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6 .\" without modifications are expressly permitted by Whistle Communications;
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9 .\" copyright notice above and the following disclaimer of warranties; and
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12 .\" COMMUNICATIONS" on advertising, endorsements, or otherwise except as
13 .\" such appears in the above copyright notice or in the software.
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
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33 .\" Author: Archie Cobbs <archie@FreeBSD.org>
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 1.3 2006/05/26 19:39:39 swildner Exp $
37 .\" $Whistle: ng_async.8,v 1.6 1999/01/25 23:46:25 archie Exp $
44 .Nd asynchronous framing netgraph node type
46 .In netgraph/async/ng_async.h
50 node type performs conversion between synchronous frames and
51 asynchronous frames, as defined for the PPP protocol in RFC 1662.
52 Asynchronous framing uses flag bytes and octet-stuffing
53 to simulate a frame oriented connection over an octet-oriented
54 asynchronous serial line.
56 The node transmits and receives asynchronous data on the
58 hook. Mbuf boundaries of incoming data are ignored.
59 Once a complete packet has been received, it is decoded and
60 stripped of all framing bytes, and transmitted out the
62 hook as a single frame.
64 Synchronous frames are transmitted and received on the
67 Packets received on this hook are encoded as asynchronous frames
70 Received packets should start with the address and control fields,
71 or the PPP protocol field if address and control field compression
72 is 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
75 is enabled for that frame (in PPP, LCP packets are always sent with
76 no address and control field compression and all control characters
81 for packets transmitted on
83 This is an optimization where the trailing flag byte
84 of one frame is shared with the opening flag byte of the next.
85 Flag sharing between frames is disabled after one second of transmit
88 This node type supports the following hooks:
90 .Bl -tag -width foobar
92 Asynchronous connection.
93 Typically this hook would be connected to a
95 node, which handles transmission of serial data over a tty device.
97 Synchronous connection. This hook sends and receives synchronous frames.
98 For PPP, these frames should contain address, control, and protocol fields,
99 but no checksum field.
100 Typically this hook would be connected to an individual link hook of a
105 This node type supports the generic control messages, plus the following:
107 .It Dv NGM_ASYNC_CMD_GET_STATS
108 This command returns a
109 .Dv "struct ng_async_stat"
110 containing node statistics for packet, octet, and error counts.
111 .It Dv NGM_ASYNC_CMD_CLR_STATS
112 Clears the node statistics.
113 .It Dv NGM_ASYNC_CMD_SET_CONFIG
114 Sets the node configuration, which is described by a
115 .Dv "struct ng_async_cfg" :
116 .Bd -literal -offset 4n
117 struct ng_async_cfg {
118 u_char enabled; /* Turn encoding on/off */
119 u_int16_t amru; /* Max receive async frame len */
120 u_int16_t smru; /* Max receive sync frame len */
121 u_int32_t accm; /* ACCM encoding */
127 field enables or disables all encoding/decoding functions (default disabled).
128 When disabled, the node operates in simple
135 fields are the asynchronous and synchronous MRU (maximum receive unit) values,
136 respectively. These both default to 1600; note that the async MRU
137 applies to the incoming frame length after asynchronous decoding.
140 field is the asynchronous character control map, which controls the escaping
141 of characters 0x00 thorough 0x1f (default 0xffffffff).
142 .It Dv NGM_ASYNC_CMD_GET_CONFIG
143 This command returns the current configuration structure.
146 This node shuts down upon receipt of a
148 control message, or when all hooks have been disconnected.
156 .%T "PPP in HDLC-link Framing"
161 .%T "The Point-to-Point Protocol (PPP)"
167 node type was implemented in
170 .An Archie Cobbs Aq archie@FreeBSD.org