Re: [Xen-devel] [PATCH 5/7] xen-netfront: reduce gso_max_size to account for ethernet header

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2013-04-12 at 09:48 +0100, Wei Liu wrote:
> On Fri, Apr 12, 2013 at 09:18:04AM +0100, Ian Campbell wrote:
> > On Thu, 2013-04-11 at 21:04 +0100, Wei Liu wrote:
> > > On Tue, Apr 09, 2013 at 12:07:33PM +0100, Wei Liu wrote:
> > > > The maximum packet including ethernet header that can be handled by 
> > > > netfront /
> > > > netback wire format is 65535. Reduce gso_max_size accordingly.
> > > > 
> > > > Drop skb and print warning when skb->len > 65535. This can 1) save the 
> > > > effort
> > > > to send malformed packet to netback, 2) help spotting misconfiguration 
> > > > of
> > > > netfront in the future.
> > > > 
> > > 
> > > Any opinion on how much space should be reserved? From a previous thread
> > > Ben seemed to suggest 90 (Ethernet + VLAN tag + IPv6 + TCP + timestamp
> > > option = 90 bytes).
> > 
> > I trust Ben and that seems as good as anything to me.
> > 
> > Is this the sort of limit others might be interested in, should we have
> > a global #define?
> > 
> 
> We shall have a global define in this case.
> 
> #define XEN_NETFRONT_MAX_HEADER ? I'm bad at naming things.

I meant an include/linux/skbuff.h (or some suitable header) #define
SKB_MAX_FOO type thing...

Ian.


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