Editorial review of first 1/2 of Dial-in Service.
Sponsored by: iXsystems
This commit is contained in:
Dru Lavigne
parent
77e993c3f6
commit
67995497aa
Notes:
svn2git
2020-12-08 03:00:23 +00:00
svn path=/head/; revision=44789
1 changed files with 111 additions and 216 deletions
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@ -971,48 +971,51 @@ ttyu5 "/usr/libexec/getty std.19200" vt100 on insecure</programlisting>
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</sect1>
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<sect1 xml:id="dialup">
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<!--
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<sect1info>
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<info>
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<title>Dial-in Service</title>
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<authorgroup>
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<author>
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<firstname>Guy</firstname>
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<personname>
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<firstname>Guy</firstname>
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<surname>Helmer</surname>
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</personname>
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<contrib>Contributed by </contrib>
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</author>
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</authorgroup>
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<authorgroup>
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<author>
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<personname>
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<firstname>Sean</firstname>
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<surname>Kelly</surname>
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</personname>
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<contrib>Additions by </contrib>
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</author>
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</authorgroup>
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</sect1info>
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-->
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<title>Dial-in Service</title>
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</info>
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<indexterm><primary>dial-in service</primary></indexterm>
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<para>Configuring a &os; system for dial-in service is similar
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to connecting terminals except that modems are used instead of
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to configuring terminals, except that modems are used instead of
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terminal devices. &os; supports both external and internal
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modems.</para>
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<para>External modems are more convenient for dial-up because
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they often can be semi-permanently configured via parameters
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stored in non-volatile RAM and they usually provide lighted
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indicators that display the state of important RS-232 signals,
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<para>External modems are more convenient because
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they often can be configured via parameters
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stored in non-volatile <acronym>RAM</acronym> and they usually provide lighted
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indicators that display the state of important <acronym>RS-232</acronym> signals,
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indicating whether the modem is operating properly.</para>
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<para>Internal modems usually lack non-volatile RAM, so their
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configuration may be limited to setting DIP switches. If the
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<para>Internal modems usually lack non-volatile <acronym>RAM</acronym>, so their
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configuration may be limited to setting <acronym>DIP</acronym> switches. If the
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internal modem has any signal indicator lights, they are
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difficult to view when the system's cover is in place.</para>
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<indexterm><primary>modem</primary></indexterm>
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<para>When using an external modem, a proper cable is needed. A
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standard RS-232C serial cable should suffice.</para>
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standard <acronym>RS-232C</acronym> serial cable should suffice.</para>
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<para>&os; needs the <acronym>RTS</acronym> and
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<acronym>CTS</acronym> signals for flow control at speeds
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@ -1022,7 +1025,8 @@ ttyu5 "/usr/libexec/getty std.19200" vt100 on insecure</programlisting>
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after a session is complete. Some cables are wired without all
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of the needed signals, so if a login session does not go away
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when the line hangs up, there may be a problem with the
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cable.</para>
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cable. Refer to <xref linkend="term-cables-null"/> for more
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information about these signals.</para>
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<para>Like other &unix;-like operating systems, &os; uses the
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hardware signals to find out when a call has been answered or a
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@ -1030,78 +1034,57 @@ ttyu5 "/usr/libexec/getty std.19200" vt100 on insecure</programlisting>
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call. &os; avoids sending commands to the modem or watching for
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status reports from the modem.</para>
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<sect2>
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<title>Serial Interface Considerations</title>
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<para>&os; supports the NS8250-, NS16450-, NS16550-, and
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NS16550A-based EIA RS-232C (CCITT V.24) communications
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<para>&os; supports the <acronym>NS8250</acronym>,
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<acronym>NS16450</acronym>, <acronym>NS16550</acronym>, and
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<acronym>NS16550A</acronym>-based <acronym>RS-232C</acronym>
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(<acronym>CCITT</acronym> V.24) communications
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interfaces. The 8250 and 16450 devices have single-character
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buffers. The 16550 device provides a 16-character buffer,
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which allows for better system performance. Bugs in plain
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16550's prevent the use of the 16-character buffer, so use
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16550A's if possible. Because single-character-buffer
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16550 devices prevent the use of the 16-character buffer, so use
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16550A devices if possible. Because single-character-buffer
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devices require more work by the operating system than the
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16-character-buffer devices, 16550A-based serial interface
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cards are preferred. If the system has many active serial
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ports or will have a heavy load, 16550A-based cards are better
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for low-error-rate communications.</para>
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</sect2>
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<sect2>
