feat: show list of discovered servers

src/Element.zig

@@ -3,6 +3,7 @@ pub const HBox = @import("./Element/HBox.zig");
 pub const Link = @import("./Element/Link.zig");
 pub const Page = @import("./Element/Page.zig");
 pub const Pile = @import("./Element/Pile.zig");
+pub const ServerList = @import("./Element/ServerList.zig");
 pub const Text = @import("./Element/Text.zig");
 pub const View = @import("./Element/View.zig");
 

src/Element/ServerList.zig

@@ -0,0 +1,71 @@
+allocator: std.mem.Allocator,
+discovered: *Discovered,
+
+pub const Discovered = struct {
+    allocator: std.mem.Allocator,
+    mutex: std.Thread.Mutex = .{},
+    servers: std.StringArrayHashMapUnmanaged(void) = .{},
+};
+
+pub fn create(allocator: std.mem.Allocator, discovered: *Discovered) !*@This() {
+    const this = try allocator.create(@This());
+    errdefer allocator.destroy(this);
+
+    this.* = .{
+        .allocator = allocator,
+        .discovered = discovered,
+    };
+    return this;
+}
+
+pub fn element(this: *@This()) Element {
+    return Element{
+        .pointer = this,
+        .interface = &Element.Interface{
+            .destroy = &element_destroy,
+            .minimum_size = &element_minimum_size,
+            .render = &element_render,
+            .event = &element_event,
+        },
+    };
+}
+
+pub fn element_destroy(pointer: ?*anyopaque) void {
+    const this: *@This() = @ptrCast(@alignCast(pointer));
+    this.allocator.destroy(this);
+}
+
+pub fn element_minimum_size(pointer: ?*anyopaque, render_resources: Element.RenderResources) [2]f32 {
+    const this: *@This() = @ptrCast(@alignCast(pointer));
+    _ = this;
+    return render_resources.font.textSize("example_server.xyz:5711", 1);
+}
+
+pub fn element_render(pointer: ?*anyopaque, canvas: *seizer.Canvas, render_resources: Element.RenderResources, min: [2]f32, max: [2]f32) void {
+    const this: *@This() = @ptrCast(@alignCast(pointer));
+    _ = max;
+    _ = render_resources;
+
+    var pos = min;
+
+    this.discovered.mutex.lock();
+    defer this.discovered.mutex.unlock();
+    for (this.discovered.servers.keys()) |url| {
+        const text_size = canvas.writeText(pos, url, .{});
+        pos[1] += text_size[1];
+    }
+}
+
+pub fn element_event(pointer: ?*anyopaque, event: Element.Event) ?Element.Command {
+    const this: *@This() = @ptrCast(@alignCast(pointer));
+    _ = this;
+    _ = event;
+    return null;
+}
+
+const Element = @import("../Element.zig");
+const assets = @import("../assets.zig");
+
+const seizer = @import("seizer");
+const gl = seizer.gl;
+const std = @import("std");

src/LocalUI.zig

@@ -24,9 +24,18 @@ fn main_menu_handler(_: ?*anyopaque, request: Request) Handler.Error!Response {
     return Response{ .arena = arena, .body = .{ .element = page.element() } };
 }
 
+const SERVICE_NAME = "_rummy._udp.local.";
+const SIOCGIFCONF = 0x8912;
+const SIOCGIFADDR = 0x8915;
+
 const JoinMultiplayerGame = struct {
     allocator: std.mem.Allocator,
     discovery_thread: std.Thread,
+    running: *std.atomic.Value(bool),
+
+    discovered: *Element.ServerList.Discovered,
+
+    const Server = struct { url: []const u8, port: u16 };
 
     pub const INTERFACE = &Handler.Interface{
         .create = &create,
@@ -38,11 +47,21 @@ const JoinMultiplayerGame = struct {
         const this = try allocator.create(@This());
         errdefer allocator.destroy(this);
 
