Mount dials its peer at once and fails if none answers; a peer out of reach is said as `dial failed: <reason>`

Mount took any well-formed dial and nothing was found out until the
first look through it, which then said `look: look: dial`. Mount now
probes the peer (version, attach, its root) with the turn out, and fails
its write, mounting nothing, when none answers; the dial errors read as
words, `no answer`, `timed out`, `hung up`, and a look through a peer
gone since names its path: `look: /n/peer/f: dial failed: no answer`.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 17 insertions, 0 deletions

diff --git a/src/Messages.zig b/src/Messages.zig
index c0838fb2..482ad64d 100644
--- a/src/Messages.zig
+++ b/src/Messages.zig
@@ -450,10 +450,27 @@ pub const no_pane_slots = "no space for a pane: {d} max";
 pub const no_pane_room = "no space for a pane in that column: each keeps its tag and {d} rows";
 
 /// `<operation>: <the error in words>`: FileNotFound reads "file not found".
+/// Why a peer could not be reached, in words, for an error of a 9P dial
+/// (src/9p_io.zig, Client); null for any other error.
+pub fn dialReason(err: anyerror) ?[]const u8 {
+    return switch (err) {
+        error.Dial => "no answer",
+        error.Timeout => "timed out",
+        error.Hangup => "hung up",
+        error.Botch => "protocol botch",
+        else => null,
+    };
+}
+
 pub fn reportError(p: *Pardes, id: usize, operation: []const u8, err: anyerror) void {
     var buf: [256]u8 = undefined;
     var w = std.Io.Writer.fixed(&buf);
     w.print("{s}: ", .{operation}) catch {};
+    // A peer out of reach says so, not the error's name (`dial`).
+    if (dialReason(err)) |why| {
+        w.print("dial failed: {s}", .{why}) catch {};
+        return reportFailure(p, id, w.buffered());
+    }
     // Every route that opens a pane says the cap the same way.
     if (err == error.NoPaneSlots or err == error.NoPaneRoom) {
         if (err == error.NoPaneSlots)