I'm submitting this fast-track for Erik Nordmark, it times out on
09/23/2009. The release binding is Patch.
Background:
----------
Busy DNS servers, and other servers that do UDP request/response
protocols, typically want to avoid Path MTU discovery since path MTU
discovery both adds latency (a packet would be dropped by routers
instead of being fragmented and forward) and adds state on the server
(Path MTU state would be created for the destination IP address).
That is counterproductive when there are lots of clients that do a
single UDP request/response to the server.
Details:
-------
For IPv6 we have had two socket options to control this (from RFC 3542)
IPv6_USE_MIN_MTU and IPV6_DONTFRAG.
But there is no standard for IPv4.
However, FreeBSD implements an IP_DONTFRAG socket option, which is used
by the BIND DNS server software.
This case is to introduce IP_DONTFRAG in Solaris.
Exported Interfaces
-------------------------------------------------------------
Interface Classification Comments
-------------------------------------------------------------
IP_DONTFRAG Committed ip(7P)
-------------------------------------------------------------
Man page updates:
================
Add this text to ip(7P) after IP_TOS:
IP_DONTFRAG If enabled (the default) then the Don't
Fragment flag is set on IP packets. Disabling
the option means that Don't Fragment will not
be set which will result in not creating any
Path MTU state due to this socket.
