Check to see if any routers require a host route if they are on a

different subnet.
This fixes issues with badly configured DHCP servers.
We may need to extent this check to any route with a host destination
in the future.

diff --git a/configure.c b/configure.c
index 3e6dc98f1620868db4ecba6333c2ec98c53cee0d..6ab86bd84bb25d91d16c29f9836fc30abf7cbbc5 100644 (file)
--- a/configure.c
+++ b/configure.c
@@ -567,6 +567,51 @@ add_destination_route(struct rt *rt, const struct interface *iface)
        return r;
 }
 
+/* We should check to ensure the routers are on the same subnet
+ * OR supply a host route. If not, warn and add a host route. */
+static struct rt *
+add_router_host_route(struct rt *rt, const struct interface *ifp)
+{
+       struct rt *rtp, *rtl, *rtn;
+       const char *cp, *cp2, *cp3, *cplim;
+
+       for (rtp = rt, rtl = NULL; rtp; rtl = rtp, rtp = rtp->next) {
+               if (rtp->dest.s_addr != INADDR_ANY)
+                       continue;
+               /* Scan for a route to match */
+               for (rtn = rt; rtn != rtp; rtn = rtn->next) {
+                       /* match host */
+                       if (rtn->dest.s_addr == rtp->gate.s_addr)
+                               break;
+                       /* match subnet */
+                       cp = (const char *)&rtp->gate.s_addr;
+                       cp2 = (const char *)&rtn->dest.s_addr;
+                       cp3 = (const char *)&rtn->net.s_addr;
+                       cplim = cp3 + sizeof(rtn->net.s_addr);
+                       while (cp3 < cplim) {
+                               if ((*cp++ ^ *cp2++) & *cp3++)
+                                       break;
+                       }
+                       if (cp3 == cplim)
+                               break;
+               }
+               if (rtn != rtp)
+                       continue;
+               syslog(LOG_WARNING, "%s: router %s requires a host route",
+                      ifp->name, inet_ntoa(rtp->gate));
+               rtn = xmalloc(sizeof(*rtn));
+               rtn->dest.s_addr = rtp->gate.s_addr;
+               rtn->net.s_addr = INADDR_BROADCAST;
+               rtn->gate.s_addr = rtp->gate.s_addr;
+               rtn->next = rtp;
+               if (rtl == NULL)
+                       rt = rtn;
+               else
+                       rtl->next = rtn;
+       }
+       return rt;
+}
+
 void
 build_routes(void)
 {
@@ -578,6 +623,7 @@ build_routes(void)
                        continue;
                dnr = get_routes(ifp);
                dnr = add_subnet_route(dnr, ifp);
+               dnr = add_router_host_route(dnr, ifp);
                dnr = add_destination_route(dnr, ifp);
                for (rt = dnr; rt && (rtn = rt->next, 1); lrt = rt, rt = rtn) {
                        rt->iface = ifp;