Re: [PATCH v5 1/3] qio: add support for SO_PEERCRED for socket channel

[Paolo Bonzini]

On Thu, Apr 11, 2024 at 2:14 PM Anthony Harivel <aharivel@redhat.com> wrote:
>
> The function qio_channel_get_peercred() returns a pointer to the
> credentials of the peer process connected to this socket.
>
> This credentials structure is defined in <sys/socket.h> as follows:
>
> struct ucred {
>         pid_t pid;    /* Process ID of the sending process */
>         uid_t uid;    /* User ID of the sending process */
>         gid_t gid;    /* Group ID of the sending process */
> };
>
> The use of this function is possible only for connected AF_UNIX stream
> sockets and for AF_UNIX stream and datagram socket pairs.
>
> On platform other than Linux, the function return 0.
>
> Signed-off-by: Anthony Harivel <aharivel@redhat.com>
> ---
>  include/io/channel.h | 21 +++++++++++++++++++++
>  io/channel-socket.c  | 28 ++++++++++++++++++++++++++++
>  io/channel.c         | 13 +++++++++++++
>  3 files changed, 62 insertions(+)
>
> diff --git a/include/io/channel.h b/include/io/channel.h
> index 7986c49c713a..bdf0bca92ae2 100644
> --- a/include/io/channel.h
> +++ b/include/io/channel.h
> @@ -160,6 +160,9 @@ struct QIOChannelClass {
>                                    void *opaque);
>      int (*io_flush)(QIOChannel *ioc,
>                      Error **errp);
> +    int (*io_peerpid)(QIOChannel *ioc,
> +                       unsigned int *pid,
> +                       Error **errp);
>  };
>
>  /* General I/O handling functions */
> @@ -981,4 +984,22 @@ int coroutine_mixed_fn 
> qio_channel_writev_full_all(QIOChannel *ioc,
>  int qio_channel_flush(QIOChannel *ioc,
>                        Error **errp);
>
> +/**
> + * qio_channel_get_peercred:
> + * @ioc: the channel object
> + * @pid: pointer to pid
> + * @errp: pointer to a NULL-initialized error object
> + *
> + * Returns the pid of the peer process connected to this socket.
> + *
> + * The use of this function is possible only for connected
> + * AF_UNIX stream sockets and for AF_UNIX stream and datagram
> + * socket pairs on Linux.
> + * Return -1 on error with pid -1 for the non-Linux OS.

with pid -1 -> and set *pid to -1.

> + */
>  static const TypeInfo qio_channel_socket_info = {
> diff --git a/io/channel.c b/io/channel.c
> index a1f12f8e9096..e3f17c24a00f 100644
> --- a/io/channel.c
> +++ b/io/channel.c
> @@ -548,6 +548,19 @@ void qio_channel_set_cork(QIOChannel *ioc,
>      }
>  }
>
> +int qio_channel_get_peerpid(QIOChannel *ioc,
> +                             unsigned int *pid,
> +                             Error **errp)
> +{
> +    QIOChannelClass *klass = QIO_CHANNEL_GET_CLASS(ioc);
> +
> +    if (!klass->io_peerpid) {
> +        error_setg(errp, "Channel does not support peer pid");

Missing for consistency:

+        *pid = -1;

> +        return -1;
> +    }
> +    klass->io_peerpid(ioc, pid, errp);
> +    return 0;

The error from klass->io_peerpid is ignored:

-    klass->io_peerpid(ioc, pid, errp);
-    return 0;
+    return klass->io_peerpid(ioc, pid, errp);

Paolo