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

[Pascal H. <pa...@pl...>]

Hello,

Here are two small patches for the br2684 kernel module against the 3.0
source tree. I adapted and tested them briefly on the 2.6.32 kernel I
currently use, using a pair of virtual ATM interfaces created by atmarp.

These are my first kernel patches, so please bear with me.

[PATCH 1/2] atm: br2684: Improve encapsulation checks

 - Check that the LLC header matches the expected payload type.
 - Remove the FCS bytes only if the PID is ethernet with FCS.
 - Check the data length before removing the FCS or padding bytes.

Accepting a PDU with the wrong LLC encapsulation could do nasty things.
I triggered a kernel panic by sending an LLC routed PDU to an LLC
bridged interface on a default 2.6.32 Debian kernel.

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

[PATCH 2/2] atm: br2684: Do not allocate more headroom than needed

 Routed encapsulation requires less headroom than bridged encapsulation.