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NAME

       pppd - 点对点协议守护进程

总览 SYNOPSIS

       pppd [ tty_name ] [ speed ] [ options ]

描述

       点对点协议                    (PPP)                   提供一种在点对点串列线路上传输资料流
       (datagrams)的方法。PPP是由三个部份所组成的:一个在串列线
       路上封装(encapsulating)资料流的方法,一个可延伸的连结控制
       协定(LinkControlProtocol:LCP),以及一些用来建立并配置不
       同网路层协定的网路控制协定(NetworkControlProtocols:NCP)

       封装的机制(scheme)是由核心中的驱动程式码来提供。pppd提供
       基本的LCP,验证(authentication)的支援,以及一个用来建立
       并配置网际网路协定(InternatProtocol(IP))(叫做IP控制 协定,IPCP)的NCP。

 常用选项 FREQUENTLY USED OPTIONS
       <tty_name>
               在该名称的设备上进行通讯。如果需要的话可以前置一个
              "/dev/"字串。如果没有给设备名称,pppd将会使用控制
              台的终端机(controllingteriminal),并且产生(fork)出 来时将不会把自己放到背景去。

       <speed>
               将波特率设为speed。在像是4.4BSD以及NetBSA的系
              统上,可以指定任何速率。其他系统(e.g.SunOs)只允 许有限的几种速率。

       asyncmap <map>
               把非同步(async)字元设为对照到。这个对照表
              描述哪些控制字元不能在串列线路上成功地接收。pppd将
              会要求彼端以两个位元组的逸出序列(escapesequence)来
              传送这些字元。其参数是32位元的十六进位数字而每个
              位元代表一个得避开(escape)的字元。位元0(00000001)
              代表字元0x00;位元31(80000000)代表字元0x1f或
              是^_。如果给了多个asyncmap选项,这些数值会以逻
              辑的或(OR)合在一起。如果没有给asyncmap选项,将没
              有非同步字元对照表会被加以协商来导引接收。这样彼端 将会避开所有的控制字元。

       auth   要求彼端在允许传送或接收网路封包之前先验证它自己。 This option is  the  default  if
              the  system  has  a default route.  If neither this option nor the noauth option is
              specified, pppd will only allow the peer to use IP addresses to  which  the  system
              does not already have a route.

       call name
              Read  options  from the file /etc/ppp/peers/name.  This file may contain privileged
              options, such as noauth, even if pppd is not being run by root.   The  name  string
              may  not  begin  with  /  or include .. as a pathname component.  The format of the
              options file is described below.

       connect script
               使用以所指定的可执行指令或是shell指令来设定
              串列线路。这个指令稿一般会使用"chat"程式来拨数据 机并开始远端ppp区段作业(session)。
              A value for this option from a privileged source cannot be  overridden  by  a  non-
              privileged user.

       crtscts
              使用硬体流量控制(i.e.RTS/CTS)来控制串列埠上的资料流。  If  neither the crtscts, the
              nocrtscts, the cdtrcts nor the nocdtrcts option is given, the hardware flow control
              setting  for  the  serial  port  is  left  unchanged.   Some  serial ports (such as
              Macintosh serial ports) lack a true RTS output. Such serial ports use this mode  to
              implement  unidirectional  flow  control. The serial port will suspend transmission
              when requested by the modem (via CTS) but will be unable to request the modem  stop
              sending  to  the  computer.  This  mode  retains  the ability to use DTR as a modem
              control line.

       defaultroute
               当IPCP协商完全成功时,增加一个预设递送路径到系统
              的递送表,将彼端当作闸道器使用。这个项目在ppp连线 中断後会移除。

       disconnect script
               在pppd已经终结该连线之後执行以所指定的可执行
              指令或是shell指令。这个指令稿可以用来,例如,如果
              硬体的数据机控制信号无法使用时,发出指令给数据机使   其挂断电话。   The  disconnect
              script is not run if the modem has already hung up.  A value for this option from a
              privileged source cannot be overridden by a non-privileged user.

       escape xx,yy,...
               指定在传输上确实应该要避开的字元(不管对方是否有用
              它的非同步控制字元对照表要求避开它们)。这些要被避
              开的字元是以用逗号隔开的一串十六进位数字指定的。要
              注意到几乎任何字元都可以用escape选项指定避开,不
              像asyncmap选项只允许指定控制字元。不能避开的字元
              是那些有十六进位值0x20-0x3f或是0x5e者。

       file name
               从档案里读取选项(其格式叙述在後) The file must be readable by the user  who  has
              invoked pppd.

       init script
              Run  the  executable  or shell command specified by script to initialize the serial
              line.  This script would typically use the chat(8) program to configure  the  modem
              to  enable auto answer.  A value for this option from a privileged source cannot be
              overridden by a non-privileged user.

       lock   指定pppd应该在此串列设备上使用UUCP式的锁定以确 定对该设备为互斥(exclusive)存取。

       mru n  把MRU[MaximumReceiveUnit最大接收单元]的值设为
              n来进行协商。pppd将会要求彼端传送不比位元组
              更长的封包。最小的MRU值是128。预设的MRU值则是
              1500。对於慢速线路上的建议值是296(其中40个位元
              组给TCP/IP表头+256个位元组的资料)。
               (Note that for IPv6 MRU must be at least 1280)

       mtu n
               将MTU[MaximumTransmitUnit最大传输单元]的值设
              为n。除非彼端经由MRU协商要求一个更小的值,pppd
              将会要求核心网路程式码透过PPP网路界面所传送的资料 封包不超过n个位元组。
               (Note that for IPv6 MTU must be at least 1280)

       passive
               在LCP中开启"passive"选项。加上这个选项,pppd将
              会试图初使一个连线;如果没有从彼端接收到回应,那麽
              pppd将只会被动地等待从彼端所传来的一个有效LCP封
              包(代替结束离开,就像它在没有这个选项时所作的)。

选项 OPTIONS

       <local_IP_address>:<remote_IP_address>
               设定本地以及/或是远端界面的IP位址。两者之中的任
              何一个都可以省略。该IP位址可以利用主机名称或者是
              十进位数值加小数点符号指定(e.g.150.234.56.78)。
              预设的本地位址是系统的(第一个)IP位址(除非有加上
              noipdefault选项)。远端位址如果没有在任何选项中指
              定的话将从彼端取得。因此,在简单的案例中,这个选项
              不是必须的。如果有一个本地以及/或是远端的IP位址
              以这个选项加以指定的话,pppd将不会接受在IPCP协商
              中从彼端所传来不同的值,除非加上ipcp-accept-local            以及/或是ipcp-accept-
              remote选项,个别地。

       ipv6 <local_interface_identifier>,<remote_interface_identifier>
              Set the local and/or remote 64-bit interface identifier. Either one may be omitted.
              The identifier must be specified in standard ascii notation of IPv6 addresses (e.g.
              ::dead:beef). If the ipv6cp-use-ipaddr option is given, the local identifier is the
              local  IPv4 address (see above).  On systems which supports a unique persistent id,
              such as EUI-48 derived from the Ethernet MAC address, ipv6cp-use-persistent  option
              can  be  used to replace the ipv6 <local>,<remote> option. Otherwise the identifier
              is randomized.

       active-filter filter-expression
              Specifies a packet filter to be applied to data packets to determine which  packets
              are  to  be regarded as link activity, and therefore reset the idle timer, or cause
              the link to be brought up in  demand-dialling  mode.   This  option  is  useful  in
              conjunction  with  the  idle  option  if  there  are packets being sent or received
              regularly over the link (for example,  routing  information  packets)  which  would
              otherwise  prevent  the link from ever appearing to be idle.  The filter-expression
              syntax  is  as  described  for  tcpdump(1),  except  that  qualifiers   which   are
              inappropriate  for a PPP link, such as ether and arp, are not permitted.  Generally
              the filter expression should be enclosed in single-quotes to prevent whitespace  in
              the  expression  from being interpreted by the shell. This option is currently only
              available under NetBSD, and then only if both the kernel  and  pppd  were  compiled
              with PPP_FILTER defined.

