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man/orig/ng nat

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NG_NAT(4) FreeBSD Kernel Interfaces Manual NG_NAT(4)


[править] NAME

    ng_nat -- NAT netgraph node type

[править] SYNOPSIS

    #include <netgraph/ng_nat.h>


    An ng_nat node performs network address translation (NAT) of packets
    passing through it.  A nat node uses libalias(3) engine for packet alias-

[править] HOOKS

    This node type has two hooks:
    out     Packets received on this hook are considered outgoing and will be
            masqueraded to a configured address.
    in      Packets coming on this hook are considered incoming and will be


    This node type supports the generic control messages, plus the following:
    NGM_NAT_SET_IPADDR (setaliasaddr)
            Configure aliasing address for a node.  After both hooks have
            been connected and aliasing address was configured, a node is
            ready for aliasing operation.
    NGM_NAT_SET_MODE (setmode)
            Set node's operation mode using supplied struct ng_nat_mode.
            struct ng_nat_mode {
                    uint32_t        flags;
                    uint32_t        mask;
            /* Supported flags: */
            #define NG_NAT_LOG                      0x01
            #define NG_NAT_DENY_INCOMING            0x02
            #define NG_NAT_SAME_PORTS               0x04
            #define NG_NAT_UNREGISTERED_ONLY        0x10
            #define NG_NAT_RESET_ON_ADDR_CHANGE     0x20
            #define NG_NAT_PROXY_ONLY               0x40
            #define NG_NAT_REVERSE                  0x80
    NGM_NAT_SET_TARGET (settarget)
            Configure target address for a node.  When an incoming packet not
            associated with any pre-existing aliasing link arrives at the
            host machine, it will be sent to the specified address.
    NGM_NAT_REDIRECT_PORT (redirectport)
            Redirect incoming connections arriving to given port(s) to
            another host and port(s).  The following struct
            ng_nat_redirect_port must be supplied as argument.
            #define NG_NAT_DESC_LENGTH      64
            struct ng_nat_redirect_port {
                    struct in_addr  local_addr;
                    struct in_addr  alias_addr;
                    struct in_addr  remote_addr;
                    uint16_t        local_port;
                    uint16_t        alias_port;
                    uint16_t        remote_port;
                    uint8_t         proto;
                    char            description[NG_NAT_DESC_LENGTH];
            Redirection is assigned an unique ID which is returned as
            response to this message, and information about redirection added
            to list of static redirects which later can be retrieved by
            NGM_NAT_LIST_REDIRECTS message.
    NGM_NAT_REDIRECT_ADDR (redirectaddr)
            Redirect traffic for public IP address to a machine on the local
            network.  This function is known as static NAT.  The following
            struct ng_nat_redirect_addr must be supplied as argument.
            struct ng_nat_redirect_addr {
                    struct in_addr  local_addr;
                    struct in_addr  alias_addr;
                    char            description[NG_NAT_DESC_LENGTH];
            Unique ID for this redirection is returned as response to this
    NGM_NAT_REDIRECT_PROTO (redirectproto)
            Redirect incoming IP packets of protocol proto (see protocols(5))
            to a machine on the local network.  The following struct
            ng_nat_redirect_proto must be supplied as argument.
            struct ng_nat_redirect_proto {
                    struct in_addr  local_addr;
                    struct in_addr  alias_addr;
                    struct in_addr  remote_addr;
                    uint8_t         proto;
                    char            description[NG_NAT_DESC_LENGTH];
            Unique ID for this redirection is returned as response to this
    NGM_NAT_REDIRECT_DYNAMIC (redirectdynamic)
            Mark redirection with specified ID as dynamic, i.e., it will
            serve for exactly one next connection and then will be automati-
            cally deleted from internal links table.  Only fully specified
            links can be made dynamic.  The redirection with this ID is also
            immediately deleted from user-visible list of static redirects
            (available through NGM_NAT_LIST_REDIRECTS message).
    NGM_NAT_REDIRECT_DELETE (redirectdelete)
            Delete redirection with specified ID (currently active connec-
            tions are not affected).
    NGM_NAT_ADD_SERVER (addserver)
            Add another server to a pool.  This is used to transparently
            offload network load on a single server and distribute the load
            across a pool of servers, also known as LSNAT (RFC 2391).  The
            following struct ng_nat_add_server must be supplied as argument.
            struct ng_nat_add_server {
                    uint32_t        id;
                    struct in_addr  addr;
                    uint16_t        port;
            First, the redirection is set up by NGM_NAT_REDIRECT_PORT or
            NGM_NAT_REDIRECT_ADDR.  Then, ID of that redirection is used in
            multiple NGM_NAT_ADD_SERVER messages to add necessary number of
            servers.  For redirections created by NGM_NAT_REDIRECT_ADDR, the
            port is ignored and could have any value.  Original redirection's
            parameters local_addr and local_port are also ignored after
            NGM_NAT_ADD_SERVER was used (they are effectively replaced by
            server pool).
    NGM_NAT_LIST_REDIRECTS (listredirects)
            Return list of configured static redirects as struct
            struct ng_nat_listrdrs_entry {
                    uint32_t        id;             /* Anything except zero */
                    struct in_addr  local_addr;
                    struct in_addr  alias_addr;
                    struct in_addr  remote_addr;
                    uint16_t        local_port;
                    uint16_t        alias_port;
                    uint16_t        remote_port;
                    uint16_t        proto;          /* Valid proto or NG_NAT_REDIRPROTO_ADDR */
                    uint16_t        lsnat;          /* LSNAT servers count */
                    char            description[NG_NAT_DESC_LENGTH];
            struct ng_nat_list_redirects {
                    uint32_t                total_count;
                    struct ng_nat_listrdrs_entry redirects[];
            #define NG_NAT_REDIRPROTO_ADDR  (IPPROTO_MAX + 3)
            Entries of the redirects array returned in the unified format for
            all redirect types.  Ports are meaningful only if protocol is
            either TCP or UDP and static NAT redirection (created by
            NGM_NAT_REDIRECT_ADDR) is indicated by proto set to
            NG_NAT_REDIRPROTO_ADDR.  If lsnat servers counter is greater than
            zero, then local_addr and local_port are also meaningless.
    NGM_NAT_PROXY_RULE (proxyrule)
            Specify a transparent proxying rule (string must be supplied as
            argument).  See libalias(3) for details.
    In all redirection messages local_addr and local_port mean address and
    port of target machine in the internal network, respectively.  If
    alias_addr is zero, then default aliasing address (set by
    NGM_NAT_SET_IPADDR) is used.  Connections can also be restricted to be
    accepted only from specific external machines by using non-zero
    remote_addr and/or remote_port.  Each redirection assigned an ID which
    can be later used for redirection manipulation on individual basis (e.g.,
    removal).  This ID guaranteed to be unique until the node shuts down (it
    will not be reused after deletion), and is returned to user after making
    each new redirection or can be found in the stored list of all redirec-
    tions.  The description passed to and from node unchanged, together with
    ID providing a way for several entities to concurrently manipulate redi-
    rections in automated way.

