How to implement VPN split tunneling to exclude certain IPs from the VPN tunnel?

[katarina-ziv]

I am trying to implement split tunneling in an Android VPN application. Specifically, I want all traffic to go through the VPN by default, but certain IPs should bypass the VPN and use the regular internet connection.

I guess I have to add it to this part, but I'm not sure how it goes.

when (profile.route) {
    Acl.ALL, Acl.BYPASS_CHN, Acl.CUSTOM_RULES -> {
        builder.addRoute("0.0.0.0", 0)
        if (profile.ipv6) builder.addRoute("::", 0)
    }
    else -> {
        resources.getStringArray(R.array.bypass_private_route).forEach {
            val subnet = Subnet.fromString(it)!!
            builder.addRoute(subnet.address.hostAddress!!, subnet.prefixSize)
        }
        builder.addRoute(PRIVATE_VLAN4_ROUTER, 32)
        // https://issuetracker.google.com/issues/149636790
        if (profile.ipv6) builder.addRoute("2000::", 3)
    }
}

[katarina-ziv]

We managed to implement split tunneling with the following approach:

For Android 33+, we used builder.excludeRoute to exclude the desired IPs from the VPN.
For versions below Android 33, we relied on builder.addRoute and included the required IP addresses calculated using the WireGuard AllowedIPs Calculator.