NG_PPTPGRE(4) BSD Kernel Interfaces Manual NG_PPTPGRE(4)NAMEng_pptpgre — PPTP GRE protocol netgraph node type
SYNOPSIS
#include <netgraph/pptpgre/ng_pptpgre.h>
DESCRIPTION
The pptpgre node type performs Generic Routing Encapsulation (GRE) over
IP for the PPTP protocol as specified by RFC 2637. This involves packet
encapsulation, sequencing, acknowledgement, and an adaptive timeout slid‐
ing window mechanism. This node type does not handle any of the TCP con‐
trol protocol or call negotiation defined by PPTP.
This node type expects to receive complete IP packets, including the IP
header, on the “lower” hook, but it transmits outgoing frames without any
IP header. The typical use for this node type would be to connect the
“upper” hook to one of the link hooks of a ng_ppp(4) node, and the
“lower” hook to the “inet/raw/gre” hook of a ng_ksocket(4) node.
HOOKS
This node type supports the following hooks:
upper Connection to the upper protocol layers
lower Connection to the lower protocol layers
CONTROL MESSAGES
This node type supports the generic control messages, plus the following:
NGM_PPTPGRE_SET_CONFIG
This command resets and configures the node for a session. This
command takes a struct ng_pptpgre_conf as an argument:
/* Configuration for a session */
struct ng_pptpgre_conf {
u_char enabled; /* enables traffic flow */
u_char enableDelayedAck; /* enables delayed acks */
u_char enableAlwaysAck; /* always send ack with data */
u_int16_t cid; /* my call id */
u_int16_t peerCid; /* peer call id */
u_int16_t recvWin; /* peer recv window size */
u_int16_t peerPpd; /* peer packet processing delay
(in 1/10 of a second) */
};
The enabled field enables traffic flow through the node. The
enableDelayedAck field enables delayed acknowledgement (maximum
250 milliseconds), which is a useful optimization and should gen‐
erally be turned on. enableAlwaysAck field enables sending
acknowledgements with every data packet, which is probably help‐
ful as well. The remaining fields are as supplied by the PPTP
virtual call setup process.
NGM_PPTPGRE_GET_CONFIG
Returns the current configuration as a struct ng_pptpgre_conf.
NGM_PPTPGRE_GET_STATS
This command returns a struct ng_pptpgre_stats containing various
node statistics.
NGM_PPTPGRE_CLR_STATS
This command resets the node statistics.
NGM_PPTPGRE_GETCLR_STATS
This command atomically gets and resets the node statistics,
returning a struct ng_pptpgre_stats.
SHUTDOWN
This node shuts down upon receipt of a NGM_SHUTDOWN control message, or
when both hooks have been disconnected.
SEE ALSOnetgraph(4), ng_ksocket(4), ng_ppp(4), ngctl(8)
K. Hamzeh, G. Pall, W. Verthein, J. Taarud, W. Little, and G. Zorn,
Point-to-Point Tunneling Protocol (PPTP), RFC 2637.
S. Hanks, T. Li, D. Farinacci, and P. Traina, Generic Routing
Encapsulation over IPv4 networks, RFC 1702.
HISTORY
The ng_pptpgre node type was implemented in FreeBSD 4.0.
AUTHORS
Archie Cobbs ⟨archie@FreeBSD.org⟩
BUGS
The node should not expect incoming GRE packets to have an IP header.
This behavior is inherited from the (converse) behavior of raw IP sock‐
ets. An intermediate node that strips IP headers in one direction should
be used instead.
BSD December 7, 2001 BSD
