Generic HDLC layer for Linux

General HDLC layer for Linux is an interface between low-level hardware drivers for synchronous serial (HDLC) cards and the rest of kernel networking. The following protocols are supported:

raw HDLC - IP protocol only and Ethernet device emulation
Cisco HDLC (HDLC encapsulation used by Cisco® routers) - IP, IPv6 and IPX protocols
Point-to-Point Protocol (PPP) - IP and probably IPX protocols (uses syncppp.c module)
X.25 (using standard X.25 stack)
Frame Relay (using ANSI, CCITT, Cisco or no LMI) - IP, IPv6 and IPX protocols - both DTE (normal) and DCE (FR switch side) modes are supported. Ethernet-bridged interface mode is available as well.

Generic HDLC layer is included in the official Linux kernel.

Ethernet framing using HDLC or FR PVC is compatible with 802.1Q VLAN and 802.1D Ethernet bridging.

A list of supported cards is here.

Linux kernel support by version is here.

Short info about using the drivers and sethdlc utility is here.

An experimental Inverse ARP daemon program is here. You may need it if your Frame-Relay IP provider requires you to use InARP.

A small utility for testing synchronous serial cards is here.

Synchronous HDLC cards supported via generic HDLC layer

Currently, low-level drivers for the following devices use the generic HDLC layer:

MultiLink router manufactured by Goramo
Dedicated device using Intel IXP425 CPU, running Linux 2.6, max clock rate on V.35 interfaces - 8 Mb/s.
PCI200SYN cards manufactured by Goramo
PCI bus, Hitachi/Renesas HD64572 SCA-II chip, max clock rate 10 Mb/s or more.
PC300 cards manufactured by Cyclades Corp.
PCI bus, Hitachi/Renesas HD64572 SCA-II chip, max clock rate ca. 5 Mb/s (electrical limits of line driver chips).
wanXL cards manufactured by SBE Inc.
PCI bus, Motorola 68EN360 QUICC processor, max clock rate 2 Mb/s.
RISCom/N2 cards manufactured by SDL Communications, Inc.
ISA bus, 1 or 2 ports, Hitachi HD64570 SCA chip, max clock rate ca. 7 Mb/s.
C101 (ISA) cards manufactured by Moxa Technologies Co., Ltd.
ISA bus, Hitachi HD64570 SCA chip, using 8-bit shared ISA memory, max clock rate ca. 7 Mb/s.
Set the jumper on your C101 card to "IN" position if you're using external RX/TX clock source (the most common case), and to "OUT" position otherwise.
FarSync T-Series cards manufactured by FarSite Communications Ltd. (driver written by R. J. Dunlop)
Etinc PCISYNC cards using DSCC4 controller (driver written by Francois Romieu)

Other cards may be supported by drivers available from card manufacturers.

Linux kernel support by version

Linux 2.6

All listed cards are supported.
SBE wanXL cards are supported with an experimental driver - tested with wanXL-400, it should work with wanXL-200 as well, and probably requires minor tweaking for wanXL-100. Firmware for this driver is included within the kernel.
No patches are needed.

Sethdlc utility for 2.4/2.6 kernels can be found here.

Linux 2.4

All listed cards are supported except wanXL. If you have a PC300RSV or PC300X21 card you can choose between a driver written by Cyclades Corp or one written by me.

If you wish to use C101, N2 and/or PCI200SYN card(s), and/or PC300RSV/X21 with my driver, consult the following list and patch your kernel to use 1.14a or later version of the generic HDLC layer. If you have other card(s) please check the documentation provided by the manufacturer or the driver's author.

Linux 2.4.20 and older 2.4 kernels contain version 1.02 of generic HDLC layer.
Apply this patch to your kernel tree first. For PCI200SYN and/or PC300RSV/X21 drivers apply this patch as well. Rebuild your kernel even if the HDLC layer and/or hardware drivers are configured as modules.
If you really have to use the old 1.02 code, grab the old sethdlc utility from here.
Linux 2.4.21 and 2.4.22 kernels contain version 1.11 of generic HDLC layer.
Apply this patch to your kernel tree first. For PCI200SYN and/or PC300RSV/X21 drivers apply this patch as well.
Linux 2.4.21-ac and 2.4.22-ac kernels (and some distributions, including Red Hat 9 Linux) contain version 1.12 of generic HDLC layer.
Apply this patch to your kernel tree first. For PCI200SYN and/or PC300RSV/X21 drivers apply this patch as well.
Linux 2.4.23 and 2.4.24 kernels contain version 1.14a of generic HDLC layer. For PCI200SYN and/or PC300RSV/X21 drivers apply this patch.
Linux 2.4.25 and later 2.4 kernels contain version 1.14b (a cosmetic update to version 1.14a) of the generic HDLC layer. PCI200SYN driver is now included in the official kernel tree.
For PC300RSV/X21 driver apply this patch.

