added .InterfaceAddrs(..), mainly for Android support

conn.go

@@ -62,19 +62,18 @@ type conn struct {
 	c6     *conn6
 	ifaces map[int]*connInterface // key: iface.Index
 
-	// Used initially and on reload to filter interfaces to use
-	ifacesFn func() ([]net.Interface, error)
+	opts *options
 }
 
-func newConn(ifacesFn func() ([]net.Interface, error), network string) (*conn, error) {
+func newConn(opts *options) (*conn, error) {
 
 	c := &conn{
-		ifaces:   make(map[int]*connInterface),
-		ifacesFn: ifacesFn,
+		ifaces: make(map[int]*connInterface),
+		opts:   opts,
 	}
 
 	var err4, err6 error
-	switch network {
+	switch opts.network {
 	case "udp":
 		c.c4, err4 = newConn4()
 		c.c6, err6 = newConn6()
@@ -96,15 +95,15 @@ func newConn(ifacesFn func() ([]net.Interface, error), network string) (*conn, e
 // Load (or reload) ifaces and return whether anything (addresses in particular) have changed.
 func (c *conn) loadIfaces() (changed bool, err error) {
 	ifaces := make(map[int]*connInterface) // new ifaces
-	netIfaces, err := c.ifacesFn()
+	netIfaces, err := c.opts.ifacesFn()
 	if err != nil {
 		return false, err
 	}
 	for _, netIface := range netIfaces {
 		if !isMulticastInterface(netIface) {
 			continue
 		}
-		v4, v6, err := netIfaceAddrs(netIface)
+		v4, v6, err := c.netIfaceAddrs(&netIface)
 		if err != nil {
 			return false, err
 		}
@@ -246,9 +245,9 @@ func (c *conn) Close() error {
 }
 
 // Returns mDNS-suitable unicast addresses for a net.Interface
-func netIfaceAddrs(iface net.Interface) (v4, v6 []netip.Addr, err error) {
+func (c *conn) netIfaceAddrs(iface *net.Interface) (v4, v6 []netip.Addr, err error) {
 	var v6local []netip.Addr
-	ifaceAddrs, err := iface.Addrs()
+	ifaceAddrs, err := c.opts.ifaceAddrsFn(iface)
 	if err != nil {
 		return nil, nil, err
 	}

options.go

@@ -19,17 +19,21 @@ type options struct {
 	browser *browser
 	publish *Service
 
-	ifacesFn func() ([]net.Interface, error)
-	network  string
-	expiry   time.Duration
-	srcAddrs bool
+	ifacesFn     func() ([]net.Interface, error)
+	ifaceAddrsFn func(*net.Interface) ([]net.Addr, error)
+	network      string
+	expiry       time.Duration
+	srcAddrs     bool
 }
 
 func defaultOpts() *options {
 	return &options{
 		logger:   slog.Default(),
 		network:  "udp",
 		ifacesFn: net.Interfaces,
+		ifaceAddrsFn: func(ifi *net.Interface) ([]net.Addr, error) {
+			return ifi.Addrs()
+		},
 	}
 }
 
@@ -100,11 +104,19 @@ func (c *Client) Logger(l *slog.Logger) *Client {
 }
 
 // Use custom network interfaces. The default is `net.Interfaces`.
+// For Android support, see https://github.com/wlynxg/anet
 func (c *Client) Interfaces(fn func() ([]net.Interface, error)) *Client {
 	c.opts.ifacesFn = fn
 	return c
 }
 
+// Use custom addrs for an interface. The default is `iface.Addrs()`.
+// For Android support, see https://github.com/wlynxg/anet
+func (c *Client) InterfaceAddrs(fn func(*net.Interface) ([]net.Addr, error)) *Client {
+	c.opts.ifaceAddrsFn = fn
+	return c
+}
+
 // Use the source addr of the UDP packets instead of the self-reported addrs over mDNS.
 // This should be more accurate and also works with link-local ipv6 addresses, but it's a
 // little unorthodox and not tested widely. It also prevents proxy use-cases.