target/linux/generic/pending-4.9/613-netfilter_optional_tcp_window_check.patch

   1 From: Felix Fietkau <nbd@nbd.name>
   2 Subject: netfilter: optional tcp window check
   3
   4 Signed-off-by: Felix Fietkau <nbd@nbd.name>
   5 ---
   6  net/netfilter/nf_conntrack_proto_tcp.c | 13 +++++++++++++
   7  1 file changed, 13 insertions(+)
   8
   9 diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c
  10 index 69f687740c76..f24b62668dc8 100644
  11 --- a/net/netfilter/nf_conntrack_proto_tcp.c
  12 +++ b/net/netfilter/nf_conntrack_proto_tcp.c
  13 @@ -33,6 +33,9 @@
  14  #include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
  15  #include <net/netfilter/ipv6/nf_conntrack_ipv6.h>
  16
  17 +/* Do not check the TCP window for incoming packets  */
  18 +static int nf_ct_tcp_no_window_check __read_mostly = 1;
  19 +
  20  /* "Be conservative in what you do,
  21      be liberal in what you accept from others."
  22      If it's non-zero, we mark only out of window RST segments as INVALID. */
  23 @@ -513,6 +516,9 @@ static bool tcp_in_window(const struct nf_conn *ct,
  24         s32 receiver_offset;
  25         bool res, in_recv_win;
  26
  27 +       if (nf_ct_tcp_no_window_check)
  28 +               return true;
  29 +
  30         /*
  31          * Get the required data from the packet.
  32          */
  33 @@ -1479,6 +1485,13 @@ static struct ctl_table tcp_sysctl_table[] = {
  34                 .mode           = 0644,
  35                 .proc_handler   = proc_dointvec,
  36         },
  37 +       {
  38 +               .procname       = "nf_conntrack_tcp_no_window_check",
  39 +               .data           = &nf_ct_tcp_no_window_check,
  40 +               .maxlen         = sizeof(unsigned int),
  41 +               .mode           = 0644,
  42 +               .proc_handler   = proc_dointvec,
  43 +       },
  44         { }
  45  };
  46  #endif /* CONFIG_SYSCTL */
  47 --
  48 2.11.0
  49