dialplan_functions: wrong srtp use status report of a dialplan function

If asterisk offer an endpoint with SRTP and that endpoint respond
with non srtp, in that case channel(rtp,secure,audio) reply wrong
status.

Why delete flag AST_SRTP_CRYPTO_OFFER_OK while check identical remote_key:
Currently this flag has being set redundantly. In either case identical
or different remote_key this flag has being set. So if we
don't set it while we receive identical remote_key or non SRTP SDP
response then we can take decision of srtp use by using that flag.

ASTERISK-27999

Change-Id: I29dc2843cf4e5ae2604301cb4ff258f1822dc2d7

channels/pjsip/dialplan_functions.c

@@ -530,7 +530,13 @@ static int channel_read_rtp(struct ast_channel *chan, const char *type, const ch
 	} else if (!strcmp(type, "direct")) {
 		ast_copy_string(buf, ast_sockaddr_stringify(&media->direct_media_addr), buflen);
 	} else if (!strcmp(type, "secure")) {
-		snprintf(buf, buflen, "%d", media->srtp ? 1 : 0);
+		if (media->srtp) {
+			struct ast_sdp_srtp *srtp = media->srtp;
+			int flag = ast_test_flag(srtp, AST_SRTP_CRYPTO_OFFER_OK);
+			snprintf(buf, buflen, "%d", flag ? 1 : 0);
+		} else {
+			snprintf(buf, buflen, "%d", 0);
+		}
 	} else if (!strcmp(type, "hold")) {
 		snprintf(buf, buflen, "%d", media->held ? 1 : 0);
 	} else {

main/sdp_srtp.c

@@ -350,7 +350,6 @@ int ast_sdp_crypto_process(struct ast_rtp_instance *rtp, struct ast_sdp_srtp *sr
 
 	if (!memcmp(crypto->remote_key, remote_key, sizeof(crypto->remote_key))) {
 		ast_debug(1, "SRTP remote key unchanged; maintaining current policy\n");
-		ast_set_flag(srtp, AST_SRTP_CRYPTO_OFFER_OK);
 		return 0;
 	}
 	memcpy(crypto->remote_key, remote_key, sizeof(crypto->remote_key));