Setting up diald for Linux - an example

GNU Copyright by Harish Pillay 1996

The following is an example of a setup I have running on many machines that allow automatic installation of diald upon boot-up. When a connection request comes along, it automatically dials up my preferred ISP, Pacific Internet here in Singapore.

Many thanks to Eric Schenk for the super tool diald.


#! /bin/sh
# Put any local setup commands in here
# Running gpm
echo "Running gpm..."
gpm -t ms &

# starting innd

# starting CERN httpd
echo "Starting CERN httpd with proxy and caching."

# loading modules that are needed

# starting diald
echo "Starting diald daemon to Pacific Internet ..."
cd /usr/lib/ppp


/usr/sbin/diald /dev/ttyS1 /dev/ttyS1 lock debug 20 -m ppp local \
  remote defaultroute modem crtscts \ 
  connect "chat -v -f /usr/lib/ppp/pppchat.pi" \
  dynamic -- debug noipdefault  



Blind PPP script

My /etc/diald.conf file (unchanged from stock distribution):

# This is a pretty complicated set of filter rules.
# (These are the rules I use myself.)
# I've divided the rules up into four sections.
# TCP packets, UDP packets, ICMP packets and a general catch all rule
# at the end.
# Rules for TCP packets.
# General comments on the rule set:
# In general we would like to treat only data on a TCP link as signficant
# for timeouts. Therefore, we try to ignore packets with no data.
# Since the shortest possible set of headers in a TCP/IP packet is 40 bytes.
# Any packet with length 40 must have no data riding in it.
# We may miss some empty packets this way (optional routing information
# and other extras may be present in the IP header), but we should get
# most of them. Note that we don't want to filter out packets with
# clear, since we use them later to speedup disconnects
# on some TCP links.
# We also want to make sure WWW packets live even if the TCP socket
# is shut down. We do this because WWW doesn't keep connections open
# once the data has been transfered, and it would be annoying to have the link
# keep bouncing up and down every time you get a document.
# Outside of WWW the most common use of TCP is for long lived connections,
# that once they are gone mean we no longer need the network connection.
# We don't neccessarily want to wait 10 minutes for the connection
# to go down when we don't have any telnet's or rlogin's running,
# so we want to speed up the timeout on TCP connections that have
# shutdown. We do this by catching packets that do not have the live flag set.

# --- start of rule set proper ---

# When initiating a connection we only give the link 15 seconds initially.
# The idea here is to deal with possibility that the network on the opposite
# end of the connection is unreachable. In this case you don't really
# want to give the link 10 minutes up time. With the rule below
# we only give the link 15 seconds initially. If the network is reachable
# then we will normally get a response that actually contains some
# data within 15 seconds. If this causes problems because you have a slow
# response time at some site you want to regularly access, you can either
# increase the timeout or remove this rule.
accept tcp 15 tcp.syn

# Keep named xfers from holding the link up
ignore tcp tcp.dest=tcp.domain
ignore tcp tcp.source=tcp.domain

# (Ack! SCO telnet starts by sending empty SYNs and only opens the
# connection if it gets a response. Sheesh..)
accept tcp 5 ip.tot_len=40,tcp.syn

# keep empty packets from holding the link up (other than empty SYN packets)
ignore tcp ip.tot_len=40,

# make sure http transfers hold the link for 2 minutes, even after they end.
# NOTE: Your /etc/services may not define the tcp service www, in which
# case you should comment out the following two lines or get a more
# up to date /etc/services file. See the FAQ for information on obtaining
# a new /etc/services file.
accept tcp 120 tcp.dest=tcp.www
accept tcp 120 tcp.source=tcp.www

# Once the link is no longer live, we try to shut down the connection
# quickly. Note that if the link is already down, a state change
# will not bring it back up.
keepup tcp 5 !
ignore tcp !

