Re: [libnbd PATCH v3 14/22] info: Expose extended-headers support through nbdinfo

[Richard W.M. Jones]

On Thu, May 25, 2023 at 08:01:00AM -0500, Eric Blake wrote:
> Add another bit of overall server information, as well as a '--can
> extended-headers' silent query.  For now, the testsuite is written
> assuming that when nbdkit finally adds extended headers support, it
> will also add a --no-eh kill switch comparable to its existing --no-sr
> switch.
> 
> Signed-off-by: Eric Blake <eblake@redhat.com>
> ---
>  info/nbdinfo.pod     | 11 ++++++++++-
>  info/can.c           |  9 +++++++++
>  info/info-can.sh     | 27 +++++++++++++++++++++++++++
>  info/info-packets.sh | 17 ++++++++++++++++-
>  info/main.c          |  7 ++++++-
>  5 files changed, 68 insertions(+), 3 deletions(-)
> 
> diff --git a/info/nbdinfo.pod b/info/nbdinfo.pod
> index 7eb3c1a0..9ea4a278 100644
> --- a/info/nbdinfo.pod
> +++ b/info/nbdinfo.pod
> @@ -86,6 +86,7 @@ the I<--json> parameter:
>     "protocol": "newstyle-fixed",
>     "TLS": false,
>     "structured": true,
> +   "extended": false,
>     "exports": [
>       {
>         "export-name": "",
> @@ -165,6 +166,11 @@ Test if the NBD URI connection is using TLS.
>  Test if server can respond with structured replies (a prerequisite
>  for supporting block status commands).
> 
> +=item nbdinfo --can extended-headers URI
> +
> +Test if server supports extended headers (a prerequisite for
> +supporting 64-bit commands; implies structured replies as well).

Maybe we should add "--has" and "--have" as yet more synonyms for
--is/--can.  "--has extended-headers" reads better.  It's only tiny
extra change to this array:

https://gitlab.com/nbdkit/libnbd/-/blob/27d4ea0bd833f17349e7696353c7a9df069a3e2a/info/main.c#L109

