option to ignore low CSeq for NOTIFY for old event sub implementations

new sems.conf option:

  Ignore too low CSeq for NOTIFYs? [yes | no]

 May be necessary to interwork with simplistic/old (following 3265
 instead of 5057) SIP event notification implementations.

 ignore_notify_lower_cseq=yes

Conflicts:

	core/AmSipDialog.cpp

core/AmConfig.cpp

@@ -77,6 +77,7 @@ string       AmConfig::NextHopIP               = "";
 unsigned int AmConfig::NextHopPort             = 0;
 bool         AmConfig::NextHopForReplies       = false;
 bool         AmConfig::ProxyStickyAuth         = false;
+bool         AmConfig::IgnoreNotifyLowerCSeq   = false;
 bool         AmConfig::DisableDNSSRV           = false;
 string       AmConfig::Signature               = "";
 unsigned int AmConfig::MaxForwards             = MAX_FORWARDS;
@@ -309,6 +310,10 @@ int AmConfig::readConfiguration()
     ProxyStickyAuth = (cfg.getParameter("proxy_sticky_auth") == "yes");
   }
 
+  if(cfg.hasParameter("ignore_notify_lower_cseq")) {
+    IgnoreNotifyLowerCSeq = (cfg.getParameter("ignore_notify_lower_cseq") == "yes");
+  }
+
   if(cfg.hasParameter("disable_dns_srv")) {
     DisableDNSSRV = (cfg.getParameter("disable_dns_srv") == "yes");
   }

core/AmConfig.h

@@ -134,6 +134,8 @@ struct AmConfig
   static bool NextHopForReplies;
   /** update ruri-host to previously resolved IP:port on SIP auth */
   static bool ProxyStickyAuth;
+  /** Ignore Low CSeq on NOTIFY  - for RFC 3265 instead of 5057 */
+  static bool IgnoreNotifyLowerCSeq;
   /** skip DNS SRV lookup for resolving destination address*/
   static bool DisableDNSSRV;
   /** Server/User-Agent header (optional) */

core/AmSipDialog.cpp

@@ -110,19 +110,25 @@ void AmSipDialog::updateStatus(const AmSipRequest& req)
 
   // Sanity checks
   if (r_cseq_i && req.cseq <= r_cseq){
-    INFO("remote cseq lower than previous ones - refusing request\n");
-    // see 12.2.2
-    string hdrs;
-    if (req.method == "NOTIFY") {
-      // clever trick to not break subscription dialog usage
-      // for implementations which follow 3265 instead of 5057
-      hdrs = SIP_HDR_COLSP(SIP_HDR_RETRY_AFTER)  "0"  CRLF;
+    string hdrs; bool i = false;
+    if (req.method == SIP_METH_NOTIFY) {
+      if (AmConfig::IgnoreNotifyLowerCSeq)
+	i = true;
+      else
+	// clever trick to not break subscription dialog usage
+	// for implementations which follow 3265 instead of 5057
+	hdrs = SIP_HDR_COLSP(SIP_HDR_RETRY_AFTER)  "0"  CRLF;
     }
 
-    reply_error(req, 500, SIP_REPLY_SERVER_INTERNAL_ERROR, hdrs,
-		next_hop_for_replies ? next_hop_ip : "",
-		next_hop_for_replies ? next_hop_port : 0);
-    return;
+    if (!i) {
+      INFO("remote cseq lower than previous ones - refusing request\n");
+      // see 12.2.2
+      reply_error(req, 500, SIP_REPLY_SERVER_INTERNAL_ERROR, hdrs,
+		  next_hop_for_replies ? next_hop_ip : "",
+		  next_hop_for_replies ? next_hop_port : 0);
+
+      return;
+    }
   }
 
   if (req.method == "INVITE") {

core/AmSipHeaders.h

@@ -9,6 +9,7 @@
 #define SIP_METH_UPDATE         "UPDATE"
 #define SIP_METH_BYE            "BYE"
 #define SIP_METH_ACK            "ACK"
+#define SIP_METH_NOTIFY         "NOTIFY"
 
 #define SIP_HDR_FROM            "From"
 #define SIP_HDR_TO              "To"

core/etc/sems.conf.sample

@@ -525,6 +525,13 @@ use_default_signature=yes
 #
 # proxy_sticky_auth=yes
 
+# Ignore too low CSeq for NOTIFYs? [yes | no]
+#
+# May be necessary to interwork with simplistic/old SIP event notification 
+# implementations.
+#
+#ignore_notify_lower_cseq=yes
+
 #
 # Accept final replies without To-tag? [yes|no]
 #