Contributed by &a.ghelmer;. This document provides suggestions for configuring a FreeBSD system to handle dialup modems. This document is written based on the author's experience with FreeBSD versions 1.0, 1.1, and 1.1.5.1 (and experience with dialup modems on other UNIX-like operating systems); however, this document may not answer all of your questions or provide examples specific enough to your environment. The author cannot be responsible if you damage your system or lose data due to attempting to follow the suggestions here. Prerequisites

To begin with, the author assumes you have some basic knowledge of FreeBSD. You need to have FreeBSD installed, know how to edit files in a UNIX-like environment, and how to look up manual pages on the system. As discussed below, you will need certain versions of FreeBSD, and knowledge of some terminology & modem and cabling. FreeBSD Version

First, it is assumed that you are using FreeBSD version 1.1 or higher (including versions 2.x). FreeBSD version 1.0 included two different serial drivers, which complicates the situation. Also, the serial device driver (Terminology

A quick rundown of terminology: If you need more information about these terms and data communications in general, the author remembers reading that External vs. Internal Modems

External modems seem to be more convenient for dialup, because external modems often can be semi-permanently configured via parameters stored in non-volatile RAM and they usually provide lighted indicators that display the state of important RS-232 signals. Blinking lights impress visitors, but lights are also very useful to see whether a modem is operating properly. Internal modems usually lack non-volatile RAM, so their configuration may be limited only to setting DIP switches. If your internal modem has any signal indicator lights, it is probably difficult to view the lights when the system's cover is in place. Modems and Cables

A background knowledge of these items is assumed You know how to connect your modem to your computer so that the two can communicate (unless you have an internal modem, which does not need such a cable) You are familiar with your modem's command set, or know where to look up needed commands You know how to configure your modem (probably via a terminal communications program) so you can set the non-volatile RAM parameters The first, connecting your modem, is usually simple - most straight-through serial cables work without any problems. You need to have a cable with appropriate connectors (DB-25 or DB-9, male or female) on each end, and the cable must be a DCE-to-DTE cable with these signals wired: Transmitted Data ( Received Data ( Request to Send ( Clear to Send ( Data Set Ready ( Data Terminal Ready ( Carrier Detect ( Signal Ground ( FreeBSD needs the Serial Interface Considerations

FreeBSD supports NS8250-, NS16450-, NS16550-, and NS16550A-based EIA RS-232C (CCITT V.24) communications interfaces. The 8250 and 16450 devices have single-character buffers. The 16550 device provides a 16-character buffer, which allows for better system performance. (Bugs in plain 16550's prevent the use of the 16-character buffer, so use 16550A's if possible). Because single-character-buffer devices require more work by the operating system than the 16-character-buffer devices, 16550A-based serial interface cards are much prefered. If the system has many active serial ports or will have a heavy load, 16550A-based cards are better for low-error-rate communications. Quick Overview

Here is the process that FreeBSD follows to accept dialup logins. A /dev/ttyd0, for our example). The command 4850 ?? I 0:00.09 /usr/libexec/getty V19200 ttyd0 When a user dials the modem's line and the modems connect, the /usr/bin/login, which completes the login by asking for the user's password and then starting the user's shell. Let's dive into the configuration... Kernel Configuration

