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No rights are granted, in any manner or form, to use Whistle .\" Communications, Inc. trademarks, including the mark "WHISTLE .\" COMMUNICATIONS" on advertising, endorsements, or otherwise except as .\" such appears in the above copyright notice or in the software. .\" .\" THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND .\" TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO .\" REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE, .\" INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF .\" MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. .\" WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY .\" REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS .\" SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE. .\" IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES .\" RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING .\" WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, .\" PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR .\" SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY .\" OF SUCH DAMAGE. .\" .\" Author: Archie Cobbs .\" .\" $FreeBSD: releng/11.0/share/man/man4/ng_async.4 267938 2014-06-26 21:46:14Z bapt $ .\" $Whistle: ng_async.8,v 1.6 1999/01/25 23:46:25 archie Exp $ .\" .Dd November 13, 2012 .Dt NG_ASYNC 4 .Os .Sh NAME .Nm ng_async .Nd asynchronous framing netgraph node type .Sh SYNOPSIS .In sys/types.h .In netgraph/ng_async.h .Sh DESCRIPTION The .Nm async node type performs conversion between synchronous frames and asynchronous frames, as defined for the PPP protocol in RFC 1662. Asynchronous framing uses flag bytes and octet-stuffing to simulate a frame oriented connection over an octet-oriented asynchronous serial line. .Pp The node transmits and receives asynchronous data on the .Dv async hook. Mbuf boundaries of incoming data are ignored. Once a complete packet has been received, it is decoded and stripped of all framing bytes, and transmitted out the .Dv sync hook as a single frame. .Pp Synchronous frames are transmitted and received on the .Dv sync hook. Packets received on this hook are encoded as asynchronous frames and sent out on .Dv async . Received packets should start with the address and control fields, or the PPP protocol field if address and control field compression is employed, and contain no checksum field. If the first four bytes are .Dv "0xff 0x03 0xc0 0x21" (an LCP protocol frame) then complete control character escaping is enabled for that frame (in PPP, LCP packets are always sent with no address and control field compression and all control characters escaped). .Pp This node supports .Dq flag sharing for packets transmitted on .Dv async . This is an optimization where the trailing flag byte of one frame is shared with the opening flag byte of the next. Flag sharing between frames is disabled after one second of transmit idle time. .Sh HOOKS This node type supports the following hooks: .Bl -tag -width ".Va async" .It Va async Asynchronous connection. Typically this hook would be connected to a .Xr ng_tty 4 node, which handles transmission of serial data over a tty device. .It Va sync Synchronous connection. This hook sends and receives synchronous frames. For PPP, these frames should contain address, control, and protocol fields, but no checksum field. Typically this hook would be connected to an individual link hook of a .Xr ng_ppp 4 type node. .El .Sh CONTROL MESSAGES This node type supports the generic control messages, plus the following: .Bl -tag -width foo .It Dv NGM_ASYNC_CMD_SET_CONFIG Pq Ic setconfig Sets the node configuration, which is described by a .Dv "struct ng_async_cfg" : .Bd -literal -offset 4n struct ng_async_cfg { u_char enabled; /* Turn encoding on/off */ uint16_t amru; /* Max receive async frame length */ uint16_t smru; /* Max receive sync frame length */ uint32_t accm; /* ACCM encoding */ }; .Ed The .Dv enabled field enables or disables all encoding/decoding functions (default disabled). When disabled, the node operates in simple .Dq pass through mode. The .Dv amru and .Dv smru fields are the asynchronous and synchronous MRU (maximum receive unit) values, respectively. These both default to 1600; note that the async MRU applies to the incoming frame length after asynchronous decoding. The .Dv accm field is the asynchronous character control map, which controls the escaping of characters 0x00 thorough 0x1f (default 0xffffffff). .It Dv NGM_ASYNC_CMD_GET_CONFIG Pq Ic getconfig This command returns the current configuration structure. .It Dv NGM_ASYNC_CMD_GET_STATS Pq Ic getstats This command returns a .Dv "struct ng_async_stat" containing node statistics for packet, octet, and error counts. .It Dv NGM_ASYNC_CMD_CLR_STATS Pq Ic clrstats Clears the node statistics. .El .Sh SHUTDOWN This node shuts down upon receipt of a .Dv NGM_SHUTDOWN control message, or when all hooks have been disconnected. .Sh SEE ALSO .Xr netgraph 4 , .Xr ng_ppp 4 , .Xr ng_tty 4 , .Xr ngctl 8 .Rs .%A W. Simpson .%T "PPP in HDLC-link Framing" .%O RFC 1662 .Re .Rs .%A W. Simpson .%T "The Point-to-Point Protocol (PPP)" .%O RFC 1661 .Re .Sh HISTORY The .Nm node type was implemented in .Fx 4.0 . .Sh AUTHORS .An Archie Cobbs Aq Mt archie@FreeBSD.org