[IP]: Simplify and consolidate MSG_PEEK error handling

When a packet is obtained from skb_recv_datagram with MSG_PEEK enabled
it is left on the socket receive queue.  This means that when we detect
a checksum error we have to be careful when trying to free the packet
as someone could have dequeued it in the time being.

Currently this delicate logic is duplicated three times between UDPv4,
UDPv6 and RAWv6.  This patch moves them into a one place and simplifies
the code somewhat.

This is based on a suggestion by Eric Dumazet.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 5 insertions, 27 deletions

diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
index a66900c..66f1d12 100644
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -32,6 +32,7 @@
 #include <linux/icmpv6.h>
 #include <linux/netfilter.h>
 #include <linux/netfilter_ipv6.h>
+#include <linux/skbuff.h>
 #include <asm/uaccess.h>
 #include <asm/ioctls.h>
 #include <asm/bug.h>
@@ -433,25 +434,14 @@ out:
 	return err;
 
 csum_copy_err:
-	/* Clear queue. */
-	if (flags&MSG_PEEK) {
-		int clear = 0;
-		spin_lock_bh(&sk->sk_receive_queue.lock);
-		if (skb == skb_peek(&sk->sk_receive_queue)) {
-			__skb_unlink(skb, &sk->sk_receive_queue);
-			clear = 1;
-		}
-		spin_unlock_bh(&sk->sk_receive_queue.lock);
-		if (clear)
-			kfree_skb(skb);
-	}
+	skb_kill_datagram(sk, skb, flags);
 
 	/* Error for blocking case is chosen to masquerade
 	   as some normal condition.
 	 */
 	err = (flags&MSG_DONTWAIT) ? -EAGAIN : -EHOSTUNREACH;
 	/* FIXME: increment a raw6 drops counter here */
-	goto out_free;
+	goto out;
 }
 
 static int rawv6_push_pending_frames(struct sock *sk, struct flowi *fl,
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 5cc8731..d8538dc 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -36,6 +36,7 @@
 #include <linux/ipv6.h>
 #include <linux/icmpv6.h>
 #include <linux/init.h>
+#include <linux/skbuff.h>
 #include <asm/uaccess.h>
 
 #include <net/sock.h>
@@ -300,20 +301,7 @@ out:
 	return err;
 
 csum_copy_err:
-	/* Clear queue. */
-	if (flags&MSG_PEEK) {
-		int clear = 0;
-		spin_lock_bh(&sk->sk_receive_queue.lock);
-		if (skb == skb_peek(&sk->sk_receive_queue)) {
-			__skb_unlink(skb, &sk->sk_receive_queue);
-			clear = 1;
-		}
-		spin_unlock_bh(&sk->sk_receive_queue.lock);
-		if (clear)
-			kfree_skb(skb);
-	}
-
-	skb_free_datagram(sk, skb);
+	skb_kill_datagram(sk, skb, flags);
 
 	if (flags & MSG_DONTWAIT) {
 		UDP6_INC_STATS_USER(UDP_MIB_INERRORS);