struct ast_format_cap *cap0 = ast_format_cap_alloc_nolock();
 	struct ast_format_cap *cap1 = ast_format_cap_alloc_nolock();
 	int unlock_chans = 1;
+	int read_ptime0, read_ptime1, write_ptime0, write_ptime1;
 
 	if (!cap0 || !cap1) {
 		unlock_chans = 0;
@@ -1568,6 +1569,18 @@ enum ast_bridge_result ast_rtp_instance_bridge(struct ast_channel *c0, struct as
 		goto done;
 	}
 
+	read_ptime0 = (ast_codec_pref_getsize(&instance0->codecs.pref, ast_channel_rawreadformat(c0))).cur_ms;
+	read_ptime1 = (ast_codec_pref_getsize(&instance1->codecs.pref, ast_channel_rawreadformat(c1))).cur_ms;
+	write_ptime0 = (ast_codec_pref_getsize(&instance0->codecs.pref, ast_channel_rawwriteformat(c0))).cur_ms;
+	write_ptime1 = (ast_codec_pref_getsize(&instance1->codecs.pref, ast_channel_rawwriteformat(c1))).cur_ms;
+
+	if (read_ptime0 != write_ptime1 || read_ptime1 != write_ptime0) {
+		ast_debug(1, "Packetization differs between RTP streams (%d != %d or %d != %d). Cannot native bridge in RTP\n",
+				read_ptime0, write_ptime1, read_ptime1, write_ptime0);
+		res = AST_BRIDGE_FAILED_NOWARN;
+		goto done;
+	}
+
 	instance0->glue = glue0;
 	instance1->glue = glue1;
 	instance0->chan = c0;