dialog: fix multi-PRACK CSeq handling and uac-auth ACK CSeq regression

* fix CSeq regression on the outbound leg, prioritize .last_gen_cseq
* manual PRACK: fix matching for current leg (multi-180 scenario)
* manual PRACK: add logic for early leg creation during onreply_route.
    This allows the leg to be correctly matched and have its CSeq set.
* small fix: avoid overwriting .last_gen_cseq with smaller values

Author: liviuchircu

modules/dialog/dialog.c

@@ -2608,11 +2608,16 @@ static int dlg_send_sequential(struct sip_msg* msg, str *method, int leg,
 			return rc;
 	}
 
-	if (is_prack && msg && msg->first_line.type == SIP_REPLY)
+	if (is_prack && msg && msg->first_line.type == SIP_REPLY) {
+		if (leg != DLG_CALLER_LEG) {
+			rc = dlg_ensure_reply_leg(dlg, msg);
+			if (rc > 0)
+				leg = rc;
+		}
 		rc = send_prack_indialog_request(dlg, msg,
-				(leg == DLG_CALLER_LEG ? leg : callee_idx(dlg)), body, ct,
+				leg, body, ct,
 				(req_headers.s ? &req_headers : headers), NULL, NULL, NULL);
-	else
+	} else
 		rc = send_indialog_request(dlg, method,
 				(leg == DLG_CALLER_LEG ? leg : callee_idx(dlg)),
 				body, ct, (req_headers.s ? &req_headers : headers),

modules/dialog/dlg_handlers.c

@@ -700,8 +700,15 @@ static inline void push_reply_in_dialog(struct sip_msg *req, struct sip_msg *rpl
 			if (str2int( &(get_cseq(rpl)->number), &cseq_no) < 0) {
 				LM_ERR("Failed to convert cseq to integer \n");
 			} else {
-				LM_DBG("last_gen_cseq = cseq_no [%d] for method id [%d]\n", cseq_no, get_cseq(rpl)->method_id);
-				dlg->legs[dlg->legs_no[DLG_LEG_200OK]].last_gen_cseq = cseq_no;
+				if (dlg->legs[dlg->legs_no[DLG_LEG_200OK]].last_gen_cseq < cseq_no) {
+					LM_DBG("updating last_gen_cseq to reply cseq [%d] for method id [%d]\n",
+						cseq_no, get_cseq(rpl)->method_id);
+					dlg->legs[dlg->legs_no[DLG_LEG_200OK]].last_gen_cseq = cseq_no;
+				} else {
+					LM_DBG("keeping higher last_gen_cseq [%d] over reply cseq [%d] for method id [%d]\n",
+						dlg->legs[dlg->legs_no[DLG_LEG_200OK]].last_gen_cseq,
+						cseq_no, get_cseq(rpl)->method_id);
+				}
 			}
 		}
 
@@ -726,6 +733,21 @@ static inline void push_reply_in_dialog(struct sip_msg *req, struct sip_msg *rpl
 	dlg_unlock_dlg(dlg);
 }
 
+/* Manual PRACK may be generated from onreply_route before the dialog reply
+ * callback has materialized the current early-dialog leg. Push the reply into
+ * dialog state first, then return the matched/newly-created callee leg. */
+int dlg_ensure_reply_leg(struct dlg_cell *dlg, struct sip_msg *rpl)
+{
+	long leg_idx = -1;
+	str empty = {0, 0};
+
+	if (!dlg || !rpl || rpl == FAKED_REPLY)
+		return -1;
+
+	push_reply_in_dialog(NULL, rpl, NULL, dlg, &empty, &empty, &leg_idx);
+	return (int)leg_idx;
+}
+
 static void _dlg_setup_reinvite_callbacks(struct cell *t, struct sip_msg *req,
 		struct dlg_cell *dlg);
 
@@ -2415,13 +2437,13 @@ void dlg_onroute(struct sip_msg* req, str *route_params, void *param)
 				LM_DBG("dlg_leg_get_cseq(dlg, [%d], req)\n", src_leg);
 				update_val = dlg_leg_get_cseq(dlg, src_leg, req);
 				if (update_val == 0) {
-					if (str2int(&dlg->legs[src_leg].inv_cseq, &update_val) == 0) {
+					if (dlg->legs[dst_leg].last_gen_cseq) {
+						LM_DBG("using last generated cseq [%d] for ACK on leg [%d]\n",
+							dlg->legs[dst_leg].last_gen_cseq, dst_leg);
+						update_val = dlg->legs[dst_leg].last_gen_cseq;
+					} else if (str2int(&dlg->legs[src_leg].inv_cseq, &update_val) == 0) {
 						LM_DBG("using INVITE cseq [%d] for ACK on leg [%d]\n",
 							update_val, src_leg);
-					} else if (dlg->legs[dst_leg].last_gen_cseq) {
-						LM_DBG("dlg->legs[%d].last_gen_cseq=[%d]\n",
-							dst_leg, dlg->legs[dst_leg].last_gen_cseq);
-						update_val = dlg->legs[dst_leg].last_gen_cseq;
 					} else {
 						update_val = 0;
 					}

modules/dialog/dlg_handlers.h

@@ -143,6 +143,7 @@ int send_prack_indialog_request(struct dlg_cell *dlg, struct sip_msg *rpl,
 		void *param, indialog_release_f release);
 int dlg_prepare_prack_headers(struct sip_msg *msg, str *headers, str *out,
 		int enforce_onreply_route);
+int dlg_ensure_reply_leg(struct dlg_cell *dlg, struct sip_msg *rpl);
 
 void unreference_dialog(void *dialog);
 

modules/dialog/dlg_req_within.c

@@ -229,6 +229,32 @@ static struct dlg_auto_prack_ctx *dlg_build_auto_prack_ctx(struct sip_msg *rpl)
 	return ctx;
 }
 
+/* Resolve the PRACK leg by matching the reply To-tag,
+ * use the current primary callee as a default. */
+static int dlg_get_prack_leg(struct dlg_cell *dlg, struct sip_msg *rpl, int dst_leg)
+{
+	str *tag;
+	int i;
+
+	if (!rpl)
+		return dst_leg;
+	if ((!rpl->to && parse_headers(rpl, HDR_TO_F, 0) < 0) || !rpl->to)
+		return dst_leg;
+
+	tag = &get_to(rpl)->tag_value;
+	if (!tag->len)
+		return dst_leg;
+
+	for (i = DLG_FIRST_CALLEE_LEG; i < dlg->legs_no[DLG_LEGS_USED]; i++) {
+		if (dlg->legs[i].tag.len != tag->len)
+			continue;
+		if (strncmp(dlg->legs[i].tag.s, tag->s, tag->len) == 0)
+			return i;
+	}
+
+	return dst_leg;
+}
+
 int free_tm_dlg(dlg_t *td)
 {
 	if(td)
@@ -1406,6 +1432,8 @@ int send_prack_indialog_request(struct dlg_cell *dlg, struct sip_msg *rpl,
 	dlg_t *dialog_info = NULL;
 	int result;
 
+	dstleg = dlg_get_prack_leg(dlg, rpl, dstleg);
+
 	if (!dlg_get_leg_hdrs(dlg, other_leg(dlg, dstleg), dstleg, ct, hdrs,
 			&extra_headers)) {
 		LM_ERR("could not build extra headers!\n");