All rights reserved.
Subject to the following obligations and disclaimer of warranty, use and
redistribution of this software, in source or object code forms, with or
without modifications are expressly permitted by Whistle Communications;
provided, however, that:
1. Any and all reproductions of the source or object code must include the
copyright notice above and the following disclaimer of warranties; and
2. 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 <archie@whistle.com>
$FreeBSD: head/share/man/man4/ng_ppp.4 52978 1999-11-08 03:13:28Z archie $
$Whistle: ng_ppp.8,v 1.3 1999/01/25 23:46:27 archie Exp $
.Dd January 19, 1999 .Dt NG_PPP 8 .Os FreeBSD .Sh NAME .Nm ng_ppp .Nd PPP protocol netgraph node type .Sh SYNOPSIS .Fd #include <netgraph/ng_ppp.h> .Sh DESCRIPTION The .Nm ppp node type performs multiplexing for the PPP protocol. It handles only packets that contain data, and forwards protocol negotiation and control packets to a separate controlling entity (e.g., a user-land daemon). This approach combines the fast dispatch of kernel implementations with the configuration flexibility of a user-land implementations. The PPP node type directly supports multi-link PPP, Van Jacobsen compression, PPP compression, PPP encryption, and the IP, IPX, and AppleTalk protocols. A single PPP node corresponds to one PPP multi-link bundle.
p There is a separate hook for each PPP link in the bundle, plus several hooks corresponding to the directly supported protocols. For compression and encryption, separate attached nodes are required to do the actual work. The node type used will of course depend on the algorithm negotiated. There is also a .Dv bypass hook which is used to handle any protocol not directly supported by the node. This includes all of the control protocols: LCP, IPCP, CCP, etc. Typically this node is connected to a user-land daemon via a .Xr ng_socket(8) type node. .Sh ENABLING FUNCTIONALITY In general, the PPP node enables a specific link or functionality when (a) a .Dv NGM_PPP_SET_CONFIG message has been received which enables it, and (b) the corresponding hook(s) are connected. This allows the controlling entity to use either method (a) or (b) (or both) to control the node's behavior. When a link is connected but disabled, traffic can still flow on the link via the .Dv bypass hook (see below). .Sh LINK HOOKS During normal operation, the individual PPP links are connected to hooks .Dv link0 , .Dv link1 , etc. Up to .Dv NG_PPP_MAX_LINKS links are supported. These device-independent hooks transmit and receive full PPP frames, which include the PPP protocol field, but no address, control or checksum fields. On outgoing frames, when protocol compression has been enabled and the protocol number is suitable for compression, the protocol field will be compressed (i.e., sent as one byte instead of two). Either compressed or uncompressed protocol fields are accepted on incoming frames.
p Since all negotiation is handled outside the PPP node, the links should not be connected and enabled until the corresponding link has reached the network phase (i.e., LCP negotiation and authentication have completed successfully) and the PPP node has been informed of the link parameters via the .Dv NGM_PPP_LINK_CONFIG message.
p When a link is connected but disabled, all received frames are forwarded directly out the .Dv bypass hook, and conversely, frames may be transmitted via the .Dv bypass hook as well. This mode is appropriate for the link authentication phase. As soon as the link is enabled, the PPP node will begin processing frames received on the link. .Sh COMPRESSION AND ENCRYPTION
p Compression is supported via two hooks, .Dv compress and .Dv decompress . When enabled and connected, the PPP node writes outgoing frames on the .Dv comp hook and expects to receive back the compressed frame on the same hook. Similarly, the .Dv decompress hook is used to uncompress incoming frames when decompression is negotiated (compression and decompression are independently negotiable). The type of node attached to these hooks should correspond to the type of compression negotiated, e.g., Deflate, Predictor-1, etc.
p Encryption works exactly analogously via the .Dv encrypt and .Dv decrypt nodes. Data is always compressed before being encrypted, and decrypted before being decompressed.
p Only bundle-level compression and encryption is directly supported; link-level compression and encryption can be handled transparently by downstream nodes. .Sh VAN JACOBSEN COMPRESSION When all of the .Dv vjc_ip , .Dv vjc_vjcomp , .Dv vjc_vjuncomp , and .Dv vjc_vjip hooks are connected, and the corresponding configuration flag is enabled, Van Jacobsen compression and/or decompression will become active. Normally these hooks connect to the corresponding hooks of a single .Xr ng_vjc 8 node. The PPP node is compatible with the ``pass through'' modes of the .Xr ng_vjc 8 node type. .Sh BYPASS HOOK When a frame is received on a link with an unsupported protocol, or a protocol which is disabled or for which the corresponding hook is unconnected, the PPP node forwards the frame out the .Dv bypass hook, prepended with a four byte prefix. This first two bytes of the prefix indicate the link number on which the frame was received (in network order). For such frames received over the bundle (i.e., encapsulated in the multi-link protocol), the special link number .Dv NG_PPP_BUNDLE_LINKNUM is used. After the two byte link number is the two byte PPP protocol number (also in network order). The PPP protocol number is two bytes long even if the original frame was protocol compressed.
