[PATCH v2 1/3] qio: add support for SO_PEERCRED for socket channel

[Anthony Harivel <aharivel@redhat.com>]

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.

Signed-off-by: Anthony Harivel <aharivel@redhat.com>
---
 include/io/channel.h | 20 ++++++++++++++++++++
 io/channel-socket.c  | 17 +++++++++++++++++
 io/channel.c         | 12 ++++++++++++
 3 files changed, 49 insertions(+)

diff --git a/include/io/channel.h b/include/io/channel.h
index 5f9dbaab65b0..99c02d61c3d9 100644
--- a/include/io/channel.h
+++ b/include/io/channel.h
@@ -149,6 +149,9 @@ struct QIOChannelClass {
                                   void *opaque);
     int (*io_flush)(QIOChannel *ioc,
                     Error **errp);
+    void (*io_peercred)(QIOChannel *ioc,
+                        struct ucred *cred,
+                        Error **errp);
 };
 
 /* General I/O handling functions */
@@ -898,4 +901,21 @@ 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
+ * @cred: pointer to ucred struct
+ * @errp: pointer to a NULL-initialized error object
+ *
+ * Returns the credentials 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 datagra
+ * socket pairs.
+ *
+ */
+void qio_channel_get_peercred(QIOChannel *ioc,
+                              struct ucred *cred,
+                              Error **errp);
+
 #endif /* QIO_CHANNEL_H */
diff --git a/io/channel-socket.c b/io/channel-socket.c
index 02ffb51e9957..b8285eb8ae49 100644
--- a/io/channel-socket.c
+++ b/io/channel-socket.c
@@ -836,6 +836,22 @@ qio_channel_socket_set_cork(QIOChannel *ioc,
     socket_set_cork(sioc->fd, v);
 }
 
+static void
+qio_channel_socket_get_peercred(QIOChannel *ioc,
+                                struct ucred *cred,
+                                Error **errp)
+{
+    QIOChannelSocket *sioc = QIO_CHANNEL_SOCKET(ioc);
+    socklen_t len = sizeof(struct ucred);
+    Error *err = NULL;
+
+    if (getsockopt(sioc->fd,
+               SOL_SOCKET, SO_PEERCRED,
+               cred, &len) == -1) {
+        error_setg_errno(&err, errno, "Unable to get peer credentials");
+        error_propagate(errp, err);
+    }
+}
 
 static int
 qio_channel_socket_close(QIOChannel *ioc,
@@ -933,6 +949,7 @@ static void qio_channel_socket_class_init(ObjectClass *klass,
 #ifdef QEMU_MSG_ZEROCOPY
     ioc_klass->io_flush = qio_channel_socket_flush;
 #endif
+    ioc_klass->io_peercred = qio_channel_socket_get_peercred;
 }
 
 static const TypeInfo qio_channel_socket_info = {
diff --git a/io/channel.c b/io/channel.c
index 86c5834510ff..6dccccba5242 100644
--- a/io/channel.c
+++ b/io/channel.c
@@ -490,6 +490,18 @@ void qio_channel_set_cork(QIOChannel *ioc,
     }
 }
 
+void qio_channel_get_peercred(QIOChannel *ioc,
+                              struct ucred *cred,
+                              Error **errp)
+{
+    QIOChannelClass *klass = QIO_CHANNEL_GET_CLASS(ioc);
+
+    if (!klass->io_peercred) {
+        error_setg(errp, "Channel does not support random access");
+        return;
+    }
+    klass->io_peercred(ioc, cred, errp);
+}
 
 off_t qio_channel_io_seek(QIOChannel *ioc,
                           off_t offset,
-- 
2.41.0