/share/man/man4/ng_pptpgre.4

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 33.\" Author: Archie Cobbs <archie@FreeBSD.org>
 34.\"
 35.\" $FreeBSD$
 36.\" $Whistle: ng_pptpgre.8,v 1.2 1999/12/08 00:20:53 archie Exp $
 37.\"
 38.Dd March 29, 2008
 39.Dt NG_PPTPGRE 4
 40.Os
 41.Sh NAME
 42.Nm ng_pptpgre
 43.Nd PPTP GRE protocol netgraph node type
 44.Sh SYNOPSIS
 45.In sys/types.h
 46.In netgraph/ng_pptpgre.h
 47.Sh DESCRIPTION
 48The
 49.Nm pptpgre
 50node type performs Generic Routing Encapsulation (GRE) over IP
 51for the PPTP protocol as specified by RFC 2637.
 52This involves packet
 53encapsulation, sequencing, acknowledgement, and an adaptive timeout
 54sliding window mechanism.
 55This node type does not handle any of
 56the TCP control protocol or call negotiation defined by PPTP.
 57.Pp
 58This node type expects to receive complete IP packets,
 59including the IP header, on the
 60.Dq Li lower
 61hook, but it transmits outgoing frames without any IP header.
 62The typical use for this node type would be to connect the
 63.Dq Li upper
 64hook to one of the link hooks of a
 65.Xr ng_ppp 4
 66node, and the
 67.Dq Li lower
 68hook to the
 69.Dq Li "inet/raw/gre"
 70hook of a
 71.Xr ng_ksocket 4
 72node.
 73.Sh HOOKS
 74This node type supports the following hooks:
 75.Pp
 76.Bl -tag -compact -width ".Li session_hhhh"
 77.It Li session_hhhh
 78Session 0xhhhh data packets to the upper protocol layers
 79.It Li upper
 80Same as session_hhhh, but for single session with configurable cid (legacy)
 81.It Li lower
 82Connection to the lower protocol layers
 83.El
 84.Sh CONTROL MESSAGES
 85This node type supports the generic control messages, plus the following:
 86.Bl -tag -width indent
 87.It Dv NGM_PPTPGRE_SET_CONFIG
 88This command resets and configures hook for a session. If corresponding
 89session_hhhh hook is not connected, upper hook will be configured.
 90This command takes a
 91.Vt "struct ng_pptpgre_conf"
 92as an argument:
 93.Bd -literal
 94/* Configuration for a session */
 95struct ng_pptpgre_conf {
 96    u_char      enabled;          /* enables traffic flow */
 97    u_char      enableDelayedAck; /* enables delayed acks */
 98    u_char      enableAlwaysAck;  /* always send ack with data */
 99    u_char      enableWindowing;  /* enable windowing algorithm */
100    uint16_t    cid;              /* my call id */
101    uint16_t    peerCid;          /* peer call id */
102    uint16_t    recvWin;          /* peer recv window size */
103    uint16_t    peerPpd;          /* peer packet processing delay
104                                     (in 1/10 of a second) */
105};
106.Ed
107.Pp
108The
109.Va enabled
110field enables traffic flow through the node.
111The
112.Va enableDelayedAck
113field enables delayed acknowledgement (maximum 250 milliseconds), which
114is a useful optimization and should generally be turned on.
115.Va enableAlwaysAck
116field enables sending acknowledgements with every data packet, which
117is probably helpful as well.
118.Pp
119.Va enableWindowing
120enables the PPTP packet windowing mechanism specified by the protocol.
121Disabling this will cause the node to violate the protocol, possibly
122confusing other PPTP peers, but often results in better performance.
123The windowing mechanism is a design error in the PPTP protocol;
124L2TP, the successor to PPTP, removes it.
125.Pp
126The remaining fields are as supplied by the PPTP virtual call setup process.
127.It Dv NGM_PPTPGRE_GET_CONFIG
128Takes two byte argument as cid and returns the current configuration as a
129.Vt "struct ng_pptpgre_conf" .
130.It Dv NGM_PPTPGRE_GET_STATS
131This command returns a
132.Vt "struct ng_pptpgre_stats"
133containing various node statistics.
134.It Dv NGM_PPTPGRE_CLR_STATS
135This command resets the node statistics.
136.It Dv NGM_PPTPGRE_GETCLR_STATS
137This command atomically gets and resets the node statistics, returning a
138.Vt "struct ng_pptpgre_stats" .
139.El
140.Sh SHUTDOWN
141This node shuts down upon receipt of a
142.Dv NGM_SHUTDOWN
143control message, or when both hooks have been disconnected.
144.Sh SEE ALSO
145.Xr netgraph 4 ,
146.Xr ng_ksocket 4 ,
147.Xr ng_ppp 4 ,
148.Xr ngctl 8
149.Rs
150.%A K. Hamzeh
151.%A G. Pall
152.%A W. Verthein
153.%A J. Taarud
154.%A W. Little
155.%A G. Zorn
156.%T "Point-to-Point Tunneling Protocol (PPTP)"
157.%O RFC 2637
158.Re
159.Rs
160.%A S. Hanks
161.%A T. \&Li
162.%A D. Farinacci
163.%A P. Traina
164.%T "Generic Routing Encapsulation over IPv4 networks"
165.%O RFC 1702
166.Re
167.Sh HISTORY
168The
169.Nm
170node type was implemented in
171.Fx 4.0 .
172.Sh AUTHORS
173.An Archie Cobbs Aq archie@FreeBSD.org
174.Sh BUGS
175The node should not expect incoming GRE packets to have an IP header.
176This behavior is inherited from the (converse) behavior of raw IP sockets.
177An intermediate node that strips IP headers in one direction
178should be used instead.