From 552b84f630fdfc386dc5fa101531327d6b95bcb2 Mon Sep 17 00:00:00 2001
From: Matthias Schiffer <mschiffer@universe-factory.net>
Date: Sat, 2 Oct 2021 17:19:13 +0200
Subject: [PATCH] collector: set IPV6_MULTICAST_IF on UDP socket

Required to use the correct interface for non-link-local bind address.

Closes: #167
---
 go.mod               |  2 +-
 go.sum               |  2 ++
 respond/collector.go | 16 ++++++++++++++++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/go.mod b/go.mod
index 0c09c20..7bbd349 100644
--- a/go.mod
+++ b/go.mod
@@ -19,7 +19,7 @@ require (
 	github.com/stretchr/testify v1.5.1
 	github.com/tidwall/gjson v1.6.5
 	golang.org/x/net v0.0.0-20201021035429-f5854403a974 // indirect
-	golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4 // indirect
+	golang.org/x/sys v0.0.0-20211002104244-808efd93c36d // indirect
 	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
 	gopkg.in/fgrosse/graphigo.v2 v2.0.0-20151220153422-55a0a92a7030 // indirect
 	gopkg.in/yaml.v2 v2.2.8 // indirect
diff --git a/go.sum b/go.sum
index cd1d2c9..868dd8f 100644
--- a/go.sum
+++ b/go.sum
@@ -165,6 +165,8 @@ golang.org/x/sys v0.0.0-20191120155948-bd437916bb0e/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4 h1:myAQVi0cGEoqQVR5POX+8RR2mrocKqNN1hmeMqhX27k=
 golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20211002104244-808efd93c36d h1:SABT8Vei3iTiu+Gy8KOzpSNz+W1EQ5YBCRtiEETxF+0=
+golang.org/x/sys v0.0.0-20211002104244-808efd93c36d/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.3 h1:cokOdA+Jmi5PJGXLlLllQSgYigAEfHXJAERHVMaCc2k=
 golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
diff --git a/respond/collector.go b/respond/collector.go
index 97037d7..79472b1 100644
--- a/respond/collector.go
+++ b/respond/collector.go
@@ -5,6 +5,8 @@ import (
 	"net"
 	"time"
 
+	"golang.org/x/sys/unix"
+
 	"github.com/bdlm/log"
 
 	"github.com/FreifunkBremen/yanic/data"
@@ -89,6 +91,20 @@ func (coll *Collector) listenUDP(iface InterfaceConfig) {
 	}
 	conn.SetReadBuffer(MaxDataGramSize)
 
+	raw, err := conn.SyscallConn()
+	if err != nil {
+		log.Panic(err)
+	}
+	err = raw.Control(func(fd uintptr) {
+		err = unix.SetsockoptInt(int(fd), unix.IPPROTO_IPV6, unix.IPV6_MULTICAST_IF, ifaceInfo.Index)
+		if err != nil {
+			log.Panic(err)
+		}
+	})
+	if err != nil {
+		log.Panic(err)
+	}
+
 	coll.connections = append(coll.connections, multicastConn{
 		Conn:             conn,
 		SendRequest:      !iface.SendNoRequest,