Automatic LAN Subnet Reassignment

[Imre Kaloz]

Hi Rich,

Basic (v4 only) version of these (as well automatic wan proto detection) was implemented and rejected some years ago :)

Both are quite easy to do, that version used the following hotplug script:

===
#!/bin/sh

if [ "$INTERFACE" = "wan" ] && [ "$ACTION" = "ifup" ]
then
        # Get subnets for lan and wan
        lan_subnet=$(uci get network.lan.ipaddr | cut -d '.' -f3)
        wan_subnet=$(ifconfig wan | grep -w "inet" | awk '{print $2}' | cut -d ':' -f2 | cut -d '.' -f3)

        # If subnet is the same, randomize lan IP
        if [[ $lan_subnet == $wan_subnet ]]; then
                rn=$(awk 'function rn(n) { return int(rand()*n); } BEGIN {{ srand(); }{ printf("%d.%d", rn(254), rn    (254    ))}}')
                uci set network.lan.ipaddr=10.$rn.1
                uci commit network

                # Restart network to refresh changes
                /etc/init.d/network restart
        fi
fi
===

Setup of redirection ran as an init script:

===
#!/bin/sh

START=55
boot() {

lanip=$(uci get network.lan.ipaddr)

grep -q "myrouter.local/$lanip" /etc/config/dhcp
if [ $? -eq 1 ] ; then
# add a redirect myrouter.local to our IP
        uci add_list dhcp. at dnsmasq[0].address="/myrouter.local/$lanip"
        uci commit dhcp
fi
}
===


Best,
Imre

________________________________________
From: openwrt-adm <openwrt-adm-bounces at lists.openwrt.org> on behalf of Rich Brown <richb.hanover at gmail.com>
Sent: Monday, February 21, 2022 22:38
To: OpenWrt Project Administration; openwrt-devel at lists.openwrt.org
Cc: Richard E. Brown
Subject: Automatic LAN Subnet Reassignment

There is a new RFC on the OpenWrt forum proposing "Automatic LAN Subnet Reassignment" https://forum.openwrt.org/t/rfc-automatic-lan-subnet-reassignment-upon-conflict-with-wan/120938 The RFC responds to the advice given at last week's OpenWrt-Adm meeting (https://etherpad.wikimedia.org/p/ZlZiTcud3wufcSX9-1jD)

The intent of the proposal is for the default configuration to assign a LAN subnet that avoids a conflict with the WAN subnet, and provide a mDNS name such at OpenWrt.lan for connections.

I have two requests:

1) Please make comments on the technical merits of the proposal on the OpenWrt forum at the link above.

2) If the proposal seems to make sense, please consider the process by which we would incorporate this into the main release (likely, not for 22.0x, but perhaps the next release?)

Thank you.

Rich



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