kernel: avoid flow offload for connections with xfrm on the dst entry (should fix IPSec)

Signed-off-by: Felix Fietkau <nbd@nbd.name>

target/linux/generic/hack-4.14/650-netfilter-add-xt_OFFLOAD-target.patch

@@ -98,7 +98,7 @@ Signed-off-by: Felix Fietkau <nbd@nbd.name>
  obj-$(CONFIG_NETFILTER_XT_TARGET_LED) += xt_LED.o
 --- /dev/null
 +++ b/net/netfilter/xt_FLOWOFFLOAD.c
-@@ -0,0 +1,365 @@
+@@ -0,0 +1,368 @@
 +/*
 + * Copyright (C) 2018 Felix Fietkau <nbd@nbd.name>
 + *
@@ -326,6 +326,9 @@ Signed-off-by: Felix Fietkau <nbd@nbd.name>
 +	if (!this_dst || !other_dst)
 +		return -ENOENT;
 +
++	if (dst_xfrm(this_dst) || dst_xfrm(other_dst))
++		return -EINVAL;
++
 +	route->tuple[dir].dst		= this_dst;
 +	route->tuple[dir].ifindex	= xt_in(par)->ifindex;
 +	route->tuple[!dir].dst		= other_dst;