netfilter: synproxy: fix erroneous tcp mss option

Now synproxy sends the mss value set by the user on client syn-ack packet
instead of the mss value that client announced.

Fixes: 48b1de4c110a ("netfilter: add SYNPROXY core/target")
Signed-off-by: Fernando Fernandez Mancera <ffmancera@riseup.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/net/ipv4/netfilter/ipt_SYNPROXY.c b/net/ipv4/netfilter/ipt_SYNPROXY.c
index 8e7f84ec783d..0e70f3f65f6f 100644
--- a/net/ipv4/netfilter/ipt_SYNPROXY.c
+++ b/net/ipv4/netfilter/ipt_SYNPROXY.c
@@ -36,6 +36,8 @@ synproxy_tg4(struct sk_buff *skb, const struct xt_action_param *par)
                         opts.options |= XT_SYNPROXY_OPT_ECN;
 
                 opts.options &= info->options;
+                opts.mss_encode = opts.mss;
+                opts.mss = info->mss;
                 if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP)
                         synproxy_init_timestamp_cookie(info, &opts);
                 else