isisd: fix circuit state machine

isisd has a so-called circuit state machine that takes care about
the interface state changes, such as initializing, down, up. When
an interface was brought down by a link failure, the interface
information was deleted and set to NULL. When the link was restored
later, the interface was looked up by the old pointer, but since it
was cleared, it was never found again, resulting in an interface
never entering the up state again.

Also, the program regularly crashed because of a deleted pointer in
the same context which was later accessed without any further
checking.

Signed-off-by: Fritz Reichmann <fritz@reichmann.nl>

1 files changed, 69 insertions, 60 deletions

diff --git a/isisd/isis_pdu.c b/isisd/isis_pdu.c
index 0896d540..4c602eea 100644
--- a/isisd/isis_pdu.c
+++ b/isisd/isis_pdu.c
@@ -1916,6 +1916,9 @@ send_hello (struct isis_circuit *circuit, int level)
   unsigned long len_pointer, length;
   int retval;
 
+  if (circuit->state != C_STATE_UP || circuit->interface == NULL)
+    return ISIS_WARNING;
+
   if (circuit->interface->mtu == 0)
     {
       zlog_warn ("circuit has zero MTU");
@@ -2222,6 +2225,9 @@ send_csnp (struct isis_circuit *circuit, int level)
   struct listnode *node;
   struct isis_lsp *lsp;
 
+  if (circuit->state != C_STATE_UP || circuit->interface == NULL)
+    return ISIS_WARNING;
+
   memset (start, 0x00, ISIS_SYS_ID_LEN + 2);
   memset (stop, 0xff, ISIS_SYS_ID_LEN + 2);
 
@@ -2387,6 +2393,9 @@ send_psnp (int level, struct isis_circuit *circuit)
   struct list *list = NULL;
   struct listnode *node;
 
+  if (circuit->state != C_STATE_UP || circuit->interface == NULL)
+    return ISIS_WARNING;
+
   if ((circuit->circ_type == CIRCUIT_T_BROADCAST &&
        !circuit->u.bc.is_dr[level - 1]) ||
       circuit->circ_type != CIRCUIT_T_BROADCAST)
@@ -2493,85 +2502,85 @@ send_lsp (struct thread *thread)
   circuit = THREAD_ARG (thread);
   assert (circuit);
 
-  if (circuit->state == C_STATE_UP)
+  if (circuit->state != C_STATE_UP || circuit->interface == NULL)
+    return ISIS_WARNING;
+
+  lsp = listgetdata ((node = listhead (circuit->lsp_queue)));
+
+  /*
+   * Do not send if levels do not match
+   */
+  if (!(lsp->level & circuit->circuit_is_type))
+    goto dontsend;
+
+  /*
+   * Do not send if we do not have adjacencies in state up on the circuit
+   */
+  if (circuit->upadjcount[lsp->level - 1] == 0)
+    goto dontsend;
+  /* only send if it needs sending */
+  if ((time (NULL) - lsp->last_sent) >=
+      circuit->area->lsp_gen_interval[lsp->level - 1])
     {
-      lsp = listgetdata ((node = listhead (circuit->lsp_queue)));
 
-      /*
-       * Do not send if levels do not match
-       */
-      if (!(lsp->level & circuit->circuit_is_type))
-	goto dontsend;
+      if (isis->debugs & DEBUG_UPDATE_PACKETS)
+	{
+	  zlog_debug
+	    ("ISIS-Upd (%s): Sent L%d LSP %s, seq 0x%08x, cksum 0x%04x,"
+	     " lifetime %us on %s", circuit->area->area_tag, lsp->level,
+	     rawlspid_print (lsp->lsp_header->lsp_id),
+	     ntohl (lsp->lsp_header->seq_num),
+	     ntohs (lsp->lsp_header->checksum),
+	     ntohs (lsp->lsp_header->rem_lifetime),
+	     circuit->interface->name);
+	}
+	/* copy our lsp to the send buffer */
+	stream_copy (circuit->snd_stream, lsp->pdu);
+
+	retval = circuit->tx (circuit, lsp->level);
 
       /*
-       * Do not send if we do not have adjacencies in state up on the circuit
+       * If the sending succeeded, we can del the lsp from circuits
+       * lsp_queue
        */
-      if (circuit->upadjcount[lsp->level - 1] == 0)
-	goto dontsend;
-      /* only send if it needs sending */
-      if ((time (NULL) - lsp->last_sent) >=
-	  circuit->area->lsp_gen_interval[lsp->level - 1])
+      if (retval == ISIS_OK)
 	{
-
-	  if (isis->debugs & DEBUG_UPDATE_PACKETS)
-	    {
-	      zlog_debug
-		("ISIS-Upd (%s): Sent L%d LSP %s, seq 0x%08x, cksum 0x%04x,"
-		 " lifetime %us on %s", circuit->area->area_tag, lsp->level,
-		 rawlspid_print (lsp->lsp_header->lsp_id),
-		 ntohl (lsp->lsp_header->seq_num),
-		 ntohs (lsp->lsp_header->checksum),
-		 ntohs (lsp->lsp_header->rem_lifetime),
-		 circuit->interface->name);
-	    }
-	  /* copy our lsp to the send buffer */
-	  stream_copy (circuit->snd_stream, lsp->pdu);
-
-	  retval = circuit->tx (circuit, lsp->level);
+	  list_delete_node (circuit->lsp_queue, node);
 
 	  /*
-	   * If the sending succeeded, we can del the lsp from circuits
-	   * lsp_queue
+	   * On broadcast circuits also the SRMflag can be cleared
 	   */
-	  if (retval == ISIS_OK)
-	    {
-	      list_delete_node (circuit->lsp_queue, node);
+	  if (circuit->circ_type == CIRCUIT_T_BROADCAST)
+	    ISIS_CLEAR_FLAG (lsp->SRMflags, circuit);
 
+	  if (flags_any_set (lsp->SRMflags) == 0)
+	    {
 	      /*
-	       * On broadcast circuits also the SRMflag can be cleared
+	       * need to remember when we were last sent
 	       */
-	      if (circuit->circ_type == CIRCUIT_T_BROADCAST)
-		ISIS_CLEAR_FLAG (lsp->SRMflags, circuit);
-
-	      if (flags_any_set (lsp->SRMflags) == 0)
-		{
-		  /*
-		   * need to remember when we were last sent
-		   */
-		  lsp->last_sent = time (NULL);
-		}
-	    }
-	  else
-	    {
-	      zlog_debug ("sending of level %d link state failed", lsp->level);
+	      lsp->last_sent = time (NULL);
 	    }
 	}
       else
 	{
-	  /* my belief is that if it wasn't his time, the lsp can be removed
-	   * from the queue
-	   */
-	dontsend:
-	  list_delete_node (circuit->lsp_queue, node);
+	  zlog_debug ("sending of level %d link state failed", lsp->level);
 	}
-#if 0
-      /*
-       * If there are still LSPs send next one after lsp-interval (33 msecs)
+    }
+  else
+    {
+      /* my belief is that if it wasn't his time, the lsp can be removed
+       * from the queue
        */
-      if (listcount (circuit->lsp_queue) > 0)
-	thread_add_timer (master, send_lsp, circuit, 1);
-#endif
+    dontsend:
+      list_delete_node (circuit->lsp_queue, node);
     }
+#if 0
+  /*
+   * If there are still LSPs send next one after lsp-interval (33 msecs)
+   */
+  if (listcount (circuit->lsp_queue) > 0)
+    thread_add_timer (master, send_lsp, circuit, 1);
+#endif
 
   return retval;
 }