sipsess: fix PRACK offer/answer behavior (#430)

* sipsess: fix PRACK offer/answer behavior

According to RFC 3262, PRACKs and reliable 1xx responses can contain
both SDP answers and offers. E.g. if a reliable 1xx response contains an
offer, the PRACK MUST contain an answer.

* sipsess: handle stateless reply_2xx correctly

Co-authored-by: Christian Spielberger <c.spielberger@commend.com>

src/sipsess/connect.c

@@ -88,7 +88,21 @@ static void invite_resp_handler(int err, const struct sip_msg *msg, void *arg)
 		if (sip_msg_hdr_has_value(msg, SIP_HDR_REQUIRE, "100rel")
 				&& sess->rel100_supported) {
 
-			err = sip_dialog_established(sess->dlg) ?
+			if (msg && mbuf_get_left(msg->mb)) {
+				if (sess->sent_offer) {
+					sess->awaiting_answer = false;
+					err = sess->answerh(msg, sess->arg);
+					if (err)
+						goto out;
+				}
+				else {
+					sess->modify_pending = false;
+					err = sess->offerh(&desc, msg,
+							   sess->arg);
+				}
+			}
+
+			err |= sip_dialog_established(sess->dlg) ?
 					sip_dialog_update(sess->dlg, msg) :
 					sip_dialog_create(sess->dlg, msg);
 			err |= sipsess_prack(sess, msg->cseq.num, msg->rel_seq,

src/sipsess/listen.c

@@ -190,12 +190,12 @@ static void ack_handler(struct sipsess_sock *sock, const struct sip_msg *msg)
 static void prack_handler(struct sipsess_sock *sock, const struct sip_msg *msg)
 {
 	struct sipsess *sess;
-	bool awaiting_answer;
-	int err = 0;
+	struct mbuf *desc = NULL;
+	bool awaiting_answer = false;
 
 	sess = sipsess_find(sock, msg);
 
-	if (!sess || sipsess_reply_prack(sess, msg, &awaiting_answer)) {
+	if (!sess || sipsess_reply_ack(sess, msg, &awaiting_answer)) {
 		(void)sip_reply(sock->sip, msg, 481,
 				"Transaction Does Not Exist");
 		return;
@@ -212,11 +212,15 @@ static void prack_handler(struct sipsess_sock *sock, const struct sip_msg *msg)
 
 	if (awaiting_answer) {
 		sess->awaiting_answer = false;
-		err = sess->answerh(msg, sess->arg);
+		(void)sess->answerh(msg, sess->arg);
+	}
+	else if (msg && mbuf_get_left(msg->mb)) {
+		(void)sess->offerh(&desc, msg, sess->arg);
 	}
 
-	if (err)
-		sipsess_terminate(sess, err, NULL);
+	(void)sipsess_reply_2xx(sess, msg, 200, "OK", desc, NULL, NULL);
+
+	mem_deref(desc);
 }
 
 

src/sipsess/reply.c

@@ -87,25 +87,28 @@ int sipsess_reply_2xx(struct sipsess *sess, const struct sip_msg *msg,
 		      uint16_t scode, const char *reason, struct mbuf *desc,
 		      const char *fmt, va_list *ap)
 {
-	struct sipsess_reply *reply;
+	struct sipsess_reply *reply = NULL;
 	struct sip_contact contact;
-	bool is_prack = false;
 	int err = ENOMEM;
+	bool is_prack = !pl_strcmp(&msg->met, "PRACK");
 
-	reply = mem_zalloc(sizeof(*reply), destructor);
-	if (!reply)
-		goto out;
+	if (!is_prack) {
+		reply = mem_zalloc(sizeof(*reply), destructor);
+		if (!reply)
+			goto out;
 
-	list_append(&sess->replyl, &reply->le, reply);
-	reply->rel_seq = 0;
-	reply->seq  = msg->cseq.num;
-	reply->msg  = mem_ref((void *)msg);
-	reply->sess = sess;
+		list_append(&sess->replyl, &reply->le, reply);
+
+		reply->rel_seq = 0;
+		reply->seq  = msg->cseq.num;
+		reply->msg  = mem_ref((void *)msg);
+		reply->sess = sess;
+	}
 
-	is_prack = !pl_strcmp(&msg->met, "PRACK");
 	sip_contact_set(&contact, sess->cuser, &msg->dst, msg->tp);
 
-	err = sip_treplyf(is_prack ? NULL : &sess->st, &reply->mb, sess->sip,
+	err = sip_treplyf(is_prack ? NULL : &sess->st,
+			  reply ? &reply->mb : NULL, sess->sip,
 			  msg, true, scode, reason,
 			  "%H"
 			  "%v"
@@ -125,17 +128,14 @@ int sipsess_reply_2xx(struct sipsess *sess, const struct sip_msg *msg,
 	if (err)
 		goto out;
 
-	if (!is_prack) {
+	if (reply) {
 		tmr_start(&reply->tmr, 64 * SIP_T1, tmr_handler, reply);
 		tmr_start(&reply->tmrg, SIP_T1, retransmit_handler, reply);
-	}
-	else {
-		mem_deref(reply);
-	}
 
-	if (!mbuf_get_left(msg->mb) && desc) {
-		reply->awaiting_answer = true;
-		sess->awaiting_answer = true;
+		if (!mbuf_get_left(msg->mb) && desc) {
+			reply->awaiting_answer = true;
+			sess->awaiting_answer = true;
+		}
 	}
 
  out:
@@ -283,23 +283,3 @@ int sipsess_reply_ack(struct sipsess *sess, const struct sip_msg *msg,
 
 	return 0;
 }
-
-
-int sipsess_reply_prack(struct sipsess *sess, const struct sip_msg *msg,
-		      bool *awaiting_answer)
-{
-	struct sipsess_reply *reply;
-	int err;
-
-	reply = list_ledata(list_apply(&sess->replyl, false, cmp_handler,
-				       (void *)msg));
-	if (!reply)
-		return ENOENT;
-
-	*awaiting_answer = reply->awaiting_answer;
-	err = sipsess_reply_2xx(sess, msg, 200, "OK", NULL, NULL, NULL);
-
-	mem_deref(reply);
-
-	return err;
-}

src/sipsess/sipsess.h

@@ -94,8 +94,6 @@ int  sipsess_reply_1xx(struct sipsess *sess, const struct sip_msg *msg,
 		       const char *fmt, va_list *ap);
 int  sipsess_reply_ack(struct sipsess *sess, const struct sip_msg *msg,
 		       bool *awaiting_answer);
-int  sipsess_reply_prack(struct sipsess *sess, const struct sip_msg *msg,
-			 bool *awaiting_answer);
 int  sipsess_reinvite(struct sipsess *sess, bool reset_ls);
 int  sipsess_bye(struct sipsess *sess, bool reset_ls);
 int  sipsess_request_alloc(struct sipsess_request **reqp, struct sipsess *sess,