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NG_DEFLATE(4)	       FreeBSD Kernel Interfaces Manual		 NG_DEFLATE(4)

     ng_deflate	-- Deflate PPP compression (RFC	1979) netgraph node type

     #include <sys/types.h>
     #include <netgraph/ng_deflate.h>

     The deflate node type implements the Deflate sub-protocols	of the Com-
     pression Control Protocol (CCP).

     The node has two hooks, comp for compression and decomp for decompres-
     sion.  Only one of	them can be connected at the same time,	specifying
     node's operation mode.  Typically that hooks would	be connected to	the
     ng_ppp(4) node type hook of the same name.	 Corresponding ng_ppp(4) node
     hook must be switched to NG_PPP_DECOMPRESS_FULL mode to permit sending
     uncompressed frames.

     This node type supports the following hooks:

     comp    Connection	to ng_ppp(4) comp hook.	 Incoming frames are com-
	     pressed (if possible) and sent back out the same hook.
     decomp  Connection	to ng_ppp(4) decomp hook.  Incoming frames are decom-
	     pressed (if they are compressed), and sent	back out the same

     Only one hook can be connected at the same	time, specifying node's	opera-
     tion mode.

     This node type supports the generic control messages, plus	the following:

     NGM_DEFLATE_CONFIG	(config)
	  This command resets and configures the node for a session (i.e., for
	  compression or decompression).  This command takes a struct
	  ng_deflate_config as an argument:

	  struct ng_deflate_config {
		  u_char  enable;		  /* node enabled */
		  u_char  windowBits;		  /* log2(Window size) */
	  The enabled field enables traffic flow through the node.  The
	  windowBits specify compression windows size as negotiated by the
	  Compression Control Protocol (CCP) in	PPP.

     NGM_DEFLATE_RESETREQ (resetreq)
	  This message contains	no arguments, and is bi-directional.  If an
	  error	is detected during decompression, this message is sent by the
	  node to the originator of the	NGM_DEFLATE_CONFIG message that	initi-
	  ated the session.  The receiver should respond by sending a PPP CCP
	  Reset-Request	to the peer.

	  This message may also	be received by this node type when a CCP Re-
	  set-Request or Reset-Ack is received by the local PPP	entity.	 The
	  node will respond by flushing	its compression	state so the sides can

     NGM_DEFLATE_GET_STATS (getstats)
	  This control message obtains statistics for a	given hook.  The sta-
	  tistics are returned in struct ng_deflate_stats:

	  struct ng_deflate_stats {
		  uint64_t	  FramesPlain;
		  uint64_t	  FramesComp;
		  uint64_t	  FramesUncomp;
		  uint64_t	  InOctets;
		  uint64_t	  OutOctets;
		  uint64_t	  Errors;

     NGM_DEFLATE_CLR_STATS (clrstats)
	  This control message clears statistics for a given hook.

     NGM_DEFLATE_GETCLR_STATS (getclrstats)
	  This control message obtains and clears statistics for a given hook.

     This node shuts down upon receipt of a NGM_SHUTDOWN control message, or
     when hook have been disconnected.

     netgraph(4), ng_ppp(4), ngctl(8)

     J.	Woods, PPP Deflate Protocol, RFC 1979.

     W.	Simpson, The Point-to-Point Protocol (PPP), RFC	1661.

     Alexander Motin <>

     Due to nature of netgraph PPP implementation there	are possible race con-
     ditions between data packet and ResetAck CCP packet in case of packet
     loss.  As result, packet loss can produce bigger performance degradation
     than supposed by protocol.

FreeBSD	13.0		       December	23, 2006		  FreeBSD 13.0


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