kernel: fix flow offload UDP handling issue

Only run the TCP state check for TCP connections

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

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 (file)
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@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@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)))