Add soundbox.getInterface()

This is required as a temporary solution to guess the correct interface.

1 files changed, 39 insertions, 0 deletions

diff --git a/interfaces.go b/interfaces.go
new file mode 100644
index 0000000..2854b1a
--- /dev/null
+++ b/interfaces.go
@@ -0,0 +1,39 @@
+package soundbox
+
+import (
+	"fmt"
+	"net"
+)
+
+// getInterface is a function guessing which interface should be used for
+// soundbox streaming. This is required since soundbox relies on communication
+// via IPv6 link-local addresses which require a specified interface to allow
+// communication. This function returns the first interface it finds which is
+// up and has a link-local address assigned.
+func getInterface() (net.Interface, error) {
+	all, err := net.Interfaces()
+	if err != nil {
+		return net.Interface{}, err
+	}
+
+	for _, iface := range all {
+		if iface.Flags & net.FlagUp == 0 {
+			continue
+		}
+		addresses, err := iface.Addrs()
+		if err != nil {
+			return net.Interface{}, err
+		}
+		for _, addr := range addresses {
+			ip, _, err := net.ParseCIDR(addr.String())
+			if err != nil {
+				return net.Interface{}, err
+			}
+			if ip.IsLinkLocalUnicast() {
+				return iface, nil
+			}
+		}
+	}
+
+	return net.Interface{}, fmt.Errorf("No interface found for soundbox streaming")
+}