Fix: handle reload failures a bit better

client.go

@@ -75,18 +75,21 @@ loop:
 			if !timer.Stop() {
 				<-timer.C
 			}
-			bo.reset()
-			c.conn.loadIfaces()
 			now = time.Now()
+			bo.reset()
+			_, err := c.conn.loadIfaces()
+			if err != nil {
+				c.opts.logger.Warn("reload failed (ifaces unchanged)", "err", err)
+			}
 			c.opts.logger.Debug("reload", "ifaces", c.conn.ifaces)
 		case m, ok := <-msgCh:
 			if !timer.Stop() {
 				<-timer.C
 			}
+			now = time.Now()
 			if !ok {
 				break loop
 			}
-			now = time.Now()
 			msg = &m
 		case now = <-timer.C:
 		}

dual_conn.go

@@ -72,13 +72,16 @@ func newDualConn(ifacesFn func() ([]net.Interface, error), network string) (*dua
 func (c *dualConn) loadIfaces() (changed bool, err error) {
 	ifaces := make(map[int]*Interface) // new ifaces
 	netIfaces, err := c.ifacesFn()
+	if err != nil {
+		return false, err
+	}
 	for _, netIface := range netIfaces {
 		if !isMulticastInterface(netIface) {
 			continue
 		}
 		v4, v6, err := netIfaceAddrs(netIface)
 		if err != nil {
-			continue
+			return false, err
 		}
 		iface := &Interface{Interface: netIface}
 		// Join will fail if called multiple times, just attempt for now