lib/route: allow override of message type during link change

When rtnl_link_build_change_request() builds a change request,
it sets the message type to RTM_NEWLINK by default. If the
request fails, it changes the type to RTM_SETLINK, and resubmits.

For some address families, this will result in a requested change
never being applied by the kernel. An exmaple of this is the Linux
bridge. When a netlink message of type RTM_NEWLINK is recieved,
rather than failing, it simply ignores the message and does not
return a failure.

To fix this, this patch implements an override for address
families that require it. The override can be set when an address
family registers itself in libnl.

This patch adds ao_override_rtm to the rtnl_link_af_ops structure.
This patch adds a static function named af_request_type.
This patch modifies rtnl_link_build_change_request to call
  af_request_type to properly set the request type if an address
  family wishes to override.

Signed-off-by: Jef Oliver <jef.oliver@intel.com>
Signed-off-by: Thomas Haller <thaller@redhat.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/netlink-private/route/link/api.h b/include/netlink-private/route/link/api.h
index 1a793c8..1cda72e 100644
--- a/include/netlink-private/route/link/api.h
+++ b/include/netlink-private/route/link/api.h
@@ -146,6 +146,14 @@ struct rtnl_link_af_ops
 	 */
 	int		      (*ao_compare)(struct rtnl_link *,
 					    struct rtnl_link *, int, uint32_t, int);
+
+	/* RTM_NEWLINK override
+	 *
+	 * Called if a change link request is set to the kernel. If this is set
+	 * to anything other than zero, RTM_NEWLINK will be overriden with
+	 * RTM_SETLINK when rtnl_link_build_change_request() is called.
+	 */
+	const int ao_override_rtm;
 };
 
 extern struct rtnl_link_af_ops *rtnl_link_af_ops_lookup(unsigned int);