|PPPD(8)||System Manager's Manual||PPPD(8)|
pppd - 點對點協議守護程序
pppd [ tty_name ] [ speed ] [ options ]
點對點協議 (PPP) 提供一種在點對點串列線路上傳輸資料流 (datagrams)的方法。PPP是由三個部份所組成的：一個在串列線 路上封裝(encapsulating)資料流的方法，一個可延伸的連結控制 協定(LinkControlProtocol:LCP)，以及一些用來建立並配置不 同網路層協定的網路控制協定(NetworkControlProtocols:NCP)
封裝的機制(scheme)是由核心中的驅動程式碼來提供。pppd提供 基本的LCP，驗證(authentication)的支援，以及一個用來建立 並配置網際網路協定(InternatProtocol(IP))（叫做IP控制 協定，IPCP）的NCP。
常用選項 FREQUENTLY USED OPTIONS¶
在該名稱的裝置上進行通訊。如果需要的話可以前置一個 "/dev/"字串。如果沒有給裝置名稱，pppd將會使用控制 臺的終端機(controllingteriminal)，並且產生(fork)出 來時將不會把自己放到背景去。
將波特率設為speed。在像是4.4BSD以及NetBSA的系 統上，可以指定任何速率。其他系統(e.g.SunOs)只允 許有限的幾種速率。
- asyncmap <map>
把非同步(async)字元設為對照到。這個對照表 描述哪些控制字元不能在串列線路上成功地接收。pppd將 會要求彼端以兩個位元組的逸出序列(escapesequence)來 傳送這些字元。其引數是32位元的十六進位數字而每個 位元代表一個得避開(escape)的字元。位元0(00000001) 代表字元0x00；位元31(80000000)代表字元0x1f或 是^_。如果給了多個asyncmap選項，這些數值會以邏 輯的或(OR)合在一起。如果沒有給asyncmap選項，將沒 有非同步字元對照表會被加以協商來導引接收。這樣彼端 將會避開所有的控制字元。
- 要求彼端在允許傳送或接收網路封包之前先驗證它自己。 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
使用以所指定的可執行指令或是shell指令來設定 串列線路。這個指令稿一般會使用"chat"程式來撥資料 機並開始遠端ppp區段作業(session)。 A value for this option from a privileged source cannot be overridden by a non-privileged user.
- 使用硬體流量控制(i.e.RTS/CTS)來控制串列埠上的資料流。 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.
當IPCP協商完全成功時，增加一個預設遞送路徑到系統 的遞送表，將彼端當作閘道器使用。這個專案在ppp連線 中斷後會移除。
- disconnect script
在pppd已經終結該連線之後執行以所指定的可執行 指令或是shell指令。這個指令稿可以用來，例如，如果 硬體的資料機控制訊號無法使用時，發出指令給資料機使 其結束通話電話。 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,...
指定在傳輸上確實應該要避開的字元（不管對方是否有用 它的非同步控制字元對照表要求避開它們）。這些要被避 開的字元是以用逗號隔開的一串十六進位數字指定的。要 注意到幾乎任何字元都可以用escape選項指定避開，不 像asyncmap選項只允許指定控制字元。不能避開的字元 是那些有十六進位值0x20-0x3f或是0x5e者。
- file name
從檔案裡讀取選項（其格式敘述在後） 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.
- 指定pppd應該在此串列裝置上使用UUCP式的鎖定以確 定對該裝置為互斥(exclusive)存取。
- mru n
(Note that for IPv6 MRU must be at least 1280)
- mtu n
將MTU[MaximumTransmitUnit最大傳輸單元]的值設 為n。除非彼端經由MRU協商要求一個更小的值，pppd 將會要求核心網路程式碼透過PPP網路介面所傳送的資料 封包不超過n個位元組。
(Note that for IPv6 MTU must be at least 1280)
在LCP中開啟"passive"選項。加上這個選項，pppd將 會試圖初使一個連線；如果沒有從彼端接收到回應，那麼 pppd將只會被動地等待從彼端所傳來的一個有效LCP封 包（代替結束離開，就像它在沒有這個選項時所作的）。
設定本地以及／或是遠端介面的IP位址。兩者之中的任 何一個都可以省略。該IP位址可以利用主機名稱或者是 十進位數值加小數點符號指定(e.g.22.214.171.124)。 預設的本地位址是系統的（第一個）IP位址（除非有加上 noipdefault選項）。遠端位址如果沒有在任何選項中指 定的話將從彼端取得。因此，在簡單的案例中，這個選項 不是必須的。如果有一個本地以及／或是遠端的IP位址 以這個選項加以指定的話，pppd將不會接受在IPCP協商 中從彼端所傳來不同的值，除非加上ipcp-accept-local 以及／或是ipcp-accept-remote選項，個別地。
- 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.
