Masquerade NAT on one zone ONLY

Omarico · April 10, 2021, 2:33pm

i have 2 OpenVPN instances on my OpenWrt router ( it is NOT the gateway, my gateway is an xDSL router with port forwarding setup correctly)

what i'm trying to achieve is enable masquerade on only ONE instance (i named it srvr2) while keeping it disabled on the other server. what happens is that if i try to enable it. it gets enabled on BOTH servers and almost everything.. ( wireshark sees the traffic coming from 192.168.1.222 which is the wan port static address on the openwrt ) while if i disable it i can see the direct tunnel ip address ( 10.20.100.0/24) and also 200.0/24 )

setup is as follows :

router================== OpenWrt ( vpn0 ....... and ... vpn1 )
================== 192.168.1.222 | 10.20.100.1 ........ 200.1
Firewall.conf:

i want to enable masquerade on VPN1 only and not zero ( so that traffic comes out as 192.168.1.222 not the tunnel endpoint ip address ) . it never works


config defaults
	option input 'ACCEPT'
	option output 'ACCEPT'
	option forward 'DROP'

config zone
	option name 'lan'
	option input 'ACCEPT'
	option output 'ACCEPT'
	option forward 'ACCEPT'
	option network 'lan wan'

config zone
	option name 'wan'
	option input 'REJECT'
	option output 'ACCEPT'
	option forward 'REJECT'
	option masq '0'
	option mtu_fix '1'
	option network 'wan6'

config rule
	option name 'Allow-DHCP-Renew'
	option src 'wan'
	option proto 'udp'
	option dest_port '68'
	option target 'ACCEPT'
	option family 'ipv4'

config rule
	option name 'Allow-Ping'
	option src 'wan'
	option proto 'icmp'
	option icmp_type 'echo-request'
	option family 'ipv4'
	option target 'ACCEPT'

config rule
	option name 'Allow-IGMP'
	option src 'wan'
	option proto 'igmp'
	option family 'ipv4'
	option target 'ACCEPT'

config rule
	option name 'Allow-DHCPv6'
	option src 'wan'
	option proto 'udp'
	option src_ip 'fc00::/6'
	option dest_ip 'fc00::/6'
	option dest_port '546'
	option family 'ipv6'
	option target 'ACCEPT'

config rule
	option name 'Allow-MLD'
	option src 'wan'
	option proto 'icmp'
	option src_ip 'fe80::/10'
	list icmp_type '130/0'
	list icmp_type '131/0'
	list icmp_type '132/0'
	list icmp_type '143/0'
	option family 'ipv6'
	option target 'ACCEPT'

config rule
	option name 'Allow-ICMPv6-Input'
	option src 'wan'
	option proto 'icmp'
	list icmp_type 'echo-request'
	list icmp_type 'echo-reply'
	list icmp_type 'destination-unreachable'
	list icmp_type 'packet-too-big'
	list icmp_type 'time-exceeded'
	list icmp_type 'bad-header'
	list icmp_type 'unknown-header-type'
	list icmp_type 'router-solicitation'
	list icmp_type 'neighbour-solicitation'
	list icmp_type 'router-advertisement'
	list icmp_type 'neighbour-advertisement'
	option limit '1000/sec'
	option family 'ipv6'
	option target 'ACCEPT'

config rule
	option name 'Allow-ICMPv6-Forward'
	option src 'wan'
	option dest '*'
	option proto 'icmp'
	list icmp_type 'echo-request'
	list icmp_type 'echo-reply'
	list icmp_type 'destination-unreachable'
	list icmp_type 'packet-too-big'
	list icmp_type 'time-exceeded'
	list icmp_type 'bad-header'
	list icmp_type 'unknown-header-type'
	option limit '1000/sec'
	option family 'ipv6'
	option target 'ACCEPT'

config rule
	option name 'Allow-IPSec-ESP'
	option src 'wan'
	option dest 'lan'
	option proto 'esp'
	option target 'ACCEPT'

config rule
	option name 'Allow-ISAKMP'
	option src 'wan'
	option dest 'lan'
	option dest_port '500'
	option proto 'udp'
	option target 'ACCEPT'

config include
	option path '/etc/firewall.user'

config rule
	option dest_port '1723'
	option name 'pptp'
	option target 'ACCEPT'
	option proto 'all'
	option src 'lan'

config rule
	option target 'ACCEPT'
	option name 'gre'
	option src 'lan'
	option proto 'gre'
	option enabled '0'
###################################################################################
config rule
	option name 'Allow-OpenVPN-Inbound'
	option target 'ACCEPT'
	option proto 'tcp'
	option src '*'
	option dest_port '443'

config rule
	option name 'Allow-OpenVPN-UDP'
	option target 'ACCEPT'
	option proto 'udp'
	option src '*'
	option dest_port '444'

config zone
	option name 'vpn0'
	option input 'ACCEPT'
	option forward 'ACCEPT'
	option output 'ACCEPT'
	option masq '0'
	option network 'vpn0 ipsec0'
	option subnet '10.20.100.0/24'
	option mtu_fix '1'

config forwarding
	option dest 'vpn0'
	option src 'lan'

config forwarding
	option dest 'lan'
	option src 'vpn0'
################################################################################################
config zone
	option name 'vpn1'
	option input 'ACCEPT'
	option forward 'ACCEPT'
	option output 'ACCEPT'
	option network 'vpn1'
	option masq '1'
	option mtu_fix '1'

config forwarding
	option dest 'vpn1'
	option src 'lan'

config forwarding
	option dest 'lan'
	option src 'vpn1'

config include 'ipsecd'
	option type 'script'
	option path '/etc/ipsec.include'
	option reload '1'

config rule
	option dest_port '500'
	option src 'wan'
	option name 'ike'
	option target 'ACCEPT'
	option proto 'udp'

config rule
	option dest_port '4500'
	option src 'wan'
	option name 'ipsec'
	option target 'ACCEPT'
	option proto 'udp'

config rule
	option target 'ACCEPT'
	option src 'wan'
	option name 'ah'
	option proto 'ah'

config rule
	option target 'ACCEPT'
	option src 'wan'
	option name 'esp'
	option proto 'esp'

