[openwrt/openwrt] kernel: fix flow offload UDP handling issue

[LEDE Commits]

nbd pushed a commit to openwrt/openwrt.git, branch master:
https://git.lede-project.org/48d17551b6a191b596d87a9b64ed69e96b55f1d8

commit 48d17551b6a191b596d87a9b64ed69e96b55f1d8
Author: Felix Fietkau <nbd at nbd.name>
AuthorDate: Fri Mar 23 17:18:00 2018 +0100

    kernel: fix flow offload UDP handling issue
    
    Only run the TCP state check for TCP connections
    
    Signed-off-by: Felix Fietkau <nbd at nbd.name>
---
 ...f_flow_table-add-missing-condition-for-TC.patch | 48 ++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/target/linux/generic/backport-4.14/367-netfilter-nf_flow_table-add-missing-condition-for-TC.patch b/target/linux/generic/backport-4.14/367-netfilter-nf_flow_table-add-missing-condition-for-TC.patch
new file mode 100644
index 0000000..2a470f7
--- /dev/null
+++ b/target/linux/generic/backport-4.14/367-netfilter-nf_flow_table-add-missing-condition-for-TC.patch
@@ -0,0 +1,48 @@
+From: Felix Fietkau <nbd at nbd.name>
+Date: Fri, 23 Mar 2018 17:15:22 +0100
+Subject: [PATCH] netfilter: nf_flow_table: add missing condition for TCP state
+ check
+
+Avoid looking at unrelated fields in UDP packets
+
+Signed-off-by: Felix Fietkau <nbd at nbd.name>
+---
+
+--- a/net/netfilter/nf_flow_table_ip.c
++++ b/net/netfilter/nf_flow_table_ip.c
+@@ -15,11 +15,14 @@
+ #include <linux/tcp.h>
+ #include <linux/udp.h>
+ 
+-static int nf_flow_tcp_state_check(struct flow_offload *flow,
+-				   struct sk_buff *skb, unsigned int thoff)
++static int nf_flow_state_check(struct flow_offload *flow, int proto,
++			       struct sk_buff *skb, unsigned int thoff)
+ {
+ 	struct tcphdr *tcph;
+ 
++	if (proto != IPPROTO_TCP)
++		return 0;
++
+ 	if (!pskb_may_pull(skb, thoff + sizeof(*tcph)))
+ 		return -1;
+ 
+@@ -248,7 +251,7 @@ nf_flow_offload_ip_hook(void *priv, stru
+ 		return NF_DROP;
+ 
+ 	thoff = ip_hdr(skb)->ihl * 4;
+-	if (nf_flow_tcp_state_check(flow, skb, thoff))
++	if (nf_flow_state_check(flow, ip_hdr(skb)->protocol, skb, thoff))
+ 		return NF_ACCEPT;
+ 
+ 	if (flow->flags & (FLOW_OFFLOAD_SNAT | FLOW_OFFLOAD_DNAT) &&
+@@ -460,7 +463,8 @@ nf_flow_offload_ipv6_hook(void *priv, st
+ 	if (unlikely(nf_flow_exceeds_mtu(skb, flow->tuplehash[dir].tuple.mtu)))
+ 		return NF_ACCEPT;
+ 
+-	if (nf_flow_tcp_state_check(flow, skb, sizeof(*ip6h)))
++	if (nf_flow_state_check(flow, ipv6_hdr(skb)->nexthdr, skb,
++				sizeof(*ip6h)))
+ 		return NF_ACCEPT;
+ 
+ 	if (skb_try_make_writable(skb, sizeof(*ip6h)))