- 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
- chap-max-challenge n
- chap-restart n
- 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.
- 遞增偵錯層級（與-d相同）。如果加上這個選項，pppd 將以可供閱讀的格式記錄所有傳送或接收的控制封包內容。 這些封包透過syslog以facilitydaemon還有level debug加以記錄。該資訊可以適當設定/etc/syslog.conf 來導向到一個檔案去。（參閱syslog.conf(5)）。(如果 pppd以開啟擴充偵錯(extradebugging)編譯的話，它將 會使用facilitylocal2取代daemon來記錄訊息）。
- Disable asyncmap negotiation, forcing all control characters to be escaped for both the transmit and the receive direction.
- 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.)
- 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
新增領域名稱到本地主機名稱以支援驗證。例如，如 果gethostname()回應porsche這個名稱，但是完整合 格的領域名稱是porsche.Quotron.COM的話，你可以使用 domain選項來將領域名稱設為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.
- 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.
- 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.
- 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.
- 加上這個選項的話，pppd將會接受彼端對於本地IP位址 的意見，即使本地的IP位址已經在某個選項中指定。
- 加上這個選項的話，pppd將會接受彼端對於它的IP位址 的意見，即使遠端的IP位址已經在某個選項中指定。
- ipcp-max-configure n
- ipcp-max-failure n
- 將開始傳送配置拒絕(configure-Rejects)之前的IPCP配 置未接收(configure-NAKs)的最大數目以取代n（預設 為10）。
- ipcp-max-terminate n
將IPCP終結要求(terminate-request)傳輸的最大數目設 為 n（預設為3）。
- ipcp-restart n
- 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).
- 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.
- 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.
- 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.
- 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
- 開啟核心層級中的PPP驅動程式偵錯碼。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, 引數n是一個 由下列值所組合的數字：1開啟一般偵錯訊息，2要求印 出所接收到的封包內容，而4要求印出傳輸的封包內容。 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.
- 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
如果有給這個選項，那麼如果傳送n個LCP回應要求沒 有接收到有效的LCP回應回覆的話pppd將會推測彼端是 死掉的。如果發生這種情形，pppd將會終結該連線。這個 選項的使用要求一個非零的lcp-echo-interval引數值。 這個選項可以用在硬體資料機控制線路無法使用的情況下 當實際連線被中斷之後（e.g.,資料機已經結束通話）終結 pppd的執行。
- lcp-echo-interval n
- 如果有給這個選項，pppd每秒將會送出一個LCP回 應要求(echo-request)封包(frame)給彼端。在Linux系 統下，回應要求在n秒內沒有從彼端接收到封包時會被送 出。一般彼端應該以傳送一個回應回覆(echo-reply)來反 應該回應要求。這個選項可以與lcp-echo-failure選項 一起使用來偵測不再連線的彼端。
- lcp-max-configure n
- lcp-max-failure n
將開始傳送配置拒絕(configure-Rejects)之前的LCP配 置未接收(configure-NAKs)的最大數目設定為n（預設 為10）。
- lcp-max-terminate n
- lcp-restart n
- 將LCP重新開始的間隔（重新傳輸的時間限制）設為 秒鐘（預設為3）。
- 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.
- 不要使用資料機控制線路。 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.
- 使用系統密碼資料庫驗證使用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.
- 使用資料機控制線路。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，這個選項會實作硬 體流量控制，像crtsct選項作的。
- Enables the use of PPP multilink; this is an alias for the `multilink' option. This option is currently only available under Linux.
- 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.
- 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
- 將本地系統的名稱設為用來進行驗證。 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
把該介面網路掩碼設為，這是一個以″十進位數值加 小數點″("decimaldot")符號表示的32位元網路掩碼 (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.)
