[PULL 7/7] tests/9pfs: check fid being unaffected in fs_walk_2nd_nonexistent

[Christian Schoenebeck <qemu_oss@crudebyte.com>]

Extend previously added test case by checking that fid was unaffected
by 'Twalk' request (i.e. when 2nd path component of request being
invalid). Do that by subsequently sending a 'Tgetattr' request with
the fid previously used for 'Twalk'; that 'Tgetattr' request should
return an 'Rlerror' response by 9p server with error code ENOENT as
that fid is basically invalid.

And as we are at it, also check that the QID returned by 'Twalk' is
not identical to the root node's QID.

Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Message-Id: <6f0813cafdbf683cdac8b1492dd4ef8699c5b1d9.1647339025.git.qemu_oss@crudebyte.com>
---
 tests/qtest/virtio-9p-test.c | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/tests/qtest/virtio-9p-test.c b/tests/qtest/virtio-9p-test.c
index c787ded4d2..25305a4cf7 100644
--- a/tests/qtest/virtio-9p-test.c
+++ b/tests/qtest/virtio-9p-test.c
@@ -721,14 +721,19 @@ static void fs_version(void *obj, void *data, QGuestAllocator *t_alloc)
     do_version(obj);
 }
 
-static void do_attach(QVirtio9P *v9p)
+static void do_attach_rqid(QVirtio9P *v9p, v9fs_qid *qid)
 {
     P9Req *req;
 
     do_version(v9p);
     req = v9fs_tattach(v9p, 0, getuid(), 0);
     v9fs_req_wait_for_reply(req, NULL);
-    v9fs_rattach(req, NULL);
+    v9fs_rattach(req, qid);
+}
+
+static void do_attach(QVirtio9P *v9p)
+{
+    do_attach_rqid(v9p, NULL);
 }
 
 static void fs_attach(void *obj, void *data, QGuestAllocator *t_alloc)
@@ -1101,19 +1106,32 @@ static void fs_walk_2nd_nonexistent(void *obj, void *data,
 {
     QVirtio9P *v9p = obj;
     alloc = t_alloc;
+    v9fs_qid root_qid;
     uint16_t nwqid;
+    uint32_t fid, err;
+    P9Req *req;
     g_autofree v9fs_qid *wqid = NULL;
     g_autofree char *path = g_strdup_printf(
         QTEST_V9FS_SYNTH_WALK_FILE "/non-existent", 0
     );
 
-    do_attach(v9p);
-    do_walk_rqids(v9p, path, &nwqid, &wqid);
+    do_attach_rqid(v9p, &root_qid);
+    fid = do_walk_rqids(v9p, path, &nwqid, &wqid);
     /*
      * The 9p2000 protocol spec says: "nwqid is therefore either nwname or the
      * index of the first elementwise walk that failed."
      */
     assert(nwqid == 1);
+
+    /* returned QID wqid[0] is file ID of 1st subdir */
+    g_assert(wqid && wqid[0] && !is_same_qid(root_qid, wqid[0]));
+
+    /* expect fid being unaffected by walk above */
+    req = v9fs_tgetattr(v9p, fid, P9_GETATTR_BASIC, 0);
+    v9fs_req_wait_for_reply(req, NULL);
+    v9fs_rlerror(req, &err);
+
+    g_assert_cmpint(err, ==, ENOENT);
 }
 
 static void fs_walk_none(void *obj, void *data, QGuestAllocator *t_alloc)
-- 
2.30.2