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<title>Quick Overview</title>
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<para>The rest of this section demonstrates how to configure a
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modem to receive incoming connections, how to communicate
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with the modem, and offers some troubleshooting tips.</para>
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<sect2 xml:id="dialup-ttys">
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<title>Modem Configuration</title>
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<indexterm><primary>getty</primary></indexterm>
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<para>As with terminals, <command>init</command> spawns a
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<command>getty</command> process for each configured serial
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port for dial-in connections. For example, if a modem is
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attached to <filename>/dev/ttyu0</filename>,
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<command>ps ax</command> might show this:</para>
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<screen> 4850 ?? I 0:00.09 /usr/libexec/getty V19200 ttyu0</screen>
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<para>When a user dials the modem's line and the modems connect,
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the Carrier Detect (<acronym>CD</acronym>) line is reported by
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port used for dial-in connections. When a user dials the
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modem's line and the modems connect,
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the <quote>Carrier Detect</quote> signal is reported by
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the modem. The kernel notices that the carrier has been
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detected and instructs <command>getty</command> to open the
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port. <command>getty</command> sends a
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port and display a
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<prompt>login:</prompt> prompt at the specified initial line
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speed. <command>getty</command> watches to see if legitimate
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characters are received, and, in a typical configuration, if
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it finds junk (probably due to the modem's connection speed
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being different than <command>getty</command>'s speed),
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speed. In a typical configuration, if garbage characters are
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received, usually due to the modem's connection speed
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being different than the configured speed,
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<command>getty</command> tries adjusting the line speeds until
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it receives reasonable characters.</para>
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it receives reasonable characters. After the user enters their login name,
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<command>getty</command> executes
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<command>login</command>, which completes the login process
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by asking for the user's password and then starting the user's
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shell.</para>
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<indexterm>
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<primary><command>/usr/bin/login</command></primary>
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</indexterm>
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<para>After the user enters their login name,
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<command>getty</command> executes
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<filename>/usr/bin/login</filename>, which completes the login
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by asking for the user's password and then starting the user's
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shell.</para>
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</sect2>
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<sect2>
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<title>Configuration Files</title>
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<para>There are three system configuration files in
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<filename>/etc</filename> that probably
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need to be edited to allow dial-up access to the &os; system.
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<filename>/etc/gettytab</filename> contains configuration
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information for the <filename>/usr/libexec/getty</filename>
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daemon. <filename>/etc/ttys</filename> holds information that
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tells <command>init</command> which
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<filename>tty</filename>s should have
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<command>getty</command> processes running on them. Lastly,
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port initialization commands can be placed in
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<filename>/etc/rc.d/serial</filename>.</para>
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<para>There are two schools of thought regarding dial-up modems
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on &unix;. One group likes to configure their modems and
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<para>There are two schools of thought regarding dial-up modems.
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One confiuration method is to set the modems and
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systems so that no matter at what speed a remote user dials
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in, the local computer-to-modem RS-232 interface runs at a
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in, the dial-in <acronym>RS-232</acronym>
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interface runs at a
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locked speed. The benefit of this configuration is that the
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remote user always sees a system login prompt immediately.
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The downside is that the system does not know what a user's
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@ -1110,68 +1093,44 @@ ttyu5 "/usr/libexec/getty std.19200" vt100 on insecure</programlisting>
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screen-painting methods to make their response better for
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slower connections.</para>
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<para>The other group configures their modems' RS-232 interface
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<para>The second method is to configure the <acronym>RS-232</acronym> interface
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to vary its speed based on the remote user's connection speed.
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For example, V.32bis (14.4 Kbps) connections to the modem
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might make the modem run its RS-232 interface at
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19.2 Kbps, while 2400 bps connections make the
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modem's RS-232 interface run at 2400 bps. Because
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Because
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<command>getty</command> does not understand any particular
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modem's connection speed reporting, <command>getty</command>
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modem's connection speed reporting, it
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gives a <prompt>login:</prompt> message at an initial speed
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and watches the characters that come back in response. If the
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user sees junk, it is assumed that they know they should press
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user sees junk, they should press
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<keycap>Enter</keycap> until they see a recognizable prompt.