# an ftp-data or ftp connection can be expected to show reasonably frequent
# traffic.
accept tcp 120 tcp.dest=tcp.ftp
accept tcp 120 tcp.source=tcp.ftp

#NOTE: ftp-data is not defined in the /etc/services file provided with
# the latest versions of NETKIT, so I've got this commented out here.
# If you want to define it add the following line to your /etc/services:
# ftp-data        20/tcp
# and uncomment the following two rules.
#accept tcp 120 tcp.dest=tcp.ftp-data
#accept tcp 120 tcp.source=tcp.ftp-data

# If we don't catch it above, give the link 10 minutes up time.
accept tcp 600 any

# Rules for UDP packets
# We time out domain requests right away, we just want them to bring
# the link up, not keep it around for very long.
# This is because the network will usually come up on a call
# from the resolver library (unless you have all your commonly
# used addresses in /etc/hosts, in which case you will discover
# other problems.)
# Note that you should not make the timeout shorter than the time you
# might expect your DNS server to take to respond. Otherwise
# when the initial link gets established there might be a delay
# greater than this between the initial series of packets before
# any packets that keep the link up longer pass over the link.

# Don't bring the link up for rwho.
ignore udp udp.dest=udp.who
ignore udp udp.source=udp.who
# Don't bring the link up for RIP.
ignore udp udp.dest=udp.route
ignore udp udp.source=udp.route
# Don't bring the link up for NTP or timed.
ignore udp udp.dest=udp.ntp
ignore udp udp.source=udp.ntp
ignore udp udp.dest=udp.timed
ignore udp udp.source=udp.timed
# Don't bring up on domain name requests between two running nameds.
ignore udp udp.dest=udp.domain,udp.source=udp.domain
# Bring up the network whenever we make a domain request from someplace
# other than named.
accept udp 30 udp.dest=udp.domain 
accept udp 30 udp.source=udp.domain
# Do the same for netbios-ns broadcasts
# NOTE: your /etc/services file may not define the netbios-ns service
# in which case you should comment out the next three lines.
ignore udp udp.source=udp.netbios-ns,udp.dest=udp.netbios-ns
accept udp 30 udp.dest=udp.netbios-ns
accept udp 30 udp.source=udp.netbios-ns
# keep routed and gated transfers from holding the link up
ignore udp tcp.dest=udp.route
ignore udp tcp.source=udp.route
# Anything else gest 2 minutes.
accept udp 120 any

# Catch any packets that we didn't catch above and give the connection
# 30 seconds of live time.
accept any 30 any

My diald.defs file (unchanged from stock distribution):

# Define default protocol rules
prule tcp tcp 9:12:13:14:15:16:17:18:19:+0:+1:+2:+3:9:9:9
prule udp udp 9:12:13:14:15:16:17:18:19:+0:+1:+2:+3:9:9:9
prule icmp icmp 9:12:13:14:15:16:17:18:19:9:9:9:9:9:9:9
prule any any 9:12:13:14:15:16:17:18:19:9:9:9:9:9:9:9
# Define the internet packet header fields.
var ip.ihl 0(24)&0xf
var ip.version 0(28)&0xf
var ip.tos 1(24)&0xff
var ip.tot_len 2(16)&0xffff
var 4(16)&0xffff
var ip.frag_off 6(16)&0x3fff
var ip.ttl 8(24)&0xff
var ip.protocol 9(24)&0xff
var ip.check 10(16)&0xffff
var ip.saddr 12
var ip.daddr 16
# Define the TCP packet header fields.
var tcp.source +0(16)&0xffff
var tcp.dest +2(16)&0xffff
var tcp.seq +4
var tcp.ack_seq +8
var tcp.doff +12(28)&0xf
var tcp.fin +13(24)&0x1
var tcp.syn +13(25)&0x1
var tcp.rst +13(26)&0x1
var tcp.psh +13(27)&0x1
var tcp.ack +13(28)&0x1
var tcp.urg +13(29)&0x1
var +127
# Define the UDP packet header fields.
var udp.source +0(16)&0xffff
var udp.dest +2(16)&0xffff
var udp.len +4(16)&0xffff
var udp.check +6(16)&0xffff
# Define the ICMP packet header fields.
var icmp.type +0(24)&0xff
var icmp.code +1(24)&0xff
var icmp.checksum +2(16)&0xffff
var +4(16)&0xffff
var icmp.echo.sequence +6(16)&0xffff
var icmp.gateway +4

My setup


Questions? Email Harish Pillay ->
Go back to the Harish's Home Page
Last updated June 3rd 1996

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