- Disable Address/Control compression in both directions (send and receive).
- Do not require the peer to authenticate itself. This option is privileged.
- Disables BSD-Compress compression; pppd will not request or agree to compress packets using the BSD-Compress scheme.
- 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.
- 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.
- This option is a synonym for nocrtscts. Either of these options will disable both forms of hardware flow control.
- 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.
- Disables Deflate compression; pppd will not request or agree to compress packets using the Deflate scheme.
- 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.
- 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.
- 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.
- 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.
- 關閉在沒有指定本地IP位址時所進行的預設動作，這是 用來由從主機名稱決定（如果可能的話）決定本地IP位 址。加上這個選項的話，彼端將必須在進行IPCP協商時 （除非在指令列或在選項檔中明確地指定它）提供本地的 IP位址。
- 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.
- Opposite of the ktune option; disables pppd from changing system settings.
- Do not send log messages to a file or file descriptor. This option cancels the logfd and logfile options.
- 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.
- Disables the use of PPP multilink. This option is currently only available under Linux.
- 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.
- Disables the use of PPP multilink. This option is currently only available under Linux.
- Disable protocol field compression negotiation in both the receive and the transmit direction.
- Exit once a connection has been made and terminated. This is the default unless the persist or demand option has been specified.
- Do not accept or agree to Predictor-1 compression.
- 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.
- 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.
- Disable Van Jacobson style TCP/IP header compression in both the transmit and the receive direction.
- 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.
- 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
- pap-restart n
- 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.
- 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.
- 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.
- 以彼端的IP位址以及該系統的乙太網路位址增加一個項 目到系統的ARP[AddressResolutionProtocol位址解 譯協定]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.)
- 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
- With this option, pppd will not agree to authenticate itself to the peer using CHAP.
- With this option, pppd will not agree to authenticate itself to the peer using PAP.
- Require the peer to authenticate itself using CHAP [Challenge Handshake Authentication Protocol] authentication.
- Require the peer to authenticate itself using PAP [Password Authentication Protocol] authentication.
- When logging the contents of PAP packets, this option causes pppd to show the password string in the log message.
- 加上這個選項，pppd將不會傳輸LCP封包來初使一個連 線一直到從彼端接收到一個有效的LCP封包。（就像是給 舊版pppd使用的"passive"選項）。
- 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.
- 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).
- 強迫主機名稱使用本地系統的名稱來進行驗證。（這會蓋過name選項）。 This option is not normally needed since the name option is privileged.
- 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
- 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.
選項檔案 OPTIONS FILES¶
選項可以從檔案取出使用就如同使用命令列一般。pppd在檢視指 令列之前先從檔案/etc/ppp/options以及~/.ppprc讀取選項。 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.
一個選項檔案以空白字元為界被剖析成一串單字。空白字元可以用 雙引號(")包括在一個單字裡。倒斜線引用其後的字元。而hash (#)符號開始一段註解持續到該行結束。 There is no restriction on using the file or call options within an options file.
pppd 提供系統管理人員充份的存取控制能力這表示以PPP存取一 臺伺服機器可以提供給合法的使用者使用而不必擔心危及該伺服器 或所在網路的安全性。這有一部份是以/etc/ppp/options檔案來 提供，在這裡系統管理人員可以放置在執行pppd的時候用來要求 驗證的選項，而部份是由PAP以及CHAP暗號檔案來提供，其中 系統管理人員可以限制個別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 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預設的動作是如果有要求就同意進行驗證，並且不要求從彼 端做驗證。然而如果沒有可以用來驗證的暗號則pppd將不會同意 以特殊的協定來驗證它自己。
驗證的基礎是由暗號檔案選擇的暗號（/etc/ppp/pap-secrets是 給PAP使用的，/etc/ppp/chap-secrets則是給CHAP使用）。 這兩個暗號檔案都具有相同的格式，而且兩者都可以儲放暗號給數 種伺服器（驗證彼端）及客戶（被驗證端）組合使用。注意pppd 可以最為伺服端以及客戶端，而且如果需要的話兩方可以使用不同 的協定。
一個暗號檔案如同選項檔案一般被剖析成單字。一個暗號是由最少 包含3個單字的一行所指定，依序是客戶，伺服器，暗號。在同 一行中任何跟在其後的單字都被當作是給客戶的可接受IP位址列 表。如果該行只有3個單字，這假設任何IP位址都可以；不允 許所有的IP位址的話，使用"-"。如果暗號是以'@'開始，其 後所接的單字將被假設為可以從中讀取暗號的檔案名稱。而以一個 "*"字元作為客戶或伺服端的名稱會符合任何名稱。在選擇一個暗 號時，pppd會選擇最符合的，i.e.最少萬用字元的那個。
如此一個暗號檔案包含用來驗證其它主機，以及用來為其它主機驗 證自己兩者的暗號。選擇使用哪個暗號是根據該主機（本地名稱） 以及其彼端（遠端名稱）而定。本地名稱的設定如下：
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.
