On Thu, Feb 02, 2017 at 05:16:25PM +0000, Richard W.M. Jones wrote:
> Socket activation (sometimes known as systemd socket activation)
> allows an Internet superserver to pass a pre-opened listening socket
> to the process, instead of having qemu-nbd open a socket itself. This
> is done via the LISTEN_FDS and LISTEN_PID environment variables, and a
> standard file descriptor range.
>
> This change partially implements socket activation for qemu-nbd. If
> the environment variables are set correctly, then socket activation
> will happen automatically, otherwise everything works as before. The
> limitation is that LISTEN_FDS must be 1.
>
> Signed-off-by: Richard W.M. Jones.
> ---
> qemu-nbd.c | 172
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++----
> 1 file changed, 163 insertions(+), 9 deletions(-)
>
> diff --git a/qemu-nbd.c b/qemu-nbd.c
> index c734f62..b3088d0 100644
> --- a/qemu-nbd.c
> +++ b/qemu-nbd.c
> @@ -463,6 +463,135 @@ static QCryptoTLSCreds *nbd_get_tls_creds(const char
> *id, Error **errp)
> return creds;
> }
>
> +static void setup_address_and_port(const char **address, const char **port)
> +{
> + if (*address == NULL) {
> + *address = "0.0.0.0";
> + }
> +
> + if (*port == NULL) {
> + *port = g_strdup_printf("%d", NBD_DEFAULT_PORT);;
Please stringify NBD_DEFAULT_PORT instead of using g_strdup_printf().
That avoids the memory leak.
> @@ -751,6 +881,19 @@ int main(int argc, char **argv)
> trace_init_file(trace_file);
> qemu_set_log(LOG_TRACE);
>
> + socket_activation = check_socket_activation();
> + if (socket_activation == 0) {
> + setup_address_and_port(&bindto, &port);
> + } else {
> + /* Using socket activation - check user didn't use -p etc. */
> + const char *err_msg = socket_activation_validate_opts(device,
> sockpath,
> + bindto, port);
Daemonizing is also incompatible with socket activation. We've marked
the fds O_CLOEXEC so the child won't have access to them. Please add an
error in case a user tries this.
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