-        const discovery_thread = std.Thread.spawn(.{}, find_local_games_thread, .{allocator}) catch return error.OutOfMemory;
+        const discovered = try allocator.create(Element.ServerList.Discovered);
+        errdefer allocator.destroy(discovered);
+        discovered.* = .{ .allocator = allocator };
+
+        const running = try allocator.create(std.atomic.Value(bool));
+        errdefer allocator.destroy(running);
+        running.store(true, .Monotonic);
+
+        const discovery_thread = std.Thread.spawn(.{}, find_local_games_thread, .{ running, discovered }) catch return error.OutOfMemory;
 
         this.* = .{
             .allocator = allocator,
             .discovery_thread = discovery_thread,
+            .running = running,
+            .discovered = discovered,
         };
 
         return this;
@@ -50,15 +69,17 @@ const JoinMultiplayerGame = struct {
 
     fn handler(pointer: ?*anyopaque, request: Request) Handler.Error!Response {
         const this: *@This() = @ptrCast(@alignCast(pointer));
-        _ = this;
 
         var arena = std.heap.ArenaAllocator.init(request.allocator);
         errdefer arena.deinit();
 
         var text = try Element.Text.create(arena.allocator(), try std.fmt.allocPrint(arena.allocator(), "Looking for multiplayer games", .{}));
 
+        var server_list = try Element.ServerList.create(arena.allocator(), this.discovered);
+
         var page = try Element.Page.create(request.allocator);
         try page.addElement(.{ 0.5, 0.5 }, .{ 0.5, 0.5 }, text.element());
+        try page.addElement(.{ 0.5, 0.7 }, .{ 0.5, 0.5 }, server_list.element());
 
         return Response{ .arena = arena, .body = .{ .element = page.element() } };
     }
@@ -66,12 +87,23 @@ const JoinMultiplayerGame = struct {
     fn deinit(pointer: ?*anyopaque) void {
         const this: *@This() = @ptrCast(@alignCast(pointer));
 
+        this.running.store(false, .Monotonic);
+
+        this.discovery_thread.join();
+        for (this.discovered.servers.keys()) |url| {
+            this.discovered.allocator.free(url);
+        }
+        this.discovered.servers.deinit(this.discovered.allocator);
+
+        this.allocator.destroy(this.discovered);
+        this.allocator.destroy(this.running);
+
         this.allocator.destroy(this);
     }
 
-    fn find_local_games_thread(allocator: std.mem.Allocator) !void {
-        const buffer = try allocator.alloc(u8, 2048);
-        defer allocator.free(buffer);
+    fn find_local_games_thread(running: *std.atomic.Value(bool), discovered: *Element.ServerList.Discovered) !void {
+        const buffer = try discovered.allocator.alloc(u8, 2048);
+        defer discovered.allocator.free(buffer);
 
         const log = std.log.scoped(.mdns);
         log.info("mdns discovery service started", .{});
@@ -84,15 +116,14 @@ const JoinMultiplayerGame = struct {
         const mdns_ipv6_socket = c.mdns_socket_open_ipv6(null);
         defer c.mdns_socket_close(mdns_ipv6_socket);
 
-        const service_name = "rummy._udp.local.";
         for (&[_]c_int{ mdns_ipv4_socket, mdns_ipv6_socket }) |socket| {
-            switch (c.mdns_query_send(socket, c.MDNS_RECORDTYPE_PTR, service_name.ptr, service_name.len, buffer.ptr, buffer.len, 0)) {
+            switch (c.mdns_query_send(socket, c.MDNS_RECORDTYPE_PTR, SERVICE_NAME.ptr, SERVICE_NAME.len, buffer.ptr, buffer.len, 0)) {
                 0 => {},
                 else => |err_code| log.warn("Failed to send question; error code = {}", .{err_code}),
             }
         }
 
-        while (true) {
+        while (running.load(.Monotonic)) {
             var pollfds = [_]std.os.pollfd{
                 .{ .fd = mdns_ipv4_socket, .events = std.os.POLL.IN, .revents = undefined },
                 .{ .fd = mdns_ipv6_socket, .events = std.os.POLL.IN, .revents = undefined },
@@ -100,11 +131,11 @@ const JoinMultiplayerGame = struct {
             _ = std.os.poll(&pollfds, 1000) catch break;
             for (pollfds) |pollfd| {
                 if (pollfd.revents & std.os.POLL.IN == 0) continue;
-                _ = c.mdns_query_recv(pollfd.fd, buffer.ptr, buffer.len, &find_local_games_thread_query_callback, null, 0);
+                _ = c.mdns_query_recv(pollfd.fd, buffer.ptr, buffer.len, &find_local_games_thread_query_callback, discovered, 0);
             }
         }
 
