[PATCH 5.1 04/96] netfilter: nft_flow_offload: set liberal tracking mode for tcp

Greg Kroah-Hartman
2019-07-08T15:32:28Z

From: Florian Westphal <fw@strlen.de>

commit 8437a6209f76f85a2db1abb12a9bde2170801617 upstream.

Without it, whenever a packet has to be pushed up the stack (e.g. because
of mtu mismatch), then conntrack will flag packets as invalid, which in
turn breaks NAT.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/netfilter/nft_flow_offload.c | 8 ++++++++
1 file changed, 8 insertions(+)

--- a/net/netfilter/nft_flow_offload.c
+++ b/net/netfilter/nft_flow_offload.c
@@ -72,6 +72,7 @@ static void nft_flow_offload_eval(const
struct nf_flow_route route;
struct flow_offload *flow;
enum ip_conntrack_dir dir;
+ bool is_tcp = false;
struct nf_conn *ct;
int ret;

@@ -84,6 +85,8 @@ static void nft_flow_offload_eval(const

switch (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum) {
case IPPROTO_TCP:
+ is_tcp = true;
+ break;
case IPPROTO_UDP:
break;
default:
@@ -109,6 +112,11 @@ static void nft_flow_offload_eval(const
if (!flow)
goto err_flow_alloc;

+ if (is_tcp) {
+ ct->proto.tcp.seen[0].flags |= IP_CT_TCP_FLAG_BE_LIBERAL;
+ ct->proto.tcp.seen[1].flags |= IP_CT_TCP_FLAG_BE_LIBERAL;
+ }
+
ret = flow_offload_add(flowtable, flow);
if (ret < 0)
goto err_flow_add;