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tcp: tcp_synack_options() fix 

Commit 33ad798c92 (tcp: options clean up) introduced a problem
if MD5+SACK+timestamps were used in initial SYN message.

Some stacks (old linux for example) try to negotiate MD5+SACK+TSTAMP
sessions, but since 40 bytes of tcp options space are not enough to
store all the bits needed, we chose to disable timestamps in this case.

We send a SYN-ACK _without_ timestamp option, but socket has timestamps
enabled and all further outgoing messages contain a TS block, all with
the initial timestamp of the remote peer.

Fix is to really disable timestamps option for the whole session.

Reported-by: Bijay Singh <Bijay.Singh@guavus.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 2010-05-17 22:35:36 -07:00 committed by David S. Miller
parent eedf042a63
commit de213e5eed
1 changed files with 4 additions and 5 deletions
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9
net/ipv4/tcp_output.c
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@ -668,7 +668,6 @@ static unsigned tcp_synack_options(struct sock *sk,
u8 cookie_plus = (xvp != NULL && !xvp->cookie_out_never) ?
xvp->cookie_plus :
0;
bool doing_ts = ireq->tstamp_ok;
#ifdef CONFIG_TCP_MD5SIG
*md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req);
@ -681,7 +680,7 @@ static unsigned tcp_synack_options(struct sock *sk,
* rather than TS in order to fit in better with old,
* buggy kernels, but that was deemed to be unnecessary.
*/
doing_ts &= !ireq->sack_ok;
ireq->tstamp_ok &= !ireq->sack_ok;
}
#else
*md5 = NULL;
@ -696,7 +695,7 @@ static unsigned tcp_synack_options(struct sock *sk,
opts->options |= OPTION_WSCALE;
remaining -= TCPOLEN_WSCALE_ALIGNED;
}
if (likely(doing_ts)) {
if (likely(ireq->tstamp_ok)) {
opts->options |= OPTION_TS;
opts->tsval = TCP_SKB_CB(skb)->when;
opts->tsecr = req->ts_recent;
@ -704,7 +703,7 @@ static unsigned tcp_synack_options(struct sock *sk,
}
if (likely(ireq->sack_ok)) {
opts->options |= OPTION_SACK_ADVERTISE;
if (unlikely(!doing_ts))
if (unlikely(!ireq->tstamp_ok))
remaining -= TCPOLEN_SACKPERM_ALIGNED;
}
@ -712,7 +711,7 @@ static unsigned tcp_synack_options(struct sock *sk,
* If the <SYN> options fit, the same options should fit now!
*/
if (*md5 == NULL &&
doing_ts &&
ireq->tstamp_ok &&
cookie_plus > TCPOLEN_COOKIE_BASE) {
int need = cookie_plus; /* has TCPOLEN_COOKIE_BASE */