linux-kernel - Re: [PATCH] Add missing skb->dev assignment in Frame Relay RX code

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Message-ID: <m3od5kaqx8.fsf@maximus.localdomain>
Date:	Sun, 29 Jun 2008 23:10:11 +0200
From:	Krzysztof Halasa <khc@...waw.pl>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	Jeff Garzik <jeff@...zik.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	<netdev@...r.kernel.org>, lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Add missing skb->dev assignment in Frame Relay RX code

Stephen Hemminger <shemminger@...tta.com> writes:

>> --- a/drivers/net/wan/hdlc_fr.c
>> +++ b/drivers/net/wan/hdlc_fr.c
>> @@ -1008,6 +1008,7 @@ static int fr_rx(struct sk_buff *skb)
>>  		stats->rx_bytes += skb->len;
>>  		if (pvc->state.becn)
>>  			stats->rx_compressed++;
>> +		skb->dev = dev;
>>  		netif_rx(skb);
>>  		return NET_RX_SUCCESS;
>>  	} else {
>
> Better to use netdev_alloc_skb for receive buffers instead.
> --- a/drivers/net/wan/hdlc_fr.c	2008-06-29 13:02:42.000000000 -0700
> +++ b/drivers/net/wan/hdlc_fr.c	2008-06-29 13:04:01.000000000 -0700
> @@ -515,7 +515,7 @@ static void fr_lmi_send(struct net_devic
>  		}
>  	}
>  
> -	skb = dev_alloc_skb(len);
> +	skb = netdev_alloc_skb(dev, len);
>  	if (!skb) {
>  		printk(KERN_WARNING "%s: Memory squeeze on fr_lmi_send()\n",
>  		       dev->name);

Well, no, that's another story - the missing assignment is in fr_rx(),
in the regular receive path (similar to 802.1q case, ethX ->
ethX.VLAN_ID transition). I.e., we get incoming packet from a hardware
driver, with skb->dev pointing to hardware hdlcX device, and we change
it to point to a logical pvcX device.

fr_lmi_send() is for control messages (generated locally) only, in TX
path. IOW we alloc skb and send it through hw driver immediately. Not
related to the bug.

That said, perhaps I should indeed use netdev_alloc_skb() for those
control messages? Or is it RX-only?
-- 
Krzysztof Halasa
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