netfilter: nf_conntrack_sip: remove direct dependency on IPv6

Previous implementation was not usable with CONFIG_IPV6=m.

Fixes: a3419ce3 ("netfilter: nf_conntrack_sip: add sip_external_media logic")
Signed-off-by: Alin Nastac <alin.nastac@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_conntrack_sip.c

@@ -20,9 +20,9 @@
 #include <linux/udp.h>
 #include <linux/tcp.h>
 #include <linux/netfilter.h>
+#include <linux/netfilter_ipv4.h>
+#include <linux/netfilter_ipv6.h>
 
-#include <net/route.h>
-#include <net/ip6_route.h>
 #include <net/netfilter/nf_conntrack.h>
 #include <net/netfilter/nf_conntrack_core.h>
 #include <net/netfilter/nf_conntrack_expect.h>
@@ -871,39 +871,34 @@ static int set_expected_rtp_rtcp(struct sk_buff *skb, unsigned int protoff,
 	} else if (sip_external_media) {
 		struct net_device *dev = skb_dst(skb)->dev;
 		struct net *net = dev_net(dev);
-		struct rtable *rt;
-		struct flowi4 fl4 = {};
-#if IS_ENABLED(CONFIG_IPV6)
-		struct flowi6 fl6 = {};
-#endif
+		struct flowi fl;
 		struct dst_entry *dst = NULL;
 
+		memset(&fl, 0, sizeof(fl));
+
 		switch (nf_ct_l3num(ct)) {
 			case NFPROTO_IPV4:
-				fl4.daddr = daddr->ip;
-				rt = ip_route_output_key(net, &fl4);
-				if (!IS_ERR(rt))
-					dst = &rt->dst;
+				fl.u.ip4.daddr = daddr->ip;
+				nf_ip_route(net, &dst, &fl, false);
 				break;
 
-#if IS_ENABLED(CONFIG_IPV6)
 			case NFPROTO_IPV6:
-				fl6.daddr = daddr->in6;
-				dst = ip6_route_output(net, NULL, &fl6);
-				if (dst->error) {
-					dst_release(dst);
-					dst = NULL;
-				}
+				fl.u.ip6.daddr = daddr->in6;
+				nf_ip6_route(net, &dst, &fl, false);
 				break;
-#endif
 		}
 
 		/* Don't predict any conntracks when media endpoint is reachable
 		 * through the same interface as the signalling peer.
 		 */
-		if (dst && dst->dev == dev)
+		if (dst) {
+			bool external_media = (dst->dev == dev);
+
+			dst_release(dst);
+			if (external_media)
 				return NF_ACCEPT;
 		}
+	}
 
 	/* We need to check whether the registration exists before attempting
 	 * to register it since we can see the same media description multiple