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Old 02-14-2013, 11:21 AM   #1
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Registered: Feb 2013
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samba, iptables windows names resolving not working unless open all incoming udp

This is my iptables script:


/sbin/modprobe ip_conntrack_ftp

/sbin/iptables -F
/sbin/iptables -F -t nat
/sbin/iptables -F -t mangle

/sbin/iptables -t filter -A INPUT --in-interface eth0 -m conntrack --ctstate INVALID -j DROP
/sbin/iptables -t filter -A INPUT --in-interface eth0 -m conntrack --ctstate ESTABLISHED -j ACCEPT
/sbin/iptables -t filter -A INPUT --in-interface eth0 -m conntrack --ctstate RELATED -j ACCEPT

/sbin/iptables -t filter -A INPUT --in-interface eth0 -m conntrack --ctstate NEW -p tcp --dport 22 -j ACCEPT

/sbin/iptables -t filter -A INPUT --in-interface eth0 -m conntrack --ctstate NEW -p tcp --dport 139 -j ACCEPT
/sbin/iptables -t filter -A INPUT --in-interface eth0 -m conntrack --ctstate NEW -p tcp --dport 445 -j ACCEPT

/sbin/iptables -t filter -A INPUT -m udp -p udp --dport 137 -j ACCEPT
/sbin/iptables -t filter -A INPUT -m udp -p udp --dport 138 -j ACCEPT

/sbin/iptables -t filter -A INPUT --in-interface eth0 -m conntrack --ctstate NEW -p icmp -j ACCEPT

# --------> Without this line samba not resolving windows names: -------<<<<<<<
/sbin/iptables -t filter -A INPUT --in-interface eth0 -m conntrack --ctstate NEW -p udp -j ACCEPT

/sbin/iptables -t filter -A INPUT --in-interface eth0 -m conntrack --ctstate NEW -j DROP

/bin/echo 1 >/proc/sys/net/ipv4/ip_forward

/sbin/iptables -t nat -A POSTROUTING -s -o eth0 -j MASQUERADE

So I forced to open all incoming udp packets, otherwise netbios names resolving not working.
Old 02-15-2013, 03:54 AM   #2
Registered: Aug 2004
Location: Europe
Posts: 608

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I don't know much about netbios name resolution but I see at least 2 ways you could tacke this:

1. Is eth0 your public (e.g. internet) device? If it is, then why are you even using netbios over internet? If it is a private network, you could as well enable UDP on it.

2. You can track your packets using tcpdump, try to have a look at what ports/protocols are necessary and make specific rules allowing just the necessary ports. I don't believe it would be all random ports.


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