chan_sip: keep same local (from) tag for outgoing register requests

For outbound register requests the tag on the From line was
updated every 20 seconds prior to a successful registration
and also once for each registration renewal.  That behavior
can possibly cause the registration to be denied because of
the different tag, and is not aligned with the intention of
RFC 3261 8.1.3.5 "... request constitutes a new transaction
and SHOULD have the same value of the Call-ID, To, and From
of the previous request...".  This updates chan_sip to have
a field to keep the local tag in the registration structure
and use that tag for registration requests where the callid
is also unchanged.

(closes issue ASTERISK-12117)
Reported by: Pawel Pierscionek
Review: https://reviewboard.asterisk.org/r/2988/
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Merged revisions 402604 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 402605 from http://svn.asterisk.org/svn/asterisk/branches/11
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Merged revisions 402606 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@402607 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -1483,6 +1483,7 @@ static char *generate_random_string(char *buf, size_t size);
 static void build_callid_pvt(struct sip_pvt *pvt);
 static void change_callid_pvt(struct sip_pvt *pvt, const char *callid);
 static void build_callid_registry(struct sip_registry *reg, const struct ast_sockaddr *ourip, const char *fromdomain);
+static void build_localtag_registry(struct sip_registry *reg);
 static void make_our_tag(struct sip_pvt *pvt);
 static int add_header(struct sip_request *req, const char *var, const char *value);
 static int add_max_forwards(struct sip_pvt *dialog, struct sip_request *req);
@@ -8759,6 +8760,12 @@ static void build_callid_registry(struct sip_registry *reg, const struct ast_soc
 	ast_string_field_build(reg, callid, "%s@%s", generate_random_string(buf, sizeof(buf)), host);
 }
 
+/*! \brief Build SIP From tag value for REGISTER */
+static void build_localtag_registry(struct sip_registry *reg)
+{
+	ast_string_field_build(reg, localtag, "as%08lx", ast_random());
+}
+
 /*! \brief Make our SIP dialog tag */
 static void make_our_tag(struct sip_pvt *pvt)
 {
@@ -15396,13 +15403,13 @@ static int transmit_register(struct sip_registry *r, int sipmethod, const char *
 			return 0;
 		} else {
 			p = dialog_ref(r->call, "getting a copy of the r->call dialog in transmit_register");
-			make_our_tag(p);	/* create a new local tag for every register attempt */
 			ast_string_field_set(p, theirtag, NULL);	/* forget their old tag, so we don't match tags when getting response */
 		}
 	} else {
 		/* Build callid for registration if we haven't registered before */
 		if (!r->callid_valid) {
 			build_callid_registry(r, &internip, default_fromdomain);
+			build_localtag_registry(r);
 			r->callid_valid = TRUE;
 		}
 		/* Allocate SIP dialog for registration */
@@ -15411,6 +15418,9 @@ static int transmit_register(struct sip_registry *r, int sipmethod, const char *
 			return 0;
 		}
 
+		/* reset tag to consistent value from registry */
+		ast_string_field_set(p, tag, r->localtag);
+
 		if (p->do_history) {
 			append_history(p, "RegistryInit", "Account: %s@%s", r->username, r->hostname);
 		}

channels/sip/include/sip.h

@@ -1390,6 +1390,7 @@ struct sip_registry {
 		AST_STRING_FIELD(md5secret);  /*!< Password in md5 */
 		AST_STRING_FIELD(callback);   /*!< Contact extension */
 		AST_STRING_FIELD(peername);   /*!< Peer registering to */
+		AST_STRING_FIELD(localtag);   /*!< Local tag generated same time as callid */
 	);
 	enum ast_transport transport;   /*!< Transport for this registration UDP, TCP or TLS */
 	int portno;                     /*!< Optional port override */