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.\" $DragonFly: src/share/man/man4/ng_async.4,v 1.4 2008/05/02 02:05:05 swildner Exp $ 37.\" $Whistle: ng_async.8,v 1.6 1999/01/25 23:46:25 archie Exp $ 38.\" 39.Dd January 19, 1999 40.Dt NG_ASYNC 4 41.Os 42.Sh NAME 43.Nm ng_async 44.Nd asynchronous framing netgraph node type 45.Sh SYNOPSIS 46.In netgraph/async/ng_async.h 47.Sh DESCRIPTION 48The 49.Nm async 50node type performs conversion between synchronous frames and 51asynchronous frames, as defined for the PPP protocol in RFC 1662. 52Asynchronous framing uses flag bytes and octet-stuffing 53to simulate a frame oriented connection over an octet-oriented 54asynchronous serial line. 55.Pp 56The node transmits and receives asynchronous data on the 57.Dv async 58hook. Mbuf boundaries of incoming data are ignored. 59Once a complete packet has been received, it is decoded and 60stripped of all framing bytes, and transmitted out the 61.Dv sync 62hook as a single frame. 63.Pp 64Synchronous frames are transmitted and received on the 65.Dv sync 66hook. 67Packets received on this hook are encoded as asynchronous frames 68and sent out on 69.Dv async . 70Received packets should start with the address and control fields, 71or the PPP protocol field if address and control field compression 72is employed, and contain no checksum field. If the first four bytes are 73.Dv "0xff 0x03 0xc0 0x21" 74(an LCP protocol frame) then complete control character escaping 75is enabled for that frame (in PPP, LCP packets are always sent with 76no address and control field compression and all control characters 77escaped). 78.Pp 79This node supports 80.Dq flag sharing 81for packets transmitted on 82.Dv async . 83This is an optimization where the trailing flag byte 84of one frame is shared with the opening flag byte of the next. 85Flag sharing between frames is disabled after one second of transmit 86idle time. 87.Sh HOOKS 88This node type supports the following hooks: 89.Bl -tag -width foobar 90.It Dv async 91Asynchronous connection. 92Typically this hook would be connected to a 93.Xr ng_tty 4 94node, which handles transmission of serial data over a tty device. 95.It Dv sync 96Synchronous connection. This hook sends and receives synchronous frames. 97For PPP, these frames should contain address, control, and protocol fields, 98but no checksum field. 99Typically this hook would be connected to an individual link hook of a 100.Xr ng_ppp 4 101type node. 102.El 103.Sh CONTROL MESSAGES 104This node type supports the generic control messages, plus the following: 105.Bl -tag -width foo 106.It Dv NGM_ASYNC_CMD_GET_STATS 107This command returns a 108.Dv "struct ng_async_stat" 109containing node statistics for packet, octet, and error counts. 110.It Dv NGM_ASYNC_CMD_CLR_STATS 111Clears the node statistics. 112.It Dv NGM_ASYNC_CMD_SET_CONFIG 113Sets the node configuration, which is described by a 114.Dv "struct ng_async_cfg" : 115.Bd -literal -offset 4n 116struct ng_async_cfg { 117 u_char enabled; /* Turn encoding on/off */ 118 u_int16_t amru; /* Max receive async frame len */ 119 u_int16_t smru; /* Max receive sync frame len */ 120 u_int32_t accm; /* ACCM encoding */ 121}; 122.Ed 123.Pp 124The 125.Dv enabled 126field enables or disables all encoding/decoding functions (default disabled). 127When disabled, the node operates in simple 128.Dq pass through 129mode. 130The 131.Dv amru 132and 133.Dv smru 134fields are the asynchronous and synchronous MRU (maximum receive unit) values, 135respectively. These both default to 1600; note that the async MRU 136applies to the incoming frame length after asynchronous decoding. 137The 138.Dv accm 139field is the asynchronous character control map, which controls the escaping 140of characters 0x00 thorough 0x1f (default 0xffffffff). 141.It Dv NGM_ASYNC_CMD_GET_CONFIG 142This command returns the current configuration structure. 143.El 144.Sh SHUTDOWN 145This node shuts down upon receipt of a 146.Dv NGM_SHUTDOWN 147control message, or when all hooks have been disconnected. 148.Sh SEE ALSO 149.Xr netgraph 4 , 150.Xr ng_ppp 4 , 151.Xr ng_tty 4 , 152.Xr ngctl 8 153.Rs 154.%A W. Simpson 155.%T "PPP in HDLC-link Framing" 156.%O RFC 1662 157.Re 158.Rs 159.%A W. Simpson 160.%T "The Point-to-Point Protocol (PPP)" 161.%O RFC 1661 162.Re 163.Sh HISTORY 164The 165.Nm 166node type was implemented in 167.Fx 4.0 . 168.Sh AUTHORS 169.An Archie Cobbs Aq archie@FreeBSD.org 170