Re-send non-100 provisional responses to prevent cancellation

From section 13.3.1.1 of RFC 3261:

   If the UAS desires an extended period of time to answer the INVITE,
   it will need to ask for an "extension" in order to prevent proxies
   from canceling the transaction. A proxy has the option of canceling
   a transaction when there is a gap of 3 minutes between responses in a
   transaction. To prevent cancellation, the UAS MUST send a non-100
   provisional response at every minute, to handle the possibility of
   lost provisional responses.

(closes issue #11157)
Reported by: rjain
Tested by: twilson

Review: https://reviewboard.asterisk.org/r/315/


git-svn-id: http://svn.digium.com/svn/asterisk/branches/1.4@215682 f38db490-d61c-443f-a65b-d21fe96a405b

1 files changed, 72 insertions, 7 deletions

diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index 87b4c6aa3..684bff098 100644
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -211,6 +211,7 @@ static char seen_lastms = 0;
                                                       \todo Use known T1 for timeout (peerpoke)
                                                       */
 #define DEFAULT_TRANS_TIMEOUT        -1               /* Use default SIP transaction timeout */
+#define PROVIS_KEEPALIVE_TIMEOUT     60000            /*!< How long to wait before retransmitting a provisional response (rfc 3261 13.3.1.1) */
 #define MAX_AUTHTRIES                3                /*!< Try authentication three times, then fail */
 
 #define SIP_MAX_HEADERS              64               /*!< Max amount of SIP headers to read */
@@ -1034,6 +1035,8 @@ static struct sip_pvt {
 	struct ast_variable *chanvars;		/*!< Channel variables to set for inbound call */
 	AST_LIST_HEAD_NOLOCK(request_queue, sip_request) request_queue; /*!< Requests that arrived but could not be processed immediately */
 	int request_queue_sched_id;		/*!< Scheduler ID of any scheduled action to process queued requests */
+	int provisional_keepalive_sched_id; /*!< Scheduler ID for provisional responses that need to be sent out to avoid cancellation */
+	const char *last_provisional;   /*!< The last successfully transmitted provisonal response message */
 	struct sip_pvt *next;			/*!< Next dialog in chain */
 	struct sip_invite_param *options;	/*!< Options for INVITE */
 	int autoframing;
@@ -1290,6 +1293,7 @@ static int transmit_response_with_date(struct sip_pvt *p, const char *msg, const
 static int transmit_response_with_sdp(struct sip_pvt *p, const char *msg, const struct sip_request *req, enum xmittype reliable);
 static int transmit_response_with_unsupported(struct sip_pvt *p, const char *msg, const struct sip_request *req, const char *unsupported);
 static int transmit_response_with_auth(struct sip_pvt *p, const char *msg, const struct sip_request *req, const char *rand, enum xmittype reliable, const char *header, int stale);
+static int transmit_provisional_response(struct sip_pvt *p, const char *msg, const struct sip_request *req, int with_sdp);
 static int transmit_response_with_allow(struct sip_pvt *p, const char *msg, const struct sip_request *req, enum xmittype reliable);
 static void transmit_fake_auth_response(struct sip_pvt *p, int sipmethod, struct sip_request *req, enum xmittype reliable);
 static int transmit_request(struct sip_pvt *p, int sipmethod, int inc, enum xmittype reliable, int newbranch);
@@ -2321,6 +2325,46 @@ static void add_blank(struct sip_request *req)
 	}
 }
 