FreeBSD kernels typically come prepared to search for four serial ports, known in the PC-DOS world as /sbin/dmesg command to replay the kernel's boot messages. In particular, look for messages that start with the characters /sbin/dmesg | grep 'sio' For example, on a system with four serial ports, these are the serial-port specific kernel boot messages: sio0 at 0x3f8-0x3ff irq 4 on isa sio0: type 16550A sio1 at 0x2f8-0x2ff irq 3 on isa sio1: type 16550A sio2 at 0x3e8-0x3ef irq 5 on isa sio2: type 16550A sio3 at 0x2e8-0x2ef irq 9 on isa sio3: type 16550A If your kernel does not recognize all of your serial ports, you will probably need to configure a custom FreeBSD kernel for your system. Please see the BSD System Manager's Manual chapter on ``Building Berkeley Kernels with Config'' [the source for which is in /usr/src/share/doc/smm] and ``FreeBSD Configuration Options'' [in /sys/conf/options and in /sys/arch/conf/options.arch, with arch for example being i386] for more information on configuring and building kernels. You may have to unpack the kernel source distribution if have not installed the system sources already (srcdist/srcsys.?? in FreeBSD 1.1, srcdist/sys.?? in FreeBSD 1.1.5.1, or the entire source distribution in FreeBSD 2.0) to be able to configure and build kernels. Create a kernel configuration file for your system (if you have not already) by /sys/i386/conf. Then, if you are creating a new custom configuration file, copy the file GENERICAH (or GENERICBT, if you have a BusTek SCSI controller on FreeBSD 1.x) to device sio0 at isa? port "IO_COM1" tty irq 4 vector siointr device sio1 at isa? port "IO_COM2" tty irq 3 vector siointr device sio2 at isa? port "IO_COM3" tty irq 5 vector siointr device sio3 at isa? port "IO_COM4" tty irq 9 vector siointr You can comment-out or completely remove lines for devices you do not have. If you have a multiport serial board, such as the Boca Board BB2016, please see the cannot share interrupts on ISA-bus PCs (multiport boards have on-board electronics that allow all the 16550A's on the board to share one or two interrupt request lines). When you are finished adjusting the kernel configuration file, use the program Device Special Files

Most devices in the kernel are accessed through ``device special files'', which are located in the /dev directory. The /dev/ttyd? (dial-in) and /dev/cua0? (call-out) devices. On FreeBSD version 1.1.5 and higher, there are also initialization devices (/dev/ttyid? and /dev/cuai0?) and locking devices (/dev/ttyld? and /dev/cual0?). The initialization devices are used to initialize communications port parameters each time a port is opened, such as crtscts for modems which use CTS/RTS signaling for flow control. The locking devices are used to lock flags on ports to prevent users or programs changing certain parameters; see the manual pages Making Device Special Files

A shell script called /dev directory manages the device special files. (The manual page for /dev and issue the command /dev/ttyd? device special files, but also creates the /dev/cua0? (and all of the initializing and locking special files under FreeBSD 1.1.5 and up) and removes the hardwired terminal special file /dev/tty0?, if it exists. After making new device special files, be sure to check the permissions on the files (especially the /dev/cua* files) to make sure that only users who should have access to those device special files can read & write on them - you probably do not want to allow your average user to use your modems to dialout. The default permissions on the /dev/cua* files should be sufficient: crw-rw---- 1 uucp dialer 28, 129 Feb 15 14:38 /dev/cua01 crw-rw---- 1 uucp dialer 28, 161 Feb 15 14:38 /dev/cuai01 crw-rw---- 1 uucp dialer 28, 193 Feb 15 14:38 /dev/cual01 These permissions allow the user Configuration Files

There are three system configuration files in the /etc directory that you will probably need to edit to allow dialup access to your FreeBSD system. The first, /etc/gettytab, contains configuration information for the /usr/libexec/getty daemon. Second, /etc/ttys holds information that tells /sbin/init what /etc/rc.serial script if you have FreeBSD 1.1.5.1 or higher; otherwise, you can initialize ports in the /etc/rc.local script. There are two schools of thought regarding dialup modems on UNIX. One group likes to configure their modems and system so that no matter at what speed a remote user dials in, the local computer-to-modem RS-232 interface runs at a locked speed. The benefit of this configuration is that the remote user always sees a system login prompt immediately. The downside is that the system does not know what a user's true data rate is, so full-screen programs like Emacs will not adjust their screen-painting methods to make their response better for slower connections. The other school configures their modems' RS-232 interface to vary its speed based on the remote user's connection speed. For example, V.32bis (14.4 Kbps) connections to the modem might make the modem run its RS-232 interface at 19.2 Kbps, while 2400 bps connections make the modem's RS-232 interface run at 2400 bps. Because <Enter> key until they see a recognizable prompt. If the data rates do not match, /etc/gettytab

