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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.\" $Whistle: ng_vjc.8,v 1.4 1999/01/25 23:46:28 archie Exp $ 35.\" 36.Dd January 19, 1999 37.Dt NG_VJC 4 38.Os 39.Sh NAME 40.Nm ng_vjc 41.Nd Van Jacobson compression netgraph node type 42.Sh SYNOPSIS 43.In sys/types.h 44.In netinet/in.h 45.In netinet/in_systm.h 46.In netinet/ip.h 47.In net/slcompress.h 48.In netgraph/ng_vjc.h 49.Sh DESCRIPTION 50The 51.Nm vjc 52node type performs Van Jacobson compression, which is used 53over PPP, SLIP, and other point-to-point IP connections to 54compress TCP packet headers. 55The 56.Dv ip 57hook represents the uncompressed side of the node, while the 58.Dv vjcomp , 59.Dv vjuncomp , 60and 61.Dv vjip 62hooks represent the compressed side of the node. 63Packets received on the 64.Dv ip 65will be compressed or passed through as appropriate. 66Packets received on the other three hooks will be uncompressed as appropriate. 67This node also supports 68.Dq always pass through 69mode in either direction. 70.Pp 71Van Jacobson compression only applies to TCP packets. 72Only 73.Dq normal 74(i.e., common case) TCP packets are actually compressed. 75These are output on the 76.Dv vjcomp 77hook. 78Other TCP packets are run through the state machine but not 79compressed; these appear on the 80.Dv vjuncomp 81hook. 82Other non-TCP IP packets are forwarded unchanged to 83.Dv vjip . 84.Pp 85When connecting to a 86.Xr ng_ppp 4 87node, the 88.Dv ip , 89.Dv vjuncomp , 90.Dv vjcomp , 91and 92.Dv vjip 93hooks should be connected to the 94.Xr ng_ppp 4 95node's 96.Dv vjc_ip , 97.Dv vjc_vjcomp , 98.Dv vjc_vjuncomp , 99and 100.Dv vjc_ip 101hooks, respectively. 102.Sh HOOKS 103This node type supports the following hooks: 104.Bl -tag -width ".Va vjuncomp" 105.It Va ip 106Upstream (uncompressed) IP packets. 107.It Va vjcomp 108Downstream compressed TCP packets. 109.It Va vjuncomp 110Downstream uncompressed TCP packets. 111.It Va vjip 112Downstream uncompressed IP packets. 113.El 114.Sh CONTROL MESSAGES 115This node type supports the generic control messages, plus the following: 116.Bl -tag -width foo 117.It Dv NGM_VJC_SET_CONFIG Pq Ic setconfig 118This command resets the compression state and configures it according 119to the supplied 120.Dv "struct ngm_vjc_config" 121argument. 122This structure contains the following fields: 123.Bd -literal -offset 4n 124struct ngm_vjc_config { 125 u_char enableComp; /* Enable compression */ 126 u_char enableDecomp; /* Enable decompression */ 127 u_char maxChannel; /* Number of outgoing channels - 1 */ 128 u_char compressCID; /* OK to compress outgoing CID's */ 129}; 130.Ed 131.Pp 132When 133.Dv enableComp 134is set to zero, all packets received on the 135.Dv ip 136hook are forwarded unchanged out the 137.Dv vjip 138hook. 139Similarly, when 140.Dv enableDecomp 141is set to zero, all packets received on the 142.Dv vjip 143hook are forwarded unchanged out the 144.Dv ip 145hook, and packets are not accepted on the 146.Dv vjcomp 147and 148.Dv vjuncomp 149hooks. 150When a node is first created, 151both compression and decompression are disabled and the node is 152therefore operating in bi-directional 153.Dq pass through 154mode. 155.Pp 156When enabling compression, 157.Dv maxChannel 158should be set to the number of outgoing compression channels minus one, 159and is a value between 3 and 15, inclusive. 160The 161.Dv compressCID 162field indicates whether it is OK to compress the CID header field for 163outgoing compressed TCP packets. 164This value should be zero unless 165either (a) it is not possible for an outgoing frame to be lost, or 166(b) lost frames can be reliably detected and immediately 167reported to the peer's decompression engine (see 168.Dv NGM_VJC_RECV_ERROR 169below). 170.It Dv NGM_VJC_GET_STATE Pq Ic getstate 171This command returns the node's current state described by the 172.Dv "struct slcompress" 173structure, which is defined in 174.In net/slcompress.h . 175.It Dv NGM_VJC_CLR_STATS Pq Ic clrstats 176Clears the node statistics counters. 177Statistics are also cleared whenever the 178.Dv enableComp 179or 180.Dv enableDecomp 181fields are changed from zero to one by a 182.Dv NGM_VJC_SET_CONFIG 183control message. 184.It Dv NGM_VJC_RECV_ERROR Pq Ic recverror 185When the peer has CID header field compression enabled, 186this message must be sent to the local 187.Nm vjc 188node immediately 189after detecting that a received frame has been lost, due to a bad 190checksum or for any other reason. 191Failing to do this can result in corrupted TCP stream data. 192.El 193.Sh SHUTDOWN 194This node shuts down upon receipt of a 195.Dv NGM_SHUTDOWN 196control message, or when all hooks have been disconnected. 197.Sh SEE ALSO 198.Xr netgraph 4 , 199.Xr ng_iface 4 , 200.Xr ng_ppp 4 , 201.Xr ngctl 8 202.Rs 203.%A V. Jacobson 204.%T "Compressing TCP/IP Headers" 205.%O RFC 1144 206.Re 207.Rs 208.%A G. McGregor 209.%T "The PPP Internet Control Protocol (IPCP)" 210.%O RFC 1332 211.Re 212.Sh HISTORY 213The 214.Nm 215node type was implemented in 216.Fx 4.0 . 217.Sh AUTHORS 218.An Archie Cobbs Aq Mt archie@FreeBSD.org 219.Sh BUGS 220As the initialization routine in the kernel implementation of 221Van Jacobson compression initializes both compression and decompression 222at once, this node does not allow compression and decompression to 223be enabled in separate operations. 224In order to enable one when 225the other is already enabled, first both must be disabled, then 226both enabled. 227This of course resets the node state. 228This restriction may be lifted in a later version. 229.Pp 230When built as a loadable kernel module, this module includes the file 231.Pa net/slcompress.c . 232Although loading the module should fail if 233.Pa net/slcompress.c 234already exists in the kernel, currently it does not, and the duplicate 235copies of the file do not interfere. 236However, this may change in the future. 237