sctp: process sctp over udp icmp err on sctp side

Previously, sctp over udp was using udp tunnel's icmp err process, which
only does sk lookup on sctp side. However for sctp's icmp error process,
there are more things to do, like syncing assoc pmtu/retransmit packets
for toobig type err, and starting proto_unreach_timer for unreach type
err etc.

Now after adding PLPMTUD, which also requires to process toobig type err
on sctp side. This patch is to process icmp err on sctp side by parsing
the type/code/info in .encap_err_lookup and call sctp's icmp processing
functions. Note as the 'redirect' err process needs to know the outer
ip(v6) header's, we have to leave it to udp(v6)_err to handle it.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sctp/sctp.h

@@ -145,6 +145,8 @@ struct sock *sctp_err_lookup(struct net *net, int family, struct sk_buff *,
 			     struct sctphdr *, struct sctp_association **,
 			     struct sctp_transport **);
 void sctp_err_finish(struct sock *, struct sctp_transport *);
+int sctp_udp_v4_err(struct sock *sk, struct sk_buff *skb);
+int sctp_udp_v6_err(struct sock *sk, struct sk_buff *skb);
 void sctp_icmp_frag_needed(struct sock *, struct sctp_association *,
 			   struct sctp_transport *t, __u32 pmtu);
 void sctp_icmp_redirect(struct sock *, struct sctp_transport *,

net/sctp/input.c

@@ -645,6 +645,36 @@ int sctp_v4_err(struct sk_buff *skb, __u32 info)
 	return 0;
 }
 
+int sctp_udp_v4_err(struct sock *sk, struct sk_buff *skb)
+{
+	struct net *net = dev_net(skb->dev);
+	struct sctp_association *asoc;
+	struct sctp_transport *t;
+	struct icmphdr *hdr;
+	__u32 info = 0;
+
+	skb->transport_header += sizeof(struct udphdr);
+	sk = sctp_err_lookup(net, AF_INET, skb, sctp_hdr(skb), &asoc, &t);
+	if (!sk) {
+		__ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
+		return -ENOENT;
+	}
+
+	skb->transport_header -= sizeof(struct udphdr);
+	hdr = (struct icmphdr *)(skb_network_header(skb) - sizeof(struct icmphdr));
+	if (hdr->type == ICMP_REDIRECT) {
+		/* can't be handled without outer iphdr known, leave it to udp_err */
+		sctp_err_finish(sk, t);
+		return 0;
+	}
+	if (hdr->type == ICMP_DEST_UNREACH && hdr->code == ICMP_FRAG_NEEDED)
+		info = ntohs(hdr->un.frag.mtu);
+	sctp_v4_err_handle(t, skb, hdr->type, hdr->code, info);
+
+	sctp_err_finish(sk, t);
+	return 1;
+}
+
 /*
  * RFC 2960, 8.4 - Handle "Out of the blue" Packets.
  *

net/sctp/ipv6.c

@@ -188,6 +188,36 @@ static int sctp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 	return 0;
 }
 
+int sctp_udp_v6_err(struct sock *sk, struct sk_buff *skb)
+{
+	struct net *net = dev_net(skb->dev);
+	struct sctp_association *asoc;
+	struct sctp_transport *t;
+	struct icmp6hdr *hdr;
+	__u32 info = 0;
+
+	skb->transport_header += sizeof(struct udphdr);
+	sk = sctp_err_lookup(net, AF_INET6, skb, sctp_hdr(skb), &asoc, &t);
+	if (!sk) {
+		__ICMP6_INC_STATS(net, __in6_dev_get(skb->dev), ICMP6_MIB_INERRORS);
+		return -ENOENT;
+	}
+
+	skb->transport_header -= sizeof(struct udphdr);
+	hdr = (struct icmp6hdr *)(skb_network_header(skb) - sizeof(struct icmp6hdr));
+	if (hdr->icmp6_type == NDISC_REDIRECT) {
+		/* can't be handled without outer ip6hdr known, leave it to udpv6_err */
+		sctp_err_finish(sk, t);
+		return 0;
+	}
+	if (hdr->icmp6_type == ICMPV6_PKT_TOOBIG)
+		info = ntohl(hdr->icmp6_mtu);
+	sctp_v6_err_handle(t, skb, hdr->icmp6_type, hdr->icmp6_code, info);
+
+	sctp_err_finish(sk, t);
+	return 1;
+}
+
 static int sctp_v6_xmit(struct sk_buff *skb, struct sctp_transport *t)
 {
 	struct dst_entry *dst = dst_clone(t->dst);

net/sctp/protocol.c

@@ -850,23 +850,6 @@ static int sctp_udp_rcv(struct sock *sk, struct sk_buff *skb)
 	return 0;
 }
 
-static int sctp_udp_err_lookup(struct sock *sk, struct sk_buff *skb)
-{
-	struct sctp_association *asoc;
-	struct sctp_transport *t;
-	int family;
-
-	skb->transport_header += sizeof(struct udphdr);
-	family = (ip_hdr(skb)->version == 4) ? AF_INET : AF_INET6;
-	sk = sctp_err_lookup(dev_net(skb->dev), family, skb, sctp_hdr(skb),
-			     &asoc, &t);
-	if (!sk)
-		return -ENOENT;
-
-	sctp_err_finish(sk, t);
-	return 0;
-}
-
 int sctp_udp_sock_start(struct net *net)
 {
 	struct udp_tunnel_sock_cfg tuncfg = {NULL};
@@ -885,7 +868,7 @@ int sctp_udp_sock_start(struct net *net)
 
 	tuncfg.encap_type = 1;
 	tuncfg.encap_rcv = sctp_udp_rcv;
-	tuncfg.encap_err_lookup = sctp_udp_err_lookup;
+	tuncfg.encap_err_lookup = sctp_udp_v4_err;
 	setup_udp_tunnel_sock(net, sock, &tuncfg);
 	net->sctp.udp4_sock = sock->sk;
 
@@ -907,7 +890,7 @@ int sctp_udp_sock_start(struct net *net)
 
 	tuncfg.encap_type = 1;
 	tuncfg.encap_rcv = sctp_udp_rcv;
-	tuncfg.encap_err_lookup = sctp_udp_err_lookup;
+	tuncfg.encap_err_lookup = sctp_udp_v6_err;
 	setup_udp_tunnel_sock(net, sock, &tuncfg);
 	net->sctp.udp6_sock = sock->sk;
 #endif