Sethdlc utility for 2.4/2.6 kernels can be found here.
Note that it's an code no longer actively maintained by me - just use Linux 2.6.

Linux 2.2

Later Linux 2.2 kernels contain hardware drivers for C101, N2 and wanXL cards. This is really old code no longer actively maintained by me.

Sethdlc utility for Linux 2.2 can be found here.

If you have a wanXL card, you will need a firmware file (available from SBE Inc). After the wanxl.o driver module is loaded, verify that one hdlc0 device (per card) has been created, and then load the firmware using:

	sethdlc hdlc0 run /path/to/sbew400.pdm

It should create hdlcX devices for the remaining ports (in case of 2- or 4-port card).

Click here to see file directory containing files related to generic HDLC.

Using the drivers and sethdlc utility

Apply the patches if required, configure your kernel and build the driver modules. Load the modules using either insmod/modprobe programs or through /etc/modules.conf (or /etc/modprobe.conf) file. At least hdlc module and the hardware driver for your card should be loaded. Once the driver is loaded, verify that the network device(s) are created (issue "ifconfig -a" or "ip link" command and look for devices named hdlc0, hdlc1 etc.)

Get, unpack and compile the sethdlc utility. Remember to get a correct version for your kernel. If your kernel source is not in /usr/src/linux, please change the kernel include path in Makefile or use -I option to gcc. If you get "Generic HDLC layer version mismatch" error while compiling sethdlc then either your compiler is using wrong kernel headers (probably from some glibc-kernheaders package) or you haven't patched your kernel tree correctly.

As the drivers don't probe for ISA cards, you have to specify IRQ setting, RAM window address and (in case of RISCom/N2) hardware I/O port number used by the card. Use something like:

	insmod n2 hw=io,irq,ram,ports[:io,irq,...]

example:

	insmod n2 hw=0x300,10,0xD0000,01

("01" means that both ports 0 and 1 should be enabled - there is no way to detect the number of ports on RISCom/N2 card)

In case of C101 you need:

	insmod c101 hw=irq,ram[:irq,ram...]

example:

	insmod c101 hw=9,0xDC000

If you have a driver built into the kernel, pass the equivalent "n2.hw=io,irq,ram,ports:..." or "c101.hw=irq,ram:..." parameter while booting your kernel.

With Linux kernel 2.2 and 2.4 you need double quotes - use something like:

	insmod n2 '"hw=io,irq,ram,ports[:io,irq,...]"'

or, if the driver is built into the kernel, pass an equivalent "n2=io,irq,ram:..." (no "hw.") or similar parameter while booting.

Having verified that hdlcX network devices are created, you may now set the physical interface parameters and the requested protocol. Use sethdlc to set physical interface, clock rate, HDLC mode used, and add any required PVCs if using Frame Relay. Usually you need something like:

Cisco HDLC, V.35 interface and internal 128000 bps clock:

	sethdlc hdlc0 v35 clock int rate 128000
	sethdlc hdlc0 cisco interval 10 timeout 25
	ifconfig hdlc0 localIP pointopoint remoteIP

RS232/V.24 synchronous interface with external clock and Ethernet over HDLC framing:

	sethdlc hdlc0 rs232 clock ext
	sethdlc hdlc0 hdlc-eth
	ifconfig hdlc0 localIP netmask ... broadcast ...

Default physical interface with external clock and Frame-Relay with ANSI LMI:
```
	sethdlc hdlc0 clock ext
	sethdlc hdlc0 fr lmi ansi
	sethdlc hdlc0 create 99		# creates PVC with DLCI = 99
	ifconfig hdlc0 up
	ifconfig pvc0 localIP pointopoint remoteIP
```
In Frame Relay mode, "ifconfig" master hdlc device "up" (without assigning any IP address to it) before using any pvc devices.

The following command displays current settings of a given device:

	sethdlc hdlc0

	sethdlc pvc0