zebra: label manager race condition fix

This fix covers the case where two or more events are processed but only one
becoming effective. E.g. when mixing a synchronous label request from a LDP
deamon and an asynchronous request from a BGP daemon it could happen to the
BGP having the label chunk, but the LDP stuck waiting for the response.

Given e.g.

  ldpd     <-------->
  (sync label request)
                       Zebra (label proxy)  <-->  Zebra (shared label manager)
  bgpd     <-------->
  (async label request)

Sequence:

   LDP label request ----->
                               Zebra (label proxy FW) ----> Zebra (LM)
   BGP label request ----->
                               Zebra (label proxy FW) ----> Zebra (LM)
                                                      <---- Zebra (LM) RP LDP
                                                      <---- Zebra (LM) RP BGP

Signed-off-by: F. Aragon <paco@voltanet.io>

diff --git a/zebra/label_manager.c b/zebra/label_manager.c
index 1b17845e41ec14bd16893a367399b05fd4f80e8d..16d45836e00d1468344fa670004d2491b9b34c0b 100644 (file)
--- a/zebra/label_manager.c
+++ b/zebra/label_manager.c
@@ -156,11 +156,9 @@ static int lm_zclient_read(struct thread *t)
        /* read response and send it back */
        ret = relay_response_back();
 
-       /* on error, schedule another read */
-       if (ret == -1)
-               if (!zclient->t_read)
-                       thread_add_read(zclient->master, lm_zclient_read, NULL,
-                                       zclient->sock, &zclient->t_read);
+       /* re-arm read */
+       thread_add_read(zclient->master, lm_zclient_read, NULL,
+                       zclient->sock, &zclient->t_read);
        return ret;
 }