Re: [PATCH 6/6] tests/9pfs: guard recent 'Twalk' behaviour fix

[Christian Schoenebeck]

On Mittwoch, 9. März 2022 19:21:18 CET Christian Schoenebeck wrote:
> Previous 9p patch fixed 'Twalk' request handling, which was previously not
> behaving as specified by the 9p2000 protocol spec. This patch adds a new
> test case which guards the new 'Twalk' behaviour in question.
> 
> More specifically: it sends a 'Twalk' request where the 1st path component
> is valid, whereas the 2nd path component transmitted to server does not
> exist. The expected behaviour is that 9p server would respond by sending
> a 'Rwalk' response with exactly 1 QID (instead of 'Rlerror' response).
> 
> Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
> ---
>  tests/qtest/virtio-9p-test.c | 42 +++++++++++++++++++++++++++++++++---
>  1 file changed, 39 insertions(+), 3 deletions(-)
> 
> diff --git a/tests/qtest/virtio-9p-test.c b/tests/qtest/virtio-9p-test.c
> index 9098e21173..f29de1ca64 100644
> --- a/tests/qtest/virtio-9p-test.c
> +++ b/tests/qtest/virtio-9p-test.c
> @@ -638,8 +638,12 @@ static void do_version(QVirtio9P *v9p)
>      g_assert_cmpmem(server_version, server_len, version, strlen(version));
>  }
> 
> -/* utility function: walk to requested dir and return fid for that dir */
> -static uint32_t do_walk(QVirtio9P *v9p, const char *path)
> +/*
> + * utility function: walk to requested dir and return fid for that dir and
> + * the QIDs of server response
> + */
> +static uint32_t do_walk_rqids(QVirtio9P *v9p, const char *path, uint16_t
> *nwqid, +                              v9fs_qid **wqid)
>  {
>      char **wnames;
>      P9Req *req;
> @@ -649,12 +653,18 @@ static uint32_t do_walk(QVirtio9P *v9p, const char
> *path)
> 
>      req = v9fs_twalk(v9p, 0, fid, nwnames, wnames, 0);
>      v9fs_req_wait_for_reply(req, NULL);
> -    v9fs_rwalk(req, NULL, NULL);
> +    v9fs_rwalk(req, nwqid, wqid);
> 
>      split_free(&wnames);
>      return fid;
>  }
> 
> +/* utility function: walk to requested dir and return fid for that dir */
> +static uint32_t do_walk(QVirtio9P *v9p, const char *path)
> +{
> +    return do_walk_rqids(v9p, path, NULL, NULL);
> +}
> +
>  /* utility function: walk to requested dir and expect passed error response
> */ static void do_walk_expect_error(QVirtio9P *v9p, const char *path,
> uint32_t err) {
> @@ -1048,9 +1058,33 @@ static void fs_walk_nonexistent(void *obj, void
> *data, QGuestAllocator *t_alloc) alloc = t_alloc;
> 
>      do_attach(v9p);
> +    /*
> +     * The 9p2000 protocol spec sais: "If the first element cannot be
> walked +     * for any reason, Rerror is returned."
> +     */
>      do_walk_expect_error(v9p, "non-existent", ENOENT);
>  }
> 
> +static void fs_walk_2nd_nonexistent(void *obj, void *data,
> +                                    QGuestAllocator *t_alloc)
> +{
> +    QVirtio9P *v9p = obj;
> +    alloc = t_alloc;
> +    uint16_t nwqid;
> +    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);
> +    /*
> +     * The 9p2000 protocol spec sais: "nwqid is therefore either nwname or
> the +     * index of the first elementwise walk that failed."
> +     */
> +    assert(nwqid == 1);
> +}

I should probably extend this test case with a separate 7th patch to check 
that fid was really unaffected by Twalk, by comparing the QID before vs. after 
the walk (similar to what patch 3 does).

> +
>  static void fs_walk_none(void *obj, void *data, QGuestAllocator *t_alloc)
>  {
>      QVirtio9P *v9p = obj;
> @@ -1531,6 +1565,8 @@ static void register_virtio_9p_test(void)
>                   fs_walk_dotdot,  &opts);
>      qos_add_test("synth/walk/non_existent", "virtio-9p",
> fs_walk_nonexistent, &opts);
> +    qos_add_test("synth/walk/2nd_non_existent", "virtio-9p",
> +                 fs_walk_2nd_nonexistent, &opts);
>      qos_add_test("synth/lopen/basic", "virtio-9p", fs_lopen,  &opts);
>      qos_add_test("synth/write/basic", "virtio-9p", fs_write,  &opts);
>      qos_add_test("synth/flush/success", "virtio-9p", fs_flush_success,