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.Bl -tag -width foobarbazi 107.It Dv ip 108Upstream (uncompressed) IP packets. 109.It Dv vjcomp 110Downstream compressed TCP packets. 111.It Dv vjuncomp 112Downstream uncompressed TCP packets. 113.It Dv vjip 114Downstream uncompressed IP packets. 115.El 116.Sh CONTROL MESSAGES 117This node type supports the generic control messages, plus the following: 118.Bl -tag -width foo 119.It Dv NGM_VJC_SET_CONFIG 120This command resets the compression state and configures it according 121to the supplied 122.Dv "struct ngm_vjc_config" 123argument. 124This structure contains the following fields: 125.Bd -literal -offset 4n 126struct ngm_vjc_config { 127 u_char enableComp; /* Enable compression */ 128 u_char enableDecomp; /* Enable decompression */ 129 u_char maxChannel; /* Number of outgoing channels - 1 */ 130 u_char compressCID; /* OK to compress outgoing CID's */ 131}; 132.Ed 133.Pp 134When 135.Dv enableComp 136is set to zero, all packets received on the 137.Dv ip 138hook are forwarded unchanged out the 139.Dv vjip 140hook. 141Similarly, when 142.Dv enableDecomp 143is set to zero, all packets received on the 144.Dv vjip 145hook are forwarded unchanged out the 146.Dv ip 147hook, and packets are not accepted on the 148.Dv vjcomp 149and 150.Dv vjuncomp 151hooks. 152When a node is first created, 153both compression and decompression are disabled and the node is 154therefore operating in bi-directional 155.Dq pass through 156mode. 157.Pp 158When enabling compression, 159.Dv maxChannel 160should be set to the number of outgoing compression channels minus one, 161and is a value between 3 and 15, inclusive. 162The 163.Dv compressCID 164field indicates whether it is OK to compress the CID header field for 165outgoing compressed TCP packets. 166This value should be zero unless 167either (a) it is not possible for an outgoing frame to be lost, or 168(b) lost frames can be reliably detected and immediately 169reported to the peer's decompression engine (see 170.Dv NGM_VJC_RECV_ERROR 171below). 172.It Dv NGM_VJC_GET_STATE 173This command returns the node's current state described by the 174.Dv "struct slcompress" 175structure, which is defined in 176.In net/slcompress.h . 177.It Dv NGM_VJC_CLR_STATS 178Clears the node statistics counters. 179Statistics are also cleared whenever the 180.Dv enableComp 181or 182.Dv enableDecomp 183fields are changed from zero to one by a 184.Dv NGM_VJC_SET_CONFIG 185control message. 186.It Dv NGM_VJC_RECV_ERROR 187When the peer has CID header field compression enabled, 188this message must be sent to the local 189.Nm vjc 190node immediately 191after detecting that a received frame has been lost, due to a bad 192checksum or for any other reason. 193Failing to do this can result in corrupted TCP stream data. 194.El 195.Sh SHUTDOWN 196This node shuts down upon receipt of a 197.Dv NGM_SHUTDOWN 198control message, or when all hooks have been disconnected. 199.Sh SEE ALSO 200.Xr netgraph 4 , 201.Xr ng_iface 4 , 202.Xr ng_ppp 4 , 203.Xr ngctl 8 204.Rs 205.%A V. Jacobson 206.%T "Compressing TCP/IP Headers" 207.%O RFC 1144 208.Re 209.Rs 210.%A G. McGregor 211.%T "The PPP Internet Control Protocol (IPCP)" 212.%O RFC 1332 213.Re 214.Sh HISTORY 215The 216.Nm 217node type was implemented in 218.Fx 4.0 . 219.Sh AUTHORS 220.An Archie Cobbs Aq archie@FreeBSD.org 221.Sh BUGS 222As the initialization routine in the kernel implementation of 223Van Jacobson compression initializes both compression and decompression 224at once, this node does not allow compression and decompression to 225be enabled in separate operations. 226In order to enable one when 227the other is already enabled, first both must be disabled, then 228both enabled. 229This of course resets the node state. 230This restriction may be lifted in a later version. 231.Pp 232When built as a loadable kernel module, this module includes the file 233.Pa net/slcompress.c . 234Although loading the module should fail if 235.Pa net/slcompress.c 236already exists in the kernel, currently it does not, and the duplicate 237copies of the file do not interfere. 238However, this may change in the future. 239