Commit 3c16241c authored Jul 28, 2015 by Phil Sutter Committed by Pablo Neira Ayuso Aug 10, 2015

netfilter: SYNPROXY: fix sending window update to client

Upon receipt of SYNACK from the server, ipt_SYNPROXY first sends back an ACK to
finish the server handshake, then calls nf_ct_seqadj_init() to initiate
sequence number adjustment of forwarded packets to the client and finally sends
a window update to the client to unblock it's TX queue.

Since synproxy_send_client_ack() does not set synproxy_send_tcp()'s nfct
parameter, no sequence number adjustment happens and the client receives the
window update with incorrect sequence number. Depending on client TCP
implementation, this leads to a significant delay (until a window probe is
being sent).

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

parent 96fffb4f

net/ipv4/netfilter/ipt_SYNPROXY.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -226,7 +226,8 @@ synproxy_send_client_ack(const struct synproxy_net *snet,

		synproxy_build_options(nth, opts);

		synproxy_send_tcp(skb, nskb, NULL, 0, niph, nth, tcp_hdr_size);
		synproxy_send_tcp(skb, nskb, skb->nfct, IP_CT_ESTABLISHED_REPLY,
		niph, nth, tcp_hdr_size);
		}

		static bool

net/ipv6/netfilter/ip6t_SYNPROXY.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -243,7 +243,8 @@ synproxy_send_client_ack(const struct synproxy_net *snet,

		synproxy_build_options(nth, opts);

		synproxy_send_tcp(snet, skb, nskb, NULL, 0, niph, nth, tcp_hdr_size);
		synproxy_send_tcp(snet, skb, nskb, skb->nfct, IP_CT_ESTABLISHED_REPLY,
		niph, nth, tcp_hdr_size);
		}

		static bool