libnetlink: introduce nc_flags

Allow for a filter to ignore certain nlmsg_flags.
Signed-off-by: Phil Sutter <phil@nwl.cc>

include/libnetlink.h

@@ -60,11 +60,16 @@ struct rtnl_dump_filter_arg
 {
 	rtnl_filter_t filter;
 	void *arg1;
+	__u16 nc_flags;
 };
 
 int rtnl_dump_filter_l(struct rtnl_handle *rth,
 			      const struct rtnl_dump_filter_arg *arg);
-int rtnl_dump_filter(struct rtnl_handle *rth, rtnl_filter_t filter, void *arg);
+int rtnl_dump_filter_nc(struct rtnl_handle *rth,
+			rtnl_filter_t filter,
+			void *arg, __u16 nc_flags);
+#define rtnl_dump_filter(rth, filter, arg) \
+	rtnl_dump_filter_nc(rth, filter, arg, 0)
 int rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
 	      struct nlmsghdr *answer, size_t len)
 	__attribute__((warn_unused_result));

lib/libnetlink.c

@@ -259,6 +259,8 @@ int rtnl_dump_filter_l(struct rtnl_handle *rth,
 			while (NLMSG_OK(h, msglen)) {
 				int err = 0;
 
+				h->nlmsg_flags &= ~a->nc_flags;
+
 				if (nladdr.nl_pid != 0 ||
 				    h->nlmsg_pid != rth->local.nl_pid ||
 				    h->nlmsg_seq != rth->dump)
@@ -317,13 +319,13 @@ skip_it:
 	}
 }
 
-int rtnl_dump_filter(struct rtnl_handle *rth,
+int rtnl_dump_filter_nc(struct rtnl_handle *rth,
 		     rtnl_filter_t filter,
-		     void *arg1)
+		     void *arg1, __u16 nc_flags)
 {
 	const struct rtnl_dump_filter_arg a[2] = {
-		{ .filter = filter, .arg1 = arg1, },
-		{ .filter = NULL,   .arg1 = NULL, },
+		{ .filter = filter, .arg1 = arg1, .nc_flags = nc_flags, },
+		{ .filter = NULL,   .arg1 = NULL, .nc_flags = 0, },
 	};
 
 	return rtnl_dump_filter_l(rth, a);