>  =item nbdinfo --is rotational URI
> 
>  Test if the server export is backed by something which behaves like a
> @@ -312,6 +318,8 @@ Display brief command line help and exit.
> 
>  =item B<--can df>
> 
> +=item B<--can extended-headers>
> +
>  =item B<--can fast-zero>
> 
>  =item B<--can flush>
> @@ -341,7 +349,8 @@ and the following libnbd functions: L<nbd_can_cache(3)>,
>  L<nbd_can_df(3)>, L<nbd_can_fast_zero(3)>, L<nbd_can_flush(3)>,
>  L<nbd_can_fua(3)>, L<nbd_can_multi_conn(3)>, L<nbd_can_trim(3)>,
>  L<nbd_can_zero(3)>, L<nbd_is_read_only(3)>,
> -L<nbd_get_structured_replies_negotiated(3)>.
> +L<nbd_get_structured_replies_negotiated(3)>,
> +L<nbd_get_extended_headers_negotiated(3)>.
> 
>  =item B<--color>
> 
> diff --git a/info/can.c b/info/can.c
> index 01ab4806..31c4a1ca 100644
> --- a/info/can.c
> +++ b/info/can.c
> @@ -50,6 +50,15 @@ do_can (void)
>             strcasecmp (can, "structured_replies") == 0)
>      feature = nbd_get_structured_replies_negotiated (nbd);
> 
> +  else if (strcasecmp (can, "eh") == 0 ||
> +           strcasecmp (can, "extended header") == 0 ||
> +           strcasecmp (can, "extended-header") == 0 ||
> +           strcasecmp (can, "extended_header") == 0 ||
> +           strcasecmp (can, "extended headers") == 0 ||
> +           strcasecmp (can, "extended-headers") == 0 ||
> +           strcasecmp (can, "extended_headers") == 0)
> +    feature = nbd_get_extended_headers_negotiated (nbd);
> +
>    else if (strcasecmp (can, "readonly") == 0 ||
>             strcasecmp (can, "read-only") == 0 ||
>             strcasecmp (can, "read_only") == 0)
> diff --git a/info/info-can.sh b/info/info-can.sh
> index 6cc8cbf4..8154d1ce 100755
> --- a/info/info-can.sh
> +++ b/info/info-can.sh
> @@ -61,6 +61,33 @@ esac
>  EOF
>  test $st = 2
> 
> +# --can extended-headers cannot be positively tested until nbdkit gains
> +# --no-eh support.  Otherwise, it is similar to --can structured-reply.
> +
> +no_eh=
> +if nbdkit --no-eh --help >/dev/null 2>/dev/null; then
> +    no_eh=--no-eh
> +    nbdkit -v -U - sh - \
> +           --run '$VG nbdinfo --can extended-headers 
> "nbd+unix:///?socket=$unixsocket"' <<'EOF'
> +case "$1" in
> +  get_size) echo 1024 ;;
> +  pread) ;;
> +  *) exit 2 ;;
> +esac
> +EOF
> +fi
> +
> +st=0
> +nbdkit -v -U - $no_eh sh - \
> +       --run '$VG nbdinfo --can extended-headers 
> "nbd+unix:///?socket=$unixsocket"' <<'EOF' || st=$?
> +case "$1" in
> +  get_size) echo 1024 ;;
> +  pread) ;;
> +  *) exit 2 ;;
> +esac
> +EOF
> +test $st = 2
> +
>  # --can cache and --can fua require special handling because in
>  # nbdkit-sh-plugin we must print "native" or "none".  Also the can_fua
>  # flag is only sent if the export is writable (hence can_write below).
> diff --git a/info/info-packets.sh b/info/info-packets.sh
> index 2460052e..410faef8 100755
> --- a/info/info-packets.sh
> +++ b/info/info-packets.sh
> @@ -27,12 +27,27 @@ requires nbdkit --no-sr memory --version
>  out=info-packets.out
>  cleanup_fn rm -f $out
> 
> +# Older nbdkit does not support extended headers; --no-eh is a reliable
> +# witness of whether nbdkit is new enough.
> +
> +no_eh=
> +if nbdkit --no-eh --help >/dev/null 2>/dev/null; then
> +    no_eh=--no-eh
> +fi
> +
>  nbdkit --no-sr -U - memory size=1M \
>         --run '$VG nbdinfo "nbd+unix:///?socket=$unixsocket"' > $out
>  cat $out
>  grep "protocol: .*using simple packets" $out
> 
> -nbdkit -U - memory size=1M \
> +nbdkit $no_eh -U - memory size=1M \
>         --run '$VG nbdinfo "nbd+unix:///?socket=$unixsocket"' > $out
>  cat $out
>  grep "protocol: .*using structured packets" $out
> +
> +if test x != "x$no_eh"; then
> +    nbdkit -U - memory size=1M \
> +           --run '$VG nbdinfo "nbd+unix:///?socket=$unixsocket"' > $out
> +    cat $out
> +    grep "protocol: .*using extended packets" $out
> +fi
> diff --git a/info/main.c b/info/main.c
> index 1b99e089..8c923266 100644
> --- a/info/main.c
> +++ b/info/main.c
> @@ -302,11 +302,13 @@ main (int argc, char *argv[])
>      const char *protocol;
>      int tls_negotiated;
>      int sr_negotiated;
> +    int eh_negotiated;
> 
>      /* Print per-connection fields. */
>      protocol = nbd_get_protocol (nbd);
>      tls_negotiated = nbd_get_tls_negotiated (nbd);
>      sr_negotiated = nbd_get_structured_replies_negotiated (nbd);
> +    eh_negotiated = nbd_get_extended_headers_negotiated (nbd);
> 
>      if (!json_output) {
>        if (protocol) {
> @@ -314,8 +316,9 @@ main (int argc, char *argv[])
>          fprintf (fp, "protocol: %s", protocol);
>          if (tls_negotiated >= 0)
>            fprintf (fp, " %s TLS", tls_negotiated ? "with" : "without");
> -        if (sr_negotiated >= 0)
> +        if (eh_negotiated >= 0 && sr_negotiated >= 0)
>            fprintf (fp, ", using %s packets",
> +                   eh_negotiated ? "extended" :
>                     sr_negotiated ? "structured" : "simple");
>          fprintf (fp, "\n");
>          ansi_restore (fp);
> @@ -333,6 +336,8 @@ main (int argc, char *argv[])
>          fprintf (fp, "\"TLS\": %s,\n", tls_negotiated ? "true" : "false");
>        if (sr_negotiated >= 0)
>          fprintf (fp, "\"structured\": %s,\n", sr_negotiated ? "true" : 
> "false");
> +      if (eh_negotiated >= 0)
> +        fprintf (fp, "\"extended\": %s,\n", eh_negotiated ? "true" : 
> "false");
>      }
> 
>      if (!list_all)
> -- 
> 2.40.1

Reviewed-by: Richard W.M. Jones <rjones@redhat.com>

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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