Run a web server inside LAN

Run a web server inside LAN is a simple script to run a WWW server inside a Local Area Network. Run a web server inside LAN script assume all iptables features are compiled statically in the kernel, or all modules are loaded.

Otherwise you may encounter some surprises trying to utilize the more featureful and creative commandlines that I've come up with.

Sample:

#external and internal interfaces
EXT=eth0
INT=eth1

# clear everything, and create my cascading chains
iptables -F
iptables -N e0
iptables -N tcpin
iptables -N udpin

# e0 is the name of our chain for eth0
iptables -I INPUT -i $EXT -j e0

# OUTPUT Chain
iptables -A OUTPUT -o $EXT -j DROP -p icmp --icmp-type ! echo-request

# remote gnutella queries were really pissing me off one day
# iptables -A OUTPUT -o $EXT -j DROP -p tcp ! --syn --dport 6346
# iptables -A OUTPUT -o $EXT -j DROP -p tcp ! --syn --sport 6346

# $EXT Chain
# a single rule to accept SYN Packets for multiple ports (up to 15)
iptables -A tcpin -j ACCEPT -p tcp --syn -m multiport --destination-ports 873,993,995,143,80,113,21,22,23,25,53

# stateful connection tracking is wonderful stuff
# ESTABLISHED tcp connections are let through
# If we send a SYN out, the ACK is seen as RELATED
# then further communication is accepted by the ESTABLISHED rule
iptables -A e0 -j ACCEPT -m state --state ESTABLISHED
iptables -A e0 -j ACCEPT -m state --state RELATED

# certain ports I simply DROP
iptables -A tcpin -j DROP -p tcp --syn -m multiport --destination-ports 6346,139

# UDP rules...
iptables -A udpin -j DROP -p udp -m multiport --destination-ports 137,27960

# I run a DNS server, so we must accept UDP packets on port 53
iptables -A udpin -j ACCEPT -p udp -m state --state NEW --destination-port 53

# let's log NEW udp packets on ports 1024:65535, then let them through
iptables -A udpin -j LOG -p udp -m state --state NEW --destination-port 1024:65535 --log-level debug --log-prefix UDPNEW --log-ip-options
iptables -A udpin -j ACCEPT -p udp -m state --state NEW --destination-port 1024:65535

# let's log NEW tcp packets on ports 1024:65535, then let them through
iptables -A tcpin -j LOG -p tcp --syn --destination-port 1024:65535 --log-level debug --log-prefix TCPNEW --log-tcp-options --log-ip-options
iptables -A tcpin -j ACCEPT -p tcp --syn --destination-port 1024:65535

# let's log INVALID or NEW tcp packets on priveleged ports, then DROP
# (remember I have certain ACCEPT rules higher up the chain)
iptables -A tcpin -j LOG -p tcp -m state --state INVALID,NEW --destination-port 1:1023 --log-level warn --log-prefix TCPPRIV --log-tcp-options --log-ip-options
iptables -A tcpin -j DROP -p tcp -m state --state INVALID,NEW --destination-port 1:1023

iptables -A e0 -p tcp -j tcpin
iptables -A e0 -p udp -j udpin
iptables -A e0 -j LOG --log-level debug --log-prefix NETFILTER --log-ip-options -m state --state INVALID,NEW
iptables -A e0 -j DROP

# NAT Rules
# I run a web server inside...
iptables -t nat -A PREROUTING -p tcp -i eth0 --dport 80 -j DNAT --to-destination 192.168.1.4:80

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