A Mount dial with a network pardes does not dial (`nowhere!x`) is a bad dial address, EINVAL, not a session name that does not answer

A dial with a `!` and no `/` that was neither tcp!, quic! nor unix! was
taken for a session's name, failing as `dial failed: no answer`, EIO.
It is now refused as the malformed address it is, before any dial. A
path with a `!` in it still dials.

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

2 files changed, 13 insertions, 0 deletions

diff --git a/src/9p_io.zig b/src/9p_io.zig
index a4340ddf..e199dea9 100644
--- a/src/9p_io.zig
+++ b/src/9p_io.zig
@@ -1425,6 +1425,8 @@ test "TCP addresses are numeric and normalize mapped IPv4" {
     try Client.validateDial("/tmp/pardes-owned.sock");
     try Client.validateDial("unix!/tmp/pardes-owned.sock");
     try testing.expectError(error.BadDial, Client.validateDial("unix!work"));
+    try testing.expectError(error.BadDial, Client.validateDial("nowhere!x"));
+    try Client.validateDial("/tmp/odd!name.sock");
     try testing.expectError(error.BadDial, Client.validateDial("unix!"));
     try testing.expectError(error.BadDial, Client.validateDial("unix!/tmp/a\x00b"));
     try testing.expectError(error.BadDial, Client.validateDial("tcp!localhost!5640"));
@@ -2078,6 +2080,9 @@ pub const Client = struct {
             return .{ .quic = try networkAddress(dial, false) };
         }
         const explicit_unix = std.mem.startsWith(u8, dial, "unix!");
+        // A network this does not dial (`nowhere!x`) is a malformed address,
+        // not a session named so.
+        if (!explicit_unix and std.mem.indexOfScalar(u8, dial, '/') == null and std.mem.indexOfScalar(u8, dial, '!') != null) return error.BadDial;
         const path = if (explicit_unix) dial[5..] else dial;
         if (explicit_unix and !std.mem.startsWith(u8, path, "/")) return error.BadDial;
         if (std.mem.indexOfScalar(u8, path, '/') != null) {
diff --git a/src/ninep/ctl.zig b/src/ninep/ctl.zig
index d4d09e0b..3ec1f4d6 100644
--- a/src/ninep/ctl.zig
+++ b/src/ninep/ctl.zig
@@ -4371,3 +4371,11 @@ test "DumpDir refuses a relative directory and one that may not be written, up f
     p.dumpFailed("/proc/1/root/x/pardes.dump.zon", error.FileNotFound);
     try testing.expect(std.mem.endsWith(u8, p.fs.late_failure[0..p.fs.late_failure_len], ": permission denied"));
 }
+
+test "a Mount dial with a network it does not know is a bad dial address, EINVAL" {
+    const p = try withFile(testing.allocator, "x\n");
+    defer p.deinit();
+    const r = wr(p, @intFromEnum(tree.TopFile.ctl), "Mount peer nowhere!x\n");
+    try testing.expectEqual(E.INVAL, r.errno());
+    try testing.expectStringStartsWith(r.reply.ename, "Mount: bad dial address: nowhere!x");
+}