       allow-ip address(es)
              Allow  peers  to  use  the  given  IP  address  or  subnet  without  authenticating
              themselves.  The parameter is parsed as for each element of the list of allowed  IP
              addresses in the secrets files (see the AUTHENTICATION section below).

       bsdcomp nr,nt
              Request  that  the  peer  compress  packets  that  it sends, using the BSD-Compress
              scheme, with a maximum code size of nr bits, and agree to compress packets sent  to
              the  peer with a maximum code size of nt bits.  If nt is not specified, it defaults
              to the value given for nr.  Values in the range 9 to 15 may be used for nr and  nt;
              larger   values  give  better  compression  but  consume  more  kernel  memory  for
              compression dictionaries.  Alternatively, a value  of  0  for  nr  or  nt  disables
              compression  in the corresponding direction.  Use nobsdcomp or bsdcomp 0 to disable
              BSD-Compress compression entirely.

       cdtrcts
              Use a non-standard hardware flow control (i.e. DTR/CTS) to control the flow of data
              on  the  serial  port.   If neither the crtscts, the nocrtscts, the cdtrcts nor the
              nocdtrcts option is given, the hardware flow control setting for the serial port is
              left unchanged.  Some serial ports (such as Macintosh serial ports) lack a true RTS
              output. Such serial ports use this  mode  to  implement  true  bi-directional  flow
              control.  The sacrifice is that this flow control mode does not permit using DTR as
              a modem control line.

       chap-interval n
               如果有给这个选项,pppd将会每n 秒重新盘查彼端。

       chap-max-challenge n
               将CHAP盘查(challenge)传输的最大数目设为n(预 设为10)。

       chap-restart n
               将CHAP重新开始的间隔(重新传输的时间限制)设为n 秒钟(预设为3)。

       connect-delay n
              Wait for up n milliseconds after the connect script finishes for a valid PPP packet
              from  the  peer.   At  the end of this time, or when a valid PPP packet is received
              from the peer, pppd will commence negotiation by sending its first LCP packet.  The
              default  value is 1000 (1 second).  This wait period only applies if the connect or
              pty option is used.

       debug  递增侦错层级(与-d相同)。如果加上这个选项,pppd
              将以可供阅读的格式记录所有传送或接收的控制封包内容。
              这些封包透过syslog以facilitydaemon还有level
              debug加以记录。该资讯可以适当设定/etc/syslog.conf
              来导向到一个档案去。(参阅syslog.conf(5))。(如果
              pppd以开启扩充侦错(extradebugging)编译的话,它将
              会使用facilitylocal2取代daemon来记录讯息)。

       default-asyncmap
              Disable asyncmap negotiation, forcing all control characters to be escaped for both
              the transmit and the receive direction.

       default-mru
              Disable  MRU  [Maximum  Receive Unit] negotiation.  With this option, pppd will use
              the default MRU value of 1500 bytes for both the transmit and receive direction.

       deflate nr,nt
              Request that the peer compress packets that it sends,  using  the  Deflate  scheme,
              with  a  maximum  window size of 2**nr bytes, and agree to compress packets sent to
              the peer with a maximum window size of 2**nt bytes.  If nt  is  not  specified,  it
              defaults to the value given for nr.  Values in the range 9 to 15 may be used for nr
              and nt; larger values give better compression but consume more  kernel  memory  for
              compression  dictionaries.   Alternatively,  a  value  of  0  for nr or nt disables
              compression in the corresponding direction.  Use nodeflate or deflate 0 to  disable
              Deflate   compression  entirely.   (Note:  pppd  requests  Deflate  compression  in
              preference to BSD-Compress if the peer can do either.)

       demand Initiate the link only on demand, i.e. when data traffic  is  present.   With  this
              option,  the remote IP address must be specified by the user on the command line or
              in an options file.  Pppd will initially configure the interface and enable it  for
              IP  traffic  without  connecting to the peer.  When traffic is available, pppd will
              connect to the peer and perform negotiation, authentication,  etc.   When  this  is
              completed,  pppd  will  commence passing data packets (i.e., IP packets) across the
              link.

              The demand option implies the persist option.  If this behaviour  is  not  desired,
              use the nopersist option after the demand option.  The idle and holdoff options are
              also useful in conjuction with the demand option.

       domain d
               新增领域名称到本地主机名称以支援验证。例如,如
              果gethostname()回应porsche这个名称,但是完整合
              格的领域名称是porsche.Quotron.COM的话,你可以使用
              domain选项来将领域名称设为Quotron.COM。
               Pppd  would  then  use  the name porsche.Quotron.COM for looking up secrets in the
              secrets file, and as the default name to  send  to  the  peer  when  authenticating
              itself to the peer.  This option is privileged.

       dryrun With  the  dryrun option, pppd will print out all the option values which have been
              set and then exit, after parsing the command line and options  files  and  checking
              the option values, but before initiating the link.  The option values are logged at
              level info, and also printed to standard  output  unless  the  device  on  standard
              output is the device that pppd would be using to communicate with the peer.

       dump   With  the  dump  option,  pppd will print out all the option values which have been
              set.  This option is like the dryrun option except that  pppd  proceeds  as  normal
              rather than exiting.

       endpoint <epdisc>
              Sets  the  endpoint  discriminator  sent  by  the  local machine to the peer during
              multilink negotiation to <epdisc>.  The default is to use the MAC  address  of  the
              first  ethernet  interface  on  the  system,  if  any,  otherwise  the IPv4 address
              corresponding to the hostname, if any, provided it  is  not  in  the  multicast  or
              locally-assigned  IP  address  ranges,  or  the  localhost  address.   The endpoint
              discriminator can be the string null or of the form type:value,  where  type  is  a
              decimal number or one of the strings local, IP, MAC, magic, or phone.  The value is
              an IP address in dotted-decimal notation for the IP type, or a string of  bytes  in
              hexadecimal, separated by periods or colons for the other types.  For the MAC type,
              the value may also be the name of an ethernet or similar network  interface.   This
              option is currently only available under Linux.

       hide-password
              When  logging  the  contents of PAP packets, this option causes pppd to exclude the
              password string from the log.  This is the default.

       holdoff n
              Specifies how  many  seconds  to  wait  before  re-initiating  the  link  after  it
              terminates.   This  option  only  has any effect if the persist or demand option is
              used.  The holdoff period is not applied if the link was terminated because it  was
              idle.

       idle n Specifies  that pppd should disconnect if the link is idle for n seconds.  The link
              is idle when no data packets (i.e. IP packets) are being sent or  received.   Note:
              it  is  not advisable to use this option with the persist option without the demand
              option.  If the active-filter option is given, data packets which are  rejected  by
              the specified activity filter also count as the link being idle.

       ipcp-accept-local
              加上这个选项的话,pppd将会接受彼端对於本地IP位址
              的意见,即使本地的IP位址已经在某个选项中指定。

       ipcp-accept-remote
              加上这个选项的话,pppd将会接受彼端对於它的IP位址
              的意见,即使远端的IP位址已经在某个选项中指定。

       ipcp-max-configure n
               将IPCP配置要求(configure-request)传输的最大数目设 为n(预设为10)。

       ipcp-max-failure n
              将开始传送配置拒绝(configure-Rejects)之前的IPCP配               置未接收(configure-
              NAKs)的最大数目以取代n(预设 为10)。

       ipcp-max-terminate n
               将IPCP终结要求(terminate-request)传输的最大数目设 为 n(预设为3)。

       ipcp-restart n
               将IPCP重新开始的间隔(重新传输的时间限制)设为n 秒钟(预设为3)。

       ipparam string
              Provides an extra parameter to the ip-up and ip-down scripts.  If  this  option  is
              given, the string supplied is given as the 6th parameter to those scripts.

