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NG_PPTPGRE(4) Kernel Interfaces Manual NG_PPTPGRE(4) NAME ng_pptpgre -- PPTP GRE protocol netgraph node type SYNOPSIS #include <sys/types.h> #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 sliding window mechanism. This node type does not handle any of the TCP control 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: session_hhhh Session 0xhhhh data packets to the upper protocol layers upper Same as session_hhhh, but for single session with config- urable cid (legacy) lower Connection to the lower protocol layers CONTROL MESSAGES This node type supports the generic control messages, plus the follow- ing: NGM_PPTPGRE_SET_CONFIG (setconfig) This command resets and configures hook for a session. If corre- sponding session_hhhh hook is not connected, upper hook will be configured. This command takes a struct ng_pptpgre_conf as an ar- gument: /* Configuration for a session */ struct ng_pptpgre_conf { u_char enabled; /* enables traffic flow */ u_char enableDelayedAck; /* enables delayed acks */ u_char enableAlwaysAck; /* always include ack with data */ u_char enableWindowing; /* enable windowing algorithm */ uint16_t cid; /* my call id */ uint16_t peerCid; /* peer call id */ uint16_t recvWin; /* peer recv window size */ uint16_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 ac- knowledgements with every data packet, which is probably helpful as well. enableWindowing enables the PPTP packet windowing mechanism speci- fied by the protocol. Disabling this will cause the node to vio- late the protocol, possibly confusing other PPTP peers, but often results in better performance. The windowing mechanism is a de- sign error in the PPTP protocol; L2TP, the successor to PPTP, re- moves it. The remaining fields are as supplied by the PPTP virtual call setup process. NGM_PPTPGRE_GET_CONFIG (getconfig) Takes two byte argument as cid and returns the current configura- tion as a struct ng_pptpgre_conf. NGM_PPTPGRE_GET_STATS (getstats) This command returns a struct ng_pptpgre_stats containing various node statistics. NGM_PPTPGRE_CLR_STATS (clrstats) This command resets the node statistics. NGM_PPTPGRE_GETCLR_STATS (getclrstats) This command atomically gets and resets the node statistics, re- turning 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. SYSCTL VARIABLES A set of sysctl(8) variables controls ability of this node to deal with some amount of packet reorder that sometimes happens in transit. Packet reorder results in packet drops (unless the order is restored) as PPP protocol can not deliver reordered data. These variables are shown below together with their default value and meaning: net.graph.pptpgre.reorder_max: 1 Defines maximum length of node's private reorder queue used to keep data waiting for late packets. Zero value disables re- ordering. Default value allows the node to restore the order for two packets swapped in transit. Greater values allow the node to deliver packets being late after more packets in se- quence at cost of increased kernel memory usage. net.graph.pptpgre.reorder_timeout: 1 Defines time value in miliseconds used to wait for late pack- ets. SEE ALSO netgraph(4), ng_ksocket(4), ng_ppp(4), ngctl(8), sysctl(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. FreeBSD 14.3 November 4, 2018 NG_PPTPGRE(4)
NAME | SYNOPSIS | DESCRIPTION | HOOKS | CONTROL MESSAGES | SHUTDOWN | SYSCTL VARIABLES | SEE ALSO | HISTORY | AUTHORS | BUGS
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