1 files changed, 28 insertions, 1 deletions
diff --git a/src/9p_io.zig b/src/9p_io.zig
index 0eaa2d7e..e475416e 100644
--- a/src/9p_io.zig
+++ b/src/9p_io.zig
@@ -874,7 +874,29 @@ pub fn listen(io: std.Io, gpa: std.mem.Allocator, core: *pardes.Pardes, named: [
         .greet_timeout_ms = Listener.greet_deadline_ms,
     });
     const p = socketPath(&l.path_buf, dir, entry_name).?;
-    _ = l.runner.listen(.{ .unix = p }, max_conns) catch |err| retry: {
+    // Listened on under a name of its own, then renamed into place: a client
+    // that waits for the socket to appear finds it listening already. Bound
+    // at its own name, it was there a moment before listen(2), and a connect
+    // then was refused. (No room for the longer name: bound in place.)
+    var tmp_buf: [sun_path_len]u8 = undefined;
+    if (std.fmt.bufPrintSentinel(&tmp_buf, "{s}.{d}", .{ p, libc.getpid() }, 0) catch null) |tmp| {
+        const existing = @import("fs.zig").statPath(io, p, .{ .follow_symlinks = false }) catch null;
+        if (existing != null and (existing.?.kind != .unix_domain_socket or alive(p))) {
+            log.warn("something is already listening on {s}", .{p});
+            l.deinit(gpa);
+            return null;
+        }
+        _ = libc.unlink(tmp);
+        _ = l.runner.listen(.{ .unix = tmp }, max_conns) catch {
+            l.deinit(gpa);
+            return null;
+        };
+        if (libc.chmod(tmp, 0o600) != 0 or libc.rename(tmp, p) != 0) {
+            _ = libc.unlink(tmp);
+            l.deinit(gpa);
+            return null;
+        }
+    } else _ = l.runner.listen(.{ .unix = p }, max_conns) catch |err| retry: {
         const existing = @import("fs.zig").statPath(io, p, .{ .follow_symlinks = false }) catch null;
         if (err != error.AddressInUse or existing == null or existing.?.kind != .unix_domain_socket or alive(p)) {
             log.warn("something is already listening on {s}", .{p});
@@ -1338,6 +1360,11 @@ test "a listening editor posts itself into the 9P registry and unposts on stop"
         // The socket stays exactly where pardes has always bound it:
         // adopting the registry moves nothing, it only advertises.
         try testing.expect(statNoFollow(sock) != null);
+        // It appeared already listening, renamed into place from a name of
+        // its own, which is gone.
+        try testing.expect(alive(sock));
+        var tmp_buf: [sun_path_len:0]u8 = undefined;
+        try testing.expect(statNoFollow(try std.fmt.bufPrintSentinel(&tmp_buf, "{s}.{d}", .{ sock, libc.getpid() }, 0)) == null);
         // And the registry holds a symlink to it one directory down, so
         // several editors group under /mnt/9p/pardes/ instead of
         // crowding the registry root — the layout zmx posts its