       ipv6cp-max-configure n
              Set the maximum number of IPv6CP configure-request transmissions to n (default 10).

       ipv6cp-max-failure n
              Set  the  maximum  number of IPv6CP configure-NAKs returned before starting to send
              configure-Rejects instead to n (default 10).

       ipv6cp-max-terminate n
              Set the maximum number of IPv6CP terminate-request transmissions to n (default 3).

       ipv6cp-restart n
              Set the IPv6CP restart interval (retransmission timeout) to n seconds (default 3).

       ipx    Enable the IPXCP and IPX protocols.  This option is presently only supported  under
              Linux, and only if your kernel has been configured to include IPX support.

       ipx-network n
              Set the IPX network number in the IPXCP configure request frame to n, a hexadecimal
              number (without a leading 0x).  There is no valid default.  If this option  is  not
              specified, the network number is obtained from the peer.  If the peer does not have
              the network number, the IPX protocol will not be started.

       ipx-node n:m
              Set the IPX node numbers. The two node numbers are separated from each other with a
              colon  character.  The first number n is the local node number. The second number m
              is the peer's node number. Each node number is a hexadecimal  number,  at  most  10
              digits  long. The node numbers on the ipx-network must be unique. There is no valid
              default. If this option is not specified then the node numbers  are  obtained  from
              the peer.

       ipx-router-name <string>
              Set the name of the router. This is a string and is sent to the peer as information
              data.

       ipx-routing n
              Set the routing protocol to be received by this option. More than one  instance  of
              ipx-routing  may  be  specified. The 'none' option (0) may be specified as the only
              instance of ipx-routing. The values may be 0 for NONE, 2 for  RIP/SAP,  and  4  for
              NLSP.

       ipxcp-accept-local
              Accept  the  peer's  NAK for the node number specified in the ipx-node option. If a
              node number was specified, and non-zero, the default is to insist that the value be
              used.  If  you  include  this  option then you will permit the peer to override the
              entry of the node number.

       ipxcp-accept-network
              Accept the peer's NAK for the network number specified in the  ipx-network  option.
              If  a network number was specified, and non-zero, the default is to insist that the
              value be used. If you include this option then you will permit the peer to override
              the entry of the node number.

       ipxcp-accept-remote
              Use  the  peer's network number specified in the configure request frame. If a node
              number was specified for the peer and this option was not specified, the peer  will
              be forced to use the value which you have specified.

       ipxcp-max-configure n
              Set the maximum number of IPXCP configure request frames which the system will send
              to n. The default is 10.

       ipxcp-max-failure n
              Set the maximum number of IPXCP NAK frames which the local system will send  before
              it rejects the options. The default value is 3.

       ipxcp-max-terminate n
              Set  the  maximum  nuber  of IPXCP terminate request frames before the local system
              considers that the peer is not listening to them. The default value is 3.

       kdebug n
              开启核心层级中的PPP驱动程式侦错码。The  argument  values  depend  on  the  specific
              kernel  driver,  but  in  general  a  value  of  1 will enable general kernel debug
              messages.  (Note that these messages are usually  only  useful  for  debugging  the
              kernel   driver   itself.)    For   the  Linux  2.2.x  kernel  driver,  参数n是一个
              由下列值所组合的数字:1开启一般侦错讯息,2要求印
              出所接收到的封包内容,而4要求印出传输的封包内容。 On most systems, messages printed
              by the kernel are logged by syslog(1) to a file as directed in the /etc/syslog.conf
              configuration file.

       ktune  Enables  pppd  to  alter  kernel  settings  as appropriate.  Under Linux, pppd will
              enable IP forwarding (i.e. set /proc/sys/net/ipv4/ip_forward to 1) if the  proxyarp
              option  is  used,  and  will  enable  the  dynamic  IP  address  option  (i.e.  set
              /proc/sys/net/ipv4/ip_dynaddr to 1) in demand mode if the local address changes.

       lcp-echo-failure n
               如果有给这个选项,那麽如果传送n个LCP回应要求没
              有接收到有效的LCP回应回覆的话pppd将会推测彼端是
              死掉的。如果发生这种情形,pppd将会终结该连线。这个     选项的使用要求一个非零的lcp-
              echo-interval参数值。            这个选项可以用在硬体数据机控制线路无法使用的情况下
              当实际连线被中断之後(e.g.,数据机已经挂断)终结 pppd的执行。

       lcp-echo-interval n
              如果有给这个选项,pppd每秒将会送出一个LCP回                            应要求(echo-
              request)封包(frame)给彼端。在Linux系
              统下,回应要求在n秒内没有从彼端接收到封包时会被送
              出。一般彼端应该以传送一个回应回覆(echo-reply)来反 应该回应要求。这个选项可以与lcp-
              echo-failure选项 一起使用来侦测不再连线的彼端。

       lcp-max-configure n
               将LCP配置要求(configure-request)传输的最大数目设 为n(预设为10)。

       lcp-max-failure n
               将开始传送配置拒绝(configure-Rejects)之前的LCP配               置未接收(configure-
              NAKs)的最大数目设置为n(预设 为10)。

       lcp-max-terminate n
               将LCP终结要求(terminate-request)传输的最大数目设 为n(预设为3)。

       lcp-restart n
              将LCP重新开始的间隔(重新传输的时间限制)设为 秒钟(预设为3)。

       linkname name
              Sets  the  logical  name  of  the link to name.  Pppd will create a file named ppp-
              name.pid in /var/run (or /etc/ppp on some systems) containing its process ID.  This
              can  be useful in determining which instance of pppd is responsible for the link to
              a given peer system.  This is a privileged option.

       local  不要使用数据机控制线路。  With this option, pppd will ignore the state  of  the  CD
              (Carrier  Detect)  signal  from  the modem and will not change the state of the DTR
              (Data Terminal Ready) signal.

       logfd n
              Send log messages to file descriptor n.  Pppd will send log messages to at most one
              file  or  file  descriptor (as well as sending the log messages to syslog), so this
              option and the logfile option are mutually exclusive.  The default is for  pppd  to
              send  log messages to stdout (file descriptor 1), unless the serial port is already
              open on stdout.

       logfile filename
              Append log messages to the file filename (as well as sending the  log  messages  to
              syslog).   The  file is opened with the privileges of the user who invoked pppd, in
              append mode.

       login  使用系统密码资料库验证使用PAP的彼端。 and record the user in the system wtmp  file.
              Note  that  the peer must have an entry in the /etc/ppp/pap-secrets file as well as
              the system password database to be allowed access.

       maxconnect n
              Terminate the connection when it has been  available  for  network  traffic  for  n
              seconds (i.e. n seconds after the first network control protocol comes up).

       maxfail n
              Terminate  after  n  consecutive failed connection attempts.  A value of 0 means no
              limit.  The default value is 10.

       modem  使用数据机控制线路。This option is the default.  With this option, pppd  will  wait
              for  the  CD (Carrier Detect) signal from the modem to be asserted when opening the
              serial device (unless a connect script is specified), and  it  will  drop  the  DTR
              (Data  Terminal  Ready) signal briefly when the connection is terminated and before
              executing       the       connect       script.        在Ultrix上,这个选项会实作硬
              体流量控制,像crtsct选项作的。

       mp     Enables  the  use  of  PPP  multilink; this is an alias for the `multilink' option.
              This option is currently only available under Linux.

       mpshortseq
              Enables the use of short (12-bit) sequence numbers in multilink headers, as opposed
              to  24-bit  sequence  numbers.  This option is only available under Linux, and only
              has any effect if multilink is enabled (see the multilink option).

       mrru n Sets the Maximum Reconstructed Receive Unit to n.  The MRRU is the maximum size for
              a  received  packet  on  a  multilink  bundle,  and is analogous to the MRU for the
              individual links.  This option is currently only available under  Linux,  and  only
              has any effect if multilink is enabled (see the multilink option).

