UDP dont fragment bit

[Robert Watson]

On Wed, 21 Sep 2005, Andre Oppermann wrote:

> I can think of a couple of uses to say IP DF on a UDP socket.  Will cook 
> up a patch to add such a sysctl in a few hours.

The problem is that I think this solves only half of the likely problem. 
If what application developers really want is a way to do PMTU for 
UDP-based applications, the other half has to be done too: the ability to 
receive and process MTU data on the socket.  Given that UDP sockets are 
often used unconnected, this means providing at least two additional 
pieces of information for ICMP MTU events: host/path information, and the 
MTU cap reported.  And as UDP sockets are often used for quite a bit of 
traffic to different hosts at once, we might want to find a way to do this 
under load with an event stream rather than a condition queried using a 
simple socket option.

So I think learning a bit more about the specific applications would be 
quite helpful -- in particular, what ICMP/MTU information they want, and 
how they will use it.

Robert N M Watson