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Subject[PATCH] tcp: restore rcv_wscale in a repair mode
Date
rcv_wscale is a symetric parameter with snd_wscale.

Both this parameters are set on a connection handshake.

Without this value a remote window size can not be interpreted correctly,
because a value from a packet should be shifted on rcv_wscale.

And one more thing is that wscale_ok should be set too.

This patch doesn't break a backward compatibility.
If someone uses it in a old scheme, a rcv window
will be restored with the same bug (rcv_wscale = 0).

Cc: David S. Miller <davem@davemloft.net>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: James Morris <jmorris@namei.org>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Cc: Patrick McHardy <kaber@trash.net>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrew Vagin <avagin@openvz.org>
---
net/ipv4/tcp.c | 20 ++++++++++++++++----
1 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index df83d74..ed22cd7 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2348,10 +2348,22 @@ static int tcp_repair_options_est(struct tcp_sock *tp,
tp->rx_opt.mss_clamp = opt.opt_val;
break;
case TCPOPT_WINDOW:
- if (opt.opt_val > 14)
- return -EFBIG;
-
- tp->rx_opt.snd_wscale = opt.opt_val;
+ {
+ union {
+ struct {
+ u16 snd_wscale;
+ u16 rcv_wscale;
+ };
+ u32 raw;
+ } val = { .raw = opt.opt_val };
+
+ if (val.snd_wscale > 14 || val.rcv_wscale > 14)
+ return -EFBIG;
+
+ tp->rx_opt.snd_wscale = val.snd_wscale;
+ tp->rx_opt.rcv_wscale = val.rcv_wscale;
+ tp->rx_opt.wscale_ok = 1;
+ }
break;
case TCPOPT_SACK_PERM:
if (opt.opt_val != 0)
--
1.7.1


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