ipvs: add function to find tunnels

Add ip_vs_find_tunnel() to match tunnel headers
by family, address and optional port. Use it to
properly find the tunnel real server used in
received ICMP errors.
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/ip_vs.h

@@ -1404,6 +1404,9 @@ bool ip_vs_has_real_service(struct netns_ipvs *ipvs, int af, __u16 protocol,
 struct ip_vs_dest *
 ip_vs_find_real_service(struct netns_ipvs *ipvs, int af, __u16 protocol,
 			const union nf_inet_addr *daddr, __be16 dport);
+struct ip_vs_dest *ip_vs_find_tunnel(struct netns_ipvs *ipvs, int af,
+				     const union nf_inet_addr *daddr,
+				     __be16 tun_port);
 
 int ip_vs_use_count_inc(void);
 void ip_vs_use_count_dec(void);

net/netfilter/ipvs/ip_vs_core.c

@@ -1598,6 +1598,7 @@ ip_vs_in_icmp(struct netns_ipvs *ipvs, struct sk_buff *skb, int *related,
 	struct ip_vs_proto_data *pd;
 	unsigned int offset, offset2, ihl, verdict;
 	bool ipip, new_cp = false;
+	union nf_inet_addr *raddr;
 
 	*related = 1;
 
@@ -1636,15 +1637,22 @@ ip_vs_in_icmp(struct netns_ipvs *ipvs, struct sk_buff *skb, int *related,
 	cih = skb_header_pointer(skb, offset, sizeof(_ciph), &_ciph);
 	if (cih == NULL)
 		return NF_ACCEPT; /* The packet looks wrong, ignore */
+	raddr = (union nf_inet_addr *)&cih->daddr;
 
 	/* Special case for errors for IPIP packets */
 	ipip = false;
 	if (cih->protocol == IPPROTO_IPIP) {
+		struct ip_vs_dest *dest;
+
 		if (unlikely(cih->frag_off & htons(IP_OFFSET)))
 			return NF_ACCEPT;
 		/* Error for our IPIP must arrive at LOCAL_IN */
 		if (!(skb_rtable(skb)->rt_flags & RTCF_LOCAL))
 			return NF_ACCEPT;
+		dest = ip_vs_find_tunnel(ipvs, AF_INET, raddr, 0);
+		/* Only for known tunnel */
+		if (!dest || dest->tun_type != IP_VS_CONN_F_TUNNEL_TYPE_IPIP)
+			return NF_ACCEPT;
 		offset += cih->ihl * 4;
 		cih = skb_header_pointer(skb, offset, sizeof(_ciph), &_ciph);
 		if (cih == NULL)

net/netfilter/ipvs/ip_vs_ctl.c

@@ -617,6 +617,35 @@ struct ip_vs_dest *ip_vs_find_real_service(struct netns_ipvs *ipvs, int af,
 	return NULL;
 }
 
+/* Find real service record by <af,addr,tun_port>.
+ * In case of multiple records with the same <af,addr,tun_port>, only
+ * the first found record is returned.
+ *
+ * To be called under RCU lock.
+ */
+struct ip_vs_dest *ip_vs_find_tunnel(struct netns_ipvs *ipvs, int af,
+				     const union nf_inet_addr *daddr,
+				     __be16 tun_port)
+{
+	struct ip_vs_dest *dest;
+	unsigned int hash;
+
+	/* Check for "full" addressed entries */
+	hash = ip_vs_rs_hashkey(af, daddr, tun_port);
+
+	hlist_for_each_entry_rcu(dest, &ipvs->rs_table[hash], d_list) {
+		if (dest->tun_port == tun_port &&
+		    dest->af == af &&
+		    ip_vs_addr_equal(af, &dest->addr, daddr) &&
+		    IP_VS_DFWD_METHOD(dest) == IP_VS_CONN_F_TUNNEL) {
+			/* HIT */
+			return dest;
+		}
+	}
+
+	return NULL;
+}
+
 /* Lookup destination by {addr,port} in the given service
  * Called under RCU lock.
  */