[Feature] Support for policy on local address

[kmala]

Currently we can apply policy to verify the upstream address

go-proxyproto/protocol.go

Lines 70 to 81 in e5b291b

	if p.Policy != nil {
	proxyHeaderPolicy, err = p.Policy(conn.RemoteAddr())
	if err != nil {
	// can't decide the policy, we can't accept the connection
	conn.Close()
	return nil, err
	}
	// Handle a connection as a regular one
	if proxyHeaderPolicy == SKIP {
	return conn, nil
	}
	}

. There could be scenarios where there are multiple interfaces the server is listening on and we may want to enable the proxy protocol on only 1 interface. It would help to have policy support verifying the local address.
I can create a PR if the feature is okay to be implemented.