/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
  48. The
  49. .Nm pptpgre
  50. node type performs Generic Routing Encapsulation (GRE) over IP
  51. for the PPTP protocol as specified by RFC 2637.
  52. This involves packet
  53. encapsulation, sequencing, acknowledgement, and an adaptive timeout
  54. sliding window mechanism.
  55. This node type does not handle any of
  56. the TCP control protocol or call negotiation defined by PPTP.
  57. .Pp
  58. This node type expects to receive complete IP packets,
  59. including the IP header, on the
  60. .Dq Li lower
  61. hook, but it transmits outgoing frames without any IP header.
  62. The typical use for this node type would be to connect the
  63. .Dq Li upper
  64. hook to one of the link hooks of a
  65. .Xr ng_ppp 4
  66. node, and the
  67. .Dq Li lower
  68. hook to the
  69. .Dq Li "inet/raw/gre"
  70. hook of a
  71. .Xr ng_ksocket 4
  72. node.
  73. .Sh HOOKS
  74. This node type supports the following hooks:
  75. .Pp
  76. .Bl -tag -compact -width ".Li session_hhhh"
  77. .It Li session_hhhh
  78. Session 0xhhhh data packets to the upper protocol layers
  79. .It Li upper
  80. Same as session_hhhh, but for single session with configurable cid (legacy)
  81. .It Li lower
  82. Connection to the lower protocol layers
  83. .El
  84. .Sh CONTROL MESSAGES
  85. This node type supports the generic control messages, plus the following:
  86. .Bl -tag -width indent
  87. .It Dv NGM_PPTPGRE_SET_CONFIG
  88. This command resets and configures hook for a session. If corresponding
  89. session_hhhh hook is not connected, upper hook will be configured.
  90. This command takes a
  91. .Vt "struct ng_pptpgre_conf"
  92. as an argument:
  93. .Bd -literal
  94. /* Configuration for a session */
  95. struct 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
  108. The
  109. .Va enabled
  110. field enables traffic flow through the node.
  111. The
  112. .Va enableDelayedAck
  113. field enables delayed acknowledgement (maximum 250 milliseconds), which
  114. is a useful optimization and should generally be turned on.
  115. .Va enableAlwaysAck
  116. field enables sending acknowledgements with every data packet, which
  117. is probably helpful as well.
  118. .Pp
  119. .Va enableWindowing
  120. enables the PPTP packet windowing mechanism specified by the protocol.
  121. Disabling this will cause the node to violate the protocol, possibly
  122. confusing other PPTP peers, but often results in better performance.
  123. The windowing mechanism is a design error in the PPTP protocol;
  124. L2TP, the successor to PPTP, removes it.
  125. .Pp
  126. The remaining fields are as supplied by the PPTP virtual call setup process.
  127. .It Dv NGM_PPTPGRE_GET_CONFIG
  128. Takes 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
  131. This command returns a
  132. .Vt "struct ng_pptpgre_stats"
  133. containing various node statistics.
  134. .It Dv NGM_PPTPGRE_CLR_STATS
  135. This command resets the node statistics.
  136. .It Dv NGM_PPTPGRE_GETCLR_STATS
  137. This command atomically gets and resets the node statistics, returning a
  138. .Vt "struct ng_pptpgre_stats" .
  139. .El
  140. .Sh SHUTDOWN
  141. This node shuts down upon receipt of a
  142. .Dv NGM_SHUTDOWN
  143. control 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
  168. The
  169. .Nm
  170. node type was implemented in
  171. .Fx 4.0 .
  172. .Sh AUTHORS
  173. .An Archie Cobbs Aq archie@FreeBSD.org
  174. .Sh BUGS
  175. The node should not expect incoming GRE packets to have an IP header.
  176. This behavior is inherited from the (converse) behavior of raw IP sockets.
  177. An intermediate node that strips IP headers in one direction
  178. should be used instead.