-        log.info("mdns service stopping", .{});
+        log.info("mdns discovery service stopping", .{});
     }
 
     fn find_local_games_thread_query_callback(
@@ -126,8 +157,9 @@ const JoinMultiplayerGame = struct {
     ) callconv(.C) c_int {
         const log = std.log.scoped(.mdns);
 
+        const discovered: *Element.ServerList.Discovered = @ptrCast(@alignCast(userdata));
+
         _ = rclass;
-        _ = userdata;
         _ = ttl;
         _ = name_length;
         _ = sock;
@@ -159,9 +191,6 @@ const JoinMultiplayerGame = struct {
             c.MDNS_RECORDTYPE_TXT => "TXT",
             else => "???",
         };
-        if (rtype == c.MDNS_RECORDTYPE_PTR) {
-            log.info("{?} : {s} {s} \"{}\"", .{ std_from, entrytype_str, recordtype_str, std.zig.fmtEscapes(name) });
-        }
 
         switch (rtype) {
             c.MDNS_RECORDTYPE_PTR => {
@@ -169,6 +198,30 @@ const JoinMultiplayerGame = struct {
                 const namestr = c.mdns_record_parse_ptr(data_ptr_opaque, data_len, record_offset, record_length, &namebuffer, namebuffer.len);
                 log.info("{?} : {s} {s} \"{}\"", .{ std_from, entrytype_str, recordtype_str, std.zig.fmtEscapes(namestr.str[0..namestr.length]) });
             },
+            c.MDNS_RECORDTYPE_SRV => {
+                var strbuffer: [128]u8 = undefined;
+                const record = c.mdns_record_parse_srv(data_ptr_opaque, data_len, record_offset, record_length, &strbuffer, strbuffer.len);
+                log.info("{?} : {s} {s} \"{}\":{}", .{ std_from, entrytype_str, recordtype_str, std.zig.fmtEscapes(record.name.str[0..record.name.length]), record.port });
+
+                const url = std.fmt.allocPrint(discovered.allocator, "{s}:{}", .{ record.name.str[0..record.name.length], record.port }) catch unreachable;
+                discovered.mutex.lock();
+                defer discovered.mutex.unlock();
+
+                const gop = discovered.servers.getOrPut(discovered.allocator, url) catch unreachable;
+                if (gop.found_existing) {
+                    discovered.allocator.free(url);
+                }
+            },
+            c.MDNS_RECORDTYPE_A => {
+                var std_address: std.net.Ip4Address = undefined;
+                _ = c.mdns_record_parse_a(data_ptr_opaque, data_len, record_offset, record_length, @ptrCast(&std_address.sa));
+                log.info("{?} : {s} {s} \"{}\" -> {}", .{ std_from, entrytype_str, recordtype_str, std.zig.fmtEscapes(name), std_address });
+            },
+            c.MDNS_RECORDTYPE_AAAA => {
+                var std_address: std.net.Ip6Address = undefined;
+                _ = c.mdns_record_parse_aaaa(data_ptr_opaque, data_len, record_offset, record_length, @ptrCast(&std_address.sa));
+                log.info("{?} : {s} {s} \"{}\" -> {}", .{ std_from, entrytype_str, recordtype_str, std.zig.fmtEscapes(name), std_address });
+            },
             else => {},
         }
         return 0;
@@ -213,6 +266,7 @@ const HostMultiplayerGame = struct {
         if (server == null) {
             return error.OutOfMemory; // TODO: add better error message
         }
+        errdefer c.enet_host_destroy(server);
 
         // setup mDNS discovery service
 
@@ -315,22 +369,6 @@ const HostMultiplayerGame = struct {
             interface: c_int,
         };
 
