generic l2tp: drop flow hash on forward

Drop the flow-hash of the skb when forwarding to the L2TP netdev.

This avoids the L2TP qdisc from using the flow-hash from the outer
packet, which is identical for every flow within the tunnel.

This does not affect every platform but is specific for the ethernet
driver. It depends on the platform including L4 information in the
flow-hash.

Signed-off-by: David Bauer <mail@david-bauer.net>
(cherry picked from commit 35a5e62da7275a4a1423df6238340dd08eeff3c9)

diff --git a/target/linux/generic/pending-5.15/778-net-l2tp-drop-flow-hash-on-forward.patch b/target/linux/generic/pending-5.15/778-net-l2tp-drop-flow-hash-on-forward.patch
new file mode 100644 (file)
index 0000000..a2c0edc
--- /dev/null
+++ b/target/linux/generic/pending-5.15/778-net-l2tp-drop-flow-hash-on-forward.patch
@@ -0,0 +1,31 @@
+From 4a44a52f16ccd3d03e0cb5fb437a5eb31a5f9f05 Mon Sep 17 00:00:00 2001
+From: David Bauer <mail@david-bauer.net>
+Date: Mon, 26 Feb 2024 21:39:34 +0100
+Subject: [PATCH] net l2tp: drop flow hash on forward
+
+Drop the flow-hash of the skb when forwarding to the L2TP netdev.
+
+This avoids the L2TP qdisc from using the flow-hash from the outer
+packet, which is identical for every flow within the tunnel.
+
+This does not affect every platform but is specific for the ethernet
+driver. It depends on the platform including L4 information in the
+flow-hash.
+
+Signed-off-by: David Bauer <mail@david-bauer.net>
+---
+ net/l2tp/l2tp_eth.c | 3 +++
+ 1 file changed, 3 insertions(+)
+
+--- a/net/l2tp/l2tp_eth.c
++++ b/net/l2tp/l2tp_eth.c
+@@ -136,6 +136,9 @@ static void l2tp_eth_dev_recv(struct l2t
+       /* checksums verified by L2TP */
+       skb->ip_summed = CHECKSUM_NONE;
+ 
++      /* drop outer flow-hash */
++      skb_clear_hash(skb);
++
+       skb_dst_drop(skb);
+       nf_reset_ct(skb);
+