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_async.8,v 1.6 1999/01/25 23:46:25 archie Exp $ 37.\" 38.Dd January 19, 1999 39.Dt NG_ASYNC 8 40.Os FreeBSD 3 41.Sh NAME 42.Nm ng_async 43.Nd asynchronous framing netgraph node type 44.Sh SYNOPSIS 45.Fd #include <netgraph/ng_async.h> 46.Sh DESCRIPTION 47The 48.Nm async 49node type performs conversion between synchronous frames and 50asynchronous frames, as defined for the PPP protocol in RFC 1662. 51Asynchronous framing uses flag bytes and octet-stuffing 52to simulate a frame oriented connection over an octet-oriented 53asynchronous line. 54.Pp 55The node trasmits and receives asynchronous data on the 56.Dv async 57hook. Incoming data mbuf boundaries are ignored, while 58outgoing data is sent as a complete frame at a time. 59.Pp 60There are two synchronous hooks, 61.Dv sync 62and 63.Dv sync2 . 64For both hooks, received packets are encoded as asynchronous frames 65and sent out on 66.Dv async . 67Hook 68.Dv sync2 69differs from 70.Dv sync 71only in that any configured address and control field compression 72and/or control character escaping is disabled when the frame is encoded. 73This is useful for transmitting PPP LCP packets, which are always sent 74this way. 75.Pp 76This node supports ``flag sharing'' for packets transmitted on 77.Dv async . 78This is an optimization where the trailing flag byte 79of one frame is shared with the opening flag byte of the next. 80Flag sharing between frames is disabled after one second of transmit 81idle time. 82.Sh HOOKS 83This node type supports the following hooks: 84.Pp 85.Bl -tag -width foobar 86.It Dv async 87Asynchronous connection. 88Typically this hook would be connected to a 89.Xr ng_tty 8 90node, which handles transmission of serial data over a tty device. 91.It Dv sync 92Synchronous connection. This hook sends and receives synchronous frames. 93For PPP, these frames contain no address, control, or checksum fields; 94each frame begins with the PPP protocol number. Typically this hook would 95be connected to the 96.Dv downstream 97hook of a 98.Xr ng_ppp 8 99type node. 100.El 101.Sh CONTROL MESSAGES 102This node type supports the generic control messages, plus the following: 103.Bl -tag -width foo 104.It Dv NGM_ASYNC_CMD_GET_STATS 105This command returns a 106.Dv "struct ng_async_stat" 107containing node statistics for packet, octet, and error counts. 108.It Dv NGM_ASYNC_CMD_CLR_STATS 109Clears the node statistics. 110.It Dv NGM_ASYNC_CMD_SET_CONFIG 111Sets the node configuration, which is described by a 112.Dv "struct ng_async_cfg" : 113.Bd -literal -offset 4n 114struct ng_async_cfg { 115 u_char enabled; /* Turn encoding on/off */ 116 u_char acfcomp; /* Address/control field comp. */ 117 u_int16_t amru; /* Max receive async frame len */ 118 u_int16_t smru; /* Max receive sync frame len */ 119 u_int32_t accm; /* ACCM encoding */ 120}; 121.Ed 122.Pp 123The 124.Dv enabled 125field enables or disables all encoding/decoding functions (default disabled). 126When disabled, the node operates in simple ``pass through'' mode. Setting 127.Dv acfcomp 128enables address and control field compression on transmission (for packets 129received on the 130.Dv sync 131hook only; default off). 132.Dv amru 133and 134.Dv smru 135are the asynchronous and synchronous MRU (maximum receive unit) values, 136respectively. These both default to 1600; note that the async MRU 137applies to the incoming frame length after asynchronous decoding. 138Finally, 139.Dv accm 140is the asynchronous character control map, which controls the escaping 141of characters 0x00 thorough 0x1f (default 0xffffffff). 142.It Dv NGM_ASYNC_CMD_GET_CONFIG 143This command returns the current configuration structure. 144.El 145.Sh SHUTDOWN 146This node shuts down upon receipt of a 147.Dv NGM_SHUTDOWN 148control message, or when all hooks have been disconnected. 149.Sh SEE ALSO 150.Xr netgraph 4 , 151.Xr ng_ppp 8 , 152.Xr ng_tty 8 , 153.Xr ngctl 8 . 154.Rs 155.%A W. Simpson 156.%T "PPP in HDLC-link Framing" 157.%O RFC 1662 158.Re 159.Sh AUTHOR 160Archie Cobbs <archie@whistle.com> 161