Using PPP Options in Files and on the Command Line

Solaris PPP 4.0 contains a large set of options, which you use to define your PPP configuration. You use these options in the PPP configuration files, or on the command line, or by using a combination of files and command-line options. This section contains detailed information about the use of PPP options in configuration files and as arguments to PPP commands.

Where to Define PPP Options

Solaris PPP 4.0 configuration is very flexible.You can define PPP options in the following places:

PPP configuration files
PPP commands that are issued on the command line
A combination of both places

The next table lists the PPP configuration files and commands.

Table 22-1 Summary of PPP Configuration Files and Commands

File or Command	Definition	For Information
`/etc/ppp/options`	A file that contains characteristics that apply by default to all PPP links on the system, for example, whether the machine requires peers to authenticate themselves. If this file is absent, nonroot users are prohibited from using PPP.	`/etc/ppp/options` Configuration File
`/etc/ppp/options.`ttyname	A file that describes the characteristics of all communications over the serial port ttyname.	`/etc/ppp/options`.ttyname Configuration File
`/etc/ppp/peers`	Directory that usually contains information about peers with which a dial-out machine connects. Files in this directory are used with the `call` option of the `pppd` command.	Specifying Information for Communicating With the Dial-in Server
`/etc/ppp/peers/`peer-name	A file that contains characteristics of the remote peer peer-name. Typical characteristics include the remote peer's phone number and chat script for negotiating the link with the peer.	`/etc/ppp/peers/`peer-name File
`/etc/ppp/pap-secrets`	A file that contains the necessary security credentials for Password Authentication Protocol (PAP) authentication.	`/etc/ppp/pap-secrets` File
`/etc/ppp/chap-secrets`	A file that contains the necessary security credentials for Challenge-Handshake Authentication Protocol (CHAP) authentication.	`/etc/ppp/chap-secrets` File
`~/.ppprc`	File in the home directory of a PPP user, most often used with dial-in servers. This file contains specific information about each user's configuration.	Configuring `$HOME/.ppprc` on a Dial-in Server
`pppd` options	Command and options for initiating a PPP link and describing its characteristics.	How PPP Options Are Processed

Refer to the pppd(1M) man page for details on the PPP files. pppd (1M) also includes comprehensive descriptions of all options that are available to the pppd command. Sample templates for all the PPP configuration files are available in /etc/ppp.

How PPP Options Are Processed

The pppd daemon parses the following:
All Solaris PPP 4.0 operations are handled by the pppd daemon, which starts when a user runs the pppd command. When a user calls a remote peer, the following occurs:
- /etc/ppp/options
- $HOME/.ppprc
- Any files that are opened by the file or call option in /etc/ppp/options and $HOME/.ppprc
pppd scans the command line to determine the device in use. The daemon does not yet interpret any options that are encountered.
pppd tries to discover the serial device to use by using these criteria:
- If a serial device is specified on the command line, or a previously processed configuration file, pppd uses the name of that device.
- If no serial device is named, then pppd searches for the notty, pty, or socket option on the command line. If one of these options is specified, pppd assumes that no device name exists.
- Otherwise, if pppd discovers that standard input is attached to a tty, then the name of the tty is used.
- If pppd still cannot find a serial device, pppd terminates the connection and issues an error.
pppd then checks for the existence of the /etc/ppp/options.ttyname file. If the file is found, pppd parses the file.
pppd processes any options on the command line.
pppd negotiates the Link Control Protocol (LCP) to set up the link.
(Optional) If authentication is required, pppd reads /etc/ppp/pap-secrets or /etc/ppp/chap-secrets to authenticate the opposite peer.

The file /etc/ppp/peers/peer-name is read when the pppd daemon encounters the option call peer-name on the command line or in the other configuration files.

How PPP Configuration File Privileges Work

Solaris PPP 4.0 configuration includes the concept of privileges. Privileges determine the precedence of configuration options, particularly when the same option is invoked in more than one place. An option that is invoked from a privileged source takes precedence over the same option that is invoked from a nonprivileged source.

User Privileges

The only privileged user is superuser (root), with the UID of zero. All other users are not privileged.