       ms-dns <addr>
              If  pppd  is  acting  as a server for Microsoft Windows clients, this option allows
              pppd to supply one or two DNS (Domain Name Server) addresses to the  clients.   The
              first  instance  of  this  option  specifies  the  primary  DNS address; the second
              instance (if given) specifies the secondary DNS address.  (This option was  present
              in some older versions of pppd under the name dns-addr.)

       ms-wins <addr>
              If pppd is acting as a server for Microsoft Windows or "Samba" clients, this option
              allows pppd to supply one or two  WINS  (Windows  Internet  Name  Services)  server
              addresses  to the clients.  The first instance of this option specifies the primary
              WINS address; the second instance (if given) specifies the secondary WINS address.

       multilink
              Enables the use  of  the  PPP  multilink  protocol.   If  the  peer  also  supports
              multilink,  then this link can become part of a bundle between the local system and
              the peer.  If there is an existing bundle to the peer, pppd will join this link  to
              that  bundle,  otherwise  pppd will create a new bundle.  See the MULTILINK section
              below.  This option is currently only available under Linux.

       name name
              将本地系统的名称设为用来进行验证。 This is a privileged option.  With this  option,
              pppd  will  use lines in the secrets files which have name as the second field when
              looking for a secret to use  in  authenticating  the  peer.   In  addition,  unless
              overridden  with the user option, name will be used as the name to send to the peer
              when authenticating the local system to the peer.  (Note that pppd does not  append
              the domain name to name.)

       netmask n
               把该界面网路掩码设为,这是一个以″十进位数值加
              小数点″("decimaldot")符号表示的32位元网路掩码 (e.g.255.255.255.0)。If  this  option
              is  given,  the  value  specified  is  ORed  with the default netmask.  The default
              netmask is chosen based on the negotiated remote IP address; it is the  appropriate
              network mask for the class of the remote IP address, ORed with the netmasks for any
              non point-to-point network interfaces in the system which are on the same  network.
              (Note:  on some platforms, pppd will always use 255.255.255.255 for the netmask, if
              that is the only appropriate value for a point-to-point interface.)

       noaccomp
              Disable Address/Control compression in both directions (send and receive).

       noauth Do not require the peer to authenticate itself.  This option is privileged.

       nobsdcomp
              Disables BSD-Compress compression; pppd will  not  request  or  agree  to  compress
              packets using the BSD-Compress scheme.

       noccp  Disable CCP (Compression Control Protocol) negotiation.  This option should only be
              required if the peer is buggy and gets confused  by  requests  from  pppd  for  CCP
              negotiation.

       nocrtscts
              Disable  hardware  flow  control (i.e. RTS/CTS) on the serial port.  If neither the
              crtscts nor the nocrtscts nor the cdtrcts nor the nocdtrcts option  is  given,  the
              hardware flow control setting for the serial port is left unchanged.

       nocdtrcts
              This  option  is a synonym for nocrtscts. Either of these options will disable both
              forms of hardware flow control.

       nodefaultroute
              Disable the defaultroute option.  The system administrator who  wishes  to  prevent
              users  from  creating  default routes with pppd can do so by placing this option in
              the /etc/ppp/options file.

       nodeflate
              Disables Deflate compression; pppd will not request or agree  to  compress  packets
              using the Deflate scheme.

       nodetach
              Don't  detach  from  the  controlling  terminal.   Without this option, if a serial
              device other than the terminal on the standard input is specified, pppd  will  fork
              to become a background process.

       noendpoint
              Disables  pppd  from sending an endpoint discriminator to the peer or accepting one
              from the peer (see the MULTILINK  section  below).   This  option  should  only  be
              required if the peer is buggy.

       noip   Disable IPCP negotiation and IP communication.  This option should only be required
              if the peer is buggy and gets confused by requests from pppd for IPCP negotiation.

       noipv6 Disable IPv6CP negotiation and IPv6  communication.  This  option  should  only  be
              required  if  the  peer is buggy and gets confused by requests from pppd for IPv6CP
              negotiation.

       noipdefault
              关闭在没有指定本地IP位址时所进行的预设动作,这是
              用来由从主机名称决定(如果可能的话)决定本地IP位
              址。加上这个选项的话,彼端将必须在进行IPCP协商时
              (除非在指令列或在选项档中明确地指定它)提供本地的 IP位址。

       noipx  Disable  the  IPXCP  and IPX protocols.  This option should only be required if the
              peer is buggy and gets confused by requests from pppd for IPXCP negotiation.

       noktune
              Opposite of the ktune option; disables pppd from changing system settings.

       nolog  Do not send log messages to a file or file descriptor.   This  option  cancels  the
              logfd and logfile options.

       nomagic
              Disable  magic  number negotiation.  With this option, pppd cannot detect a looped-
              back line.  This option should only be needed if the peer is buggy.

       nomp   Disables the use of PPP multilink.  This option is currently only  available  under
              Linux.

       nompshortseq
              Disables  the use of short (12-bit) sequence numbers in the PPP multilink protocol,
              forcing the use  of  24-bit  sequence  numbers.   This  option  is  currently  only
              available under Linux, and only has any effect if multilink is enabled.

       nomultilink
              Disables  the  use of PPP multilink.  This option is currently only available under
              Linux.

       nopcomp
              Disable protocol field compression negotiation in both the receive and the transmit
              direction.

       nopersist
              Exit  once  a  connection has been made and terminated.  This is the default unless
              the persist or demand option has been specified.

       nopredictor1
              Do not accept or agree to Predictor-1 compression.

       noproxyarp
              Disable the proxyarp option.  The system administrator who wishes to prevent  users
              from  creating  proxy ARP entries with pppd can do so by placing this option in the
              /etc/ppp/options file.

       notty  Normally, pppd requires a terminal device.  With this option,  pppd  will  allocate
              itself  a  pseudo-tty  master/slave  pair and use the slave as its terminal device.
              Pppd will create a child  process  to  act  as  a  `character  shunt'  to  transfer
              characters  between  the pseudo-tty master and its standard input and output.  Thus
              pppd will transmit characters on its standard output and receive characters on  its
              standard  input  even  if they are not terminal devices.  This option increases the
              latency and CPU overhead of transferring data over the ppp interface as all of  the
              characters  sent  and  received  must flow through the character shunt process.  An
              explicit device name may not be given if this option is used.

       novj   Disable Van Jacobson style TCP/IP header compression in both the transmit  and  the
              receive direction.

       novjccomp
              Disable  the  connection-ID  compression option in Van Jacobson style TCP/IP header
              compression.  With this option, pppd will not omit the connection-ID byte from  Van
              Jacobson compressed TCP/IP headers, nor ask the peer to do so.

       papcrypt
              Indicates  that  all  secrets  in  the /etc/ppp/pap-secrets file which are used for
              checking the identity of the peer are encrypted, and thus pppd should not accept  a
              password   which,   before   encryption,  is  identical  to  the  secret  from  the
              /etc/ppp/pap-secrets file.

       pap-max-authreq n
               将PAP验证要求(authenticate-request)传输的最大数目 设为n(预设为10)。

       pap-restart n
               将PAP重新开始的间隔(重新传输的时间限制)设为n 秒钟(预设为3)。

       pap-timeout n
              Set the maximum time that pppd will wait for the peer to authenticate  itself  with
              PAP to n seconds (0 means no limit).

