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tcp: Set CHECKSUM_UNNECESSARY in tcp_init_nondata_skb

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Back in commit 04a0551c87
("loopback: Drop obsolete ip_summed setting") we stopped
setting CHECKSUM_UNNECESSARY in the loopback xmit.

This is because such a setting was a lie since it implies that the
checksum field of the packet is properly filled in.

Instead what happens normally is that CHECKSUM_PARTIAL is set and
skb->csum is calculated as needed.

But this was only happening for TCP data packets (via the
skb->ip_summed assignment done in tcp_sendmsg()).  It doesn't
happen for non-data packets like ACKs etc.

Fix this by setting skb->ip_summed in the common non-data packet
constructor.  It already is setting skb->csum to zero.

But this reminds us that we still have things like ip_output.c's
ip_dev_loopback_xmit() which sets skb->ip_summed to the value
CHECKSUM_UNNECESSARY, which Herbert's patch teaches us is not
valid.  So we'll have to address that at some point too.

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2010-04-08 11:32:30 -07:00
parent 1223c67c09
commit 2626419ad5
1 changed files with 1 additions and 0 deletions
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net/ipv4/tcp_output.c
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@ -349,6 +349,7 @@ static inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb,
*/
static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
{
skb->ip_summed = CHECKSUM_PARTIAL;
skb->csum = 0;
TCP_SKB_CB(skb)->flags = flags;