[Ns-developers] icmpv4 stack for merging

[Tom Henderson]

>> Mathieu Lacage wrote:
>> 
>> I think the behavior you want to implement, if MtuDiscover attribute is 
>> set, is the following:
>> i) set the DF bit
>> ii) keep a member mtu variable around that is initialized to the 
>> outgoing interface MTU
>
>The problem with the above is that we have to do a route lookup for
>every outgoing packet: we can't do a single lookup at the start and,
>then, assume that the result of the lookup will be the same all the time
>because:
>  1) the destination address could change
>  2) the forwarding table content could change
>
>> iii) update this local mtu variable upon receipt of ICMP messages
>> iv) if (p->GetSize > mtu) then set EMSGSIZE errno
>
>I was really hoping that, instead, the mtu would be set in the
>forwarding table when/if you complete your ipv4 rework. 

The mtu should be settable in the routing cache entry when the IPv4 rework is done.  I was just suggesting an interim solution for the current codebase, but it would probably be just as well to pick this up as part of the IPv4 rework.

Tom