Re: PMTU issues due to TOS field manipulation (for DSCP)

[Julian Anastasov <ja@xxxxxx>]

        Hello,

On Wed, 10 Dec 2003, Andi Kleen wrote:

> I don't think the network users will be very happy if you require changing all
> end hosts this way. How about the following hack? For DF=1 packets
> the ipid field is useless. When you rewrite the TOS to DSCP save
> the old TOS in the ipid field.  When you see an ICMP fragment required
> message with the right DSCP on the router restore the old TOS from the ipid
> field.

        It can be an option: pmtu_promisc or whatever (default 0).
We should avoid using TOS as hash key and if the var is 1 we should
ignore matching the tos keys in ip_rt_frag_needed and ip_rt_redirect.
By this way, all cache entries between saddr and daddr will be updated, no 
matter the TOS or even OIF keys. Comments?

Regards

--
Julian Anastasov <ja@xxxxxx>