From 586e7c571d106f842c8567012dacd28d73fcf966 Mon Sep 17 00:00:00 2001
From: cpuchip <cpuchip@gmail.com>
Date: Sun, 7 Aug 2022 13:54:55 -0600
Subject: [PATCH] Fix windows libp2p (#29)

* Fix client multicast sending on Windows

* Put in a platform dependent fix for windows to WriteTo on client.go and server.go to allow Multicast transmit

Co-authored-by: Dave Flowerday <davidf@pier13.com>
Co-authored-by: Michael Stufflebeam <michaels@gradecam.com>
---
 client.go | 26 ++++++++++++++++++++++++--
 server.go | 45 +++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 65 insertions(+), 6 deletions(-)

diff --git a/client.go b/client.go
index 33e4c0fa..c0b2cae1 100644
--- a/client.go
+++ b/client.go
@@ -3,8 +3,10 @@ package zeroconf
 import (
 	"context"
 	"fmt"
+	"log"
 	"math/rand"
 	"net"
+	"runtime"
 	"strings"
 	"time"
 
@@ -436,16 +438,36 @@ func (c *client) sendQuery(msg *dns.Msg) error {
 		return err
 	}
 	if c.ipv4conn != nil {
+		// See https://pkg.go.dev/golang.org/x/net/ipv4#pkg-note-BUG
+		// As of Golang 1.18.4
+		// On Windows, the ControlMessage for ReadFrom and WriteTo methods of PacketConn is not implemented.
 		var wcm ipv4.ControlMessage
 		for ifi := range c.ifaces {
-			wcm.IfIndex = c.ifaces[ifi].Index
+			switch runtime.GOOS {
+			case "darwin", "ios", "linux":
+				wcm.IfIndex = c.ifaces[ifi].Index
+			default:
+				if err := c.ipv4conn.SetMulticastInterface(&c.ifaces[ifi]); err != nil {
+					log.Printf("[WARN] mdns: Failed to set multicast interface: %v", err)
+				}
+			}
 			c.ipv4conn.WriteTo(buf, &wcm, ipv4Addr)
 		}
 	}
 	if c.ipv6conn != nil {
+		// See https://pkg.go.dev/golang.org/x/net/ipv6#pkg-note-BUG
+		// As of Golang 1.18.4
+		// On Windows, the ControlMessage for ReadFrom and WriteTo methods of PacketConn is not implemented.
 		var wcm ipv6.ControlMessage
 		for ifi := range c.ifaces {
-			wcm.IfIndex = c.ifaces[ifi].Index
+			switch runtime.GOOS {
+			case "darwin", "ios", "linux":
+				wcm.IfIndex = c.ifaces[ifi].Index
+			default:
+				if err := c.ipv6conn.SetMulticastInterface(&c.ifaces[ifi]); err != nil {
+					log.Printf("[WARN] mdns: Failed to set multicast interface: %v", err)
+				}
+			}
 			c.ipv6conn.WriteTo(buf, &wcm, ipv6Addr)
 		}
 	}
diff --git a/server.go b/server.go
index fb4b4976..2dbf536e 100644
--- a/server.go
+++ b/server.go
@@ -6,6 +6,7 @@ import (
 	"math/rand"
 	"net"
 	"os"
+	"runtime"
 	"strings"
 	"sync"
 	"time"
@@ -764,26 +765,62 @@ func (s *Server) multicastResponse(msg *dns.Msg, ifIndex int) error {
 		return fmt.Errorf("failed to pack msg %v: %w", msg, err)
 	}
 	if s.ipv4conn != nil {
+		// See https://pkg.go.dev/golang.org/x/net/ipv4#pkg-note-BUG
+		// As of Golang 1.18.4
+		// On Windows, the ControlMessage for ReadFrom and WriteTo methods of PacketConn is not implemented.
 		var wcm ipv4.ControlMessage
 		if ifIndex != 0 {
-			wcm.IfIndex = ifIndex
+			switch runtime.GOOS {
+			case "darwin", "ios", "linux":
+				wcm.IfIndex = ifIndex
+			default:
+				iface, _ := net.InterfaceByIndex(ifIndex)
+				if err := s.ipv4conn.SetMulticastInterface(iface); err != nil {
+					log.Printf("[WARN] mdns: Failed to set multicast interface: %v", err)
+				}
+			}
 			s.ipv4conn.WriteTo(buf, &wcm, ipv4Addr)
 		} else {
 			for _, intf := range s.ifaces {
-				wcm.IfIndex = intf.Index
+				switch runtime.GOOS {
+				case "darwin", "ios", "linux":
+					wcm.IfIndex = intf.Index
+				default:
+					if err := s.ipv4conn.SetMulticastInterface(&intf); err != nil {
+						log.Printf("[WARN] mdns: Failed to set multicast interface: %v", err)
+					}
+				}
 				s.ipv4conn.WriteTo(buf, &wcm, ipv4Addr)
 			}
 		}
 	}
 
 	if s.ipv6conn != nil {
+		// See https://pkg.go.dev/golang.org/x/net/ipv6#pkg-note-BUG
+		// As of Golang 1.18.4
+		// On Windows, the ControlMessage for ReadFrom and WriteTo methods of PacketConn is not implemented.
 		var wcm ipv6.ControlMessage
 		if ifIndex != 0 {
-			wcm.IfIndex = ifIndex
+			switch runtime.GOOS {
+			case "darwin", "ios", "linux":
+				wcm.IfIndex = ifIndex
+			default:
+				iface, _ := net.InterfaceByIndex(ifIndex)
+				if err := s.ipv6conn.SetMulticastInterface(iface); err != nil {
+					log.Printf("[WARN] mdns: Failed to set multicast interface: %v", err)
+				}
+			}
 			s.ipv6conn.WriteTo(buf, &wcm, ipv6Addr)
 		} else {
 			for _, intf := range s.ifaces {
-				wcm.IfIndex = intf.Index
+				switch runtime.GOOS {
+				case "darwin", "ios", "linux":
+					wcm.IfIndex = intf.Index
+				default:
+					if err := s.ipv6conn.SetMulticastInterface(&intf); err != nil {
+						log.Printf("[WARN] mdns: Failed to set multicast interface: %v", err)
+					}
+				}
 				s.ipv6conn.WriteTo(buf, &wcm, ipv6Addr)
 			}
 		}