Network.conf

config interface 'loopback'
	option ifname 'lo'
	option proto 'static'
	option ipaddr '127.0.0.1'
	option netmask '255.0.0.0'

config globals 'globals'
	option ula_prefix 'fdc1:2325:d70e::/48'

config interface 'lan'
	option type 'bridge'
	option ifname 'eth0'
	option proto 'static'
	option netmask '255.255.255.0'
	option ip6assign '60'
	option ipaddr '192.168.2.1'
	option ipv6 '0'

config interface 'wan'
	option ifname 'eth1'
	option _orig_ifname 'eth1'
	option _orig_bridge 'false'
	option proto 'static'
	option ipaddr '192.168.1.222'
	option netmask '255.255.255.0'
	option gateway '192.168.1.1'
	option broadcast '255.255.255.255'
	option dns '8.8.8.8 208.67.222.222 8.8.4.4'
	option ipv6 '0'

config interface 'wan6'
	option ifname 'eth1'
	option proto 'none'

config switch
	option name 'switch0'
	option reset '1'
	option enable_vlan '1'

config switch_vlan
	option device 'switch0'
	option vlan '1'
	option ports '1 2 3 4 0'

config interface 'vpn0'
	option ifname 'tun0'
	option proto 'none'
	option auto '1'

config interface 'vpn1'
	option ifname 'tun1'
	option proto 'none'
	option auto '1'

config interface 'ipsec0'
	option ifname 'ipsec0'
	option _orig_ifname 'ipsec0'
	option _orig_bridge 'false'
	option proto 'none'

pavelgl · April 10, 2021, 4:07pm

What you want to achieve seems very exotic to me. I don't know if it is possible without a custom firewall rule. Disable the fw3 masquerading and try this:

iptables -t nat -I POSTROUTING -s 10.20.200.0/24 -o eth1 -j MASQUERADE

Omarico · April 10, 2021, 4:11pm

I thought that I could set masq '0' on one zone and '1' on the other and it'll work. but it enables it on the WHOLE router. I'll give that rule a try and report back to you.

also I'm not confined to UCI, if there's a firewall rule yeah I'd be more than welcome to try. looks like it's not as simple as setting zero and one beside an option

Omarico · April 10, 2021, 6:59pm

IT WORKS !! at first i used -o LAN and not eth1 which is why it didn't work. thank you soo much !

what is really strange is that the UCI firewall.conf adds a referenced chain with the exact same ( src, dest, target etc.. ) and never works.. i hope someone also has an explanation since i can't really get why it never works

here it is :

trendy · April 10, 2021, 7:13pm

There is an easy way to accomplish this.
In firewall configuration there is masq_dest option, where you can define what destination addresses will or will not be masqueraded.

Omarico · April 10, 2021, 7:52pm

already did, src and dest and it didn't work. i did it after i made that post. and by the way the screenshot that i posted is what's defined by the firewall configuration with masq_src and masq_dest. that's why i posted here because i was losing my mind over it and had enough of it
324235

trendy · April 10, 2021, 9:24pm

Negation is possible by prefixing the subnet with !

The way you have it is defining which will be masqueraded.

Omarico · April 10, 2021, 9:46pm

I didn't get you.

What's wrong with ( masq src = the ip range (subnet))
and
masq dest = any any ?

since it makes sense. I want anything coming from my vpn network to come out using the server's own LAN ip address because I don't want that specific vpn instance to be using a different subnet and deal with routed networks ( it is working on the other instance by the way. I just want this instance to be masqueraded )

trendy · April 10, 2021, 9:49pm

Both vpn0 and vpn1 are servers, right?
And you want the hosts which will connect to these two servers to continue to the wan interface towards the internet with vpn0 not masqueraded and vpn1 masqueraded, right?
Then this will do.

config zone
	option name 'lan'
	option input 'ACCEPT'
	option output 'ACCEPT'
	option forward 'ACCEPT'
	option network 'lan'

config zone
	option name 'wan'
	option input 'REJECT'
	option output 'ACCEPT'
	option forward 'REJECT'
	option masq '1'
	option mtu_fix '1'
	option network 'wan wan6'
	option masq_src '!10.20.100.0/24'

config zone
	option name 'vpn0'
	option input 'ACCEPT'
	option forward 'ACCEPT'
	option output 'ACCEPT'
	option network 'vpn0 ipsec0'

config zone
	option name 'vpn1'
	option input 'ACCEPT'
	option forward 'ACCEPT'
	option output 'ACCEPT'
	option network 'vpn1'

system · April 20, 2021, 9:49pm

This topic was automatically closed 10 days after the last reply. New replies are no longer allowed.