OpenWrt – Rev 1

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From: Felix Fietkau <nbd@nbd.name>
Subject: netfilter: optional tcp window check

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 net/netfilter/nf_conntrack_proto_tcp.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

--- a/net/netfilter/nf_conntrack_proto_tcp.c
+++ b/net/netfilter/nf_conntrack_proto_tcp.c
@@ -34,6 +34,9 @@
 #include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
 #include <net/netfilter/ipv6/nf_conntrack_ipv6.h>
 
+/* Do not check the TCP window for incoming packets  */
+static int nf_ct_tcp_no_window_check __read_mostly = 1;
+
 /* "Be conservative in what you do,
     be liberal in what you accept from others."
     If it's non-zero, we mark only out of window RST segments as INVALID. */
@@ -483,6 +486,9 @@ static bool tcp_in_window(const struct n
        s32 receiver_offset;
        bool res, in_recv_win;
 
+       if (nf_ct_tcp_no_window_check)
+               return true;
+
        /*
         * Get the required data from the packet.
         */
@@ -1476,6 +1482,13 @@ static struct ctl_table tcp_sysctl_table
                .mode           = 0644,
                .proc_handler   = proc_dointvec,
        },
+       {
+               .procname       = "nf_conntrack_tcp_no_window_check",
+               .data           = &nf_ct_tcp_no_window_check,
+               .maxlen         = sizeof(unsigned int),
+               .mode           = 0644,
+               .proc_handler   = proc_dointvec,
+       },
        { }
 };
 #endif /* CONFIG_SYSCTL */