From 69bfc6026141b494df834704f8c8e08d06973ae0 Mon Sep 17 00:00:00 2001
From: Muaz Ahmad <mahmad2000@protonmail.com>
Date: Sat, 18 May 2024 13:53:12 +0500
Subject: [PATCH] Bind to interface instead of implicitly binding to first
 interface

---
 src/mdns.zig | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/src/mdns.zig b/src/mdns.zig
index 020dcc3..3b9b88c 100644
--- a/src/mdns.zig
+++ b/src/mdns.zig
@@ -8,6 +8,7 @@ const MDNSError = error{
     NotResponse,
     NoMatchingAddress,
     AddressBadFormat,
+    SocketBindFail,
 };
 
 pub fn get_mdns(domain: util.Domain, ip_info: util.IPInfo) !util.IP {
@@ -43,6 +44,9 @@ fn get_mdns_socket(ip_info: util.IPInfo) !socket {
     if (std.c.setsockopt(sock, std.c.SOL.SOCKET, std.c.SO.RCVTIMEO, &timeout, @intCast(@sizeOf(std.c.timeval))) == -1) {
         return MDNSError.SocketInitFail;
     }
+    if (std.c.setsockopt(sock, std.c.SOL.SOCKET, std.c.SO.BINDTOIFINDEX, &ip_info.interface, @sizeOf(c_int)) == -1) {
+        return MDNSError.SocketBindFail;
+    }
     return sock;
 }
 
@@ -81,13 +85,7 @@ fn construct_mdns_query(domain: util.Domain, ip_info: util.IPInfo, buff: []u8) !
 fn get_target_address(ip_info: util.IPInfo) !std.net.Address {
     const target_addr: []const u8 = switch (ip_info.version) {
         .IPv4 => "224.0.0.251",
-        .IPv6 => blk: {
-            var buf: [50]u8 = undefined;
-            var byte_buf = std.io.fixedBufferStream(&buf);
-            const writer = byte_buf.writer();
-            try std.fmt.format(writer, "ff02::fb%{d}", .{ip_info.interface});
-            break :blk buf[0..writer.context.pos];
-        },
+        .IPv6 => "ff02::fb",
         else => unreachable,
     };
     return std.net.Address.resolveIp(target_addr, 5353);