1 files changed, 64 insertions, 0 deletions
diff --git a/monitor.go b/monitor.go
new file mode 100644
index 0000000..d3631c0
--- /dev/null
+++ b/monitor.go
@@ -0,0 +1,64 @@
+package main
+
+import (
+	"net"
+	"time"
+)
+
+func monitor4(conf *config, update4 chan<- net.IPAddr) {
+	refresh := time.NewTicker(conf.Interval)
+	for range refresh.C {
+		link, err := net.InterfaceByName(conf.Link4)
+		if err != nil {
+			logger.Printf("can't find interface %s: %v", conf.Link4, err)
+			continue
+		}
+
+		addrs, err := link.Addrs()
+		if err != nil {
+			const format = "can't read IPv4 addresses from %s: %v"
+			logger.Printf(format, conf.Link4, err)
+			continue
+		}
+
+		var addr4 *net.IPAddr
+		for _, netAddr := range addrs {
+			addr := netAddr.(*net.IPAddr)
+
+			if addr.To4() != nil && !addr.IP.IsPrivate() {
+				addr4 = addr
+				break
+			}
+		}
+	}
+}
+
+func monitor6(conf *config, update6 chan<- net.IPNet) {
+	refresh := time.NewTicker(conf.Interval)
+	for range refresh.C {
+		link, err := net.InterfaceByName(conf.Link6)
+		if err != nil {
+			logger.Printf("can't find interface %s: %v", conf.Link6, err)
+			continue
+		}
+
+		addrs, err := link.Addrs()
+		if err != nil {
+			const format = "can't read IPv6 addresses from %s: %v"
+			logger.Printf(format, conf.Link6, err)
+			continue
+		}
+
+		var prefix6 *net.IPNet
+		for _, netAddr := range addrs {
+			addr := netAddr.(*net.IPAddr)
+
+			if addr.To4() == nil && addr.IP.IsGlobalUnicast() {
+				cidr := net.CIDRMask(conf.PrefixLen, 128)
+				prefix6 = addr.IP.Mask(cidr)
+
+				break
+			}
+		}
+	}
+}