當以PAP驗證彼端時，一個""暗號符合任何由彼端所提供密碼。 如果密碼不符合暗號，密碼被以crypt()編碼並且再次檢查暗號； 因此驗證彼端的暗號可以編碼方式儲放。
如果指定有login選項， 使用者名稱以及密碼也會被以系統的密碼資料庫檢查。因此係統管 理人員可以設定pap-secrets檔案以便只允許某些使用者以PPP 連線，並且限制每個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.
驗證必須在IPCP（或任何其它網路控制協定）開始之前被完全地 滿足。如果驗證失敗，pppd將會終結連線（關閉LCP）。如果 IPCP協商出一個無法接受的遠端主機IP位址，IPCP將會關閉。 IP封包只有在IPCP開啟的時候才能傳送或接收。
即使本地主機一般會要求驗證，在某些案例中會希望允一些無法驗 證它們自己的主機連線並使用所限制的IP位址其中之一。如果彼 在被要求時拒絕驗證它自己，pppd將會把它當成等於是在使用者 名稱以及密碼上使用空字串來以PAP驗證。所以，藉由增加一行 指定空字串為客戶以及密碼到pap-secrets檔案去，允許拒絕驗 證自己的主機進行有限制的存取是可能的。
當IPCP協商成功地完成時，pppd將會通知核心該ppp介面本地 以及遠端的IP位址。這足夠用來建立一個主機到該連線遠端的遞 送路徑，該路徑將使兩端能交換IP封包。與其它的機器進行通訊 往往需要更進一步地修改遞送表格(routingtables)以及／或是 ARP（位址解譯協定）表格。在某些案例中這將透過routed或是 gated隱形程式的動作自動地完成，但是在大部分的案例中需要更 進一步的介入。
有時候會希望透過遠端主機來增加一個預設遞送路徑，像是在一臺 只透過ppp介面連線到Internet的機器。此defaultroute選 項使得pppd在IPCP完成時建立起這麼一個預設的遞送路徑，並 且在該線路被終結時將之刪除。
在某些情況下會希望使用proxyARP，例如在一臺連結到區域網 路的伺服機器上，為了能夠允許其它的主機與遠端主機進行通訊。 proxyarp選項引發pppd去尋找一個與遠端主機在相同子網路上 的網路介面（一個支援廣播(boardcast)以及ARP的介面，不但要 是可用的並且不是一個點對點或回授介面）。如果找到，pppd會 以該遠端主機的IP位址以及所找到的網路介面之硬體位址建立一 個永久的，公開的ARP專案。
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 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.
範例 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'
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 "NO ANSWER"
ABORT "Username/Password Incorrect"
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.
如果你的串列連線比直接以線路連線更復雜的話，你可能會需要做 些調整以便避開一些控制字元。特別是，通常避開XON(^Q)以及 XOFF(^S)是有用的，可以使用asyncmapa0000。如果該路徑包 含telnet的話，你可能應該也要避開^](asyncmap200a0000)。 如果該路徑包含rlogin的話，你將需要在執行rlogin的客戶端 上使用escapeff選項，因為許多rlogin的實作並非是透通的； 它們將會從資料流中移除[0xff,0xff,0x73,0x73,跟隨的任何 8位元組]這些序列。
訊息使用facilityLOG_DAEMON送到syslog隱形程式。（這個 可以藉著以所要的facility定義LOG_PPP巨集來重新編譯pppd 加以改變。）為了能夠看到錯誤以及偵錯訊息，你將需要編輯你的 /etc/syslog.conf檔案來將訊息導向到所希望的裝置或檔案。
debug選項使得所有送出以及接收的控制封包內容都被記錄下來， 這是指所有的LCP,PAP,CHAP,或是IPCP封包。如果PPP協商 沒有成功的話那麼這可能會有用。如果在編譯時期開啟偵錯功能的 話，pppd會使用facilityLOG_LOCAL2來取代LOG_DAEMON，而 且debug選項會使得額外的偵錯訊息被記錄下來。
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:
- Pppd has detached, or otherwise the connection was successfully established and terminated at the peer's request.
