[PATCH 1/5] lib: Introduce 'virDomainQemuMonitorCommandWithFiles'

[Michal Prívozník]

On 2/3/22 15:51, Peter Krempa wrote:
> This API has the same semantics as 'virDomainQemuMonitorCommand' but
> accepts file descriptors which are then forwarded to qemu.
> 
> Signed-off-by: Peter Krempa <pkrempa at redhat.com>
> ---
>  include/libvirt/libvirt-qemu.h      |  6 +++
>  src/driver-hypervisor.h             |  8 ++++
>  src/libvirt-qemu.c                  | 71 +++++++++++++++++++++++++++++
>  src/libvirt_qemu.syms               |  5 ++
>  src/qemu_protocol-structs           |  9 ++++
>  src/remote/qemu_protocol.x          | 20 +++++++-
>  src/remote/remote_daemon_dispatch.c | 42 +++++++++++++++++
>  src/remote/remote_driver.c          | 40 ++++++++++++++++
>  8 files changed, 200 insertions(+), 1 deletion(-)
> 
> diff --git a/include/libvirt/libvirt-qemu.h b/include/libvirt/libvirt-qemu.h
> index 0cc2872821..eed691ec91 100644
> --- a/include/libvirt/libvirt-qemu.h
> +++ b/include/libvirt/libvirt-qemu.h
> @@ -37,6 +37,12 @@ typedef enum {
> 
>  int virDomainQemuMonitorCommand(virDomainPtr domain, const char *cmd,
>                                  char **result, unsigned int flags);
> +int virDomainQemuMonitorCommandWithFiles(virDomainPtr domain,
> +                                         const char *cmd,
> +                                         unsigned int nfiles,
> +                                         int *files,

Do we perhaps want to have another argument for fdOut (e.g. when QEMU
would want to return an FD)? I don't think there is a command that would
do that now, but who knows, maybe there will be someday.

> +                                         char **result,
> +                                         unsigned int flags);
> 
>  virDomainPtr virDomainQemuAttach(virConnectPtr domain,
>                                   unsigned int pid_value,
> diff --git a/src/driver-hypervisor.h b/src/driver-hypervisor.h
> index c83fb648a2..b3e55cf4ac 100644
> --- a/src/driver-hypervisor.h
> +++ b/src/driver-hypervisor.h
> @@ -874,6 +874,13 @@ typedef int
>                                    const char *cmd,
>                                    char **result,
>                                    unsigned int flags);
> +typedef int
> +(*virDrvDomainQemuMonitorCommandWithFiles)(virDomainPtr domain,
> +                                           const char *cmd,
> +                                           unsigned int nfiles,
> +                                           int *files,
> +                                           char **result,
> +                                           unsigned int flags);
> 
>  typedef char *
>  (*virDrvDomainQemuAgentCommand)(virDomainPtr domain,
> @@ -1597,6 +1604,7 @@ struct _virHypervisorDriver {
>      virDrvDomainRevertToSnapshot domainRevertToSnapshot;
>      virDrvDomainSnapshotDelete domainSnapshotDelete;
>      virDrvDomainQemuMonitorCommand domainQemuMonitorCommand;
> +    virDrvDomainQemuMonitorCommandWithFiles domainQemuMonitorCommandWithFiles;
>      virDrvDomainQemuAttach domainQemuAttach;
>      virDrvDomainQemuAgentCommand domainQemuAgentCommand;
>      virDrvConnectDomainQemuMonitorEventRegister connectDomainQemuMonitorEventRegister;
> diff --git a/src/libvirt-qemu.c b/src/libvirt-qemu.c
> index 1afb5fe529..1dbe0cba54 100644
> --- a/src/libvirt-qemu.c
> +++ b/src/libvirt-qemu.c
> @@ -96,6 +96,77 @@ virDomainQemuMonitorCommand(virDomainPtr domain, const char *cmd,
>  }
> 
> 
> +/**
> + * virDomainQemuMonitorCommandWithFiles:
> + * @domain: a domain object
> + * @cmd: the qemu monitor command string
> + * @nfiles: number of filedescriptors passed in @files
> + * @files: filedescriptors to be passed to qemu with the command
> + * @result: a string returned by @cmd
> + * @flags: bitwise-or of supported virDomainQemuMonitorCommandFlags
> + *
> + * This API is QEMU specific, so it will only work with hypervisor
> + * connections to the QEMU driver with local connections using the unix socket.
> + *
> + * Send an arbitrary monitor command @cmd with file descriptors @files to
> + * @domain through the qemu monitor. There are several requirements to safely
> + * and successfully use this API:
> + *
> + *   - A @cmd that queries state without making any modifications is safe
> + *   - A @cmd that alters state that is also tracked by libvirt is unsafe,
> + *     and may cause libvirtd to crash
> + *   - A @cmd that alters state not tracked by the current version of
> + *     libvirt is possible as a means to test new qemu features before
> + *     they have support in libvirt, but no guarantees are made to safety
> + *
> + * If VIR_DOMAIN_QEMU_MONITOR_COMMAND_HMP is set, the command is
> + * considered to be a human monitor command and libvirt will automatically
> + * convert it into QMP if needed.  In that case the @result will also
> + * be converted back from QMP.
> + *
> + * If successful, @result will be filled with the string output of the
> + * @cmd, and the caller must free this string.
> + *
> + * Returns 0 in case of success, -1 in case of failure
> + */
> +int
> +virDomainQemuMonitorCommandWithFiles(virDomainPtr domain,
> +                                     const char *cmd,
> +                                     unsigned int nfiles,
> +                                     int *files,
> +                                     char **result,
> +                                     unsigned int flags)
> +{
> +    virConnectPtr conn;
> +
> +    VIR_DOMAIN_DEBUG(domain, "cmd=%s, nfiles=%u, files=%p, result=%p, flags=0x%x",
> +                     cmd, nfiles, files, result, flags);
> +
> +    virResetLastError();
> +
> +    virCheckDomainReturn(domain, -1);
> +    conn = domain->conn;
> +
> +    virCheckNonNullArgGoto(result, error);
> +    virCheckReadOnlyGoto(conn->flags, error);

Missing VIR_DRV_SUPPORTS_FEATURE(conn->driver, conn,
VIR_DRV_FEATURE_FD_PASSING); check.

> +
> +    if (conn->driver->domainQemuMonitorCommandWithFiles) {
> +        int ret;
> +        ret = conn->driver->domainQemuMonitorCommandWithFiles(domain, cmd,
> +                                                              nfiles, files,
> +                                                              result, flags);
> +        if (ret < 0)
> +            goto error;
> +        return ret;
> +    }
> +
> +    virReportUnsupportedError();
> +
> + error:
> +    virDispatchError(conn);
> +    return -1;
> +}

Michal