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Date: Thu, 7 Jan 2010 09:27:48 +0100
Message-ID: <e2d7436a1001070027u44dbb9abx94541bcf7d7e2418@mail.gmail.com>
Subject: Re: [PATCH] net: packet: option to only pass skb protocol
From: =?ISO-8859-2?Q?Micha=B3_Miros=B3aw?= <mirqus@gmail.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: David Miller <davem@davemloft.net>, cfriesen@nortel.com,
       eric.dumazet@gmail.com, nhorman@tuxdriver.com,
       linux-kernel@vger.kernel.org, netdev@vger.kernel.org
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2010/1/6 Michael S. Tsirkin <mst@redhat.com>:
> On Tue, Jan 05, 2010 at 03:51:50PM -0800, David Miller wrote:
>> From: "Chris Friesen" <cfriesen@nortel.com>
>> Date: Tue, 05 Jan 2010 16:13:29 -0600
>> > If SOCK_RAW packets are being sent, the protocol number is embedded in
>> > the packet data
>> Where exactly is that protocol value? ?Not every link level protocol
>> is ethernet.
>> We support FDDI, HIPPI, wireless, VLAN, PPP, and a host of others.
>> So you can't know for sure unless you assume ethernet, which you
>> can't do.
> You are right. ?This is TX though so the socket is bound to a specific
> device, and devices know which link protocol they use. ?So we could add a
> get_protocol operation to each device type, and call it if the protocol
> passed is ETH_P_ALL to get the real one.
>
> Like this: except I only added this for ethernet, and I would have to
> add this for the rest of device types. But I would like to hear what
> others think about this before I do the rest of the work for the rest of
> device types.
>
> Does the below look sane?
>
[...]
> diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
> index 205a1c1..3e7761d 100644
> --- a/net/ethernet/eth.c
> +++ b/net/ethernet/eth.c
> @@ -231,6 +231,17 @@ int eth_header_parse(const struct sk_buff *skb, unsigned char *haddr)
> ?EXPORT_SYMBOL(eth_header_parse);
>
> ?/**
> + * eth_get_protocol - extract protocol value from packet
> + * @skb: packet to extract protocol from
> + * @dev: source device
> + */
> +__be16 eth_get_protocol(const struct sk_buff *skb, struct net_device *dev)
> +{
> + ? ? ? const struct ethhdr *eth = eth_hdr(skb);
> + ? ? ? return eth->h_proto
> +}
[...]

You might want taking fragment of eth_type_trans() for this function
so that 802.2/IPX would be detected too.

Best Regards,
Micha? Miros?aw
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