Re: [PATCH 1/3] utils: Implement virCommandPassFDGetFDIndex

[Martin Kletzander <mkletzan@xxxxxxxxxx>]

On Mon, Feb 23, 2015 at 06:50:46AM -0500, Stefan Berger wrote:
> Implement virCommandPassFDGetFDIndex to determine the index a given
> file descriptor will have when passed to the child process. When this
> function is called, a flag is set to prevent the reordering of the
> file descriptors.
>
> Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxxxxxxx>
> ---
> src/libvirt_private.syms |  1 +
> src/util/vircommand.c    | 33 +++++++++++++++++++++++++++++++++
> src/util/vircommand.h    |  3 +++
> 3 files changed, 37 insertions(+)
>
> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
> index c156b40..aadb833 100644
> --- a/src/libvirt_private.syms
> +++ b/src/libvirt_private.syms
> @@ -1213,6 +1213,7 @@ virCommandNewArgList;
> virCommandNewArgs;
> virCommandNonblockingFDs;
> virCommandPassFD;
> +virCommandPassFDGetFDIndex;
> virCommandPassListenFDs;
> virCommandRawStatus;
> virCommandRequireHandshake;
> diff --git a/src/util/vircommand.c b/src/util/vircommand.c
> index 6527d85..2616446 100644
> --- a/src/util/vircommand.c
> +++ b/src/util/vircommand.c
> @@ -67,6 +67,7 @@ enum {
>     VIR_EXEC_RUN_SYNC   = (1 << 3),
>     VIR_EXEC_ASYNC_IO   = (1 << 4),
>     VIR_EXEC_LISTEN_FDS = (1 << 5),
> +    VIR_EXEC_FIXED_FDS  = (1 << 6),

The descriptors shouldn't get reordered *unless* there is
VIR_EXEC_LISTEN_FDS flag added, so FIXED_FDS shouldn't be necessary.
Or is there a bug in that approach that needs fixing?

> };
>
> typedef struct _virCommandFD virCommandFD;
> @@ -214,6 +215,12 @@ virCommandReorderFDs(virCommandPtr cmd)
>     if (!cmd || cmd->has_error || !cmd->npassfd)
>         return;
>
> +    if ((cmd->flags & VIR_EXEC_FIXED_FDS)) {
> +        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> +                       _("The fds are fixed and cannot be reordered"));
> +        goto error;
> +    }
> +
>     for (i = 0; i < cmd->npassfd; i++)
>         maxfd = MAX(cmd->passfd[i].fd, maxfd);
>
> @@ -1019,6 +1026,32 @@ virCommandPassListenFDs(virCommandPtr cmd)
>     cmd->flags |= VIR_EXEC_LISTEN_FDS;
> }
>
> +/*
> + * virCommandPassFDGetFDIndex:
> + * @cmd: pointer to virCommand
> + * @fd: FD to get index of
> + *
> + * Determine the index of the FD in the transfer set.
> + *
> + * Returns index >= 0 if @set contains @fd,
> + * -1 otherwise.
> + */
> +int
> +virCommandPassFDGetFDIndex(virCommandPtr cmd, int fd)
> +{
> +    size_t i = 0;
> +
> +    while (i < cmd->npassfd) {
> +        if (cmd->passfd[i].fd == fd) {
> +            cmd->flags |= VIR_EXEC_FIXED_FDS;
> +            return i;
> +        }
> +        i++;
> +    }
> +
> +    return -1;
> +}
> +
> /**
>  * virCommandSetPidFile:
>  * @cmd: the command to modify
> diff --git a/src/util/vircommand.h b/src/util/vircommand.h
> index bf65de4..198da2f 100644
> --- a/src/util/vircommand.h
> +++ b/src/util/vircommand.h
> @@ -62,6 +62,9 @@ void virCommandPassFD(virCommandPtr cmd,
>
> void virCommandPassListenFDs(virCommandPtr cmd);
>
> +int virCommandPassFDGetFDIndex(virCommandPtr cmd,
> +                               int fd);
> +
> void virCommandSetPidFile(virCommandPtr cmd,
>                           const char *pidfile) ATTRIBUTE_NONNULL(2);
>
> --
> 1.9.3
>
> --
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