first tests

src/main.zig

@@ -16,6 +16,10 @@ pub fn main() !void {
     try bw.flush(); // don't forget to flush!
 }
 
+const Tunnel = struct {
+    name: []u8,
+};
+
 test "simple test" {
     var list = std.ArrayList(i32).init(std.testing.allocator);
     defer list.deinit(); // try commenting this out and see if zig detects the memory leak!

src/root.zig

@@ -1,10 +0,0 @@
-const std = @import("std");
-const testing = std.testing;
-
-export fn add(a: i32, b: i32) i32 {
-    return a + b;
-}
-
-test "basic add functionality" {
-    try testing.expect(add(3, 7) == 10);
-}

src/test_all.zig

@@ -0,0 +1,4 @@
+test "nyotun test suite" {
+    _ = @import("main.zig");
+    _ = @import("tunnel.zig");
+}

src/tunnel.zig

@@ -0,0 +1,62 @@
+const std = @import("std");
+const os = std.os;
+const mem = std.mem;
+const posix = std.posix;
+
+const log = std.log.scoped(.nyotun);
+
+const IFF_TUN = 0x0001; // <linux/if_tun.h>
+const IFF_NO_PI = 0x1000; // <linux/if_tun.h>
+const TUNSETIFF = 0x800454ca; // same value on all archs, see go/src/syscall/*.go
+
+dev: [posix.IFNAMESIZE - 1:0]u8,
+tunFile: posix.fd_t,
+
+pub fn init(devname: ?[]const u8) !Tunnel {
+    const tunFile = try posix.open(
+        "/dev/net/tun",
+        posix.O{
+            .ACCMODE = .RDWR,
+            .CLOEXEC = true,
+        },
+        0,
+    );
+    errdefer posix.close(tunFile);
+
+    var ifr: posix.ifreq = undefined;
+    @memset(@as([*]u8, @ptrCast(&ifr))[0..@sizeOf(posix.ifreq)], 0);
+
+    ifr.ifru.flags = IFF_TUN | IFF_NO_PI;
+
+    if (devname) |name| {
+        if (name.len >= posix.IFNAMESIZE - 1) {
+            return error.BadInterfaceName;
+        }
+        @memcpy(ifr.ifrn.name[0..name.len], name);
+    }
+
+    const err = posix.system.ioctl(tunFile, TUNSETIFF, @intFromPtr(&ifr));
+    if (posix.errno(err) != .SUCCESS) {
+        log.err("unable to set TUNSETIFF: {s}", .{@tagName(posix.errno(err))});
+        return error.OpenDevTun;
+    }
+
+    var tunnel = Tunnel{
+        .dev = undefined,
+        .tunFile = tunFile,
+    };
+    @memcpy(tunnel.dev[0..posix.IFNAMESIZE], mem.sliceTo(&ifr.ifrn.name, 0));
+
+    return tunnel;
+}
+
+pub fn close(self: *Tunnel) void {
+    posix.close(self.tunFile);
+}
+
+const Tunnel = @This();
+
+test "init tunnel" {
+    var tun = try init("nyotun");
+    tun.close();
+}