[PATCH net-next 1/3] tun: don't probe the transport header of packets written by userspace

[Antonio Quartulli <antonio@mandelbit.com>]

tun_get_user() runs the flow dissector on every written packet only to
set the transport header. Packets that need it early already get it:
skb_partial_csum_set() for NEEDS_CSUM, __virtio_net_hdr_to_skb() for
GSO. For the rest, the IPv4/IPv6 receive paths set it, as for packets
from NICs.

Drop the probe: ~200 fewer instructions per 1400-byte packet, -6.5%
when dropped at the raw table, -2.4% through conntrack and NAT
(emulated Cortex-A7).

Signed-off-by: Antonio Quartulli <antonio@mandelbit.com>
---
 drivers/net/tun.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 8920c797acfd..9fc60a73fb96 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1960,7 +1960,6 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 		net_zcopy_complete(NULL, msg_control, false);
 
 	skb_reset_network_header(skb);
-	skb_probe_transport_header(skb);
 	skb_record_rx_queue(skb, tfile->queue_index);
 
 	if (skb_xdp) {
-- 
2.56.0