From: Antonio Quartulli <antonio@mandelbit.com>
To: willemdebruijn.kernel@gmail.com, jasowangio@gmail.com
Cc: Antonio Quartulli <antonio@mandelbit.com>,
andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@kernel.org,
kuba@kernel.org, pabeni@redhat.com, ast@kernel.org,
daniel@iogearbox.net, hawk@kernel.org, john.fastabend@gmail.com,
sdf@fomichev.me, netdev@vger.kernel.org, bpf@vger.kernel.org
Subject: [PATCH net-next 3/3] tun: skip the virtio-net header parsing without IFF_VNET_HDR
Date: Thu, 12 Nov 2026 16:06:05 +0100 [thread overview]
Message-ID: <20261112150612.3866546-4-antonio@mandelbit.com> (raw)
In-Reply-To: <20261112150612.3866546-1-antonio@mandelbit.com>
Without IFF_VNET_HDR, tun_get_user() still passes an all-zero header to
tun_vnet_hdr_tnl_to_skb(), which then only resets the MAC header. Do
just that.
-1.6% instructions per 1400-byte packet dropped at the raw table, -2.2%
when written 64 per write() (emulated x86).
Signed-off-by: Antonio Quartulli <antonio@mandelbit.com>
---
drivers/net/tun.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 395923651f31..38f9da1ab462 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1943,7 +1943,10 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
break;
}
- if (tun_vnet_hdr_tnl_to_skb(tun->flags, features, skb, &hdr)) {
+ if (!(tun->flags & IFF_VNET_HDR)) {
+ /* all a zeroed header would do */
+ skb_reset_mac_header(skb);
+ } else if (tun_vnet_hdr_tnl_to_skb(tun->flags, features, skb, &hdr)) {
atomic_long_inc(&tun->rx_frame_errors);
err = -EINVAL;
goto free_skb;
--
2.56.0
prev parent reply other threads:[~2026-11-12 15:06 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-12 15:06 [PATCH net-next 0/3] tun: trim per-packet work on the write path Antonio Quartulli
2026-11-12 15:06 ` [PATCH net-next 1/3] tun: don't probe the transport header of packets written by userspace Antonio Quartulli
2026-11-12 15:06 ` [PATCH net-next 2/3] tun: don't disable BHs for the XDP program check of every packet Antonio Quartulli
2026-11-12 15:06 ` Antonio Quartulli [this message]
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