From: Roy Marples <roy@marples.name>
Date: Thu, 15 Apr 2010 13:22:41 +0000 (+0000)
Subject: Check to see if any routers require a host route if they are on a
X-Git-Tag: v5.2.3~15
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=559b81c3f1b64faa05d7350ce72adb0bd6ae202f;p=thirdparty%2Fdhcpcd.git

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 3e6dc98f..6ab86bd8 100644
--- 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;