netlink: refactor writer initialization KPI

o Allow callers to initialize a writer that will malloc(9) with M_WAITOK.
o Use size_t for expected malloc size.
o Use correct types to initialize a group writer.
o Rename functions into nl_writer_ namespace instead of nlmsg_, cause
  they are working on nl_writer, not on nlmsg.
o Make the KPI responsible to sparsely initialize the writer structure.
o Garbage collect chain writer.  Fixes 17083b94a915.

All current consumers are left as is, however some may benefit from
M_WAITOK allocation as well as supplying a correct expected size.

Reviewed by:		melifaro
Differential Revision:	https://reviews.freebsd.org/D47549

1 files changed, 5 insertions, 4 deletions

diff --git a/sys/netlink/route/rt.c b/sys/netlink/route/rt.c
index 00315afbcb02..c9b0f56498ec 100644
--- a/sys/netlink/route/rt.c
+++ b/sys/netlink/route/rt.c
@@ -350,10 +350,10 @@ static void
 report_operation(uint32_t fibnum, struct rib_cmd_info *rc,
     struct nlpcb *nlp, struct nlmsghdr *hdr)
 {
-	struct nl_writer nw = {};
+	struct nl_writer nw;
 	uint32_t group_id = family_to_group(rt_get_family(rc->rc_rt));
 
-	if (nlmsg_get_group_writer(&nw, NLMSG_SMALL, NETLINK_ROUTE, group_id)) {
+	if (nl_writer_group(&nw, NLMSG_SMALL, NETLINK_ROUTE, group_id, false)) {
 		struct route_nhop_data rnd = {
 			.rnd_nhop = rc_get_nhop(rc),
 			.rnd_weight = rc->rc_nh_weight,
@@ -1043,7 +1043,7 @@ rtnl_handle_getroute(struct nlmsghdr *hdr, struct nlpcb *nlp, struct nl_pstate *
 void
 rtnl_handle_route_event(uint32_t fibnum, const struct rib_cmd_info *rc)
 {
-	struct nl_writer nw = {};
+	struct nl_writer nw;
 	int family, nlm_flags = 0;
 
 	family = rt_get_family(rc->rc_rt);
@@ -1082,7 +1082,8 @@ rtnl_handle_route_event(uint32_t fibnum, const struct rib_cmd_info *rc)
 	};
 
 	uint32_t group_id = family_to_group(family);
-	if (!nlmsg_get_group_writer(&nw, NLMSG_SMALL, NETLINK_ROUTE, group_id)) {
+	if (!nl_writer_group(&nw, NLMSG_SMALL, NETLINK_ROUTE, group_id,
+	    false)) {
 		NL_LOG(LOG_DEBUG, "error allocating event buffer");
 		return;
 	}