From 6a5e0b0428c1a47d0321cb34f2546f50b9b0b3ea Mon Sep 17 00:00:00 2001
From: andre <andre@FreeBSD.org>
Date: Tue, 13 Nov 2012 20:52:17 +0000
Subject: [PATCH] Remove description of deprecated IP fragment checksum
 support. Since SMPng it wasn't really supported anymore and if it worked then
 only by chance.  Only very few drivers ever supported it.

Discussed with:	yongari
MFC after:	2 weeks
---
 share/man/man9/mbuf.9 | 57 +------------------------------------------
 1 file changed, 1 insertion(+), 56 deletions(-)

diff --git a/share/man/man9/mbuf.9 b/share/man/man9/mbuf.9
index 6fa131e160ec..42fe3723e40e 100644
--- a/share/man/man9/mbuf.9
+++ b/share/man/man9/mbuf.9
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd April 18, 2011
+.Dd November 13, 2012
 .Dt MBUF 9
 .Os
 .\"
@@ -1063,45 +1063,6 @@ In this case, the checksum field will be initially
 set by the TCP/IP module to the checksum of the pseudo header
 defined by the TCP and UDP specifications.
 .Pp
-For outbound packets which have been fragmented
-by the host CPU, the following will also be true,
-regardless of the checksum flag settings:
-.Bl -bullet -offset indent
-.It
-all fragments will have the flag
-.Dv M_FRAG
-set in their
-.Va m_flags
-field;
-.It
-the first and the last fragments in the chain will have
-.Dv M_FIRSTFRAG
-or
-.Dv M_LASTFRAG
-set in their
-.Va m_flags ,
-correspondingly;
-.It
-the first fragment in the chain will have the total number
-of fragments contained in its
-.Va csum_data
-field.
-.El
-.Pp
-The last rule for fragmented packets takes precedence over the one
-for a TCP or UDP checksum.
-Nevertheless, offloading a TCP or UDP checksum is possible for a
-fragmented packet if the flag
-.Dv CSUM_IP_FRAGS
-is set in the field
-.Va ifnet.if_data.ifi_hwassist
-associated with the network interface.
-However, in this case the interface is expected to figure out
-the location of the checksum field within the sequence of fragments
-by itself because
-.Va csum_data
-contains a fragment count instead of a checksum offset value.
-.Pp
 On input, an interface indicates the actions it has performed
 on a packet by setting one or more of the following flags in
 .Va csum_flags
@@ -1147,22 +1108,6 @@ It is a peculiarity of the algorithm used that the Internet checksum
 calculated over any valid packet will be
 .Li 0xFFFF
 as long as the original checksum field is included.
-.Pp
-For inbound packets which are IP fragments, all
-.Va csum_data
-fields will be summed during reassembly to obtain the final checksum
-value passed to an upper layer in the
-.Va csum_data
-field of the reassembled packet.
-The
-.Va csum_flags
-fields of all fragments will be consolidated using logical AND
-to obtain the final value for
-.Va csum_flags .
-Thus, in order to successfully
-offload checksum computation for fragmented data,
-all fragments should have the same value of
-.Va csum_flags .
 .Sh STRESS TESTING
 When running a kernel compiled with the option
 .Dv MBUF_STRESS_TEST ,