-        // TODO: get ipv4 and ipv6 adress of server to send out over mDNS
-        // const SIOCGIFADDR = 0x8915;
-        // var ifr: std.os.ifreq = undefined;
-        // ifr.ifru.addr.family = std.os.AF.INET;
-        // const interface_name = "wlp170s0";
-        // @memset(&ifr.ifrn.name, 0);
-        // @memcpy(ifr.ifrn.name[0..interface_name.len], interface_name);
-
-        // const ifr_ret_value = std.os.linux.getErrno(std.os.linux.ioctl(mdns_socket6, SIOCGIFADDR, @intFromPtr(&ifr)));
-        // std.log.scoped(.mdns).debug("ioctl({}, SIOCGIFADDR, {*}) = {}", .{ mdns_socket6, &ifr, ifr_ret_value });
-
-        // std.os.ioctl_SIOCGIFINDEX(mdns_socket6, &ifr) catch unreachable;
-        // const interface = ifr.ifru.ivalue;
-
-        // const mdns_ipv6_multicast_group = std.net.Address.parseIp6("ff02::fb", c.MDNS_PORT) catch unreachable;
-        // var socklen = mdns_sock_addr6.getOsSockLen();
         std.os.setsockopt(
             mdns_socket6,
             std.os.IPPROTO.IPV6,
@@ -344,7 +382,6 @@ const HostMultiplayerGame = struct {
         const mdns_sock_addr6 = std.net.Address.parseIp6("::", c.MDNS_PORT) catch unreachable;
         var socklen = mdns_sock_addr6.getOsSockLen();
         std.os.bind(mdns_socket6, &mdns_sock_addr6.any, socklen) catch unreachable;
-        // std.os.listen(mdns_socket6, self.kernel_backlog) catch unreachable;
 
         var mdns_listen_addr: std.net.Address = undefined;
         std.os.getsockname(mdns_socket, &mdns_listen_addr.any, &socklen) catch unreachable;
@@ -355,12 +392,7 @@ const HostMultiplayerGame = struct {
         std.os.getsockname(mdns_socket6, &mdns_listen_addr6.any, &socklen) catch unreachable;
         const ipv6_sockaddr_string = try std.fmt.allocPrint(allocator, "{}", .{mdns_listen_addr6});
 
-        // // const SIOCGIFNAME = 0x8910;
-
-        // const ipv4_sockaddr: std.os.sockaddr.in = @bitCast(ifr.ifru.addr);
-        // // const ipv4_bytes: [4]u8 = @bitCast(ipv4_sockaddr.addr);
-
-        const service_string = try allocator.dupe(u8, "rummy._udp.local.");
+        const service_string = try allocator.dupe(u8, SERVICE_NAME);
 
         var hostname_buffer: [std.os.HOST_NAME_MAX]u8 = undefined;
         const hostname = std.os.gethostname(&hostname_buffer) catch unreachable;
@@ -404,18 +436,36 @@ const HostMultiplayerGame = struct {
             .ttl = 0,
         });
 
-        // TODO: Add AAAA and A records to mdns service
-        // // DNS A that maps "<hostname>.local." to the an ip address
-        // const mdns_a_record = c.mdns_record_t{
-        //     .name = .{ .str = qualified_hostname.ptr, .length = qualified_hostname.len },
-        //     .type = c.MDNS_RECORDTYPE_A,
-        //     .data = .{ .a = .{
-        //         .addr = @bitCast(ipv4_sockaddr),
-        //     } },
-        //     .rclass = 0,
-        //     .ttl = 0,
-        // };
-        // try mdns_records.append(mdns_a_record);
+        // get a list of addresses to populate A and AAAA DNS records
+        const addresses = @import("./multiplayer.zig").getIPAddresses(allocator) catch return error.OutOfMemory;
+        defer this.allocator.free(addresses);
+
+        for (addresses) |ip_address| {
+            switch (ip_address) {
+                .ipv4 => |ipv4| {
+                    try mdns_records.append(c.mdns_record_t{
+                        .name = .{ .str = qualified_hostname.ptr, .length = qualified_hostname.len },
+                        .type = c.MDNS_RECORDTYPE_A,
+                        .data = .{ .a = .{ .addr = .{
+                            .sin_addr = @bitCast(ipv4),
+                        } } },
+                        .rclass = 0,
+                        .ttl = 0,
+                    });
+                },
+                .ipv6 => |ipv6| {
+                    try mdns_records.append(c.mdns_record_t{
+                        .name = .{ .str = qualified_hostname.ptr, .length = qualified_hostname.len },
+                        .type = c.MDNS_RECORDTYPE_AAAA,
+                        .data = .{ .aaaa = .{ .addr = .{
+                            .sin6_addr = @bitCast(ipv6),
+                        } } },
+                        .rclass = 0,
+                        .ttl = 0,
+                    });
+                },
+            }
+        }
 
