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tcp: fix tcp_trim_head()

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commit f07d960df3 (tcp: avoid frag allocation for small frames)
breaked assumption in tcp stack that skb is either linear (skb->data_len
== 0), or fully fragged (skb->data_len == skb->len)

tcp_trim_head() made this assumption, we must fix it.

Thanks to Vijay for providing a very detailed explanation.

Reported-by: Vijay Subramanian <subramanian.vijay@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2011-12-04 08:51:08 +00:00 committed by David S. Miller
parent 7d31130428
commit 4fa48bf3c7
1 changed files with 8 additions and 5 deletions
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13
net/ipv4/tcp_output.c
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@ -1093,6 +1093,13 @@ static void __pskb_trim_head(struct sk_buff *skb, int len)
{
int i, k, eat;
eat = min_t(int, len, skb_headlen(skb));
if (eat) {
__skb_pull(skb, eat);
len -= eat;
if (!len)
return;
}
eat = len;
k = 0;
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
@ -1124,11 +1131,7 @@ int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
if (skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
return -ENOMEM;
/* If len == headlen, we avoid __skb_pull to preserve alignment. */
if (unlikely(len < skb_headlen(skb)))
__skb_pull(skb, len);
else
__pskb_trim_head(skb, len - skb_headlen(skb));
__pskb_trim_head(skb, len);
TCP_SKB_CB(skb)->seq += len;
skb->ip_summed = CHECKSUM_PARTIAL;