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From: Felix Fietkau <nbd@nbd.name>
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Subject: netfilter: optional tcp window check
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Signed-off-by: Felix Fietkau <nbd@nbd.name>
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---
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net/netfilter/nf_conntrack_proto_tcp.c | 13 +++++++++++++
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1 file changed, 13 insertions(+)
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--- a/net/netfilter/nf_conntrack_proto_tcp.c
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+++ b/net/netfilter/nf_conntrack_proto_tcp.c
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@@ -34,6 +34,9 @@
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#include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
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#include <net/netfilter/ipv6/nf_conntrack_ipv6.h>
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+/* Do not check the TCP window for incoming packets */
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+static int nf_ct_tcp_no_window_check __read_mostly = 1;
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+
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/* "Be conservative in what you do,
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be liberal in what you accept from others."
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If it's non-zero, we mark only out of window RST segments as INVALID. */
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@@ -484,6 +487,9 @@ static bool tcp_in_window(const struct n
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s32 receiver_offset;
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bool res, in_recv_win;
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+ if (nf_ct_tcp_no_window_check)
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+ return true;
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+
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/*
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* Get the required data from the packet.
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*/
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@@ -1059,7 +1065,7 @@ static int tcp_packet(struct nf_conn *ct
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IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED &&
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timeouts[new_state] > timeouts[TCP_CONNTRACK_UNACK])
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timeout = timeouts[TCP_CONNTRACK_UNACK];
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- else if (ct->proto.tcp.last_win == 0 &&
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+ else if (!nf_ct_tcp_no_window_check && ct->proto.tcp.last_win == 0 &&
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timeouts[new_state] > timeouts[TCP_CONNTRACK_RETRANS])
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timeout = timeouts[TCP_CONNTRACK_RETRANS];
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else
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@@ -1508,6 +1514,13 @@ static struct ctl_table tcp_sysctl_table
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.mode = 0644,
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.proc_handler = proc_dointvec,
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},
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+ {
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+ .procname = "nf_conntrack_tcp_no_window_check",
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+ .data = &nf_ct_tcp_no_window_check,
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+ .maxlen = sizeof(unsigned int),
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+ .mode = 0644,
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+ .proc_handler = proc_dointvec,
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+ },
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{ }
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};
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#endif /* CONFIG_SYSCTL */
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