Iptables - general

On ubuntu - https://www.howtoforge.com/nat_iptables

Allow incoming ports :
iptables -A INPUT -p tcp -m tcp --dport 80 -j ACCEPT
iptables -A INPUT -p tcp -m tcp --dport 443 -j ACCEPT

Incoming ports for samba :

netbios-ns – 137/tcp # NETBIOS Name Service
netbios-dgm – 138/tcp # NETBIOS Datagram Service
netbios-ssn – 139/tcp # NETBIOS session service
microsoft-ds – 445/tcp # if you are using Active Directory
 
iptables -A INPUT -p tcp -m tcp --dport 137 -j ACCEPT
iptables -A INPUT -p tcp -m tcp --dport 138 -j ACCEPT
iptables -A INPUT -p tcp -m tcp --dport 139 -j ACCEPT
iptables -A INPUT -p tcp -m tcp --dport 445 -j ACCEPT

Good ref - https://fedoraproject.org/wiki/How_to_edit_iptables_rules#Appending_Rules
This adds a rule at the end of the specified chain - https://fedoraproject.org/wiki/How_to_edit_iptables_rules#Appending_Rules

To delete a rule you must know its position in the chain
iptables -D INPUT 5

Postion 3 looks good for insert

iptables -I INPUT 1 -p tcp -m tcp --dport 137 -j ACCEPT
iptables -I INPUT 1 -p tcp -m tcp --dport 138 -j ACCEPT
iptables -I INPUT 1 -p tcp -m tcp --dport 139 -j ACCEPT
iptables -I INPUT 1 -p tcp -m tcp --dport 445 -j ACCEPT

Suggestion for masquerading:

# /sbin/iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
# /sbin/iptables -A FORWARD -i tun0 -o eth0 -m state   --state RELATED,ESTABLISHED -j ACCEPT
# /sbin/iptables -A FORWARD -i tun0 -o eth0 -j ACCEPT

To enable natted routing in Raspberry Pi

# Generated by iptables-save v1.4.14 on Sat Nov 28 20:14:01 2015
*filter
:INPUT ACCEPT [5922:672417]
:FORWARD ACCEPT [1948640:1261159173]
:OUTPUT ACCEPT [4899:634446]
-A FORWARD -i eth0 -o usb0 -m state --state RELATED,ESTABLISHED  -j ACCEPT
COMMIT
# Completed on Sat Nov 28 20:14:01 2015
# Generated by iptables-save v1.4.14 on Sat Nov 28 20:14:01 2015
*nat
:PREROUTING ACCEPT [23978:1493968]
:INPUT ACCEPT [107:30172]
:OUTPUT ACCEPT [1193:75732]
:POSTROUTING ACCEPT [302:21040]
-A POSTROUTING -o usb0 -j MASQUERADE
COMMIT
# Completed on Sat Nov 28 20:14:01 2015
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