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 sys/types.h 46.In netinet/in.h 47.In netinet/in_systm.h 48.In netinet/ip.h 49.In net/slcompress.h 50.In netgraph/ng_vjc.h 51.Sh DESCRIPTION 52The 53.Nm vjc 54node type performs Van Jacobson compression, which is used 55over PPP, SLIP, and other point-to-point IP connections to 56compress TCP packet headers. 57The 58.Dv ip 59hook represents the uncompressed side of the node, while the 60.Dv vjcomp , 61.Dv vjuncomp , 62and 63.Dv vjip 64hooks represent the compressed side of the node. 65Packets received on the 66.Dv ip 67will be compressed or passed through as appropriate. 68Packets received on the other three hooks will be uncompressed as appropriate. 69This node also supports 70.Dq always pass through 71mode in either direction. 72.Pp 73Van Jacobson compression only applies to TCP packets. 74Only 75.Dq normal 76(i.e., common case) TCP packets are actually compressed. 77These are output on the 78.Dv vjcomp 79hook. 80Other TCP packets are run through the state machine but not 81compressed; these appear on the 82.Dv vjuncomp 83hook. 84Other non-TCP IP packets are forwarded unchanged to 85.Dv vjip . 86.Pp 87When connecting to a 88.Xr ng_ppp 4 89node, the 90.Dv ip , 91.Dv vjuncomp , 92.Dv vjcomp , 93and 94.Dv vjip 95hooks should be connected to the 96.Xr ng_ppp 4 97node's 98.Dv vjc_ip , 99.Dv vjc_vjcomp , 100.Dv vjc_vjuncomp , 101and 102.Dv vjc_ip 103hooks, respectively. 104.Sh HOOKS 105This node type supports the following hooks: 106.Pp 107.Bl -tag -width foobarbazi 108.It Dv ip 109Upstream (uncompressed) IP packets. 110.It Dv vjcomp 111Downstream compressed TCP packets. 112.It Dv vjuncomp 113Downstream uncompressed TCP packets. 114.It Dv vjip 115Downstream uncompressed IP packets. 116.El 117.Sh CONTROL MESSAGES 118This node type supports the generic control messages, plus the following: 119.Bl -tag -width foo 120.It Dv NGM_VJC_SET_CONFIG 121This command resets the compression state and configures it according 122to the supplied 123.Dv "struct ngm_vjc_config" 124argument. 125This structure contains the following fields: 126.Bd -literal -offset 4n 127struct ngm_vjc_config { 128 u_char enableComp; /* Enable compression */ 129 u_char enableDecomp; /* Enable decompression */ 130 u_char maxChannel; /* Number of outgoing channels - 1 */ 131 u_char compressCID; /* OK to compress outgoing CID's */ 132}; 133.Ed 134.Pp 135When 136.Dv enableComp 137is set to zero, all packets received on the 138.Dv ip 139hook are forwarded unchanged out the 140.Dv vjip 141hook. 142Similarly, when 143.Dv enableDecomp 144is set to zero, all packets received on the 145.Dv vjip 146hook are forwarded unchanged out the 147.Dv ip 148hook, and packets are not accepted on the 149.Dv vjcomp 150and 151.Dv vjuncomp 152hooks. 153When a node is first created, 154both compression and decompression are disabled and the node is 155therefore operating in bi-directional 156.Dq pass through 157mode. 158.Pp 159When enabling compression, 160.Dv maxChannel 161should be set to the number of outgoing compression channels minus one, 162and is a value between 3 and 15, inclusive. 163The 164.Dv compressCID 165field indicates whether it is OK to compress the CID header field for 166outgoing compressed TCP packets. 167This value should be zero unless 168either (a) it is not possible for an outgoing frame to be lost, or 169(b) lost frames can be reliably detected and immediately 170reported to the peer's decompression engine (see 171.Dv NGM_VJC_RECV_ERROR 172below). 173.It Dv NGM_VJC_GET_STATE 174This command returns the node's current state described by the 175.Dv "struct slcompress" 176structure, which is defined in 177.In net/slcompress.h . 178.It Dv NGM_VJC_CLR_STATS 179Clears the node statistics counters. 180Statistics are also cleared whenever the 181.Dv enableComp 182or 183.Dv enableDecomp 184fields are changed from zero to one by a 185.Dv NGM_VJC_SET_CONFIG 186control message. 187.It Dv NGM_VJC_RECV_ERROR 188When the peer has CID header field compression enabled, 189this message must be sent to the local 190.Nm vjc 191node immediately 192after detecting that a received frame has been lost, due to a bad 193checksum or for any other reason. 194Failing to do this can result in corrupted TCP stream data. 195.El 196.Sh SHUTDOWN 197This node shuts down upon receipt of a 198.Dv NGM_SHUTDOWN 199control message, or when all hooks have been disconnected. 200.Sh SEE ALSO 201.Xr netgraph 4 , 202.Xr ng_iface 4 , 203.Xr ng_ppp 4 , 204.Xr ngctl 8 205.Rs 206.%A V. Jacobson 207.%T "Compressing TCP/IP Headers" 208.%O RFC 1144 209.Re 210.Rs 211.%A G. McGregor 212.%T "The PPP Internet Control Protocol (IPCP)" 213.%O RFC 1332 214.Re 215.Sh HISTORY 216The 217.Nm 218node type was implemented in 219.Fx 4.0 . 220.Sh AUTHORS 221.An Archie Cobbs Aq archie@FreeBSD.org 222.Sh BUGS 223As the initialization routine in the kernel implementation of 224Van Jacobson compression initializes both compression and decompression 225at once, this node does not allow compression and decompression to 226be enabled in separate operations. 227In order to enable one when 228the other is already enabled, first both must be disabled, then 229both enabled. 230This of course resets the node state. 231This restriction may be lifted in a later version. 232.Pp 233When built as a loadable kernel module, this module includes the file 234.Pa net/slcompress.c . 235Although loading the module should fail if 236.Pa net/slcompress.c 237already exists in the kernel, currently it does not, and the duplicate 238copies of the file do not interfere. 239However, this may change in the future. 240