o Use new function ip_fillid() in all places throughout the kernel,

  where we want to create a new IP datagram.
o Add support for RFC6864, which allows to set IP ID for atomic IP
  datagrams to any value, to improve performance. The behaviour is
  controlled by net.inet.ip.rfc6864 sysctl knob, which is enabled by
  default.
o In case if we generate IP ID, use counter(9) to improve performance.
o Gather all code related to IP ID into ip_id.c.

Differential Revision:		https://reviews.freebsd.org/D2177
Reviewed by:			adrian, cy, rpaulo
Tested by:			Emeric POUPON <emeric.poupon stormshield.eu>
Sponsored by:			Netflix
Sponsored by:			Nginx, Inc.
Relnotes:			yes

1 files changed, 15 insertions, 3 deletions

diff --git a/share/man/man4/inet.4 b/share/man/man4/inet.4
index b0b5a9e..3a2bf8a 100644
--- a/share/man/man4/inet.4
+++ b/share/man/man4/inet.4
@@ -28,7 +28,7 @@
 .\"     From: @(#)inet.4	8.1 (Berkeley) 6/5/93
 .\" $FreeBSD$
 .\"
-.Dd January 26, 2012
+.Dd April 2, 2015
 .Dt INET 4
 .Os
 .Sh NAME
@@ -226,12 +226,24 @@ This
 .Xr sysctl 8
 variable affects packets destined for a local host as well as packets
 forwarded to some other host.
+.It Va ip.rfc6864
+Boolean: control IP IDs generation behaviour.
+True value enables RFC6864 support, which specifies that IP ID field of
+.Em atomic
+datagrams can be set to any value.
+The
+.Fx implementation sets it to zero.
+Enabled by default.
 .It Va ip.random_id
 Boolean: control IP IDs generation behaviour.
 Setting this
 .Xr sysctl 8
-to non-zero causes the ID field in IP packets to be randomized instead of
-incremented by 1 with each packet generated.
+to 1 causes the ID field in
+.Em non-atomic
+IP datagrams (or all IP datagrams, if
+.Va ip.rfc6864
+is disabled) to be randomized instead of incremented by 1 with each packet
+generated.
 This closes a minor information leak which allows remote observers to
 determine the rate of packet generation on the machine by watching the
 counter.