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[IP]: Simplify and consolidate MSG_PEEK error handling

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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>
This commit is contained in:
Herbert Xu
2005-12-13 23:16:37 -08:00
committed by David S. Miller
parent 57cca05af1
commit 3305b80c21
5 changed files with 44 additions and 41 deletions
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36
net/core/datagram.c
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@@ -47,6 +47,7 @@
#include <linux/rtnetlink.h>
#include <linux/poll.h>
#include <linux/highmem.h>
#include <linux/spinlock.h>
#include <net/protocol.h>
#include <linux/skbuff.h>
@@ -199,6 +200,41 @@ void skb_free_datagram(struct sock *sk, struct sk_buff *skb)
kfree_skb(skb);
}
/**
* skb_kill_datagram - Free a datagram skbuff forcibly
* @sk: socket
* @skb: datagram skbuff
* @flags: MSG_ flags
*
* This function frees a datagram skbuff that was received by
* skb_recv_datagram. The flags argument must match the one
* used for skb_recv_datagram.
*
* If the MSG_PEEK flag is set, and the packet is still on the
* receive queue of the socket, it will be taken off the queue
* before it is freed.
*
* This function currently only disables BH when acquiring the
* sk_receive_queue lock. Therefore it must not be used in a
* context where that lock is acquired in an IRQ context.
*/
void skb_kill_datagram(struct sock *sk, struct sk_buff *skb, unsigned int flags)
{
if (flags & MSG_PEEK) {
spin_lock_bh(&sk->sk_receive_queue.lock);
if (skb == skb_peek(&sk->sk_receive_queue)) {
__skb_unlink(skb, &sk->sk_receive_queue);
atomic_dec(&skb->users);
}
spin_unlock_bh(&sk->sk_receive_queue.lock);
}
kfree_skb(skb);
}
EXPORT_SYMBOL(skb_kill_datagram);
/**
* skb_copy_datagram_iovec - Copy a datagram to an iovec.
* @skb: buffer to copy