fix: always update dialog remote tag from message

Remove conditional remote tag checks and ensure tag is always updated
from incoming message's To header. This fixes inconsistencies in dialog
state management and improves reliability of SIP message handling across
all response types (including 503 and other error responses).

PySIP/sip_call.py

@@ -641,8 +641,7 @@ async def message_handler(self, msg: SipMessage):
 
         if msg.status == SIPStatus(401) and msg.method == "INVITE":
             # Handling the auth of the invite
-            if not self.dialogue.remote_tag:
-                self.dialogue.remote_tag = msg.to_tag or ""
+            self.dialogue.remote_tag = msg.to_tag
             transaction = self.dialogue.find_transaction(msg.branch)
             if not transaction:
                 return
@@ -664,8 +663,7 @@ async def message_handler(self, msg: SipMessage):
             and self.username not in msg.get_header("To")
         ):
             # Handling successfull invite response
-            if not self.dialogue.remote_tag:
-                self.dialogue.remote_tag = msg.to_tag or ""  # setting it if not set
+            self.dialogue.remote_tag = msg.to_tag or ""  # setting it if not set
             logger.log(logging.DEBUG, "INVITE Successfull, dialog is established.")
             transaction = self.dialogue.add_transaction(
                 self.sip_core.gen_branch(), "ACK"
@@ -683,8 +681,7 @@ async def message_handler(self, msg: SipMessage):
                 CallState.RINGING if msg.status is SIPStatus(180) else CallState.DIALING
             )
             await self.update_call_state(st)
-            if not self.dialogue.remote_tag:
-                self.dialogue.remote_tag = msg.to_tag or ""  # setting it if not already
+            self.dialogue.remote_tag = msg.to_tag or ""  # setting it if not already
             self.dialogue.auth_retry_count = 0  # reset the auth counter
             pass
 
@@ -751,8 +748,8 @@ async def error_handler(self, msg: SipMessage):
         if not msg.status:
             return
 
-        if not self.dialogue.remote_tag:
-            self.dialogue.remote_tag = msg.to_tag or ""
+        # reset the remote tag
+        self.dialogue.remote_tag = msg.to_tag or ""
 
         if not 400 <= msg.status.code <= 699:
             return