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Diffstat (limited to 'share/man/man4/ng_vjc.4')
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diff --git a/share/man/man4/ng_vjc.4 b/share/man/man4/ng_vjc.4 new file mode 100644 index 0000000..83f0269 --- /dev/null +++ b/share/man/man4/ng_vjc.4 @@ -0,0 +1,238 @@ +.\" Copyright (c) 1996-1999 Whistle Communications, Inc. +.\" All rights reserved. +.\" +.\" Subject to the following obligations and disclaimer of warranty, use and +.\" redistribution of this software, in source or object code forms, with or +.\" without modifications are expressly permitted by Whistle Communications; +.\" provided, however, that: +.\" 1. Any and all reproductions of the source or object code must include the +.\" copyright notice above and the following disclaimer of warranties; and +.\" 2. No rights are granted, in any manner or form, to use Whistle +.\" Communications, Inc. trademarks, including the mark "WHISTLE +.\" COMMUNICATIONS" on advertising, endorsements, or otherwise except as +.\" such appears in the above copyright notice or in the software. +.\" +.\" THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND +.\" TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO +.\" REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE, +.\" INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF +.\" MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. +.\" WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY +.\" REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS +.\" SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE. +.\" IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES +.\" RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING +.\" WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, +.\" PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR +.\" SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY +.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF +.\" THIS SOFTWARE, EVEN IF WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY +.\" OF SUCH DAMAGE. +.\" +.\" Author: Archie Cobbs <archie@FreeBSD.org> +.\" +.\" $FreeBSD$ +.\" $Whistle: ng_vjc.8,v 1.4 1999/01/25 23:46:28 archie Exp $ +.\" +.Dd January 19, 1999 +.Dt NG_VJC 4 +.Os +.Sh NAME +.Nm ng_vjc +.Nd Van Jacobson compression netgraph node type +.Sh SYNOPSIS +.In sys/types.h +.In netinet/in.h +.In netinet/in_systm.h +.In netinet/ip.h +.In net/slcompress.h +.In netgraph/ng_vjc.h +.Sh DESCRIPTION +The +.Nm vjc +node type performs Van Jacobson compression, which is used +over PPP, SLIP, and other point-to-point IP connections to +compress TCP packet headers. +The +.Dv ip +hook represents the uncompressed side of the node, while the +.Dv vjcomp , +.Dv vjuncomp , +and +.Dv vjip +hooks represent the compressed side of the node. +Packets received on the +.Dv ip +will be compressed or passed through as appropriate. +Packets received on the other three hooks will be uncompressed as appropriate. +This node also supports +.Dq always pass through +mode in either direction. +.Pp +Van Jacobson compression only applies to TCP packets. +Only +.Dq normal +(i.e., common case) TCP packets are actually compressed. +These are output on the +.Dv vjcomp +hook. +Other TCP packets are run through the state machine but not +compressed; these appear on the +.Dv vjuncomp +hook. +Other non-TCP IP packets are forwarded unchanged to +.Dv vjip . +.Pp +When connecting to a +.Xr ng_ppp 4 +node, the +.Dv ip , +.Dv vjuncomp , +.Dv vjcomp , +and +.Dv vjip +hooks should be connected to the +.Xr ng_ppp 4 +node's +.Dv vjc_ip , +.Dv vjc_vjcomp , +.Dv vjc_vjuncomp , +and +.Dv vjc_ip +hooks, respectively. +.Sh HOOKS +This node type supports the following hooks: +.Bl -tag -width ".Va vjuncomp" +.It Va ip +Upstream (uncompressed) IP packets. +.It Va vjcomp +Downstream compressed TCP packets. +.It Va vjuncomp +Downstream uncompressed TCP packets. +.It Va vjip +Downstream uncompressed IP packets. +.El +.Sh CONTROL MESSAGES +This node type supports the generic control messages, plus the following: +.Bl -tag -width foo +.It Dv NGM_VJC_SET_CONFIG Pq Ic setconfig +This command resets the compression state and configures it according +to the supplied +.Dv "struct ngm_vjc_config" +argument. +This structure contains the following fields: +.Bd -literal -offset 4n +struct ngm_vjc_config { + u_char enableComp; /* Enable compression */ + u_char enableDecomp; /* Enable decompression */ + u_char maxChannel; /* Number of outgoing channels - 1 */ + u_char compressCID; /* OK to compress outgoing CID's */ +}; +.Ed +.Pp +When +.Dv enableComp +is set to zero, all packets received on the +.Dv ip +hook are forwarded unchanged out the +.Dv vjip +hook. +Similarly, when +.Dv enableDecomp +is set to zero, all packets received on the +.Dv vjip +hook are forwarded unchanged out the +.Dv ip +hook, and packets are not accepted on the +.Dv vjcomp +and +.Dv vjuncomp +hooks. +When a node is first created, +both compression and decompression are disabled and the node is +therefore operating in bi-directional +.Dq pass through +mode. +.Pp +When enabling compression, +.Dv maxChannel +should be set to the number of outgoing compression channels minus one, +and is a value between 3 and 15, inclusive. +The +.Dv compressCID +field indicates whether it is OK to compress the CID header field for +outgoing compressed TCP packets. +This value should be zero unless +either (a) it is not possible for an outgoing frame to be lost, or +(b) lost frames can be reliably detected and immediately +reported to the peer's decompression engine (see +.Dv NGM_VJC_RECV_ERROR +below). +.It Dv NGM_VJC_GET_STATE Pq Ic getstate +This command returns the node's current state described by the +.Dv "struct slcompress" +structure, which is defined in +.In net/slcompress.h . +.It Dv NGM_VJC_CLR_STATS Pq Ic clrstats +Clears the node statistics counters. +Statistics are also cleared whenever the +.Dv enableComp +or +.Dv enableDecomp +fields are changed from zero to one by a +.Dv NGM_VJC_SET_CONFIG +control message. +.It Dv NGM_VJC_RECV_ERROR Pq Ic recverror +When the peer has CID header field compression enabled, +this message must be sent to the local +.Nm vjc +node immediately +after detecting that a received frame has been lost, due to a bad +checksum or for any other reason. +Failing to do this can result in corrupted TCP stream data. +.El +.Sh SHUTDOWN +This node shuts down upon receipt of a +.Dv NGM_SHUTDOWN +control message, or when all hooks have been disconnected. +.Sh SEE ALSO +.Xr netgraph 4 , +.Xr ng_iface 4 , +.Xr ng_ppp 4 , +.Xr ngctl 8 +.Rs +.%A V. Jacobson +.%T "Compressing TCP/IP Headers" +.%O RFC 1144 +.Re +.Rs +.%A G. McGregor +.%T "The PPP Internet Control Protocol (IPCP)" +.%O RFC 1332 +.Re +.Sh HISTORY +The +.Nm +node type was implemented in +.Fx 4.0 . +.Sh AUTHORS +.An Archie Cobbs Aq archie@FreeBSD.org +.Sh BUGS +As the initialization routine in the kernel implementation of +Van Jacobson compression initializes both compression and decompression +at once, this node does not allow compression and decompression to +be enabled in separate operations. +In order to enable one when +the other is already enabled, first both must be disabled, then +both enabled. +This of course resets the node state. +This restriction may be lifted in a later version. +.Pp +When built as a loadable kernel module, this module includes the file +.Pa net/slcompress.c . +Although loading the module should fail if +.Pa net/slcompress.c +already exists in the kernel, currently it does not, and the duplicate +copies of the file do not interfere. +However, this may change in the future. |