+static int send_provisional_keepalive_full(struct sip_pvt *pvt, int with_sdp)
+{
+	const char *msg = NULL;
+
+	if (!pvt->last_provisional || !strncasecmp(pvt->last_provisional, "100", 3)) {
+		msg = "183 Session Progress";
+	}
+
+	if (pvt->invitestate < INV_COMPLETED) {
+		if (with_sdp) {
+			transmit_response_with_sdp(pvt, S_OR(msg, pvt->last_provisional), &pvt->initreq, XMIT_UNRELIABLE);
+		} else {
+			transmit_response(pvt, S_OR(msg, pvt->last_provisional), &pvt->initreq);
+		}
+		return PROVIS_KEEPALIVE_TIMEOUT;
+	}
+
+	return 0;
+}
+
+static int send_provisional_keepalive(const void *data) {
+	struct sip_pvt *pvt = (struct sip_pvt *) data;
+
+	return send_provisional_keepalive_full(pvt, 0);
+}
+
+static int send_provisional_keepalive_with_sdp(const void *data) {
+	struct sip_pvt *pvt = (void *)data;
+
+	return send_provisional_keepalive_full(pvt, 1);
+}
+
+static void update_provisional_keepalive(struct sip_pvt *pvt, int with_sdp)
+{
+	AST_SCHED_DEL(sched, pvt->provisional_keepalive_sched_id);
+
+	pvt->provisional_keepalive_sched_id = ast_sched_add(sched, PROVIS_KEEPALIVE_TIMEOUT,
+		with_sdp ? send_provisional_keepalive_with_sdp : send_provisional_keepalive, pvt);
+}
+
 /*! \brief Transmit response on SIP request*/
 static int send_response(struct sip_pvt *p, struct sip_request *req, enum xmittype reliable, int seqno)
 {
@@ -2341,6 +2385,12 @@ static int send_response(struct sip_pvt *p, struct sip_request *req, enum xmitty
 		append_history(p, reliable ? "TxRespRel" : "TxResp", "%s / %s - %s", tmp.data, get_header(&tmp, "CSeq"), 
 			(tmp.method == SIP_RESPONSE || tmp.method == SIP_UNKNOWN) ? tmp.rlPart2 : sip_methods[tmp.method].text);
 	}
+
+	/* If we are sending a final response to an INVITE, stop retransmitting provisional responses */
+	if (p->initreq.method == SIP_INVITE && reliable == XMIT_CRITICAL) {
+		AST_SCHED_DEL(sched, p->provisional_keepalive_sched_id);
+	}
+
 	res = (reliable) ?
 		 __sip_reliable_xmit(p, seqno, 1, req->data, req->len, (reliable == XMIT_CRITICAL), req->method) :
 		__sip_xmit(p, req->data, req->len);
@@ -3228,6 +3278,7 @@ static int __sip_destroy(struct sip_pvt *p, int lockowner)
 	AST_SCHED_DEL(sched, p->waitid);
 	AST_SCHED_DEL(sched, p->autokillid);
 	AST_SCHED_DEL(sched, p->request_queue_sched_id);
+	AST_SCHED_DEL(sched, p->provisional_keepalive_sched_id);
 