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If the data rates do not match, <command>getty</command> sees
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anything the user types as <quote>junk</quote>, tries going to
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the next speed and gives the <prompt>login:</prompt> prompt
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anything the user types as junk, tries
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the next speed, and gives the <prompt>login:</prompt> prompt
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again. This procedure normally only takes a keystroke or two
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before the user sees a good prompt. This login sequence does
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not look as clean as the <quote>locked-speed</quote> method,
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not look as clean as the locked-speed method,
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but a user on a low-speed connection should receive better
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interactive response from full-screen programs.</para>
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<para>This section will try to give balanced configuration
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information, but is biased towards having the modem's data
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rate follow the connection rate.</para>
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<sect3>
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<title><filename>/etc/gettytab</filename></title>
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<indexterm>
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<primary><filename>/etc/gettytab</filename></primary>
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</indexterm>
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<para><filename>/etc/gettytab</filename> is a
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&man.termcap.5;-style file of configuration information for
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&man.getty.8;. Refer to &man.gettytab.5; for complete
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information on the format of the file and the list of
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capabilities.</para>
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<para>When locking a modem's data communications rate at a
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particular speed, no changes to
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<filename>/etc/gettytab</filename> should be needed.</para>
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<para>However, a change is needed to create a matching-speed
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configuration. Create an entry in
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<filename>/etc/gettytab</filename> to give
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<command>getty</command> information about the speeds to use
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for the modem. For a 2400 bps modem, use the existing
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<literal>D2400</literal> entry.</para>
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<programlisting>#
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# Fast dialup terminals, 2400/1200/300 rotary (can start either way)
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#
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D2400|d2400|Fast-Dial-2400:\
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:nx=D1200:tc=2400-baud:
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3|D1200|Fast-Dial-1200:\
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:nx=D300:tc=1200-baud:
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5|D300|Fast-Dial-300:\
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:nx=D2400:tc=300-baud:</programlisting>
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<para>For a higher speed modem, add an entry in
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<filename>/etc/gettytab</filename>. This entry is for a
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<filename>/etc/gettytab</filename> should be needed.
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However, for a matching-speed
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configuration, additional entries may be required in
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order to define the speeds to use
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for the modem. This example configures a
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14.4 Kbps modem with a top interface speed of
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19.2 Kbps:</para>
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19.2 Kbps using 8-bit, no parity connections. It
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configures <command>getty</command> to start the
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communications rate for a V.32bis connection at
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19.2 Kbps, then cycles
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through 9600 bps, 2400 bps,
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1200 bps, 300 bps, and back to 19.2 Kbps.
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Communications rate cycling is implemented with the
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<literal>nx=</literal> (next table)
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capability. Each line uses a
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<literal>tc=</literal> (table continuation)
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entry to pick up the rest of the
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settings for a particular data rate.</para>
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<programlisting>#
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# Additions for a V.32bis Modem
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@ -1187,24 +1146,9 @@ up|V9600|High Speed Modem at 9600,8-bit:\
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uq|V19200|High Speed Modem at 19200,8-bit:\
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:nx=V9600:tc=std.19200:</programlisting>
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<para>This will result in 8-bit, no parity connections.</para>
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<para>The example above starts the communications rate at
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19.2 Kbps (for a V.32bis connection), then cycles
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through 9600 bps (for V.32), 2400 bps,
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1200 bps, 300 bps, and back to 19.2 Kbps.
