netdev - [PATCH net 5/5] tun: implement header_ops->parse_protocol for AF

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Date:   Sat, 27 Jun 2020 02:07:13 -0600
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     netdev@...r.kernel.org, davem@...emloft.net
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>
Subject: [PATCH net 5/5] tun: implement header_ops->parse_protocol for AF_PACKET

The tun driver passes up skb->protocol to userspace in the form of PI headers.
For AF_PACKET injection, we need to support its call chain of:

    packet_sendmsg -> packet_snd -> packet_parse_headers ->
      dev_parse_header_protocol -> parse_protocol

Without a valid parse_protocol, this returns zero, and the tun driver
then gives userspace bogus values that it can't deal with.

Note that this isn't the case with tap, because tap already benefits
from the shared infrastructure for ethernet headers. But with tun,
there's nothing.

Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
 drivers/net/tun.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 858b012074bd..7adeb91bd368 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -62,6 +62,7 @@
 #include <net/rtnetlink.h>
 #include <net/sock.h>
 #include <net/xdp.h>
+#include <net/ip_tunnels.h>
 #include <linux/seq_file.h>
 #include <linux/uio.h>
 #include <linux/skb_array.h>
@@ -1351,6 +1352,7 @@ static void tun_net_init(struct net_device *dev)
 	switch (tun->flags & TUN_TYPE_MASK) {
 	case IFF_TUN:
 		dev->netdev_ops = &tun_netdev_ops;
+		dev->header_ops = &ip_tunnel_header_ops;

 		/* Point-to-Point TUN Device */
 		dev->hard_header_len = 0;
-- 
2.27.0