When using IP aliases on loopback (e.g. ip addr add 10.1.1.1/32 dev lo)
with policy routing, findInterfaceByIP() resolves the alias IP to the
loopback interface. Binding the socket to lo via SO_BINDTODEVICE prevents
outbound traffic from reaching non-local destinations.
Skip SO_BINDTODEVICE when the resolved interface is loopback — source IP
binding via LocalAddr is sufficient for policy routing to steer traffic
through the correct physical interface.
ginuerzh