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: src/share/man/man4/ng_async.4,v 1.12.2.1 2001/12/21 09:00:51 ru Exp $ 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 4 40.Os 41.Sh NAME 42.Nm ng_async 43.Nd asynchronous framing netgraph node type 44.Sh SYNOPSIS 45.In netgraph/async/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 serial line. 54.Pp 55The node transmits and receives asynchronous data on the 56.Dv async 57hook. Mbuf boundaries of incoming data are ignored. 58Once a complete packet has been received, it is decoded and 59stripped of all framing bytes, and transmitted out the 60.Dv sync 61hook as a single frame. 62.Pp 63Synchronous frames are transmitted and received on the 64.Dv sync 65hook. 66Packets received on this hook are encoded as asynchronous frames 67and sent out on 68.Dv async . 69Received packets should start with the address and control fields, 70or the PPP protocol field if address and control field compression 71is employed, and contain no checksum field. If the first four bytes are 72.Dv "0xff 0x03 0xc0 0x21" 73(an LCP protocol frame) then complete control character escaping 74is enabled for that frame (in PPP, LCP packets are always sent with 75no address and control field compression and all control characters 76escaped). 77.Pp 78This node supports 79.Dq flag sharing 80for packets transmitted on 81.Dv async . 82This is an optimization where the trailing flag byte 83of one frame is shared with the opening flag byte of the next. 84Flag sharing between frames is disabled after one second of transmit 85idle time. 86.Sh HOOKS 87This node type supports the following hooks: 88.Bl -tag -width foobar 89.It Dv async 90Asynchronous connection. 91Typically this hook would be connected to a 92.Xr ng_tty 4 93node, which handles transmission of serial data over a tty device. 94.It Dv sync 95Synchronous connection. This hook sends and receives synchronous frames. 96For PPP, these frames should contain address, control, and protocol fields, 97but no checksum field. 98Typically this hook would be connected to an individual link hook of a 99.Xr ng_ppp 4 100type node. 101.El 102.Sh CONTROL MESSAGES 103This node type supports the generic control messages, plus the following: 104.Bl -tag -width foo 105.It Dv NGM_ASYNC_CMD_GET_STATS 106This command returns a 107.Dv "struct ng_async_stat" 108containing node statistics for packet, octet, and error counts. 109.It Dv NGM_ASYNC_CMD_CLR_STATS 110Clears the node statistics. 111.It Dv NGM_ASYNC_CMD_SET_CONFIG 112Sets the node configuration, which is described by a 113.Dv "struct ng_async_cfg" : 114.Bd -literal -offset 4n 115struct ng_async_cfg { 116 u_char enabled; /* Turn encoding on/off */ 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 127.Dq pass through 128mode. 129The 130.Dv amru 131and 132.Dv smru 133fields are the asynchronous and synchronous MRU (maximum receive unit) values, 134respectively. These both default to 1600; note that the async MRU 135applies to the incoming frame length after asynchronous decoding. 136The 137.Dv accm 138field is the asynchronous character control map, which controls the escaping 139of characters 0x00 thorough 0x1f (default 0xffffffff). 140.It Dv NGM_ASYNC_CMD_GET_CONFIG 141This command returns the current configuration structure. 142.El 143.Sh SHUTDOWN 144This node shuts down upon receipt of a 145.Dv NGM_SHUTDOWN 146control message, or when all hooks have been disconnected. 147.Sh SEE ALSO 148.Xr netgraph 4 , 149.Xr ng_ppp 4 , 150.Xr ng_tty 4 , 151.Xr ngctl 8 152.Rs 153.%A W. Simpson 154.%T "PPP in HDLC-link Framing" 155.%O RFC 1662 156.Re 157.Rs 158.%A W. Simpson 159.%T "The Point-to-Point Protocol (PPP)" 160.%O RFC 1661 161.Re 162.Sh HISTORY 163The 164.Nm 165node type was implemented in 166.Fx 4.0 . 167.Sh AUTHORS 168.An Archie Cobbs Aq Mt archie@FreeBSD.org 169