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

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

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

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

     The node has two hooks, comp for compression and decomp for
     decompression.  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.

HOOKS
     This node type supports the following hooks:

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

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

CONTROL MESSAGES
     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
          initiated 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
          Reset-Request or Reset-Ack is received by the local PPP entity.  The
          node will respond by flushing its compression state so the sides can
          resynchronize.

     NGM_DEFLATE_GET_STATS (getstats)
          This control message obtains statistics for a given hook.  The
          statistics 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.

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

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

     J. Woods, PPP Deflate Protocol, RFC 1979.

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

AUTHORS
     Alexander Motin <mav@alkar.net>

BUGS
     Due to nature of netgraph PPP implementation there are possible race
     conditions 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 13.1-RELEASE-p6        December 23, 2006       FreeBSD 13.1-RELEASE-p6