linux-kernel - Re: [PATCH] NET: Proper handling of IPv6 header in tun driver when TUN_NO

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Date:	Wed, 18 Jun 2008 10:13:31 +0800
From:	Ang Way Chuang <wcang@...6.org>
To:	David Miller <davem@...emloft.net>
CC:	maxk@...lcomm.com, steve.zabele@...systems.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] NET: Proper handling of IPv6 header in tun driver when
 TUN_NO_PI is set

David Miller wrote:
> From: Max Krasnyanskiy <maxk@...lcomm.com>
> Date: Fri, 06 Jun 2008 13:21:06 -0700
> 
>> Acked-by: Max Krasnyansky <maxk@...lcomm.com>
>>
>> Dave, can you please add this patch to your tree.
> 
> I can't, the patch is severely whitespace damaged.
> 
Resend. Hopefully Thunderbird won't screw this time.

By default, tun.c running in TUN_TUN_DEV mode will set the protocol of packet
to IPv4 if TUN_NO_PI is set. My program failed to work when I assumed that
the driver will check the first nibble of packet, determine IP version and set
the appropriate protocol.

Signed-off-by: Ang Way Chuang <wcang@...6.org>
---

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 0ce07a3..f97bb9b 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -313,6 +313,21 @@ static __inline__ ssize_t tun_get_user(struct tun_struct *tun, struct iovec *iv,

        switch (tun->flags & TUN_TYPE_MASK) {
        case TUN_TUN_DEV:
+                if (tun->flags & TUN_NO_PI) {
+                        switch (skb->data[0] & 0xf0) {
+                        case 0x40:
+                                pi.proto = htons(ETH_P_IP);
+                                break;
+                        case 0x60:
+                                pi.proto = htons(ETH_P_IPV6);
+                                break;
+                        default:
+                                tun->dev->stats.rx_dropped++;
+                                kfree_skb(skb);
+                                return -EINVAL;
+                        }
+                }
+
                skb_reset_mac_header(skb);
                skb->protocol = pi.proto;
                skb->dev = tun->dev;

--
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