Re: [Libguestfs] [PATCH nbdkit 2/3] delay: Fix delay-close

See comments in the code for how this has been fixed. This only delays clients which use NBD_CMD_DISC (libnbd nbd_shutdown(3)). Clients which drop the connection obviously cannot be delayed. For example: $ nbdkit --filter=delay null delay-close=3 \ --run 'time nbdsh -u $uri -c "h.shutdown()" time nbdsh -u $uri -c "pass"' real 0m3.061s # Client used shutdown, was delayed user 0m0.028s sys 0m0.030s real 0m0.058s # Client disconnected, was not delayed user 0m0.029s sys 0m0.027s Reported-by: Ming Xie Fixes: commit de8dcd3a34a38b088a0f9a6f8ca754702ad1f598 Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1991652 --- filters/delay/nbdkit-delay-filter.pod | 13 +++++++-- filters/delay/delay.c | 42 +++++++++++++++++++-------- 2 files changed, 40 insertions(+), 15 deletions(-) diff --git a/filters/delay/nbdkit-delay-filter.pod b/filters/delay/nbdkit-delay-filter.pod index 11ae544b..bfc90dae 100644 --- a/filters/delay/nbdkit-delay-filter.pod +++ b/filters/delay/nbdkit-delay-filter.pod @@ -117,15 +117,22 @@ the plugin. =item B<delay-open=>NNB<ms> +(nbdkit E<ge> 1.28) + +Delay open (client connection) by C<SECS> seconds or C<NN> +milliseconds. + =item B<delay-close=>SECS =item B<delay-close=>NNB<ms> (nbdkit E<ge> 1.28) -Delay open and close operations by C<SECS> seconds or C<NN> -milliseconds. Open corresponds to client connection. Close may not -be visible to clients if they abruptly disconnect. +Delay close (client disconnection) by C<SECS> seconds of C<NN>

+milliseconds. This will also cause server shutdown to be delayed. +This only affects clients that gracefully disconnect (using +C<NBD_CMD_DISC> / libnbd function L<nbd_shutdown(3)>). Clients that +abruptly close the socket cannot be delayed. =back

+/* Close connection. + * + * We cannot call nbdkit_nanosleep here because the socket may have + * been closed and that function will abort and return immediately. + * However we want for force a sleep (even if the server is shutting

+ * down) so use regular nanosleep instead. + * + * We cannot use the .close callback because that happens after the + * socket has closed, thus not delaying the client. By using + * .finalize we can delay well-behaved clients (those that use + * NBD_CMD_DISC). We cannot delay clients that drop the connection. + */ +static int +delay_finalize (nbdkit_next *next, void *handle) {