Command Section
NG_MPPC(4)             FreeBSD Kernel Interfaces Manual             NG_MPPC(4)

     ng_mppc - Microsoft MPPC/MPPE compression and encryption netgraph node

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

     The mppc node type implements the Microsoft Point-to-Point Compression
     (MPPC) and Microsoft Point-to-Point Encryption (MPPE) sub-protocols of
     the PPP protocol.  These protocols are often used in conjunction with the
     Point-to-Point Tunneling Protocol (PPTP).

     The node has two hooks, comp for compression and decomp for
     decompression.  Typically one or both of these hooks would be connected
     to the ng_ppp(4) node type hook of the same name.  Each direction of
     traffic flow is independent of the other.

     This node type supports the following hooks:

     comp        Connection to ng_ppp(4) comp hook.  Incoming frames are
                 compressed and/or encrypted, and sent back out the same hook.

     decomp      Connection to ng_ppp(4) decomp hook.  Incoming frames are
                 decompressed and/or decrypted, and sent back out the same

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

          This command resets and configures the node for a session in the
          outgoing traffic direction (i.e., for compression and/or
          encryption).  This command takes a struct ng_mppc_config as an

          /* Length of MPPE key */
          #define MPPE_KEY_LEN      16

          /* MPPC/MPPE PPP negotiation bits */
          #define MPPC_BIT          0x00000001      /* mppc compression bits */
          #define MPPE_40           0x00000020      /* use 40 bit key */
          #define MPPE_56           0x00000080      /* use 56 bit key */
          #define MPPE_128          0x00000040      /* use 128 bit key */
          #define MPPE_BITS         0x000000e0      /* mppe encryption bits */
          #define MPPE_STATELESS    0x01000000      /* use stateless mode */
          #define MPPC_VALID_BITS   0x010000e1      /* possibly valid bits */

          /* Configuration for a session */
          struct ng_mppc_config {
              u_char    enable;                 /* enable */
              uint32_t  bits;                   /* config bits */
              u_char    startkey[MPPE_KEY_LEN]; /* start key */

          The enabled field enables traffic flow through the node.  The bits
          field contains the bits as negotiated by the Compression Control
          Protocol (CCP) in PPP.  The startkey is only necessary if MPPE was
          negotiated, and must be equal to the session start key as defined
          for MPPE.  This key is based on the MS-CHAP credentials used at link
          authentication time.

          This command resets and configures the node for a session in the
          incoming traffic direction (i.e., for decompression and/or
          decryption).  This command takes a struct ng_mppc_config as an

          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_MPPC_CONFIG_DECOMP 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 is received by the local PPP entity.  The node will
          respond by flushing its outgoing compression and encryption state so
          the remote side can resynchronize.

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

     are supplied to selectively compile in either or both capabilities.  At
     least one of these must be defined, or else this node type is useless.

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

     G. Pall, Microsoft Point-To-Point Compression (MPPC) Protocol, RFC 2118.

     G. S. Pall and G. Zorn, Microsoft Point-To-Point Encryption (MPPE)
     Protocol, draft-ietf-pppext-mppe-04.txt.

     K. Hamzeh, G. Pall, W. Verthein, J. Taarud, W. Little, and G. Zorn,
     Point-to-Point Tunneling Protocol (PPTP), RFC 2637.

     Archie Cobbs <[email protected]>

     In PPP, encryption should be handled by the Encryption Control Protocol
     (ECP) rather than CCP.  However, Microsoft combined both compression and
     encryption into their ``compression'' algorithm, which is confusing.

FreeBSD 11.1-RELEASE-p4          June 7, 2016          FreeBSD 11.1-RELEASE-p4
Command Section