netdev - [PATCH v2 net 4/4] ipv6: udp: Do a route lookup and update during release

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Date:	Mon, 11 Apr 2016 15:29:37 -0700
From:	Martin KaFai Lau <kafai@...com>
To:	netdev <netdev@...r.kernel.org>
CC:	Cong Wang <xiyou.wangcong@...il.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Wei Wang <weiwan@...gle.com>, Kernel Team <kernel-team@...com>
Subject: [PATCH v2 net 4/4] ipv6: udp: Do a route lookup and update during release_cb

This patch adds a release_cb for UDPv6.  It does a route lookup
and updates sk->sk_dst_cache if it is needed.  It picks up the
left-over job from ip6_sk_update_pmtu() if the sk was owned
by user during the pmtu update.

It takes a rcu_read_lock to protect the __sk_dst_get() operations
because another thread may do ip6_dst_store() without taking the
sk lock (e.g. sendmsg).

Fixes: 45e4fd26683c ("ipv6: Only create RTF_CACHE routes after encountering pmtu exception")
Signed-off-by: Martin KaFai Lau <kafai@...com>
Reported-by: Wei Wang <weiwan@...gle.com>
Cc: Cong Wang <xiyou.wangcong@...il.com>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Wei Wang <weiwan@...gle.com>
---
 include/net/ipv6.h  |  1 +
 net/ipv6/datagram.c | 20 ++++++++++++++++++++
 net/ipv6/udp.c      |  1 +
 3 files changed, 22 insertions(+)

diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index fd02e90..1be050a 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -960,6 +960,7 @@ int ip6_datagram_connect(struct sock *sk, struct sockaddr *addr, int addr_len);
 int ip6_datagram_connect_v6_only(struct sock *sk, struct sockaddr *addr,
 				 int addr_len);
 int ip6_datagram_dst_update(struct sock *sk, bool fix_sk_saddr);
+void ip6_datagram_release_cb(struct sock *sk);
 
 int ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len,
 		    int *addr_len);
diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c
index 59e01f27..9dd3882 100644
--- a/net/ipv6/datagram.c
+++ b/net/ipv6/datagram.c
@@ -119,6 +119,26 @@ out:
 	return err;
 }
 
+void ip6_datagram_release_cb(struct sock *sk)
+{
+	struct dst_entry *dst;
+
+	if (ipv6_addr_v4mapped(&sk->sk_v6_daddr))
+		return;
+
+	rcu_read_lock();
+	dst = __sk_dst_get(sk);
+	if (!dst || !dst->obsolete ||
+	    dst->ops->check(dst, inet6_sk(sk)->dst_cookie)) {
+		rcu_read_unlock();
+		return;
+	}
+	rcu_read_unlock();
+
+	ip6_datagram_dst_update(sk, false);
+}
+EXPORT_SYMBOL_GPL(ip6_datagram_release_cb);
+
 static int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 {
 	struct sockaddr_in6	*usin = (struct sockaddr_in6 *) uaddr;
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 8125931..6bc5c66 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1539,6 +1539,7 @@ struct proto udpv6_prot = {
 	.sendmsg	   = udpv6_sendmsg,
 	.recvmsg	   = udpv6_recvmsg,
 	.backlog_rcv	   = __udpv6_queue_rcv_skb,
+	.release_cb	   = ip6_datagram_release_cb,
 	.hash		   = udp_lib_hash,
 	.unhash		   = udp_lib_unhash,
 	.rehash		   = udp_v6_rehash,
-- 
2.5.1