drbd: Split off netlink mandatory attribute handling into separate file

Duplicate this file in the kernel module and in user space; both sides need it.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

1 files changed, 55 insertions, 0 deletions

diff --git a/drivers/block/drbd/drbd_nla.c b/drivers/block/drbd/drbd_nla.c
new file mode 100644
index 000000000000..fa672b6df8d6
--- /dev/null
+++ b/drivers/block/drbd/drbd_nla.c
@@ -0,0 +1,55 @@
+#include "drbd_wrappers.h"
+#include <linux/kernel.h>
+#include <net/netlink.h>
+#include <linux/drbd_genl_api.h>
+#include "drbd_nla.h"
+
+static int drbd_nla_check_mandatory(int maxtype, struct nlattr *nla)
+{
+        struct nlattr *head = nla_data(nla);
+        int len = nla_len(nla);
+        int rem;
+
+        /*
+         * validate_nla (called from nla_parse_nested) ignores attributes
+         * beyond maxtype, and does not understand the DRBD_GENLA_F_MANDATORY flag.
+         * In order to have it validate attributes with the DRBD_GENLA_F_MANDATORY
+         * flag set also, check and remove that flag before calling
+         * nla_parse_nested.
+         */
+
+        nla_for_each_attr(nla, head, len, rem) {
+                if (nla->nla_type & DRBD_GENLA_F_MANDATORY) {
+                        nla->nla_type &= ~DRBD_GENLA_F_MANDATORY;
+                        if (nla_type(nla) > maxtype)
+                                return -EOPNOTSUPP;
+                }
+        }
+        return 0;
+}
+
+int drbd_nla_parse_nested(struct nlattr *tb[], int maxtype, struct nlattr *nla,
+                          const struct nla_policy *policy)
+{
+        int err;
+
+        err = drbd_nla_check_mandatory(maxtype, nla);
+        if (!err)
+                err = nla_parse_nested(tb, maxtype, nla, policy);
+
+        return err;
+}
+
+struct nlattr *drbd_nla_find_nested(int maxtype, struct nlattr *nla, int attrtype)
+{
+        int err;
+        /*
+         * If any nested attribute has the DRBD_GENLA_F_MANDATORY flag set and
+         * we don't know about that attribute, reject all the nested
+         * attributes.
+         */
+        err = drbd_nla_check_mandatory(maxtype, nla);
+        if (err)
+                return ERR_PTR(err);
+        return nla_find_nested(nla, attrtype);
+}