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NG_PPTPGRE(4)	       FreeBSD Kernel Interfaces Manual		 NG_PPTPGRE(4)

NAME
     ng_pptpgre	-- PPTP	GRE protocol netgraph node type

SYNOPSIS
     #include <netgraph/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_char	     enableWindowing;  /* enable windowing algorithm */
		 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.

	     enableWindowing enables the PPTP packet windowing mechanism spec-
	     ified by the protocol.  Disabling this will cause the node	to
	     violate the protocol, possibly confusing other PPTP peers,	but
	     often results in better performance.  The windowing mechanism is
	     a design error in the PPTP	protocol; L2TP,	the successor to PPTP,
	     removes it.

	     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 ALSO
     netgraph(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.

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.

HISTORY
     The ng_pptpgre node type was implemented in FreeBSD 4.0.

AUTHORS
     Archie Cobbs <archie@FreeBSD.org>

FreeBSD	10.1		       December	7, 2001			  FreeBSD 10.1

NAME | SYNOPSIS | DESCRIPTION | HOOKS | CONTROL MESSAGES | SHUTDOWN | SEE ALSO | BUGS | HISTORY | AUTHORS

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