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.\" $FreeBSD$ 36.\" $Whistle: ng_async.8,v 1.6 1999/01/25 23:46:25 archie Exp $ 37.\" 38.Dd November 13, 2012 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 sys/types.h 46.In netgraph/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. 59Mbuf boundaries of incoming data are ignored. 60Once a complete packet has been received, it is decoded and 61stripped of all framing bytes, and transmitted out the 62.Dv sync 63hook as a single frame. 64.Pp 65Synchronous frames are transmitted and received on the 66.Dv sync 67hook. 68Packets received on this hook are encoded as asynchronous frames 69and sent out on 70.Dv async . 71Received packets should start with the address and control fields, 72or the PPP protocol field if address and control field compression 73is employed, and contain no checksum field. 74If the first four bytes are 75.Dv "0xff 0x03 0xc0 0x21" 76(an LCP protocol frame) then complete control character escaping 77is enabled for that frame (in PPP, LCP packets are always sent with 78no address and control field compression and all control characters 79escaped). 80.Pp 81This node supports 82.Dq flag sharing 83for packets transmitted on 84.Dv async . 85This is an optimization where the trailing flag byte 86of one frame is shared with the opening flag byte of the next. 87Flag sharing between frames is disabled after one second of transmit 88idle time. 89.Sh HOOKS 90This node type supports the following hooks: 91.Bl -tag -width ".Va async" 92.It Va async 93Asynchronous connection. 94Typically this hook would be connected to a 95.Xr ng_tty 4 96node, which handles transmission of serial data over a tty device. 97.It Va sync 98Synchronous connection. 99This hook sends and receives synchronous frames. 100For PPP, these frames should contain address, control, and protocol fields, 101but no checksum field. 102Typically this hook would be connected to an individual link hook of a 103.Xr ng_ppp 4 104type node. 105.El 106.Sh CONTROL MESSAGES 107This node type supports the generic control messages, plus the following: 108.Bl -tag -width foo 109.It Dv NGM_ASYNC_CMD_SET_CONFIG Pq Ic setconfig 110Sets the node configuration, which is described by a 111.Dv "struct ng_async_cfg" : 112.Bd -literal -offset 4n 113struct ng_async_cfg { 114 u_char enabled; /* Turn encoding on/off */ 115 uint16_t amru; /* Max receive async frame length */ 116 uint16_t smru; /* Max receive sync frame length */ 117 uint32_t accm; /* ACCM encoding */ 118}; 119.Ed 120The 121.Dv enabled 122field enables or disables all encoding/decoding functions (default disabled). 123When disabled, the node operates in simple 124.Dq pass through 125mode. 126The 127.Dv amru 128and 129.Dv smru 130fields are the asynchronous and synchronous MRU (maximum receive unit) values, 131respectively. 132These both default to 1600; note that the async MRU 133applies to the incoming frame length after asynchronous decoding. 134The 135.Dv accm 136field is the asynchronous character control map, which controls the escaping 137of characters 0x00 thorough 0x1f (default 0xffffffff). 138.It Dv NGM_ASYNC_CMD_GET_CONFIG Pq Ic getconfig 139This command returns the current configuration structure. 140.It Dv NGM_ASYNC_CMD_GET_STATS Pq Ic getstats 141This command returns a 142.Dv "struct ng_async_stat" 143containing node statistics for packet, octet, and error counts. 144.It Dv NGM_ASYNC_CMD_CLR_STATS Pq Ic clrstats 145Clears the node statistics. 146.El 147.Sh SHUTDOWN 148This node shuts down upon receipt of a 149.Dv NGM_SHUTDOWN 150control message, or when all hooks have been disconnected. 151.Sh SEE ALSO 152.Xr netgraph 4 , 153.Xr ng_ppp 4 , 154.Xr ng_tty 4 , 155.Xr ngctl 8 156.Rs 157.%A W. Simpson 158.%T "PPP in HDLC-link Framing" 159.%O RFC 1662 160.Re 161.Rs 162.%A W. Simpson 163.%T "The Point-to-Point Protocol (PPP)" 164.%O RFC 1661 165.Re 166.Sh HISTORY 167The 168.Nm 169node type was implemented in 170.Fx 4.0 . 171.Sh AUTHORS 172.An Archie Cobbs Aq Mt archie@FreeBSD.org 173