Re: Freeing skbuff (was: Re: Sending built-by-hand packet and kernel panic.)

[Muli Ben-Yehuda <mulix@mulix.org>]

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On Mon, Feb 02, 2004 at 07:51:47PM +0200, Emmanuel Guiton wrote:

> However, my overall problem is not solved. As far as my investigations 
> led me, my sk_buff structure is never released after having been sent on 
> the wire. So I guess I need an explicit destructor function in my 
> sk_buff as the following is present in the definition of struct sk_buff:
> void         (*destructor)(struct sk_buff *);    /* Destruct function  */

Note that depending on what you're doing, you might not be able to use
the destructor, because the upper layers use it without regards to
whether it was set before. To the best of my understanding, the rules
for the destructor say that it is free for the use of whatever layer
owns the skbuff at the moment. There are three ways around it - the
first and obvious is to avoid relying on the destructor. The second is
that you can use skb_clone() to get your own copy of the headers and
the destructor (but that doesn't really help you because how does the
layer that ends up freeing the skb know to use your version of the
headers?) and the third is to use this patch,
http://www.mulix.org/patches/skb-destructor-chaining-A2-2.6.1, to 
allow more than destructor per skb. 

Hope this helps, 
Muli 
-- 
Muli Ben-Yehuda
http://www.mulix.org | http://mulix.livejournal.com/

"the nucleus of linux oscillates my world" - gccbot@#offtopic


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