/etc/gettytab is a Locked-Speed Config

If you are locking your modem's data communications rate at a particular speed, you probably will not need to make any changes to /etc/gettytab. Matching-Speed Config

You will need to setup an entry in /etc/gettytab to give # # Fast dialup terminals, 2400/1200/300 rotary (can start either way) # D2400|d2400|Fast-Dial-2400:\ :nx=D1200:tc=2400-baud: 3|D1200|Fast-Dial-1200:\ :nx=D300:tc=1200-baud: 5|D300|Fast-Dial-300:\ :nx=D2400:tc=300-baud: If you have a higher speed modem, you will probably need to add an entry in /etc/gettytab; here is an entry you could use for a 14.4 Kbps modem with a top interface speed of 19.2 Kbps: # # Additions for a V.32bis Modem # um|V300|High Speed Modem at 300,8-bit:\ :nx=V19200:tc=std.300: un|V1200|High Speed Modem at 1200,8-bit:\ :nx=V300:tc=std.1200: uo|V2400|High Speed Modem at 2400,8-bit:\ :nx=V1200:tc=std.2400: up|V9600|High Speed Modem at 9600,8-bit:\ :nx=V2400:tc=std.9600: uq|V19200|High Speed Modem at 19200,8-bit:\ :nx=V9600:tc=std.19200: On FreeBSD 1.1.5 and later, this will result in 8-bit, no parity connections. Under FreeBSD 1.1, add std. entries at the top of the file for 8 bits, no parity; otherwise, the default is 7 bits, even parity. The example above starts the communications rate at 19.2 Kbps (for a V.32bis connection), then cycles through 9600 bps (for V.32), 2400 bps, 1200 bps, 300 bps, and back to 19.2 Kbps. Communications rate cycling is implemented with the # # Additions for a V.32bis or V.34 Modem # Starting at 57.6 Kbps # vm|VH300|Very High Speed Modem at 300,8-bit:\ :nx=VH57600:tc=std.300: vn|VH1200|Very High Speed Modem at 1200,8-bit:\ :nx=VH300:tc=std.1200: vo|VH2400|Very High Speed Modem at 2400,8-bit:\ :nx=VH1200:tc=std.2400: vp|VH9600|Very High Speed Modem at 9600,8-bit:\ :nx=VH2400:tc=std.9600: vq|VH57600|Very High Speed Modem at 57600,8-bit:\ :nx=VH9600:tc=std.57600: If you have a slow CPU or a heavily loaded system and you do not have 16550A-based serial ports, you may receive sio ``silo'' errors at 57.6 Kbps. /etc/ttys

/etc/ttys is the list of /etc/ttys also provides security information to /etc/ttys or add new lines to make ttyd0 "/usr/libexec/getty xxx" dialup on The first item in the above line is the device special file for this entry - /dev/ttyd0 is the file that this "/usr/libexec/getty (secure, but it should only be used for terminals which are physically secure (such as the system console). The default terminal type (/etc/ttys, you may send the kill -1 1 to send the signal. If this is your first time setting up the system, though, you may want to wait until your modem(s) are properly configured and connected before signaling Locked-Speed Config

For a locked-speed configuration, your ttyd0 "/usr/libexec/getty std.19200" dialup on If your modem is locked at a different data rate, substitute the appropriate name for the std. entry for /etc/gettytab for your modem's data rate. Matching-Speed Config

In a matching-speed configuration, your /etc/gettytab. For example, if you added the above suggested entry for a matching-speed modem that starts at 19.2 Kbps (the ttyd0 "/usr/libexec/getty V19200" dialup on /etc/rc.serial or /etc/rc.local

