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# These rules are intended for use with an dynamic IP address.
# These rules never bring up a link for a TCP connection, only for
# UDP connections and ICMP packets. This prevents the "hang" of the
# first connection, but if you don't have things configured correctly,
# then diald may never dial out.
#------------------------------------------------------------------------------
# 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
# tcp.live 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.
keepup tcp 15 tcp.syn
# Keep named xfers from holding the link up
ignore tcp tcp.dest=tcp.domain
ignore tcp tcp.source=tcp.domain
# Keep netbios from holding us up as well.
ignore tcp tcp.source=tcp.netbios-ns,tcp.dest=tcp.netbios-ns
# (Ack! SCO telnet starts by sending empty SYNs and only opens the
# connection if it gets a response. Sheesh..)
keepup 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,tcp.live
# 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.
keepup tcp 120 tcp.dest=tcp.www
keepup tcp 120 tcp.source=tcp.www
# SSL connections are usually for secure http so treat them like http.
# NOTE: Your /etc/services may not define the tcp service https, 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.
keepup tcp 120 tcp.dest=tcp.https
keepup tcp 120 tcp.source=tcp.https
# 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 !tcp.live
ignore tcp !tcp.live
# an ftp-data or ftp connection can be expected to show reasonably frequent
# traffic.
keepup tcp 120 tcp.dest=tcp.ftp
keepup 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.
#keepup tcp 120 tcp.dest=tcp.ftp-data
#keepup tcp 120 tcp.source=tcp.ftp-data
# If we don't catch it above, give the link 10 minutes up time.
keepup 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
# Ignore some background protocols.
ignore igmp any
ignore ospfigp any
# Catch any packets that we didn't catch above and give the connection
# 30 seconds of live time.
accept any 30 any
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