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Managing Serial Networks Using UUCP and PPP in Oracle® Solaris 11.4

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Updated: November 2020
 
 

Using PPP Options in Files and on the Command Line

Oracle 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

    Oracle 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 PPP configuration files and commands are described in the following list.

/etc/ppp/options

File that contains characteristics that apply by default to all PPP links on the system, for example, whether the system requires peers to authenticate themselves. If this file is absent, nonroot users are prohibited from using PPP. See /etc/ppp/options Configuration File.

/etc/ppp/options.ttyname

File that describes the characteristics of all communications over the serial port ttyname. See /etc/ppp/options.ttyname Configuration File.

/etc/ppp/peers

Directory that usually contains information about peers with which a dial-out system connects. Files in this directory are used with the call option of the pppd command. See Specifying Information for Communicating With the Dial-In Server.

/etc/ppp/peers/peer-name

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. See /etc/ppp/peers/peer-name File.

/etc/ppp/pap-secrets

File that contains the necessary security credentials for Password Authentication Protocol (PAP) authentication. See /etc/ppp/pap-secrets File.

/etc/ppp/chap-secrets

File that contains the necessary security credentials for Challenge-Handshake Authentication Protocol (CHAP) authentication. See /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. See Configuring $HOME/.ppprc on a Dial-In Server.

pppd options

Command and options for initiating a PPP link and describing its characteristics. See How PPP Options Are Processed.

Refer to the pppd(8) man page for details about the PPP files and the 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

All Oracle Solaris PPP 4.0 operations are handled by the pppd daemon, which starts when a user runs the pppd command.

    The pppd daemon parses the following:

  • /etc/ppp/options

  • $HOME/.ppprc

  • Any files that are opened by the file or call option in /etc/ppp/options and $HOME/.ppprc

    When a user calls a remote peer, the following occurs:

  1. pppd scans the command line to determine the device in use. The daemon does not yet interpret any options that are encountered.

  2. 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.

  3. pppd then checks for the existence of the /etc/ppp/options.ttyname file. If the file is found, pppd parses the file.

  4. pppd processes any options on the command line.

  5. pppd negotiates the Link Control Protocol (LCP) to set up the link.

  6. (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

Oracle 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. The only privileged user is root.

The following options require privilege:

  • allow-ip addresses
  • domain
  • linkname
  • name hostname
  • noauth
  • nopam
  • noplink
  • pam
  • plugin
  • plumbed
  • privgroup

The following tables describes the effect of privilege on specific options.

Option
Status
Explanation
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.
connect
Privileged if set in a privileged file or by a privileged user
Cannot be overridden by an nonprivileged user.
defaultroute
Privileged if nodefaultroute is set in a privileged file or by a privileged user
Cannot be overridden by an unprivileged user.
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.
disconnect
Privileged if set in a privileged file or by a privileged user
Cannot be overridden by an unprivileged user.
init
Privileged if set in a privileged file or by a privileged user
Cannot be overridden by an nonprivileged user.
proxyarp
Becomes privileged if noproxyarp has been specified
Cannot be overridden by an unprivileged user.
pty
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.
welcome
Privileged if set in a privileged file or by a privileged user
Cannot be overridden by an nonprivileged user.

/etc/ppp/options Configuration File

You use the /etc/ppp/options file to define global options for all PPP communications on the local system. /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 system does not authenticate callers


Note - The Oracle 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 system does not have an /etc/ppp/options file, only root can run pppd on that system.

You must create /etc/ppp/options by using a text editor, as shown in How to Define Communications Over a Serial Line. If a system 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 system.

/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

    Where:

  • 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

/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 system, 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 - Oracle 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(8) man page

Using /etc/ppp/options.ttyname on a Dial-Out System

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 - Oracle Solaris PPP 4.0 does not require an /etc/ppp/options.ttyname file to work correctly. A dial-out system might have only one serial line for PPP. Furthermore, the dial-out system 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 
:192.0.2.1 

    Where:

  • 38400 is the baud rate for port ttya.

  • asyncmap 0xa0000 enables the local system to communicate with broken peers.

  • :192.0.2.1 is the IP address for 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