From 7e97b691ebb6342ecbf69cfff590aff7fb251ad5 Mon Sep 17 00:00:00 2001
From: Martin/Geno <geno+dev@fireorbit.de>
Date: Tue, 8 May 2018 17:15:49 +0200
Subject: [PATCH] [TASK] improve autoselect ip_address (#137)

---
 docs/docs_configuration.md |  1 +
 respond/collector.go       | 10 ++++------
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/docs/docs_configuration.md b/docs/docs_configuration.md
index 470a5ae..826267d 100644
--- a/docs/docs_configuration.md
+++ b/docs/docs_configuration.md
@@ -120,6 +120,7 @@ ifname              = "br-ffhb"
 {% method %}
 ip address is the own address which is used for sending.
 If not set or set with empty string it will take an address of ifname.
+(If `multicast_address` is not set the link local address otherwise a global unicast address)
 {% sample lang="toml" %}
 ```toml
 ip_address          = "fe80::..."
diff --git a/respond/collector.go b/respond/collector.go
index 6908980..2ca7395 100644
--- a/respond/collector.go
+++ b/respond/collector.go
@@ -65,7 +65,7 @@ func (coll *Collector) listenUDP(iface InterfaceConfig) {
 	if iface.IPAddress != "" {
 		addr = net.ParseIP(iface.IPAddress)
 	} else {
-		addr, err = getUnicastAddr(iface.InterfaceName)
+		addr, err = getUnicastAddr(iface.InterfaceName, iface.MulticastAddress == "")
 		if err != nil {
 			log.Panic(err)
 		}
@@ -97,8 +97,8 @@ func (coll *Collector) listenUDP(iface InterfaceConfig) {
 	go coll.receiver(conn)
 }
 
-// Returns a unicast address of given interface (prefer global unicast address over link local address)
-func getUnicastAddr(ifname string) (net.IP, error) {
+// Returns a unicast address of given interface (linklocal or global unicast address)
+func getUnicastAddr(ifname string, linklocal bool) (net.IP, error) {
 	iface, err := net.InterfaceByName(ifname)
 	if err != nil {
 		return nil, err
@@ -115,9 +115,7 @@ func getUnicastAddr(ifname string) (net.IP, error) {
 		if !ok {
 			continue
 		}
-		if ipnet.IP.IsGlobalUnicast() {
-			ip = ipnet.IP
-		} else if ipnet.IP.IsLinkLocalUnicast() && ip == nil {
+		if (!linklocal && ipnet.IP.IsGlobalUnicast()) || (linklocal && ipnet.IP.IsLinkLocalUnicast()) {
 			ip = ipnet.IP
 		}
 	}