 	if (p->rtp) {
 		ast_rtp_destroy(p->rtp);
@@ -3844,7 +3895,7 @@ static int sip_write(struct ast_channel *ast, struct ast_frame *frame)
 				    !ast_test_flag(&p->flags[0], SIP_OUTGOING)) {
 					ast_rtp_new_source(p->rtp);
 					p->invitestate = INV_EARLY_MEDIA;
-					transmit_response_with_sdp(p, "183 Session Progress", &p->initreq, XMIT_UNRELIABLE);
+					transmit_provisional_response(p, "183 Session Progress", &p->initreq, 1);
 					ast_set_flag(&p->flags[0], SIP_PROGRESS_SENT);
 				} else if (p->t38.state == T38_ENABLED && !p->t38.direct) {
 					p->t38.state = T38_DISABLED;
@@ -3866,7 +3917,7 @@ static int sip_write(struct ast_channel *ast, struct ast_frame *frame)
 				    !ast_test_flag(&p->flags[0], SIP_PROGRESS_SENT) &&
 				    !ast_test_flag(&p->flags[0], SIP_OUTGOING)) {
 					p->invitestate = INV_EARLY_MEDIA;
-					transmit_response_with_sdp(p, "183 Session Progress", &p->initreq, XMIT_UNRELIABLE);
+					transmit_provisional_response(p, "183 Session Progress", &p->initreq, 1);
 					ast_set_flag(&p->flags[0], SIP_PROGRESS_SENT);	
 				}
 				p->lastrtptx = time(NULL);
@@ -4037,7 +4088,7 @@ static int sip_indicate(struct ast_channel *ast, int condition, const void *data
 			if (!ast_test_flag(&p->flags[0], SIP_PROGRESS_SENT) ||
 			    (ast_test_flag(&p->flags[0], SIP_PROG_INBAND) == SIP_PROG_INBAND_NEVER)) {				
 				/* Send 180 ringing if out-of-band seems reasonable */
-				transmit_response(p, "180 Ringing", &p->initreq);
+				transmit_provisional_response(p, "180 Ringing", &p->initreq, 0);
 				ast_set_flag(&p->flags[0], SIP_RINGING);
 				if (ast_test_flag(&p->flags[0], SIP_PROG_INBAND) != SIP_PROG_INBAND_YES)
 					break;
@@ -4082,7 +4133,7 @@ static int sip_indicate(struct ast_channel *ast, int condition, const void *data
 		    !ast_test_flag(&p->flags[0], SIP_PROGRESS_SENT) &&
 		    !ast_test_flag(&p->flags[0], SIP_OUTGOING)) {
 			p->invitestate = INV_EARLY_MEDIA;
-			transmit_response_with_sdp(p, "183 Session Progress", &p->initreq, XMIT_UNRELIABLE);
+			transmit_provisional_response(p, "183 Session Progress", &p->initreq, 1);
 			ast_set_flag(&p->flags[0], SIP_PROGRESS_SENT);	
 			break;
 		}
@@ -4594,6 +4645,7 @@ static struct sip_pvt *sip_alloc(ast_string_field callid, struct sockaddr_in *si
 	p->waitid = -1;
 	p->autokillid = -1;
 	p->request_queue_sched_id = -1;
+	p->provisional_keepalive_sched_id = -1;
 	p->subscribed = NONE;
 	p->stateid = -1;
 	p->prefs = default_prefs;		/* Set default codecs for this call */
@@ -6519,6 +6571,19 @@ static int transmit_response_with_auth(struct sip_pvt *p, const char *msg, const
 	return send_response(p, &resp, reliable, seqno);
 }
 
+/* Only use a static string for the msg, here! */
+static int transmit_provisional_response(struct sip_pvt *p, const char *msg, const struct sip_request *req, int with_sdp)
+{
+	int res;
+
+	if (!(res = with_sdp ? transmit_response_with_sdp(p, msg, req, XMIT_UNRELIABLE) : transmit_response(p, msg, req))) {
+		p->last_provisional = msg;
+		update_provisional_keepalive(p, with_sdp);
+	}
+
+	return res;
+}
+
 /*! \brief Add text body to SIP message */
 static int add_text(struct sip_request *req, const char *text)
 {
@@ -14975,7 +15040,7 @@ static int handle_request_invite(struct sip_pvt *p, struct sip_request *req, int
 		case AST_STATE_DOWN:
 			if (option_debug > 1)
 				ast_log(LOG_DEBUG, "%s: New call is still down.... Trying... \n", c->name);
-			transmit_response(p, "100 Trying", req);
+			transmit_provisional_response(p, "100 Trying", req, 0);
 			p->invitestate = INV_PROCEEDING;
 			ast_setstate(c, AST_STATE_RING);
 			if (strcmp(p->exten, ast_pickup_ext())) {	/* Call to extension -start pbx on this call */
@@ -15039,11 +15104,11 @@ static int handle_request_invite(struct sip_pvt *p, struct sip_request *req, int
 			}
 			break;
 		case AST_STATE_RING:
-			transmit_response(p, "100 Trying", req);
+			transmit_provisional_response(p, "100 Trying", req, 0);
 			p->invitestate = INV_PROCEEDING;
 			break;
 		case AST_STATE_RINGING:
-			transmit_response(p, "180 Ringing", req);
+			transmit_provisional_response(p, "180 Ringing", req, 0);
 			p->invitestate = INV_PROCEEDING;
 			break;
 		case AST_STATE_UP: