Generic HDLC layer¶
Krzysztof Halasa <email@example.com>
Generic HDLC layer currently supports:
Frame Relay (ANSI, CCITT, Cisco and no LMI)
Normal (routed) and Ethernet-bridged (Ethernet device emulation) interfaces can share a single PVC.
ARP support (no InARP support in the kernel - there is an experimental InARP user-space daemon available on: http://www.kernel.org/pub/linux/utils/net/hdlc/).
raw HDLC - either IP (IPv4) interface or Ethernet device emulation
X.25 (uses X.25 routines).
Generic HDLC is a protocol driver only - it needs a low-level driver for your particular hardware.
Ethernet device emulation (using HDLC or Frame-Relay PVC) is compatible with IEEE 802.1Q (VLANs) and 802.1D (Ethernet bridging).
Make sure the hdlc.o and the hardware driver are loaded. It should create a number of “hdlc” (hdlc0 etc) network devices, one for each WAN port. You’ll need the “sethdlc” utility, get it from:
Compile sethdlc.c utility:
gcc -O2 -Wall -o sethdlc sethdlc.c
Make sure you’re using a correct version of sethdlc for your kernel.
Use sethdlc to set physical interface, clock rate, HDLC mode used, and add any required PVCs if using Frame Relay. Usually you want something like:
sethdlc hdlc0 clock int rate 128000 sethdlc hdlc0 cisco interval 10 timeout 25
sethdlc hdlc0 rs232 clock ext sethdlc hdlc0 fr lmi ansi sethdlc hdlc0 create 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 pvc devices.
- v35 | rs232 | x21 | t1 | e1
sets physical interface for a given port if the card has software-selectable interfaces
activate hardware loopback (for testing only)
- clock ext
both RX clock and TX clock external
- clock int
both RX clock and TX clock internal
- clock txint
RX clock external, TX clock internal
- clock txfromrx
RX clock external, TX clock derived from RX clock
sets clock rate in bps (for “int” or “txint” clock only)
hdlc - sets raw HDLC (IP-only) mode
nrz / nrzi / fm-mark / fm-space / manchester - sets transmission code
no-parity / crc16 / crc16-pr0 (CRC16 with preset zeros) / crc32-itu
crc16-itu (CRC16 with ITU-T polynomial) / crc16-itu-pr0 - sets parity
hdlc-eth - Ethernet device emulation using HDLC. Parity and encoding as above.
cisco - sets Cisco HDLC mode (IP, IPv6 and IPX supported)
interval - time in seconds between keepalive packets
- timeout - time in seconds after last received keepalive packet before
we assume the link is down
ppp - sets synchronous PPP mode
x25 - sets X.25 mode
fr - Frame Relay mode
lmi ansi / ccitt / cisco / none - LMI (link management) type
dce - Frame Relay DCE (network) side LMI instead of default DTE (user).
It has nothing to do with clocks!
t391 - link integrity verification polling timer (in seconds) - user
t392 - polling verification timer (in seconds) - network
n391 - full status polling counter - user
n392 - error threshold - both user and network
n393 - monitored events count - both user and network
create n | delete n - adds / deletes PVC interface with DLCI #n. Newly created interface will be named pvc0, pvc1 etc.
create ether n | delete ether n - adds a device for Ethernet-bridged frames. The device will be named pvceth0, pvceth1 etc.
n2.o and c101.o need parameters to work:
insmod n2 hw=io,irq,ram,ports[:io,irq,...]
insmod n2 hw=0x300,10,0xD0000,01
insmod c101 hw=irq,ram[:irq,...]
insmod c101 hw=9,0xdc000
If built into the kernel, these drivers need kernel (command line) parameters:
If you have a problem with N2, C101 or PLX200SYN card, you can issue the “private” command to see port’s packet descriptor rings (in kernel logs):
sethdlc hdlc0 private
The hardware driver has to be build with #define DEBUG_RINGS. Attaching this info to bug reports would be helpful. Anyway, let me know if you have problems using this.
For patches and other info look at: <http://www.kernel.org/pub/linux/utils/net/hdlc/>.