Code paths setting gso_size

Code paths setting gso_size

[William Allen Simpson]

This is a new thread dedicated to a specific topic, spawned by an
earlier discussion.  I've CC'd only those that participated recently.

I've written:
# In this particular instance, I suggest that you take a look at all the
# places that gso_size is set, and cross index with all the code paths that
# place these TCP headers onto the txq without a check of doff -- as I did!
#
# I'll specifically mention the tun and virtio_net devices, but I'm also
# particularly concerned with af_packet.c and skbuff.c -- and the general
# problem with inet_lro.c, too.
#
# Amazingly enough, folks sometimes use Linux for routers....
#

Eric (and David) have written:
# Only *locally* generated trafic by linux kernel can enter this path.
#

So, let us begin with the tun device, and work our way through the others.

Re: Code paths setting gso_size

[Eric Dumazet]

Le samedi 13 mars 2010 à 06:22 -0500, William Allen Simpson a écrit :
> This is a new thread dedicated to a specific topic, spawned by an
> earlier discussion.  I've CC'd only those that participated recently.
> 
> I've written:
> # In this particular instance, I suggest that you take a look at all the
> # places that gso_size is set, and cross index with all the code paths that
> # place these TCP headers onto the txq without a check of doff -- as I did!
> #
> # I'll specifically mention the tun and virtio_net devices, but I'm also
> # particularly concerned with af_packet.c and skbuff.c -- and the general
> # problem with inet_lro.c, too.
> #
> # Amazingly enough, folks sometimes use Linux for routers....
> #
> 
> Eric (and David) have written:
> # Only *locally* generated trafic by linux kernel can enter this path.
> #
> 
> So, let us begin with the tun device, and work our way through the others.
> 

Thats a really good idea William, I'll start another thread to study all
the paths setting skb->len to a possible wrong value. But I'll do this
in my own time, and if I find something, I'll post a patch.

Sure we'll find some bugs by this studies, since in average we find 100
bugs per month, and introduce 90 new ones, thanks God for this.