       pass-filter filter-expression
              Specifies  a  packet  filter  to  applied to data packets being sent or received to
              determine which packets should be allowed to pass.  Packets which are  rejected  by
              the  filter  are  silently  discarded.  This option can be used to prevent specific
              network daemons (such as routed) using up link bandwidth, or  to  provide  a  basic
              firewall  capability.  The filter-expression syntax is as described for tcpdump(1),
              except that qualifiers which are inappropriate for a PPP link, such  as  ether  and
              arp,  are  not  permitted.   Generally  the filter expression should be enclosed in
              single-quotes to prevent whitespace in the expression from being interpreted by the
              shell.   Note  that  it  is possible to apply different constraints to incoming and
              outgoing packets  using  the  inbound  and  outbound  qualifiers.  This  option  is
              currently  only  available  under NetBSD, and then only if both the kernel and pppd
              were compiled with PPP_FILTER defined.

       persist
              Do not exit after a connection is terminated; instead try to reopen the connection.

       plugin filename
              Load the shared library object file filename as a plugin.   This  is  a  privileged
              option.

       predictor1
              Request  that the peer compress frames that it sends using Predictor-1 compression,
              and agree to compress transmitted  frames  with  Predictor-1  if  requested.   This
              option has no effect unless the kernel driver supports Predictor-1 compression.

       privgroup group-name
              Allows members of group group-name to use privileged options.  This is a privileged
              option.  Use of this option requires care as there is no guarantee that members  of
              group-name  cannot  use  pppd to become root themselves.  Consider it equivalent to
              putting the members of group-name in the kmem or disk group.

       proxyarp
              以彼端的IP位址以及该系统的乙太网路位址增加一个项
              目到系统的ARP[AddressResolutionProtocol位址解  译协定]表格。  This  will  have  the
              effect of making the peer appear to other systems to be on the local ethernet.

       pty script
              Specifies that the command script is to  be  used  to  communicate  rather  than  a
              specific terminal device.  Pppd will allocate itself a pseudo-tty master/slave pair
              and use the slave as its terminal device.  The  script  will  be  run  in  a  child
              process  with  the pseudo-tty master as its standard input and output.  An explicit
              device name may not be given if this option is used.  (Note: if the  record  option
              is used in conjuction with the pty option, the child process will have pipes on its
              standard input and output.)

       receive-all
              With this option, pppd will accept all control characters from the peer,  including
              those marked in the receive asyncmap.  Without this option, pppd will discard those
              characters as specified in RFC1662.  This option should only be needed if the  peer
              is buggy.

       record filename
              Specifies  that pppd should record all characters sent and received to a file named
              filename.  This file is opened  in  append  mode,  using  the  user's  user-ID  and
              permissions.   This  option  is  implemented  using  a  pseudo-tty and a process to
              transfer characters between the pseudo-tty and the real serial device, so  it  will
              increase  the latency and CPU overhead of transferring data over the ppp interface.
              The characters are stored  in  a  tagged  format  with  timestamps,  which  can  be
              displayed in readable form using the pppdump(8) program.

       remotename name
              将远端系统的假设名称设为以进行验证。

       refuse-chap
              With  this  option,  pppd  will  not agree to authenticate itself to the peer using
              CHAP.

       refuse-pap
              With this option, pppd will not agree to authenticate itself to the peer using PAP.

       require-chap
              Require  the  peer  to  authenticate  itself  using   CHAP   [Challenge   Handshake
              Authentication Protocol] authentication.

       require-pap
              Require  the  peer  to  authenticate  itself  using  PAP  [Password  Authentication
              Protocol] authentication.

       show-password
              When logging the contents of PAP packets, this  option  causes  pppd  to  show  the
              password string in the log message.

       silent 加上这个选项,pppd将不会传输LCP封包来初使一个连
              线一直到从彼端接收到一个有效的LCP封包。(就像是给 旧版pppd使用的"passive"选项)。

       sync   Use synchronous HDLC serial encoding instead of asynchronous.  The device  used  by
              pppd  with  this  option  must  have  sync  support.   Currently supports Microgate
              SyncLink adapters under Linux and FreeBSD 2.2.8 and later.

       updetach
              With this option, pppd will detach  from  its  controlling  terminal  once  it  has
              successfully  established  the ppp connection (to the point where the first network
              control protocol, usually the IP control protocol, has come up).

       usehostname
              强迫主机名称使用本地系统的名称来进行验证。(这会盖过name选项)。 This option is not
              normally needed since the name option is privileged.

       usepeerdns
              Ask  the peer for up to 2 DNS server addresses.  The addresses supplied by the peer
              (if any) are passed to the /etc/ppp/ip-up script in the environment variables  DNS1
              and  DNS2.   In  addition, pppd will create an /etc/ppp/resolv.conf file containing
              one or two nameserver lines with the address(es) supplied by the peer.

       user name
              将使用者名称设为以便让使用PAP的彼端验证这台机器时使用。

       vj-max-slots n
              Sets the number of connection slots to be used by the Van  Jacobson  TCP/IP  header
              compression  and  decompression  code  to  n,  which  must  be  between  2  and  16
              (inclusive).

       welcome script
              Run the executable or shell command  specified  by  script  before  initiating  PPP
              negotiation,  after  the  connect  script (if any) has completed.  A value for this
              option from a privileged source cannot be overridden by a non-privileged user.

       xonxoff
              使用软体流量控制(i.e.XON/XOFF)来控制串列埠上的资料流。

选项文件 OPTIONS FILES

       选项可以从档案取出使用就如同使用命令列一般。pppd在查看指
       令列之前先从档案/etc/ppp/options以及~/.ppprc读取选项。  ttyname  (in  that  order)  before
       processing the options on the command  line.   (In  fact,  the  command-line  options  are
       scanned  to  find  the terminal name before the options.ttyname file is read.)  In forming
       the name of the options.ttyname file, the initial /dev/ is removed from the terminal name,
       and any remaining / characters are replaced with dots.

       一个选项档案以空白字元为界被剖析成一串单字。空白字元可以用
       双引号(")包括在一个单字里。倒斜线引用其後的字元。而hash
       (#)符号开始一段注解持续到该行结束。  There  is  no  restriction  on using the file or call
       options within an options file.

安全 SECURITY

       pppd                                   提供系统管理人员充份的存取控制能力这表示以PPP存取一
       台伺服机器可以提供给合法的使用者使用而不必担心危及该伺服器
       或所在网路的安全性。这有一部份是以/etc/ppp/options档案来
       提供,在这里系统管理人员可以放置在执行pppd的时候用来要求
       验证的选项,而部份是由PAP以及CHAP暗号档案来提供,其中
       系统管理人员可以限制个别的使用者可以使用的一群IP位址。

       The  default  behaviour  of  pppd  is  to  allow an unauthenticated peer to use a given IP
       address only if the system does not already have a route to that IP address.  For example,
       a  system  with  a permanent connection to the wider internet will normally have a default
       route, and thus all peers will have to authenticate  themselves  in  order  to  set  up  a
       connection.   On  such  a  system,  the  auth option is the default.  On the other hand, a
       system where the PPP link is the only connection to the internet will not normally have  a
       default  route,  so  the  peer  will  be  able  to  use  almost  any  IP  address  without
       authenticating itself.

       As indicated above, some security-sensitive options are privileged, which means that  they
       may  not  be used by an ordinary non-privileged user running a setuid-root pppd, either on
       the command line, in the user's ~/.ppprc file, or in an options file read using  the  file
       option.   Privileged  options  may  be used in /etc/ppp/options file or in an options file
       read using the call option.  If pppd is being run by the root user, privileged options can
       be used without restriction.

       When  opening  the  device,  pppd  uses either the invoking user's user ID or the root UID
       (that is, 0), depending on whether the device name was specified by the user or the system
       administrator.    If   the   device   name  comes  from  a  privileged  source,  that  is,
       /etc/ppp/options or an options file read using  the  call  option,  pppd  uses  full  root
       privileges  when  opening  the  device.   Thus,  by  creating  an  appropriate  file under
       /etc/ppp/peers, the system administrator can allow users to establish a ppp connection via
       a device which they would not normally have permission to access.  Otherwise pppd uses the
       invoking user's real UID when opening the device.