File Privileges

The following configuration files are privileged regardless of their ownership:

/etc/ppp/options
/etc/ppp/options.ttyname
/etc/ppp/peers/peer-name

The file $HOME/.ppprc is owned by the user. Options that are read from $HOME/.ppprc and from the command line are privileged only if the user who is invoking pppd is root.

Arguments that follow the file option are privileged.

Effects of Option Privileges

Some options require the invoking user or source to be privileged in order to work. Options that are invoked on the command line are assigned the privileges of the user who is running the pppd command. These options are not privileged unless the user who is invoking pppd is root.

Option	Status	Explanation
`domain`	Privileged	Requires privileges for use.
`linkname`	Privileged	Requires privileges for use.
`noauth`	Privileged	Requires privileges for use.
`nopam`	Privileged	Requires privileges for use.
`pam`	Privileged	Requires privileges for use.
`plugin`	Privileged	Requires privileges for use.
`privgroup`	Privileged	Requires privileges for use.
`allow-ip` addresses	Privileged	Requires privileges for use.
`name` hostname	Privileged	Requires privileges for use.
`plink`	Privileged	Requires privileges for use.
`noplink`	Privileged	Requires privileges for use.
`plumbed`	Privileged	Requires privileges for use.
`proxyarp`	Becomes privileged if `noproxyarp` has been specified	Cannot be overridden by an unprivileged use.
`defaultroute`	Privileged if `nodefaultroute` is set in a privileged file or by a privileged user	Cannot be overridden by an unprivileged user.
`disconnect`	Privileged if set in a privileged file or by a privileged user	Cannot be overridden by an unprivileged user.
`bsdcomp`	Privileged if set in a privileged file or by a privileged user	The nonprivileged user cannot specify a code size that is larger than the privileged user has specified.
`deflate`	Privileged if set in a privileged file or by a privileged user	The nonprivileged user cannot specify a code size that is larger than the privileged user has specified.
`connect`	Privileged if set in a privileged file or by a privileged user	Cannot be overridden by an nonprivileged user.
`init`	Privileged if set in a privileged file or by a privileged user	Cannot be overridden by an nonprivileged user.
`pty`	Privileged if set in a privileged file or by a privileged user	Cannot be overridden by an nonprivileged user.
`welcome`	Privileged if set in a privileged file or by a privileged user	Cannot be overridden by an nonprivileged user.
ttyname	Privileged if set in a privileged file Not privileged if set in a nonprivileged file	Opened with root permissions regardless of who invokes `pppd`. Opened with the privileges of the user who invokes `pppd`.

`/etc/ppp/options` Configuration File

You use the /etc/ppp/options file to define global options for all PPP communications on the local machine. /etc/ppp/options is a privileged file. /etc/ppp/options should be owned by root, although pppd does not enforce this rule. Options that you define in /etc/ppp/options have precedence over definitions of the same options in all other files and the command line.

Typical options that you might use in /etc/ppp/options include the following:

lock – Enables UUCP-style file locking
noauth – Indicates that the machine does not authenticate callers

Note - The Solaris PPP 4.0 software does not include a default /etc/ppp/options file. pppd does not require the /etc/ppp/options file to work. If a machine does not have an /etc/ppp/options file, only root can run pppd on that machine.

You must create /etc/ppp/options by using a text editor, as shown in How to Define Communications Over the Serial Line. If a machine does not require global options, you can create an empty /etc/ppp/options file. Then, both root and regular users can run pppd on the local machine.

`/etc/ppp/options.tmpl` Template

The /etc/ppp/options.tmpl contains helpful comments about the /etc/ppp/options file plus three common options for the global /etc/ppp/options file.

lock
nodefaultroute
noproxyarp

Option	Definition
`lock`	Enables UUCP-style file locking
`nodefaultroute`	Specifies that no default route is defined
`noproxyarp`	Disallows `proxyarp`

To use /etc/ppp/options.tmpl as the global options file, rename /etc/ppp/options.tmpl to /etc/ppp/options. Then, modify the file contents as needed by your site.

