snmpd loses ARP table information

[Gerhard Roth]

Hi,

snmpd pernanently loses its ARP table information:

        # snmpctl walk 127.0.0.1 oid ipNetToMediaPhysAddress
        ipNetToMediaPhysAddress.2.192.168.16.1="xx:xx:xx:xx:xx:xx"
        ipNetToMediaPhysAddress.2.192.168.16.126="xx:xx:xx:xx:xx:xx"
        ipNetToMediaPhysAddress.2.192.168.19.132="xx:xx:xx:xx:xx:xx"

Query the whole tree and this information is gone:

        # snmpctl walk 127.0.0.1 oid iso.org>/dev/null
        # snmpctl walk 127.0.0.1 oid ipNetToMediaPhysAddress
        0=6

The reason is that several OIDs in mib.c call kr_updateif()
and this function deletes the kif_node and the restores it
via fetchifs(). But then the ARP information held by the
old kif_node is gone.

There is no need to delete the kif_node prior to calling
fetchifs() since it only calls rtmsg_process() which is
also called during normal processing of messages from the
routing socket.

And while here, also handle RTM_DESYNC messages.

Gerhard


Index: usr.sbin/snmpd/kroute.c
===================================================================
RCS file: /cvs/src/usr.sbin/snmpd/kroute.c,v
retrieving revision 1.31
diff -u -p -u -p -r1.31 kroute.c
--- usr.sbin/snmpd/kroute.c     18 Jul 2015 00:27:32 -0000      1.31
+++ usr.sbin/snmpd/kroute.c     2 Nov 2015 11:41:51 -0000
@@ -365,12 +365,6 @@ kr_iflastchange(void)
 int
 kr_updateif(u_int if_index)
 {
-       struct kif_node *kn;
-
-       if ((kn = kif_find(if_index)) != NULL)
-               kif_remove(kn);
-
-       /* Do not update the interface address list */
        return (fetchifs(if_index));
 }
 
@@ -1380,6 +1374,12 @@ rtmsg_process(char *buf, int len)
                        break;
                case RTM_IFANNOUNCE:
                        if_announce(next);
+                       break;
+               case RTM_DESYNC:
+                       kr_shutdown();
+                       if (fetchifs(0) == -1)
+                               fatalx("rtmsg_process: fetchifs");
+                       ktable_init();
                        break;
                default:
                        /* ignore for now */