Commit ac401485 authored by Douglas Caetano dos Santos's avatar Douglas Caetano dos Santos Committed by Greg Kroah-Hartman

tcp: fix wrong checksum calculation on MTU probing

[ Upstream commit 2fe664f1 ]

With TCP MTU probing enabled and offload TX checksumming disabled,
tcp_mtu_probe() calculated the wrong checksum when a fragment being copied
into the probe's SKB had an odd length. This was caused by the direct use
of skb_copy_and_csum_bits() to calculate the checksum, as it pads the
fragment being copied, if needed. When this fragment was not the last, a
subsequent call used the previous checksum without considering this
padding.

The effect was a stale connection in one way, as even retransmissions
wouldn't solve the problem, because the checksum was never recalculated for
the full SKB length.
Signed-off-by: default avatarDouglas Caetano dos Santos <douglascs@taghos.com.br>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent d2e01b15
......@@ -1950,12 +1950,14 @@ static int tcp_mtu_probe(struct sock *sk)
len = 0;
tcp_for_write_queue_from_safe(skb, next, sk) {
copy = min_t(int, skb->len, probe_size - len);
if (nskb->ip_summed)
if (nskb->ip_summed) {
skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
else
nskb->csum = skb_copy_and_csum_bits(skb, 0,
skb_put(nskb, copy),
copy, nskb->csum);
} else {
__wsum csum = skb_copy_and_csum_bits(skb, 0,
skb_put(nskb, copy),
copy, 0);
nskb->csum = csum_block_add(nskb->csum, csum, len);
}
if (skb->len <= copy) {
/* We've eaten all the data from this skb.
......
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