Where to Find Examples of the `/etc/ppp/options` Files

To find examples of the /etc/ppp/options file, refer to the following:

For a dial-out machine, see How to Define Communications Over the Serial Line.
For a dial-in server, see How to Define Communications Over the Serial Line (Dial-in Server).
For PAP support on a dial-in server, see How to Add PAP Support to the PPP Configuration Files (Dial-in Server).
For PAP support on a dial-out machine, see How to Add PAP Support to the PPP Configuration Files (Dial-out Machine).
For CHAP support on a dial-in server, see How to Add CHAP Support to the PPP Configuration Files (Dial-in Server).

`/etc/ppp/options`.ttyname Configuration File

You can configure the characteristics of communications on the serial line in the /etc/ppp/options.ttyname file. /etc/ppp/options.ttyname is a privileged file that is read by pppd after parsing any existing /etc/ppp/options and existing $HOME/.ppprc files. Otherwise, pppd reads /etc/ppp/options.ttyname after parsing /etc/ppp/options.

ttyname is used for both dial-up and leased-line links. ttyname represents a particular serial port on a machine, such as cua/a or cua/b, where a modem or ISDN TA might be attached.

When naming the /etc/ppp/options.ttyname file, replace the slash (/) in the device name with a dot (.). For example, the options file for device cua/b should be named /etc/ppp/options.cua.b.

Note - Solaris PPP 4.0 does not require an /etc/ppp/options.ttyname file to work correctly. Your server might have only one serial line for PPP. Furthermore, the server requires few options. In this instance, you can specify any required options in another configuration file or on the command line.

Using `/etc/ppp/options.`ttyname on a Dial-in Server

For a dial-up link, you might choose to create individual /etc/ppp/options.ttyname files for every serial port on a dial-in server with a modem attached. Typical options include the following:

IP address required by the dial-in server
Set this option if you require incoming callers on serial port ttyname to use a particular IP address. Your address space might have a limited number of IP addresses that are available for PPP in comparison to the number of potential callers. In this situation, consider assigning an IP address to each serial interface that is used for PPP on the dial-in server. This assignment implements dynamic addressing for PPP.
asyncmap map-value
The asyncmap option maps control characters that cannot be received over the serial line by the particular modem or ISDN TA. When the xonxoff option is used, pppd automatically sets an asyncmap of 0xa0000.
map-value states, in hexadecimal format, the control characters that are problematic.
init "chat -U -f /etc/ppp/mychat"
The init option tells the modem to initialize communications over the serial line by using the information in the chat -U command. The modem uses the chat string in the file /etc/ppp/mychat.
Security parameters that are listed in the pppd(1m) man page

Using `/etc/ppp/options.`ttyname on a Dial-out Machine

For a dial-out system, you can create an /etc/ppp/options.ttyname file for the serial port that is connected to the modem, or choose not to use /etc/ppp/options.ttyname.

Note - Solaris PPP 4.0 does not require an /etc/ppp/options.ttyname file to work correctly. A dial-out machine might have only one serial line for PPP. Furthermore, the dial-out machine might require few options. You can specify any required options in another configuration file or on the command line.

`options.ttya.tmpl` Template File

The /etc/ppp/options.ttya.tmpl file contains helpful comments about the /etc/ppp/options.tty-name file. The template contains three common options for the /etc/ppp/options.tty-name file.

38400 
asyncmap 0xa0000 
:192.168.1.1

Option	Definition
`38400`	Use this baud rate for port ttya.
`asyncmap 0xa0000`	Assign the asyncmap value of 0xa0000 so that the local machine can communicate with broken peers.
`:192.168.1.1`	Assign the IP address 192.168.1.1 to all peers that are calling in over the link.

To use /etc/ppp/options.ttya.tmpl at your site, rename /etc/ppp/options.tmpl to /etc/ppp/options.ttya-name. Replace ttya-name with the name of the serial port with the modem. Then modify the file contents as needed by your site.

Where to Find Examples of the `/etc/ppp/options.`ttyname Files

To find examples of the /etc/ppp/options.ttyname files, refer to the following:

For a dial-out machine, see How to Define Communications Over the Serial Line.
For a dial-in server, see How to Define Communications Over the Serial Line (Dial-in Server).