AUTHENTICATION

       Authentication is the process whereby one peer convinces the other of its identity.   This
       involves  the  first peer sending its name to the other, together with some kind of secret
       information which could only come from the genuine authorized user of that name.  In  such
       an  exchange,  we  will  call the first peer the "client" and the other the "server".  The
       client has a name by which it identifies itself to the server, and the server also  has  a
       name  by  which  it  identifies itself to the client.  Generally the genuine client shares
       some secret (or password) with the server, and authenticates itself  by  proving  that  it
       knows  that  secret.   Very  often,  the  names  used for authentication correspond to the
       internet hostnames of the peers, but this is not essential.

       At present, pppd  supports  two  authentication  protocols:  the  Password  Authentication
       Protocol  (PAP)  and the Challenge Handshake Authentication Protocol (CHAP).  PAP involves
       the client sending its name and a cleartext password to the server to authenticate itself.
       In  contrast, the server initiates the CHAP authentication exchange by sending a challenge
       to the client (the challenge packet includes the server's name).  The client must  respond
       with  a  response which includes its name plus a hash value derived from the shared secret
       and the challenge, in order to prove that it knows the secret.

       The  PPP  protocol,  being  symmetrical,  allows  both  peers  to  require  the  other  to
       authenticate  itself.  In that case, two separate and independent authentication exchanges
       will occur.  The two exchanges  could  use  different  authentication  protocols,  and  in
       principle, different names could be used in the two exchanges.

        pppd预设的动作是如果有要求就同意进行验证,并且不要求从彼
       端做验证。然而如果没有可以用来验证的暗号则pppd将不会同意 以特殊的协定来验证它自己。

        验证的基础是由暗号档案选择的暗号(/etc/ppp/pap-secrets是      给PAP使用的,/etc/ppp/chap-
       secrets则是给CHAP使用)。       这两个暗号档案都具有相同的格式,而且两者都可以储放暗号给数
       种伺服器(验证彼端)及客户(被验证端)组合使用。注意pppd
       可以最为伺服端以及客户端,而且如果需要的话两方可以使用不同 的协定。

        一个暗号档案如同选项档案一般被剖析成单字。一个暗号是由最少
       包含3个单字的一行所指定,依序是客户,伺服器,暗号。在同
       一行中任何跟在其後的单字都被当作是给客户的可接受IP位址列
       表。如果该行只有3个单字,这假设任何IP位址都可以;不允
       许所有的IP位址的话,使用"-"。如果暗号是以'@'开始,其
       後所接的单字将被假设为可以从中读取暗号的档案名称。而以一个
       "*"字元作为客户或伺服端的名称会符合任何名称。在选择一个暗
       号时,pppd会选择最符合的,i.e.最少万用字元的那个。

       如此一个暗号档案包含用来验证其它主机,以及用来为其它主机验
       证自己两者的暗号。选择使用哪个暗号是根据该主机(本地名称)
       以及其彼端(远端名称)而定。本地名称的设定如下:

       If the secret starts with an `@', what follows is assumed to be the name of  a  file  from
       which  to  read  the  secret.   A "*" as the client or server name matches any name.  When
       selecting a secret, pppd takes the best match, i.e.  the match with the fewest wildcards.

       Any following words on the same line are taken to be a list of acceptable IP addresses for
       that client.  If there are only 3 words on the line, or if the first word is "-", then all
       IP addresses are disallowed.  To allow any address, use "*".  A  word  starting  with  "!"
       indicates that the specified address is not acceptable.  An address may be followed by "/"
       and a number n, to indicate a whole subnet, i.e. all addresses which have the  same  value
       in  the most significant n bits.  In this form, the address may be followed by a plus sign
       ("+") to indicate that one address from the subnet is authorized, based on the ppp network
       interface  unit  number in use.  In this case, the host part of the address will be set to
       the unit number plus one.

       Thus a secrets file contains both secrets for use  in  authenticating  other  hosts,  plus
       secrets  which we use for authenticating ourselves to others.  When pppd is authenticating
       the peer (checking the peer's identity), it chooses a secret with the peer's name  in  the
       first  field  and the name of the local system in the second field.  The name of the local
       system defaults to the hostname, with the domain name appended if  the  domain  option  is
       used.   This  default  can be overridden with the name option, except when the usehostname
       option is used.

       When pppd is choosing a secret to use in authenticating  itself  to  the  peer,  it  first
       determines  what name it is going to use to identify itself to the peer.  This name can be
       specified by the user with the user option.  If this option is not used, the name defaults
       to  the name of the local system, determined as described in the previous paragraph.  Then
       pppd looks for a secret with this name in the first field  and  the  peer's  name  in  the
       second  field.   Pppd will know the name of the peer if CHAP authentication is being used,
       because the peer will have sent it in the challenge packet.   However,  if  PAP  is  being
       used,  pppd will have to determine the peer's name from the options specified by the user.
       The user can specify the peer's name directly with the remotename option.   Otherwise,  if
       the  remote  IP  address  was specified by a name (rather than in numeric form), that name
       will be used as the peer's name.  Failing that, pppd will  use  the  null  string  as  the
       peer's name.

        当以PAP验证彼端时,一个""暗号符合任何由彼端所提供密码。
       如果密码不符合暗号,密码被以crypt()编码并且再次检查暗号;
       因此验证彼端的暗号可以编码方式储放。

       如果指定有login选项,           使用者名称以及密码也会被以系统的密码资料库检查。因此系统管
       理人员可以设定pap-secrets档案以便只允许某些使用者以PPP
       连线,并且限制每个使用者可以使用一些IP位址。  Typically,  when using the login option, the
       secret in /etc/ppp/pap-secrets would be "", which will match any password supplied by  the
       peer.  This avoids the need to have the same secret in two places.

        验证必须在IPCP(或任何其它网路控制协定)开始之前被完全地
       满足。如果验证失败,pppd将会终结连线(关闭LCP)。如果
       IPCP协商出一个无法接受的远端主机IP位址,IPCP将会关闭。
       IP封包只有在IPCP打开的时候才能传送或接收。

        即使本地主机一般会要求验证,在某些案例中会希望允一些无法验
       证它们自己的主机连线并使用所限制的IP位址其中之一。如果彼
       在被要求时拒绝验证它自己,pppd将会把它当成等於是在使用者
       名称以及密码上使用空字串来以PAP验证。所以,藉由增加一行     指定空字串为客户以及密码到pap-
       secrets档案去,允许拒绝验 证自己的主机进行有限制的存取是可能的。

路由 ROUTING

        当IPCP协商成功地完成时,pppd将会通知核心该ppp界面本地
       以及远端的IP位址。这足够用来建立一个主机到该连线远端的递
       送路径,该路径将使两端能交换IP封包。与其它的机器进行通讯
       往往需要更进一步地修改递送表格(routingtables)以及/或是
       ARP(位址解译协定)表格。在某些案例中这将透过routed或是
       gated隐形程式的动作自动地完成,但是在大部分的案例中需要更 进一步的介入。

        有时候会希望透过远端主机来增加一个预设递送路径,像是在一台
       只透过ppp界面连线到Internet的机器。此defaultroute选
       项使得pppd在IPCP完成时建立起这麽一个预设的递送路径,并 且在该线路被终结时将之删除。

        在某些情况下会希望使用proxyARP,例如在一台连结到区域网
       路的伺服机器上,为了能够允许其它的主机与远端主机进行通讯。
       proxyarp选项引发pppd去寻找一个与远端主机在相同子网路上
       的网路界面(一个支援广播(boardcast)以及ARP的界面,不但要
       是可用的并且不是一个点对点或回授界面)。如果找到,pppd会
       以该远端主机的IP位址以及所找到的网路界面之硬体位址建立一 个永久的,公开的ARP项目。

       When the demand option is used, the interface IP addresses have already been  set  at  the
       point  when IPCP comes up.  If pppd has not been able to negotiate the same addresses that
       it used to configure the interface (for example when the peer is an ISP that uses  dynamic
       IP  address  assignment),  pppd has to change the interface IP addresses to the negotiated
       addresses.  This may disrupt existing connections, and the use  of  demand  dialling  with
       peers that do dynamic IP address assignment is not recommended.

