ospfd: warn when a neighbor changes its ip address

[Remi Locherer]

I'd like to get a notification when a neighbor changes the src IP address
for hello packets. Either it is a planned change or something bad happens
in the network.

OK?

Remi


Index: hello.c
===================================================================
RCS file: /cvs/src/usr.sbin/ospfd/hello.c,v
retrieving revision 1.23
diff -u -p -r1.23 hello.c
--- hello.c     15 Jul 2019 18:26:39 -0000      1.23
+++ hello.c     11 Aug 2019 09:36:13 -0000
@@ -189,10 +189,16 @@ recv_hello(struct iface *iface, struct i
                nbr->dr.s_addr = hello.d_rtr;
                nbr->bdr.s_addr = hello.bd_rtr;
                nbr->priority = hello.rtr_priority;
+               /* XXX neighbor address shouldn't be stored on virtual links */
+               nbr->addr.s_addr = src.s_addr;
+       }
+
+       if (nbr->addr.s_addr != src.s_addr) {
+               log_warnx("%s: neighbor ID %s changed its IP address",
+                   __func__, inet_ntoa(nbr->id));
+               nbr->addr.s_addr = src.s_addr;
        }
 
-       /* actually the neighbor address shouldn't be stored on virtual links */
-       nbr->addr.s_addr = src.s_addr;
        nbr->options = hello.opts;
 
        nbr_fsm(nbr, NBR_EVT_HELLO_RCVD);