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 ,