p Conversely, any data written to the .Dv bypass hook is assumed to be in this same format. The four byte header is stripped off, the PPP protocol number is prepended (possibly compressed), and the frame is delivered over the desired link. If the link number is .Dv NG_PPP_BUNDLE_LINKNUM the frame will be delivered over the multi-link bundle; or, if multi-link is disabled, over the (single) PPP link.
p Typically when the controlling entity receives a packet on the bypass hook it responds either by dropping the frame (if it's not ready for the protocol) or with an LCP protocol reject (if it doesn't recognize or expect the protocol). .Sh MULTILINK OPERATION To enable multi-link PPP, the corresponding configuration flag must be set and at least one link connected. The PPP node will not allow more than one link to be connected if multi-link is not enabled, nor will it allow certain multi-link settings to be changed while multi-link operation is active (e.g., short sequence number header format).
p Because packets are sent as fragments across multiple individual links, it is important that when a link goes down the PPP node is notified immediately, either by disconnecting the corresponding hook or disabling the link via the .Dv NGM_PPP_SET_CONFIG control message.
p Each link has configuration parameters for latency (specified in milliseconds) and bandwidth (specified in tens of bytes per second). The PPP node can be configured for .Em round-robin or .Em optimized packet delivery.
p When configured for round-robin delivery, the latency and bandwidth values are ignored and the PPP node simply sends each frame as a single fragment, alternating frames across all the links in the bundle. This scheme has the advantage that even if one link fails silently, some packets will still get through. It has the disadvantage of sub-optimal overall bundle latency, which is important for interactive response time, and sub-optimal overall bundle bandwidth when links with different bandwidths exist in the same bundle.
p When configured for optimal delivery, the PPP node distributes the packet across the links in a way that minimizes the time it takes for the completed packet to be received by the far end. This involves taking into account each link's latency, bandwidth, and current queue length. Therefore these numbers should be configured as accurately as possible. The algorithm does require some computation, so may not be appropriate for very slow machines and/or very fast links.
p As a special case, if all links have identical latency and bandwidth, then the above algorithm is disabled (because it is unnecessary) and the PPP node simply fragments frames into equal sized portions across all of the links. .Sh HOOKS This node type supports the following hooks:
p l -tag -compact -width vjc_vjuncomp t Dv link<N> Individual PPP link number .Dv <N> t Dv compress Connection to compression engine t Dv decompress Connection to decompression engine t Dv encrypt Connection to encryption engine t Dv decrypt Connection to decryption engine t Dv vjc_ip Connection to .Xr ng_vjc 8 .Dv ip hook t Dv vjc_vjcomp Connection to .Xr ng_vjc 8 .Dv vjcomp hook t Dv vjc_vjuncomp Connection to .Xr ng_vjc 8 .Dv vjuncomp hook t Dv vjc_vjip Connection to .Xr ng_vjc 8 .Dv vjip hook t Dv inet IP packet data t Dv atalk AppleTalk packet data t Dv ipx IPX packet data t Dv bypass Bypass hook; frames have a four byte header consisting of a link number and a PPP protocol number. .El
p .Sh CONTROL MESSAGES This node type supports the generic control messages, plus the following: l -tag -width foo t Dv NGM_PPP_SET_CONFIG This command configures all aspects of the node. This includes enabling multi-link PPP, encryption, compression, Van Jacobsen compression, and IP, AppleTalk, and IPX packet delivery. It includes per-link configuration, including enabling the link, setting latency and bandwidth parameters, and enabling protocol field compression. Note that no link or functionality is active until the corresponding hook is also connected. This command takes a .Dv "struct ng_ppp_node_config" as an argument. t Dv NGM_PPP_GET_CONFIG Returns the current configuration as a .Dv "struct ng_ppp_node_config" . t Dv NGM_PPP_GET_LINK_STATS This command takes a two byte link number as an argument and returns a .Dv "struct ng_ppp_link_stat" containing statistics for the corresponding link. Here .Dv NG_PPP_BUNDLE_LINKNUM is a valid link number corresponding to the multi-link bundle. t Dv NGM_PPP_CLR_LINK_STATS This command takes a two byte link number as an argument and clears the statistics for that link. t Dv NGM_PPP_GETCLR_LINK_STATS Same as .Dv NGM_PPP_GET_LINK_STATS , but also atomically clears the statistics as well. .El
p This node type also accepts the control messages accepted by the .Xr ng_vjc 8 node type. When received, these messages are simply forwarded to the adjacent .Xr ng_vjc 8 node, if any. .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_async 8 , .Xr ng_iface 8 , .Xr ng_vjc 8 , .Xr ngctl 8 . .Rs .%A W. Simpson .%T "The Point-to-Point Protocol (PPP)" .%O RFC 1661 .Re .Rs .%A K. Sklower .%A B. Lloyd .%A G. McGregor .%A D. Carr .%A T. Coradetti .%T "The PPP Multilink Protocol (MP)" .%O RFC 1990 .Re .Sh AUTHOR Archie Cobbs <archie@whistle.com>