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Communications rate cycling is implemented with the
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<literal>nx=</literal> (<quote>next table</quote>)
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capability. Each of the lines uses a
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<literal>tc=</literal> (<quote>table continuation</quote>)
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entry to pick up the rest of the <quote>standard</quote>
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settings for a particular data rate.</para>
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<para>For a 28.8 Kbps modem or to take advantage of
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<para>For a 28.8 Kbps modem, or to take advantage of
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compression on a 14.4 Kbps modem, use a higher
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communications rate than 19.2 Kbps. Here is an
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example of a <filename>gettytab</filename> entry starting
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a 57.6 Kbps:</para>
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communications rate, as seen in this example:</para>
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<programlisting>#
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# Additions for a V.32bis or V.34 Modem
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@ -1221,116 +1165,71 @@ vp|VH9600|Very High Speed Modem at 9600,8-bit:\
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vq|VH57600|Very High Speed Modem at 57600,8-bit:\
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:nx=VH9600:tc=std.57600:</programlisting>
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<para>For a slow CPU or a heavily loaded system without
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16550A-based serial ports, there may be
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<para>For a slow <acronym>CPU</acronym> or a heavily loaded system without
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16550A-based serial ports, this configuration may produce
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<errorname>sio</errorname>
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<quote>silo</quote> errors at 57.6 Kbps.</para>
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</sect3>
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<sect3 xml:id="dialup-ttys">
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<title><filename>/etc/ttys</filename></title>
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<indexterm>
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<primary><filename>/etc/ttys</filename></primary>
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</indexterm>
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<para>Configuration of <filename>/etc/ttys</filename>
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is covered in <xref linkend="ex-etc-ttys"/>.
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Configuration for modems is similar, but a different
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argument is passed to <command>getty</command> and a
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different terminal type is specified. The general format
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for both locked-speed and matching-speed configurations
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is:</para>
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<para>The configuration of <filename>/etc/ttys</filename>
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is similar to <xref linkend="ex-etc-ttys"/>,
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but a different
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argument is passed to <command>getty</command> and
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<literal>dialup</literal> is used for the terminal type.
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Replace
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<replaceable>xxx</replaceable> with the process
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<command>init</command> will run on the device:</para>
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<programlisting>ttyu0 "/usr/libexec/getty <replaceable>xxx</replaceable>" dialup on</programlisting>
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<para>The first item in the above line is the device special
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file for this entry. <literal>ttyu0</literal> indicates
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that <command>getty</command> is watching
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<filename>/dev/ttyu0</filename>. The
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<replaceable>xxx</replaceable> will replace the initial
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<filename>gettytab</filename> capability and is the process
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<command>init</command> will run on the device. The third
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item, <literal>dialup</literal>, is the default terminal
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type. The fourth parameter, <literal>on</literal>,
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indicates to <command>init</command> that the line is
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operational. There can be a fifth parameter,
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<literal>secure</literal>, but it should only be used for
|
||||
terminals which are physically secure, such as the system
|
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console.</para>
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<para>The default terminal type, <literal>dialup</literal> in
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this example, may depend on local preferences.
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<literal>dialup</literal> is the traditional default
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terminal type on dial-up lines so that users may customize
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their login scripts to notice when the terminal is
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<literal>dialup</literal> and automatically adjust their
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terminal type. Setting <literal>vt102</literal> as the
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default terminal type allows users to use VT102 emulation on
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<para>The <literal>dialup</literal> terminal type can be
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changed. For example, setting <literal>vt102</literal> as the
|
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default terminal type allows users to use <acronym>VT102</acronym> emulation on
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their remote systems.</para>
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<para>After editing <filename>/etc/ttys</filename>, send the
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<command>init</command> process a <acronym>HUP</acronym>
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signal to re-read the file:</para>
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<screen>&prompt.root; <userinput>kill -HUP 1</userinput></screen>
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<para>Wait until the modem is properly configured and
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connected before signaling <command>init</command>.</para>
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||||
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||||
<para>For a locked-speed configuration, the
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||||
<filename>ttys</filename> entry needs to have a
|
||||
fixed-speed entry provided to <command>getty</command>.
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For a modem whose port speed is locked at 19.2 Kbps,
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the <filename>ttys</filename> entry might look like
|
||||
this:</para>
|
||||
|
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<programlisting>ttyu0 "/usr/libexec/getty std.19200" dialup on</programlisting>
|
||||
|
||||
<para>If the modem is locked at a different data rate,
|
||||
substitute the appropriate value for
|
||||
<literal>std.<replaceable>speed</replaceable></literal>
|
||||
instead of <literal>std.19200</literal>. Make sure to use
|
||||
<para>For a locked-speed configuration, specify the speed with
|
||||
a valid type listed in
|
||||
<filename>/etc/gettytab</filename>.</para>
|
||||
<filename>/etc/gettytab</filename>.
