1.\" 2.\" Copyright (c) 1997, 2001 Joerg Wunsch 3.\" 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR 16.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, 19.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25.\" 26.\" $FreeBSD$ 27.\" 28.Dd May 25, 2008 29.Dt SPPP 4 30.Os 31.Sh NAME 32.Nm sppp 33.Nd point to point protocol network layer for synchronous lines 34.Sh SYNOPSIS 35.Cd "device sppp" 36.Sh DESCRIPTION 37The 38.Nm 39network layer implements the state machine and the Link Control 40Protocol (LCP) of the 41.Em point to point protocol (PPP) 42as described in RFC 1661. 43Note that this layer does not provide 44network interfaces of its own, it is rather intended to be layered on 45top of drivers providing a synchronous point-to-point connection that 46wish to run a PPP stack over it. 47The corresponding network interfaces 48have to be provided by these hardware drivers. 49.Pp 50The 51.Nm 52layer provides three basic modes of operation. 53The default mode, 54with no special flags to be set, is to create the PPP connection 55(administrative 56.Em Open 57event to the LCP layer) as soon as the interface is taken up with the 58.Xr ifconfig 8 59command. 60Taking the interface down again will terminate the LCP layer 61and thus all other layers on top. 62The link will also terminate itself as 63soon as no Network Control Protocol (NCP) is open anymore, indicating 64that the lower layers are no longer needed. 65.Pp 66Setting the link-level flag 67.Em link0 68with 69.Xr ifconfig 8 70will cause the respective network interface to go into 71.Em passive 72mode. 73This means, the administrative 74.Em Open 75event to the LCP layer will be delayed until after the lower layers 76signals an 77.Em Up 78event (rise of 79.Dq carrier ) . 80This can be used by lower layers to support 81a dialin connection where the physical layer is not available 82immediately at startup, but only after some external event arrives. 83Receipt of a 84.Em Down 85event from the lower layer will not take the interface completely down 86in this case. 87.Pp 88Finally, setting the flag 89.Em link1 90will cause the interface to operate in 91.Em dial-on-demand 92mode. 93This is also only useful if the lower layer supports the notion 94of a carrier. 95Upon configuring the 96respective interface, it will delay the administrative 97.Em Open 98event to the LCP layer until either an outbound network packet 99arrives, or until the lower layer signals an 100.Em Up 101event, indicating an inbound connection. 102As with passive mode, receipt 103of a 104.Em Down 105event (loss of carrier) will not automatically take the interface down, 106thus it remains available for further connections. 107.Pp 108The 109.Nm 110layer supports the 111.Em debug 112interface flag that can be set with 113.Xr ifconfig 8 . 114If this flag is set, the various control protocol packets being 115exchanged as well as the option negotiation between both ends of the 116link will be logged at level 117.Dv LOG_DEBUG . 118This can be helpful to examine configuration problems during the first 119attempts to set up a new configuration. 120Without this flag being set, 121only the major phase transitions will be logged at level 122.Dv LOG_INFO . 123.Pp 124It is possible to leave the local interface IP address open for 125negotiation by setting it to 0.0.0.0. 126This requires that the remote 127peer can correctly supply a value for it based on the identity of the 128caller, or on the remote address supplied by this side. 129Due to the 130way the IPCP option negotiation works, this address is being supplied 131late during the negotiation, which might cause the remote peer to make 132wrong assumptions. 133.Pp 134In a similar spirit the remote address can be set to the magical 135value 136.Li 0.0.0. Ns Em * 137which means that we do not care what address the remote 138side will use, as long as it is not 0.0.0.0. 139This is useful if your ISP has several dial-in 140servers. 141You can of course 142.Nm route Cm add Ar something_or_other 0.0.0. Ns Em * 143and it will do exactly what you would want it to. 144.Pp 145The PAP and CHAP authentication protocols as described in RFC 1334, 146and RFC 1994 resp., are also implemented. 147Their parameters are being 148controlled by the 149.Xr spppcontrol 8 150utility. 151.Pp 152VJ header compression is implemented, and enabled by default. 153It can be 154disabled using 155.Xr spppcontrol 8 . 156.Sh DIAGNOSTICS 157.Bl -diag 158.It <ifname><ifnum>: <proto> illegal <event> in state <statename> 159An event happened that should not happen for the current state 160the respective control protocol is in. 161See RFC 1661 for a description 162of the state automaton. 163.It <ifname><ifnum>: loopback 164The state automaton detected a line loopback (that is, it was talking 165with itself). 166The interface will be temporarily disabled. 167.It <ifname><ifnum>: up 168The LCP layer is running again, after a line loopback had previously 169been detected. 170.It <ifname><ifnum>: down 171The keepalive facility detected the line being unresponsive. 172Keepalive must be explicitly requested by the lower layers in order to 173take place. 174.El 175.Sh SEE ALSO 176.Xr inet 4 , 177.Xr intro 4 , 178.Xr ppp 4 , 179.Xr ifconfig 8 , 180.Xr spppcontrol 8 181.Rs 182.%A W. Simpson, Editor 183.%T "The Point-to-Point Protocol (PPP)" 184.%O RFC 1661 185.Re 186.Rs 187.%A G. McGregor 188.%T "The PPP Internet Protocol Control Protocol (IPCP)" 189.%O RFC 1332 190.Re 191.Rs 192.%A B. Lloyd 193.%A W. Simpson 194.%T "PPP Authentication Protocols" 195.%O RFC 1334 196.Re 197.Rs 198.%A W. Simpson 199.%T "PPP Challenge Handshake Authentication Protocol (CHAP)" 200.%O RFC 1994 201.Re 202.Sh AUTHORS 203.An -nosplit 204The original implementation of 205.Nm 206was written in 1994 at Cronyx Ltd., Moscow by 207.An Serge Vakulenko Aq Mt vak@cronyx.ru . 208.An J\(:org Wunsch Aq Mt joerg_wunsch@uriah.heep.sax.de 209rewrote a large part in 1997 in order 210to fully implement the state machine as described in RFC 1661, so it 211could also be used for dialup lines. 212He also wrote this man page. 213Serge later on wrote a basic implementation for PAP and CHAP, which 214served as the base for the current implementation, done again by 215.An J\(:org Wunsch . 216.Sh BUGS 217Many. 218.Pp 219Currently, only the 220.Em IPCP 221control protocol and 222.Xr ip 4 223network protocol is supported. 224More NCPs should be implemented, as well as other control protocols 225for authentication and link quality reporting. 226.Pp 227Negotiation loop avoidance is not fully implemented. 228If the negotiation 229does not converge, this can cause an endless loop. 230.Pp 231The various parameters that should be adjustable per RFC 1661 are 232currently hard-coded into the kernel, and should be made accessible 233through 234.Xr spppcontrol 8 . 235.Pp 236.Em Passive 237mode has not been tested extensively. 238.Pp 239Link-level compression protocols should be supported. 240