[править] SHUTDOWN

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

[править] EXAMPLES

    In the following example, the packets are injected into a nat node using
    the ng_ipfw(4) node.
          # Create NAT node
          ngctl mkpeer ipfw: nat 60 out
          ngctl name ipfw:60 nat
          ngctl connect ipfw: nat: 61 in
          ngctl msg nat: setaliasaddr x.y.35.8
          # Divert traffic into NAT node
          ipfw add 300 netgraph 61 all from any to any in via fxp0
          ipfw add 400 netgraph 60 all from any to any out via fxp0
          # Let packets continue with after being (de)aliased
          sysctl net.inet.ip.fw.one_pass=0
    The ng_nat node can be inserted right after the ng_iface(4) node in the
    graph.  In the following example, we perform masquerading on a serial
    line with HDLC encapsulation.
          /usr/sbin/ngctl -f- <<-SEQ
                  mkpeer cp0: cisco rawdata downstream
                  name cp0:rawdata hdlc
                  mkpeer hdlc: nat inet in
                  name hdlc:inet nat
                  mkpeer nat: iface out inet
                  msg nat: setaliasaddr x.y.8.35
          ifconfig ng0 x.y.8.35 x.y.8.1

[править] SEE ALSO

libalias(3), ng_ipfw(4), natd(8), ngctl(8)

[править] HISTORY

    The ng_nat node type was implemented in FreeBSD 6.0.

[править] AUTHORS

    Gleb Smirnoff <glebius@FreeBSD.org>

FreeBSD 9.0 March 1, 2008 FreeBSD 9.0


Источник — «http://m.xgu.ru/wiki/man/orig/ng_nat»