|
||||
This example is for a modem whose port speed is locked at
|
||||
19.2 Kbps:</para>
|
||||
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||||
<programlisting>ttyu0 "/usr/libexec/getty std.<replaceable>19200</replaceable>" dialup on</programlisting>
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||||
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||||
<para>In a matching-speed configuration, the
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||||
<filename>ttys</filename> entry needs to reference the
|
||||
entry needs to reference the
|
||||
appropriate beginning <quote>auto-baud</quote> entry in
|
||||
<filename>/etc/gettytab</filename>. For example, for the
|
||||
above suggested entry for a matching-speed modem that
|
||||
starts at 19.2 Kbps, the
|
||||
<filename>/etc/ttys</filename> entry might look like
|
||||
this:</para>
|
||||
<filename>/etc/gettytab</filename>. To continue the example
|
||||
for a matching-speed modem that
|
||||
starts at 19.2 Kbps, use this entry:</para>
|
||||
|
||||
<programlisting>ttyu0 "/usr/libexec/getty V19200" dialup on</programlisting>
|
||||
</sect3>
|
||||
|
||||
<sect3>
|
||||
<title><filename>/etc/rc.d/serial</filename></title>
|
||||
<para>After editing <filename>/etc/ttys</filename>, wait until
|
||||
the modem is properly configured and
|
||||
connected before signaling <command>init</command>:</para>
|
||||
|
||||
<screen>&prompt.root; <userinput>kill -HUP 1</userinput></screen>
|
||||
|
||||
<indexterm>
|
||||
<primary>rc files</primary>
|
||||
<secondary><filename>rc.serial</filename></secondary>
|
||||
</indexterm>
|
||||
|
||||
<para>High-speed modems, like V.32, V.32bis, and V.34 modems,
|
||||
need to use hardware (<literal>RTS/CTS</literal>) flow
|
||||
control. <command>stty</command> can be used to set the
|
||||
hardware flow control flag in the &os; kernel for the modem
|
||||
ports.</para>
|
||||
|
||||
<para>For example, to set the <literal>termios</literal> flag
|
||||
<varname>crtscts</varname> on
|
||||
<para>High-speed modems, like <acronym>V.32</acronym>,
|
||||
<acronym>V.32bis</acronym>, and <acronym>V.34</acronym> modems,
|
||||
use hardware (<literal>RTS/CTS</literal>) flow
|
||||
control. Use <command>stty</command> to set the
|
||||
hardware flow control flag for the modem
|
||||
port. This example sets the
|
||||
<varname>crtscts</varname> flag on
|
||||
<filename>COM2</filename>'s dial-in and dial-out
|
||||
initialization devices, the following lines could be added
|
||||
to <filename>/etc/rc.d/serial</filename>:</para>
|
||||
initialization devices:</para>
|
||||
|
||||
<programlisting># Serial port initial configuration
|
||||
stty -f /dev/ttyu1.init crtscts
|
||||
stty -f /dev/cuau1.init crtscts</programlisting>
|
||||
|
||||
</sect3>
|
||||
<screen>&prompt.root; <userinput>stty -f /dev/ttyu1.init crtscts</userinput>
|
||||
&prompt.root; <userinput>stty -f /dev/cuau1.init crtscts</userinput></screen>
|
||||
</sect2>
|
||||
|
||||
<sect2>
|
||||
|
|
@ -1462,9 +1361,6 @@ AT&B1&W</programlisting>
|
|||
<programlisting>ATZ
|
||||
AT&B2&W</programlisting>
|
||||
|
||||
<sect3>
|
||||
<title>Checking the Modem's Configuration</title>
|
||||
|
||||
<para>Most high-speed modems provide commands to view the
|
||||
modem's current operating parameters in a somewhat
|
||||
human-readable fashion. On the &usrobotics; &sportster;
|
||||
|
|
@ -1477,7 +1373,6 @@ AT&B2&W</programlisting>
|
|||
<para>For a different brand of modem, check the modem's manual
|
||||
to see how to double-check the modem's configuration
|
||||
parameters.</para>
|
||||
</sect3>
|
||||
</sect2>
|
||||
|
||||
<sect2>
|
||||
|
|
|
|||
Loading…
Reference in a new issue