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@whistle.com> 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 8 40.Os FreeBSD 41.Sh NAME 42.Nm ng_vjc 43.Nd Van Jacobsen compression netgraph node type 44.Sh SYNOPSIS 45.Fd #include <net/slcompress.h> 46.Fd #include <netgraph/ng_vjc.h> 47.Sh DESCRIPTION 48The 49.Nm vjc 50node type performs Van Jacobsen 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 Jacobsen 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 8 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 8 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.Sh CONTROL MESSAGES 110This node type supports the generic control messages, plus the following: 111.Bl -tag -width foo 112.It Dv NGM_VJC_SET_CONFIG 113This command resets the compression state and configures it according 114to the supplied 115.Dv "struct ngm_vjc_config" 116argument. This structure contains the following fields: 117.Bd -literal -offset 4n 118struct ngm_vjc_config { 119 u_char enableComp; /* Enable compression */ 120 u_char enableDecomp; /* Enable decompression */ 121 u_char maxChannel; /* Number of outgoing channels - 1 */ 122 u_char compressCID; /* OK to compress outgoing CID's */ 123}; 124.Ed 125.Pp 126When 127.Dv enableComp 128is set to zero, all packets received on the 129.Dv ip 130hook are forwarded unchanged out the 131.Dv vjip 132hook. Similarly, when 133.Dv enableDecomp 134is set to zero, all packets received on the 135.Dv vjip 136hook are forwarded unchanged out the 137.Dv ip 138hook, and packets are not accepted on the 139.Dv vjcomp 140and 141.Dv vjuncomp 142hooks. 143When a node is first created, 144both compression and decompression are disabled and the node is 145therefore operating in bi-directional 146.Dq pass through 147mode. 148.Pp 149When enabling compression, 150.Dv maxChannel 151should be set to the number of outgoing compression channels minus one, 152and is a value between 3 and 15, inclusive. The 153.Dv compressCID 154field indicates whether it is OK to compress the CID header field for 155outgoing compressed TCP packets. This value should be zero unless 156either (a) it is not possible for an outgoing frame to be lost, or 157(b) lost frames can be reliably detected and immediately 158reported to the peer's decompression engine (see 159.Dv NGM_VJC_RECV_ERROR 160below). 161.It Dv NGM_VJC_GET_STATE 162This command returns the node's current state described by the 163.Dv "struct slcompress" 164structure, which is defined in 165.Pa net/slcompress.h . 166.It Dv NGM_VJC_CLR_STATS 167Clears the node statistics counters. Statistics are also cleared whenever the 168.Dv enableComp 169or 170.Dv enableDecomp 171fields are changed from zero to one by a 172.Dv NGM_VJC_SET_CONFIG 173control message. 174.It Dv NGM_VJC_RECV_ERROR 175When the peer has CID header field compression enabled, 176this message must be sent to the local 177.Nm vjc 178node immediately 179after detecting that a received frame has been lost, due to a bad 180checksum or for any other reason. Failing to do this can result 181in corrupted TCP stream data. 182.Sh SHUTDOWN 183This node shuts down upon receipt of a 184.Dv NGM_SHUTDOWN 185control message, or when all hooks have been disconnected. 186.Sh BUGS 187Because the initialization routine in the kernel implementation of 188Van Jacobsen compression initializes both compression and decompression 189at once, this node does not allow compression and decompression to 190be enabled in separate operations. In order to enable one when 191the other is already enabled, first both must be disabled, then 192both enabled. This of course resets the node state. This restriction 193may be lifted in a later version. 194.Pp 195When built as a loadable kernel module, this module includes the file 196.Pa net/slcompress.c . 197Although loading the module should fail if 198.Pa net/slcompress.c 199already exists in the kernel, currently it does not, and the duplicate 200copies of the file do not interfere. 201However, this may change in the future. 202.Sh SEE ALSO 203.Xr netgraph 4 , 204.Xr ng_ppp 8 , 205.Xr ng_iface 8 , 206.Xr ngctl 8 . 207.Rs 208.%A V. Jacobsen 209.%T "Compressing TCP/IP Headers" 210.%O RFC 1144 211.Re 212.Rs 213.%A G. McGregor 214.%T "The PPP Internet Control Protocol (IPCP)" 215.%O RFC 1332 216.Re 217.Sh HISTORY 218The 219.Nm 220node type was implemented in 221.Fx 4.0 . 222.Sh AUTHORS 223.An Archie Cobbs Aq archie@whistle.com 224