diff mbox series

[nf-next,v2,2/6] netfilter: nft_flow_offload: update tcp state flags under lock

Message ID 20250114162702.9128-2-pablo@netfilter.org
State Accepted
Headers show
Series [nf-next,v2,1/6] netfilter: nft_flow_offload: clear tcp MAXACK flag before moving to slowpath | expand

Commit Message

Pablo Neira Ayuso Jan. 14, 2025, 4:26 p.m. UTC 
From: Florian Westphal <fw@strlen.de>

The conntrack entry is already public, there is a small chance that another
CPU is handling a packet in reply direction and racing with the tcp state
update.

Move this under ct spinlock.

This is done once, when ct is about to be offloaded, so this should
not result in a noticeable performance hit.

Fixes: 8437a6209f76 ("netfilter: nft_flow_offload: set liberal tracking mode for tcp")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
v2: no changes

 net/netfilter/nft_flow_offload.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)
diff mbox series

Patch

diff --git a/net/netfilter/nft_flow_offload.c b/net/netfilter/nft_flow_offload.c
index 3b474d235663..221d50223018 100644
--- a/net/netfilter/nft_flow_offload.c
+++ b/net/netfilter/nft_flow_offload.c
@@ -289,6 +289,15 @@  static bool nft_flow_offload_skip(struct sk_buff *skb, int family)
 	return false;
 }
 
+static void flow_offload_ct_tcp(struct nf_conn *ct)
+{
+	/* conntrack will not see all packets, disable tcp window validation. */
+	spin_lock_bh(&ct->lock);
+	ct->proto.tcp.seen[0].flags |= IP_CT_TCP_FLAG_BE_LIBERAL;
+	ct->proto.tcp.seen[1].flags |= IP_CT_TCP_FLAG_BE_LIBERAL;
+	spin_unlock_bh(&ct->lock);
+}
+
 static void nft_flow_offload_eval(const struct nft_expr *expr,
 				  struct nft_regs *regs,
 				  const struct nft_pktinfo *pkt)
@@ -356,11 +365,8 @@  static void nft_flow_offload_eval(const struct nft_expr *expr,
 		goto err_flow_alloc;
 
 	flow_offload_route_init(flow, &route);
-
-	if (tcph) {
-		ct->proto.tcp.seen[0].flags |= IP_CT_TCP_FLAG_BE_LIBERAL;
-		ct->proto.tcp.seen[1].flags |= IP_CT_TCP_FLAG_BE_LIBERAL;
-	}
+	if (tcph)
+		flow_offload_ct_tcp(ct);
 
 	__set_bit(NF_FLOW_HW_BIDIRECTIONAL, &flow->flags);
 	ret = flow_offload_add(flowtable, flow);