MULTILINK

       Multilink  PPP  provides the capability to combine two or more PPP links between a pair of
       machines into a single `bundle', which appears as a single virtual PPP link which has  the
       combined  bandwidth  of  the individual links.  Currently, multilink PPP is only supported
       under Linux.

       Pppd detects that the link it is controlling is connected to the same peer as another link
       using  the peer's endpoint discriminator and the authenticated identity of the peer (if it
       authenticates itself).  The endpoint discriminator is a block of data which  is  hopefully
       unique  for  each  peer.   Several  types  of data can be used, including locally-assigned
       strings of bytes, IP addresses, MAC addresses, randomly strings of bytes, or  E-164  phone
       numbers.   The  endpoint  discriminator  sent  to  the  peer  by pppd can be set using the
       endpoint option.

       In circumstances the peer may send no endpoint discriminator or a non-unique  value.   The
       optional  bundle  option  adds  an  extra  string  which  is  added to the peer's endpoint
       discriminator and authenticated identity when matching up links to be joined together in a
       bundle.  The bundle option can also be used to allow the establishment of multiple bundles
       between the local system and the peer.  Pppd uses a TDB database in  /var/run/pppd.tdb  to
       match up links.

       Assuming  that  multilink  is enabled and the peer is willing to negotiate multilink, then
       when pppd is invoked to bring up the first link to the peer, it will detect that no  other
       link  is  connected  to  the  peer  and  create a new bundle, that is, another ppp network
       interface unit.  When another pppd is invoked to bring up another link  to  the  peer,  it
       will  detect  the  existing  bundle and join its link to it.  Currently, if the first pppd
       terminates (for example, because  of  a  hangup  or  a  received  signal)  the  bundle  is
       destroyed.

范例 EXAMPLE S

       The  following examples assume that the /etc/ppp/options file contains the auth option (as
       in the default /etc/ppp/options file in the ppp distribution).

       Probably the most common use of pppd is to dial out to an ISP.  This can be  done  with  a
       command such as

              pppd call isp

       where  the  /etc/ppp/peers/isp  file  is  set  up  by  the system administrator to contain
       something like this:

              ttyS0 19200 crtscts
              connect '/usr/sbin/chat -v -f /etc/ppp/chat-isp'
              noauth

       In this example, we are using chat to dial the  ISP's  modem  and  go  through  any  logon
       sequence  required.  The /etc/ppp/chat-isp file contains the script used by chat; it could
       for example contain something like this:

              ABORT "NO CARRIER"
              ABORT "NO DIALTONE"
              ABORT "ERROR"
              ABORT "NO ANSWER"
              ABORT "BUSY"
              ABORT "Username/Password Incorrect"
              "" "at"
              OK "at&d0&c1"
              OK "atdt2468135"
              "name:" "^Umyuserid"
              "word:" "\qmypassword"
              "ispts" "\q^Uppp"
              "~-^Uppp-~"

       See the chat(8) man page for details of chat scripts.

       Pppd can also be used to provide a dial-in ppp service for users.  If  the  users  already
       have login accounts, the simplest way to set up the ppp service is to let the users log in
       to their accounts and run pppd (installed setuid-root) with a command such as

              pppd proxyarp

       To allow a user to use the PPP facilities, you need to allocate an  IP  address  for  that
       user's  machine  and  create  an  entry  in  /etc/ppp/pap-secrets or /etc/ppp/chap-secrets
       (depending on which authentication method the PPP implementation  on  the  user's  machine
       supports),  so that the user's machine can authenticate itself.  For example, if Joe has a
       machine called "joespc" which is to be allowed to dial in to the machine  called  "server"
       and  use  the  IP address joespc.my.net, you would add an entry like this to /etc/ppp/pap-
       secrets or /etc/ppp/chap-secrets:

              joespc    server    "joe's secret" joespc.my.net

       Alternatively, you can create a username called (for example) "ppp", whose login shell  is
       pppd  and  whose home directory is /etc/ppp.  Options to be used when pppd is run this way
       can be put in /etc/ppp/.ppprc.

        如果你的串列连线比直接以线路连接更复杂的话,你可能会需要做
       些调整以便避开一些控制字元。特别是,通常避开XON(^Q)以及
       XOFF(^S)是有用的,可以使用asyncmapa0000。如果该路径包
       含telnet的话,你可能应该也要避开^](asyncmap200a0000)。
       如果该路径包含rlogin的话,你将需要在执行rlogin的客户端
       上使用escapeff选项,因为许多rlogin的实作并非是透通的;
       它们将会从资料流中移除[0xff,0xff,0x73,0x73,跟随的任何 8位元组]这些序列。

诊断 DIAGNOSTICS

        讯息使用facilityLOG_DAEMON送到syslog隐形程式。(这个
       可以藉著以所要的facility定义LOG_PPP巨集来重新编译pppd
       加以改变。)为了能够看到错误以及侦错讯息,你将需要编辑你的
       /etc/syslog.conf档案来将讯息导向到所希望的设备或档案。

       debug选项使得所有送出以及接收的控制封包内容都被记录下来,
       这是指所有的LCP,PAP,CHAP,或是IPCP封包。如果PPP协商
       没有成功的话那麽这可能会有用。如果在编译时期开启侦错功能的
       话,pppd会使用facilityLOG_LOCAL2来取代LOG_DAEMON,而
       且debug选项会使得额外的侦错讯息被记录下来。

       侦错功能也可以藉著传送一个SIGUSR1到pppd程序来启动。侦
       错功能可以藉著传送一个SIGUSR2到pppd程序来关闭。

EXIT STATUS

       The exit status of pppd is set to indicate whether any error was detected, or  the  reason
       for the link being terminated.  The values used are:

       0      Pppd  has  detached,  or  otherwise the connection was successfully established and
              terminated at the peer's request.

       1      An immediately fatal error of some kind occurred, such as an essential system  call
              failing, or running out of virtual memory.

       2      An  error  was  detected  in  processing  the  options  given, such as two mutually
              exclusive options being used.

       3      Pppd is not setuid-root and the invoking user is not root.

       4      The kernel does not support PPP, for example, the PPP kernel driver is not included
              or cannot be loaded.

       5      Pppd terminated because it was sent a SIGINT, SIGTERM or SIGHUP signal.

       6      The serial port could not be locked.

       7      The serial port could not be opened.

       8      The connect script failed (returned a non-zero exit status).

       9      The command specified as the argument to the pty option could not be run.

       10     The  PPP  negotiation failed, that is, it didn't reach the point where at least one
              network protocol (e.g. IP) was running.

       11     The peer system failed (or refused) to authenticate itself.

       12     The link was established successfully and terminated because it was idle.

       13     The link was established successfully and terminated because the connect time limit
              was reached.

       14     Callback was negotiated and an incoming call should arrive shortly.

       15     The link was terminated because the peer is not responding to echo requests.

       16     The link was terminated by the modem hanging up.

       17     The PPP negotiation failed because serial loopback was detected.

       18     The init script failed (returned a non-zero exit status).

       19     We failed to authenticate ourselves to the peer.

SCRIPTS

       Pppd  invokes  scripts  at  various  stages in its processing which can be used to perform
       site-specific ancillary processing.  These scripts are usually shell scripts, but could be
       executable code files instead.  Pppd does not wait for the scripts to finish.  The scripts
       are executed as root (with the real and effective user-id set to 0), so that they  can  do
       things  such  as  update  routing  tables  or run privileged daemons.  Be careful that the
       contents of these scripts do not compromise your system's security.  Pppd runs the scripts
       with  standard  input,  output  and error redirected to /dev/null, and with an environment
       that is empty except for some environment variables that give information about the  link.
       The environment variables that pppd sets are:

       DEVICE The name of the serial tty device being used.