High-speed modems, like V.32, V.32bis, and V.34 modems, need to use hardware (RTS/CTS) flow control. You can add /etc/rc.serial on FreeBSD 1.1.5.1 and up, or /etc/rc.local on FreeBSD 1.1, to set the hardware flow control flag in the FreeBSD kernel for the modem ports. For example, on a sample FreeBSD 1.1.5.1 system, /etc/rc.serial reads: #!/bin/sh # # Serial port initial configuration stty -f /dev/ttyid1 crtscts stty -f /dev/cuai01 crtscts which sets the # Set serial ports to use RTS/CTS flow control stty -f /dev/ttyd0 crtscts stty -f /dev/ttyd1 crtscts stty -f /dev/ttyd2 crtscts stty -f /dev/ttyd3 crtscts Since there is no initialization device special file on FreeBSD 1.1, one has to just set the flags on the sole device special file and hope the flags are not cleared by a miscreant. Modem Settings

If you have a modem whose parameters may be permanently set in non-volatile RAM, you will need to use a terminal program (such as Telix under PC-DOS or Disable XON/XOFF flow control Quiet mode (no result codes) No command echo Please read the documentation for your modem to find out what commands and/or DIP switch settings you need to give it. For example, to set the above parameters on a USRobotics Sportster 14,400 external modem, one could give these commands to the modem: ATZ AT&C1&D2&H1&I0&R2&W You might also want to take this opportunity to adjust other settings in the modem, such as whether it will use V.42bis and/or MNP5 compression. The USR Sportster 14,400 external modem also has some DIP switches that need to be set; for other modems, perhaps you can use these settings as an example: Switch 1: UP - DTR Normal Switch 2: Do not care (Verbal Result Codes/Numeric Result Codes) Switch 3: UP - Suppress Result Codes Switch 4: DOWN - No echo, offline commands Switch 5: UP - Auto Answer Switch 6: UP - Carrier Detect Normal Switch 7: UP - Load NVRAM Defaults Switch 8: Do not care (Smart Mode/Dumb Mode) Result codes should be disabled/suppressed for dialup modems to avoid problems that can occur if Locked-speed Config

For a locked-speed configuration, you will need to configure the modem to maintain a constant modem-to-computer data rate independent of the communications rate. On a USR Sportster 14,400 external modem, these commands will lock the modem-to-computer data rate at the speed used to issue the commands: ATZ AT&B1&W Matching-speed Config

For a variable-speed configuration, you will need to configure your modem to adjust its serial port data rate to match the incoming call rate. On a USR Sportster 14,400 external modem, these commands will lock the modem's error-corrected data rate to the speed used to issue the commands, but allow the serial port rate to vary for non-error-corrected connections: ATZ AT&B2&W Checking the Modem's Configuration

Most high-speed modems provide commands to view the modem's current operating parameters in a somewhat human-readable fashion. On the USR Sportster 14,400 external modems, the command Troubleshooting

Here are a few steps you can follow to check out the dialup modem on your system. Checking out the FreeBSD system

Hook up your modem to your FreeBSD system, boot the system, and, if your modem has status indication lights, watch to see whether the modem's 114 ?? I 0:00.10 /usr/libexec/getty V19200 ttyd0 115 ?? I 0:00.10 /usr/libexec/getty V19200 ttyd1 If you see something different, like this: 114 d0 I 0:00.10 /usr/libexec/getty V19200 ttyd0 ^^ and the modem has not accepted a call yet, this means that /etc/ttys to see if there are any mistakes there. Also, check the log file /var/log/messages to see if there are any log messages from /etc/ttys and /etc/gettytab, as well as the appropriate device special files /dev/ttyd?, for any mistakes, missing entries, or missing device special files. Try Dialing In

Try dialing into the system; be sure to use 8 bits, no parity, 1 stop bit on the remote system. If you do not get a prompt right away, or get garbage, try pressing <Enter> about once per second. If you still do not see a BREAK. If you are using a high-speed modem to do the dialing, try dialing again after locking the dialing modem's interface speed (via AT&B1 on a USR Sportster, for example). If you still cannot get a /etc/gettytab again and double-check that The initial capability name specified in /etc/ttys for the line matches a name of a capability in /etc/gettytab Each Each If you dial but the modem on the FreeBSD system will not answer, make sure that the modem is configured to answer the phone when Acknowledgments

Thanks to these people for comments and advice: &a.kelly for a number of good suggestions