         const mdns_record_slice = try mdns_records.toOwnedSlice();
         errdefer allocator.free(mdns_record_slice);
@@ -482,6 +532,14 @@ const HostMultiplayerGame = struct {
         this.allocator.destroy(this);
     }
 
+    const nlmsghdr = extern struct {
+        len: u32,
+        type: u16,
+        flags: u16,
+        seq: u32,
+        pid: u32,
+    };
+
     fn mdns_thread_main(this: *@This()) !void {
         const buffer = try this.allocator.alloc(u8, 2048);
         defer this.allocator.free(buffer);
@@ -516,7 +574,8 @@ const HostMultiplayerGame = struct {
                 .{ .fd = this.mdns_socket6, .events = std.os.POLL.IN, .revents = undefined },
             };
             _ = std.os.poll(&pollfds, 1000) catch break;
-            for (pollfds) |pollfd| {
+            // listen for mdns messages
+            for (pollfds[0..2]) |pollfd| {
                 if (pollfd.revents & std.os.POLL.IN == 0) continue;
                 _ = c.mdns_socket_listen(pollfd.fd, buffer.ptr, buffer.len, &mdns_thread_service_callback, this);
             }
@@ -562,7 +621,7 @@ const HostMultiplayerGame = struct {
 
         const std_from: ?std.net.Address = if (from) |f| std.net.Address{ .any = @bitCast(f.*) } else null;
 
-        if (std.mem.eql(u8, name, DNS_SD)) {
+        if (std.mem.eql(u8, name, DNS_SD) and (rtype == c.MDNS_RECORDTYPE_PTR or rtype == c.MDNS_RECORDTYPE_ANY)) {
             const answer = c.mdns_record_t{
                 .name = .{ .str = name.ptr, .length = name.len },
                 .type = c.MDNS_RECORDTYPE_PTR,
@@ -605,7 +664,7 @@ const HostMultiplayerGame = struct {
                     log.warn("{s}:{} failed to answer query, error code = {}", .{ @src().file, @src().line, ret_val });
                 }
             }
-        } else if (std.mem.eql(u8, name, this.service_string)) {
+        } else if (std.mem.eql(u8, name, this.service_string) and (rtype == c.MDNS_RECORDTYPE_PTR or rtype == c.MDNS_RECORDTYPE_ANY)) {
             const answer = this.mdns_records[0];
             const additional = this.mdns_records[1..];
 
@@ -649,8 +708,9 @@ const HostMultiplayerGame = struct {
                     log.warn("{s}:{} failed to answer query with multicast, error code = {}", .{ @src().file, @src().line, ret_val });
                 }
             }
-        } else if (std.mem.eql(u8, name, this.service_instance_string)) {
+        } else if (std.mem.eql(u8, name, this.service_instance_string) and (rtype == c.MDNS_RECORDTYPE_SRV or rtype == c.MDNS_RECORDTYPE_ANY)) {
             const answer = this.mdns_records[1];
+            const additional = this.mdns_records[2..];
 
             var sendbuffer: [1024]u8 = undefined;
             if (rclass & c.MDNS_UNICAST_RESPONSE != 0) {
@@ -667,8 +727,8 @@ const HostMultiplayerGame = struct {
                     answer,
                     null,
                     0,
-                    null,
-                    0,
+                    additional.ptr,
+                    additional.len,
                 );
             } else {
                 _ = c.mdns_query_answer_multicast(
@@ -678,8 +738,8 @@ const HostMultiplayerGame = struct {
                     answer,
                     null,
                     0,
-                    null,
-                    0,
+                    additional.ptr,
+                    additional.len,
                 );
             }
         }