       IFNAME The name of the network interface being used.

       IPLOCAL
              The  IP address for the local end of the link.  This is only set when IPCP has come
              up.

       IPREMOTE
              The IP address for the remote end of the link.  This is only set when IPCP has come
              up.

       PEERNAME
              The  authenticated  name  of  the peer.  This is only set if the peer authenticates
              itself.

       SPEED  The baud rate of the tty device.

       ORIG_UID
              The real user-id of the user who invoked pppd.

       PPPLOGNAME
              The username of the real user-id that invoked pppd. This is always set.

       For the ip-down and auth-down scripts, pppd  also  sets  the  following  variables  giving
       statistics for the connection:

       CONNECT_TIME
              The  number  of  seconds from when the PPP negotiation started until the connection
              was terminated.

       BYTES_SENT
              The number of bytes sent (at the level of the serial port) during the connection.

       BYTES_RCVD
              The number of bytes  received  (at  the  level  of  the  serial  port)  during  the
              connection.

       LINKNAME
              The logical name of the link, set with the linkname option.

       Pppd  invokes  the  following  scripts,  if  they exist.  It is not an error if they don't
       exist.

       /etc/ppp/auth-up
              A program or  script  which  is  executed  after  the  remote  system  successfully
              authenticates itself.  It is executed with the parameters

              interface-name peer-name user-name tty-device speed

              Note  that this script is not executed if the peer doesn't authenticate itself, for
              example when the noauth option is used.

       /etc/ppp/auth-down
              A program or script which is executed when the link goes down, if  /etc/ppp/auth-up
              was  previously  executed.   It  is  executed  in  the  same  manner  with the same
              parameters as /etc/ppp/auth-up.

       /etc/ppp/ip-up
              当线路可以传送以及接收IP封包时(也就是IPCP完成
              时)执行的一支程式或指令稿。它是以界面的名称、终端
              设备、速度、本地-IP-位址、远端-IP-位址为参数执行。

              interface-name tty-device speed local-IP-address remote-IP-address ipparam

       /etc/ppp/ip-down
              当线路不再允许传送以及接收IP封包时执行的一支程式
              或指令稿。这个指令稿可以用来回复/etc/ppp/ip-up指              令稿的影响。它以与ip-
              up指令稿相同的参数启动。

       /etc/ppp/ipv6-up
              Like /etc/ppp/ip-up, except that it is executed when  the  link  is  available  for
              sending and receiving IPv6 packets. It is executed with the parameters

              interface-name  tty-device speed local-link-local-address remote-link-local-address
              ipparam

       /etc/ppp/ipv6-down
              Similar to /etc/ppp/ip-down, but it is executed when IPv6 packets can no longer  be
              transmitted  on  the  link.  It is executed with the same parameters as the ipv6-up
              script.

       /etc/ppp/ipx-up
              A program or script which is executed when the link is available  for  sending  and
              receiving  IPX  packets  (that  is,  IPXCP  has  come up).  It is executed with the
              parameters

              interface-name tty-device speed network-number  local-IPX-node-address  remote-IPX-
              node-address   local-IPX-routing-protocol   remote-IPX-routing-protocol  local-IPX-
              router-name remote-IPX-router-name ipparam pppd-pid

              The local-IPX-routing-protocol and remote-IPX-routing-protocol field may be one  of
              the following:

              NONE      to indicate that there is no routing protocol
              RIP       to indicate that RIP/SAP should be used
              NLSP      to indicate that Novell NLSP should be used
              RIP NLSP  to indicate that both RIP/SAP and NLSP should be used

       /etc/ppp/ipx-down
              A  program  or  script  which  is executed when the link is no longer available for
              sending and receiving IPX packets.  This script can be used for undoing the effects
              of  the /etc/ppp/ipx-up script.  It is invoked in the same manner and with the same
              parameters as the ipx-up script.

文件 FILES

       /var/run/pppn.pid (BSD or Linux), /etc/ppp/pppn.pid (others)
              在ppp界面单元n上的ppp程序之Process-ID。

       /var/run/ppp-name.pid (BSD or Linux), /etc/ppp/ppp-name.pid (others)
              Process-ID for pppd process for logical link name (see the linkname option).

       /etc/ppp/pap-secrets
               由PAP验证所使用的使用者名称、密码以及IP位址。 This file should be  owned  by  root
              and not readable or writable by any other user.  Pppd will log a warning if this is
              not the case.

       /etc/ppp/chap-secrets
               由CHAP验证所使用的名称、暗号以及IP位址。
               As for /etc/ppp/pap-secrets, this file should be owned by root and not readable or
              writable by any other user.  Pppd will log a warning if this is not the case.

       /etc/ppp/options
               pppd的系统预设选项,在使用者预设选项或指令列选项之前读取。

       ~/.ppprc
               使用者预设选项,在指令列选项之前读取。

       /etc/ppp/options.ttyname
               所要使用之串列埠的系统预设选项,在指令列之後读取。read after ~/.ppprc.  In forming
              the ttyname part of this filename, an initial /dev/ is stripped from the port  name
              (if present), and any slashes in the remaining part are converted to dots.

       /etc/ppp/peers
              A  directory containing options files which may contain privileged options, even if
              pppd was invoked by a user other than root.  The system  administrator  can  create
              options  files in this directory to permit non-privileged users to dial out without
              requiring the peer to authenticate, but only to certain trusted peers.

参见 SEE ALSO

       RFC1144
              Jacobson, V.  Compressing TCP/IP headers  for  low-speed  serial  links.   February
              1990.

       RFC1321
              Rivest, R.  The MD5 Message-Digest Algorithm.  April 1992.

       RFC1332
              McGregor, G.  PPP Internet Protocol Control Protocol (IPCP).  May 1992.

       RFC1334
              Lloyd, B.; Simpson, W.A.  PPP authentication protocols.  October 1992.

       RFC1661
              Simpson, W.A.  The Point-to-Point Protocol (PPP).  July 1994.

       RFC1662
              Simpson, W.A.  PPP in HDLC-like Framing.  July 1994.

       RFC2472
              Haskin, D.  IP Version 6 over PPP December 1998.

 注意 NOTES
       下列信号传送到pppd程序时有特别的影响

       SIGINT, SIGTERM
              这些信号使得pppd终止该连线(关闭LCP),回存串列 串列设备的设定,并结束离开。

       SIGHUP 指出实体层已经被断线。pppd将会试图回存串列设备的设
              定(这可能会在Suns上产生错误讯息),然後结束离开。
               If the persist or demand option has been specified, pppd will try  to  reopen  the
              serial  device  and start another connection (after the holdoff period).  Otherwise
              pppd will exit.  If this signal is received during the holdoff  period,  it  causes
              pppd to end the holdoff period immediately.

       SIGUSR1
              This signal toggles the state of the debug option.

       SIGUSR2
              This  signal  causes  pppd  to  renegotiate compression.  This can be useful to re-
              enable compression after it has been disabled as a result of a fatal  decompression
              error.   (Fatal  decompression  errors  generally  indicate  a  bug in one or other
              implementation.)

作者 AUTHOR S

       Paul Mackerras (Paul.Mackerras@cs.anu.edu.au), based on earlier work by Drew Perkins, Brad
       Clements, Karl Fox, Greg Christy, and Brad Parker.

[中文版维护人]

       软件教程之Linux Man <asdchen@pc2.hinet.net> <Best Linux> 1999

[中文版最新更新]

       1995/10/08

《中国linux论坛man手册页翻译计划》:

       http://cmpp.linuxforum.net

                                                                                          PPPD(8)