1.\" Copyright (c) 1996-1999 Whistle Communications, Inc. 2.\" All rights reserved. 3.\" 4.\" Subject to the following obligations and disclaimer of warranty, use and 5.\" redistribution of this software, in source or object code forms, with or 6.\" without modifications are expressly permitted by Whistle Communications; 7.\" provided, however, that: 8.\" 1. Any and all reproductions of the source or object code must include the 9.\" copyright notice above and the following disclaimer of warranties; and 10.\" 2. No rights are granted, in any manner or form, to use Whistle 11.\" Communications, Inc. trademarks, including the mark "WHISTLE 12.\" COMMUNICATIONS" on advertising, endorsements, or otherwise except as 13.\" such appears in the above copyright notice or in the software. 14.\" 15.\" THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND 16.\" TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO 17.\" REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE, 18.\" INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF 19.\" MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. 20.\" WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY 21.\" REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS 22.\" SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE. 23.\" IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES 24.\" RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING 25.\" WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, 26.\" PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR 27.\" SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY 28.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 29.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 30.\" THIS SOFTWARE, EVEN IF WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY 31.\" OF SUCH DAMAGE. 32.\" 33.\" Author: Archie Cobbs <archie@FreeBSD.org> 34.\" 35.\" $FreeBSD$ 36.\" $Whistle: ng_vjc.8,v 1.4 1999/01/25 23:46:28 archie Exp $ 37.\" 38.Dd January 19, 1999 39.Dt NG_VJC 4 40.Os 41.Sh NAME 42.Nm ng_vjc 43.Nd Van Jacobson compression netgraph node type 44.Sh SYNOPSIS 45.In net/slcompress.h 46.In netgraph/ng_vjc.h 47.Sh DESCRIPTION 48The 49.Nm vjc 50node type performs Van Jacobson compression, which is used 51over PPP, SLIP, and other point-to-point IP connections to 52compress TCP packet headers. The 53.Dv ip 54hook represents the uncompressed side of the node, while the 55.Dv vjcomp , 56.Dv vjuncomp , 57and 58.Dv vjip 59hooks represent the compressed side of the node. Packets received on the 60.Dv ip 61will be compressed or passed through as appropriate. Packets received 62on the other three hooks will be uncompressed as appropriate. 63This node also supports 64.Dq always pass through 65mode in either direction. 66.Pp 67Van Jacobson compression only applies to TCP packets. 68Only 69.Dq normal 70(i.e., common case) TCP packets are actually compressed. 71These are output on the 72.Dv vjcomp 73hook. Other TCP packets are run through the state machine but not 74compressed; these appear on the 75.Dv vjuncomp 76hook. 77Other non-TCP IP packets are forwarded unchanged to 78.Dv vjip . 79.Pp 80When connecting to a 81.Xr ng_ppp 4 82node, the 83.Dv ip , 84.Dv vjuncomp , 85.Dv vjcomp , 86and 87.Dv vjip 88hooks should be connected to the 89.Xr ng_ppp 4 90node's 91.Dv vjc_ip , 92.Dv vjc_vjcomp , 93.Dv vjc_vjuncomp , 94and 95.Dv vjc_ip 96hooks, respectively. 97.Sh HOOKS 98This node type supports the following hooks: 99.Pp 100.Bl -tag -width foobarbazi 101.It Dv ip 102Upstream (uncompressed) IP packets. 103.It Dv vjcomp 104Downstream compressed TCP packets. 105.It Dv vjuncomp 106Downstream uncompressed TCP packets. 107.It Dv vjip 108Downstream uncompressed IP packets. 109.El 110.Sh CONTROL MESSAGES 111This node type supports the generic control messages, plus the following: 112.Bl -tag -width foo 113.It Dv NGM_VJC_SET_CONFIG 114This command resets the compression state and configures it according 115to the supplied 116.Dv "struct ngm_vjc_config" 117argument. This structure contains the following fields: 118.Bd -literal -offset 4n 119struct ngm_vjc_config { 120 u_char enableComp; /* Enable compression */ 121 u_char enableDecomp; /* Enable decompression */ 122 u_char maxChannel; /* Number of outgoing channels - 1 */ 123 u_char compressCID; /* OK to compress outgoing CID's */ 124}; 125.Ed 126.Pp 127When 128.Dv enableComp 129is set to zero, all packets received on the 130.Dv ip 131hook are forwarded unchanged out the 132.Dv vjip 133hook. Similarly, when 134.Dv enableDecomp 135is set to zero, all packets received on the 136.Dv vjip 137hook are forwarded unchanged out the 138.Dv ip 139hook, and packets are not accepted on the 140.Dv vjcomp 141and 142.Dv vjuncomp 143hooks. 144When a node is first created, 145both compression and decompression are disabled and the node is 146therefore operating in bi-directional 147.Dq pass through 148mode. 149.Pp 150When enabling compression, 151.Dv maxChannel 152should be set to the number of outgoing compression channels minus one, 153and is a value between 3 and 15, inclusive. The 154.Dv compressCID 155field indicates whether it is OK to compress the CID header field for 156outgoing compressed TCP packets. This value should be zero unless 157either (a) it is not possible for an outgoing frame to be lost, or 158(b) lost frames can be reliably detected and immediately 159reported to the peer's decompression engine (see 160.Dv NGM_VJC_RECV_ERROR 161below). 162.It Dv NGM_VJC_GET_STATE 163This command returns the node's current state described by the 164.Dv "struct slcompress" 165structure, which is defined in 166.Pa net/slcompress.h . 167.It Dv NGM_VJC_CLR_STATS 168Clears the node statistics counters. Statistics are also cleared whenever the 169.Dv enableComp 170or 171.Dv enableDecomp 172fields are changed from zero to one by a 173.Dv NGM_VJC_SET_CONFIG 174control message. 175.It Dv NGM_VJC_RECV_ERROR 176When the peer has CID header field compression enabled, 177this message must be sent to the local 178.Nm vjc 179node immediately 180after detecting that a received frame has been lost, due to a bad 181checksum or for any other reason. Failing to do this can result 182in corrupted TCP stream data. 183.El 184.Sh SHUTDOWN 185This node shuts down upon receipt of a 186.Dv NGM_SHUTDOWN 187control message, or when all hooks have been disconnected. 188.Sh BUGS 189Because the initialization routine in the kernel implementation of 190Van Jacobson compression initializes both compression and decompression 191at once, this node does not allow compression and decompression to 192be enabled in separate operations. In order to enable one when 193the other is already enabled, first both must be disabled, then 194both enabled. This of course resets the node state. This restriction 195may be lifted in a later version. 196.Pp 197When built as a loadable kernel module, this module includes the file 198.Pa net/slcompress.c . 199Although loading the module should fail if 200.Pa net/slcompress.c 201already exists in the kernel, currently it does not, and the duplicate 202copies of the file do not interfere. 203However, this may change in the future. 204.Sh SEE ALSO 205.Xr netgraph 4 , 206.Xr ng_iface 4 , 207.Xr ng_ppp 4 , 208.Xr ngctl 8 209.Rs 210.%A V. Jacobson 211.%T "Compressing TCP/IP Headers" 212.%O RFC 1144 213.Re 214.Rs 215.%A G. McGregor 216.%T "The PPP Internet Control Protocol (IPCP)" 217.%O RFC 1332 218.Re 219.Sh HISTORY 220The 221.Nm 222node type was implemented in 223.Fx 4.0 . 224.Sh AUTHORS 225.An Archie Cobbs Aq archie@FreeBSD.org 226