src/multiplayer.zig

@@ -0,0 +1,186 @@
+const IpAddress = union(enum) {
+    ipv4: [4]u8,
+    ipv6: [16]u8,
+
+    pub fn format(
+        this: @This(),
+        comptime fmt: []const u8,
+        options: std.fmt.FormatOptions,
+        writer: anytype,
+    ) !void {
+        _ = fmt;
+        _ = options;
+        switch (this) {
+            .ipv4 => |ip| return std.fmt.format(writer, "{}.{}.{}.{}", .{ ip[0], ip[1], ip[2], ip[3] }),
+            .ipv6 => |ip| {
+                const sextets: [8][2]u8 = @bitCast(ip);
+                for (sextets, 0..) |sextet, i| {
+                    if (i > 0) {
+                        try std.fmt.format(writer, ":{}", .{std.fmt.fmtSliceHexLower(&sextet)});
+                    } else {
+                        try std.fmt.format(writer, "{}", .{std.fmt.fmtSliceHexLower(&sextet)});
+                    }
+                }
+            },
+        }
+    }
+};
+
+pub fn getIPAddresses(allocator: std.mem.Allocator) ![]IpAddress {
+    const rtnetlink_socket = try std.os.socket(std.os.AF.NETLINK, std.os.SOCK.DGRAM, std.os.linux.NETLINK.ROUTE);
+    defer std.os.closeSocket(rtnetlink_socket);
+
+    const rtnetlink_addr = std.os.sockaddr.nl{
+        .pid = @intCast(std.os.linux.getpid()),
+        .groups = 0,
+    };
+    try std.os.bind(rtnetlink_socket, @ptrCast(&rtnetlink_addr), @sizeOf(std.os.sockaddr.nl));
+
+    var addresses = std.ArrayList(IpAddress).init(allocator);
+    defer addresses.deinit();
+
+    const msg_get_links = addrmsg_t{
+        .hdr = std.os.linux.nlmsghdr{
+            .len = @sizeOf(addrmsg_t),
+            .type = .RTM_GETADDR,
+            .flags = std.os.linux.NLM_F_REQUEST | std.os.linux.NLM_F_DUMP,
+            .seq = 2,
+            .pid = @intCast(std.os.linux.getpid()),
+        },
+        .body = ifaddrmsg_t{
+            .family = 0,
+            .prefixlen = 0,
+            .flags = 0,
+            .scope = 0,
+            .interface_index = 0,
+        },
+    };
+    const iovs = [_]std.os.iovec_const{
+        .{ .iov_base = &std.mem.toBytes(msg_get_links), .iov_len = @sizeOf(addrmsg_t) },
+    };
+    _ = try std.os.sendmsg(rtnetlink_socket, &std.os.msghdr_const{
+        .name = @ptrCast(&std.os.sockaddr.nl{ .pid = 0, .groups = 0 }),
+        .namelen = @sizeOf(std.os.sockaddr.nl),
+        .iov = &iovs,
+        .iovlen = iovs.len,
+        .control = null,
+        .controllen = 0,
+        .flags = 0,
+    }, 0);
+
+    // listen for netlink messages
+    netlink_loop: while (true) {
+        var buf: [8192]u8 = undefined;
+
+        var kernel_addr = std.os.sockaddr.nl{ .pid = 0, .groups = 0 };
+        var recv_iovs = [_]std.os.iovec{
+            .{ .iov_base = &buf, .iov_len = buf.len },
+        };
+        var recv_hdr = std.os.linux.msghdr{
+            .name = @ptrCast(&kernel_addr),
+            .namelen = @sizeOf(std.os.sockaddr.nl),
+            .iov = &recv_iovs,
+            .iovlen = recv_iovs.len,
+            .control = null,
+            .controllen = 0,
+            .flags = 0,
+        };
+        const recv_msg_len = std.os.linux.recvmsg(rtnetlink_socket, &recv_hdr, 0);
+        const recv_msg = buf[0..recv_msg_len];
+
+        var nlmsg_offset: usize = 0;
+        while (nlmsg_offset < recv_msg.len) {
+            const recv_nlmsghdr: *std.os.linux.nlmsghdr = @ptrCast(@alignCast(recv_msg[nlmsg_offset..][0..@sizeOf(std.os.linux.nlmsghdr)]));
+            defer nlmsg_offset += recv_nlmsghdr.len;
+
