From mboxrd@z Thu Jan  1 00:00:00 1970
From: lw@cn.fujitsu.com (Li Wei)
Date: Tue, 13 May 2014 11:04:32 +0800
Subject: Regarding skb and skb_frags
In-Reply-To: <CA+aCy1EhbKOxj9sdkEjdBWO=3TZE+gUqx6dROMvnSPfkW+hFoA@mail.gmail.com>
References: <CA+aCy1EhbKOxj9sdkEjdBWO=3TZE+gUqx6dROMvnSPfkW+hFoA@mail.gmail.com>
Message-ID: <53718BC0.90108@cn.fujitsu.com>
To: kernelnewbies@lists.kernelnewbies.org
List-Id: kernelnewbies.lists.kernelnewbies.org



On 05/01/2014 06:42 PM, Pranay Srivastava wrote:
> I was going through a function
> 
> dev_alloc_skb
> 
> and it seems that the skb_frags are created only if the data length
> passed is > PAGE_SIZE.
> 
> My question is that an Ethernet frame won't be bigger than 1500 bytes
> [correct?] so there never will be skb_frags for Ethernet frames.

No, you should consider TSO and GSO things.

Thanks

> However I've seen skb_frags appeared when sending large data.
> 
> I'm not sure how to understand this. Does the driver pokes IP header
> to check how many fragments would be coming and decides (on the rcv
> side) how much to pass in dev_alloc_skb ?
> 
> Thanks
>