Re: [Linux-ATM-General] [RFC][PATCH 0/2] atm: br2682: Improve encapsulation checks and headroom allocation

[chas w. - C. <ch...@cm...>]

On Wed, 03 Aug 2011 22:22:33 +0200
Pascal Hambourg <pa...@pl...> wrote:

> Discussion :
> Should we check the padding bytes value in received bridged PDUs ?


> Or should we follow the saying "be conservative in what you send, and
> liberal in what you accept" ?

it would say probably not.  the rfc says should be padded with octets
of 0x0, but should means:

3. SHOULD   This word, or the adjective "RECOMMENDED", mean that there
   may exist valid reasons in particular circumstances to ignore a
   particular item, but the full implications must be understood and
   carefully weighed before choosing a different course.

we are talking about PAD_BRIDGED right?

> Currently, it is checked in VC-MUX mode, but not in LLC mode.

we should probably be consistent.

> [PATCH 2/2] atm: br2684: Do not allocate more headroom than needed
> 
>  Routed encapsulation requires less headroom than bridged encapsulation.

i have meant to check into this for a while.  shouldnt hard_header_len
be set correctly when the interface is configured in the first place to
make the whole skb_headroom() < minheadroom unlikely?