+            const nlmsg_data = recv_msg[nlmsg_offset..][0..recv_nlmsghdr.len];
+
+            if (recv_nlmsghdr.type == .DONE) {
+                break :netlink_loop;
+            } else if (recv_nlmsghdr.type == .RTM_NEWADDR) {
+                const address_message: *ifaddrmsg_t = @ptrCast(@alignCast(nlmsg_data[@sizeOf(std.os.linux.nlmsghdr)..][0..@sizeOf(ifaddrmsg_t)]));
+
+                switch (@as(RtScope, @enumFromInt(address_message.scope))) {
+                    .universe, .site, .link => {},
+                    // ignore IPs relevant only to the current machine
+                    .host, .nowhere => continue,
+                }
+
+                var attr_offset: usize = std.mem.alignForward(usize, @sizeOf(ifaddrmsg_t) + @sizeOf(std.os.linux.nlmsghdr), @alignOf(std.os.linux.rtattr));
+                while (attr_offset < nlmsg_data.len) {
+                    const attr_hdr: std.os.linux.rtattr = @bitCast(nlmsg_data[attr_offset..][0..@sizeOf(std.os.linux.rtattr)].*);
+
+                    const attr_len_u32: u32 = @intCast(attr_hdr.len);
+                    const attr_len_aligned = std.mem.alignForward(usize, @sizeOf(std.os.linux.rtattr) + attr_len_u32, @alignOf(std.os.linux.rtattr));
+
+                    const attr_data_offset = std.mem.alignForward(usize, attr_offset + @sizeOf(std.os.linux.rtattr), @alignOf(std.os.linux.rtattr));
+
+                    switch (attr_hdr.type) {
+                        .ADDRESS => {
+                            const attr_data = nlmsg_data[attr_data_offset..][0 .. attr_hdr.len - @sizeOf(std.os.linux.rtattr)];
+                            switch (address_message.family) {
+                                std.os.linux.AF.INET => try addresses.append(.{ .ipv4 = attr_data[0..4].* }),
+                                std.os.linux.AF.INET6 => try addresses.append(.{ .ipv6 = attr_data[0..16].* }),
+                                else => {},
+                            }
+                        },
+                        else => {},
+                    }
+
+                    attr_offset += attr_len_aligned;
+                }
+            } else if (recv_nlmsghdr.type == .ERROR) {
+                const nlmsgerr_t = extern struct {
+                    @"error": c_int,
+                    hdr: std.os.linux.nlmsghdr,
+                };
+                const err: *nlmsgerr_t = @ptrCast(@alignCast(nlmsg_data[@sizeOf(std.os.linux.nlmsghdr)..][0..@sizeOf(nlmsgerr_t)]));
+                std.log.warn("errno = {}", .{err.@"error"});
+            }
+        }
+    }
+
+    return addresses.toOwnedSlice();
+}
+
+const IFF = struct {
+    const UP = 1 << 0;
+    const BROADCAST = 1 << 1;
+    const DEBUG = 1 << 2;
+    const LOOPBACK = 1 << 3;
+    const POINTOPOINT = 1 << 4;
+    const NOTRAILERS = 1 << 5;
+    const RUNNING = 1 << 6;
+    const NOARP = 1 << 7;
+    const PROMISC = 1 << 8;
+    const ALLMULTI = 1 << 9;
+    const MASTER = 1 << 10;
+    const SLAVE = 1 << 11;
+    const MULTICAST = 1 << 12;
+    const PORTSEL = 1 << 13;
+    const AUTOMEDIA = 1 << 14;
+    const DYNAMIC = 1 << 15;
+};
+
+const RtScope = enum(c_int) {
+    universe = 0,
+    site = 200,
+    link = 253,
+    host = 254,
+    nowhere = 255,
+};
+
+const ifaddrmsg_t = extern struct {
+    family: u8,
+    prefixlen: u8,
+    flags: u8,
+    scope: u8,
+    interface_index: c_uint,
+};
+
+const addrmsg_t = extern struct {
+    hdr: std.os.linux.nlmsghdr,
+    body: ifaddrmsg_t,
+};
+
+const std = @import("std");