- An immediately fatal error of some kind occurred, such as an essential system call failing, or running out of virtual memory.
- An error was detected in processing the options given, such as two mutually exclusive options being used.
- Pppd is not setuid-root and the invoking user is not root.
- The kernel does not support PPP, for example, the PPP kernel driver is not included or cannot be loaded.
- Pppd terminated because it was sent a SIGINT, SIGTERM or SIGHUP signal.
- The serial port could not be locked.
- The serial port could not be opened.
- The connect script failed (returned a non-zero exit status).
- The command specified as the argument to the pty option could not be run.
- The PPP negotiation failed, that is, it didn't reach the point where at least one network protocol (e.g. IP) was running.
- The peer system failed (or refused) to authenticate itself.
- The link was established successfully and terminated because it was idle.
- The link was established successfully and terminated because the connect time limit was reached.
- Callback was negotiated and an incoming call should arrive shortly.
- The link was terminated because the peer is not responding to echo requests.
- The link was terminated by the modem hanging up.
- The PPP negotiation failed because serial loopback was detected.
- The init script failed (returned a non-zero exit status).
- We failed to authenticate ourselves to the peer.
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:
- The name of the serial tty device being used.
- The name of the network interface being used.
- The IP address for the local end of the link. This is only set when IPCP has come up.
- The IP address for the remote end of the link. This is only set when IPCP has come up.
- The authenticated name of the peer. This is only set if the peer authenticates itself.
- The baud rate of the tty device.
- The real user-id of the user who invoked pppd.
- 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:
- The number of seconds from when the PPP negotiation started until the connection was terminated.
- The number of bytes sent (at the level of the serial port) during the connection.
- The number of bytes received (at the level of the serial port) during the connection.
- 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.
- 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.
- 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.
- 當線路可以傳送以及接收IP封包時（也就是IPCP完成 時）執行的一支程式或指令稿。它是以介面的名稱、終端 裝置、速度、本地-IP-位址、遠端-IP-位址為引數執行。
- interface-name tty-device speed local-IP-address remote-IP-address ipparam
- 當線路不再允許傳送以及接收IP封包時執行的一支程式 或指令稿。這個指令稿可以用來回復/etc/ppp/ip-up指 令稿的影響。它以與ip-up指令稿相同的引數啟動。
- 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
- 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.
- 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
- 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.
- /var/run/pppn.pid (BSD or Linux), /etc/ppp/pppn.pid (others)
- /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).
由PAP驗證所使用的使用者名稱、密碼以及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.
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.
所要使用之串列埠的系統預設選項，在指令列之後讀取。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.
- 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.
參見 SEE ALSO¶
- Jacobson, V. Compressing TCP/IP headers for low-speed serial links. February 1990.
- Rivest, R. The MD5 Message-Digest Algorithm. April 1992.
- McGregor, G. PPP Internet Protocol Control Protocol (IPCP). May 1992.
- Lloyd, B.; Simpson, W.A. PPP authentication protocols. October 1992.
- Simpson, W.A. The Point-to-Point Protocol (PPP). July 1994.
- Simpson, W.A. PPP in HDLC-like Framing. July 1994.
- Haskin, D. IP Version 6 over PPP December 1998.
- SIGINT, SIGTERM
- 這些訊號使得pppd終止該連線（關閉LCP），回存串列 串列裝置的設定，並結束離開。
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.
- This signal toggles the state of the debug option.
- 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.
軟體教程之Linux Man <firstname.lastname@example.org> <Best Linux> 1999
中文 man 手冊頁計劃：https://github.com/man-pages-zh/manpages-zh