From 656a39c1a062411dca09d1566a7a0709c30f3bc7 Mon Sep 17 00:00:00 2001
From: "Alexander V. Chernikov" <melifaro@FreeBSD.org>
Date: Sat, 27 May 2023 11:11:04 +0000
Subject: [PATCH] netlink: use newly-added snl(3) array parsing for handling
 multipath routes.

MFC after:	2 weeks
---
 sbin/route/route_netlink.c              | 12 ++++----
 sys/netlink/netlink_snl_route_parsers.h | 37 ++++++-------------------
 usr.bin/netstat/route_netlink.c         |  6 ++--
 3 files changed, 17 insertions(+), 38 deletions(-)

diff --git a/sbin/route/route_netlink.c b/sbin/route/route_netlink.c
index 01494fbefd51..0dbd90151e10 100644
--- a/sbin/route/route_netlink.c
+++ b/sbin/route/route_netlink.c
@@ -533,14 +533,14 @@ print_nlmsg_route(struct nl_helper *h, struct nlmsghdr *hdr,
 		return;
 	}
 
-	if (r.rta_multipath != NULL) {
+	if (r.rta_multipath.num_nhops != 0) {
 		bool first = true;
 
 		memset(buf, ' ', sizeof(buf));
 		buf[len] = '\0';
 
-		for (int i = 0; i < r.rta_multipath->num_nhops; i++) {
-			struct rta_mpath_nh *nh = &r.rta_multipath->nhops[i];
+		for (uint32_t i = 0; i < r.rta_multipath.num_nhops; i++) {
+			struct rta_mpath_nh *nh = r.rta_multipath.nhops[i];
 
 			if (!first)
 				printf("%s", buf);
@@ -834,9 +834,9 @@ flushroute_one(struct nl_helper *h, struct snl_parsed_route *r)
 		print_nlmsg(h, hdr, &attrs);
 	}
 	else {
-		if (r->rta_multipath != NULL) {
-			for (int i = 0; i < r->rta_multipath->num_nhops; i++) {
-				struct rta_mpath_nh *nh = &r->rta_multipath->nhops[i];
+		if (r->rta_multipath.num_nhops != 0) {
+			for (uint32_t i = 0; i < r->rta_multipath.num_nhops; i++) {
+				struct rta_mpath_nh *nh = r->rta_multipath.nhops[i];
 
 				print_flushed_route(r, nh->gw);
 			}
diff --git a/sys/netlink/netlink_snl_route_parsers.h b/sys/netlink/netlink_snl_route_parsers.h
index 0ab338cbe6e8..a89462210133 100644
--- a/sys/netlink/netlink_snl_route_parsers.h
+++ b/sys/netlink/netlink_snl_route_parsers.h
@@ -90,48 +90,27 @@ SNL_DECLARE_PARSER_EXT(_mpath_nh_parser, sizeof(struct rtnexthop),
 		_cb_p_mp_nh);
 
 struct rta_mpath {
-	int num_nhops;
-	struct rta_mpath_nh nhops[0];
+	uint32_t num_nhops;
+	struct rta_mpath_nh **nhops;
 };
 
 static bool
-nlattr_get_multipath(struct snl_state *ss, struct nlattr *nla, const void *arg __unused,
+nlattr_get_multipath(struct snl_state *ss, struct nlattr *nla, const void *arg,
     void *target)
 {
-	int data_len = nla->nla_len - sizeof(struct nlattr);
-	struct rtnexthop *rtnh;
+	uint32_t start_size = 4;
 
-	int max_nhops = data_len / sizeof(struct rtnexthop);
-	size_t sz = (max_nhops + 2) * sizeof(struct rta_mpath_nh);
+	while (start_size < NLA_DATA_LEN(nla) / sizeof(struct rtnexthop))
+		start_size *= 2;
 
-	struct rta_mpath *mp = snl_allocz(ss, sz);
-	if (mp == NULL)
-		return (false);
-	mp->num_nhops = 0;
-
-	for (rtnh = (struct rtnexthop *)(void *)(nla + 1); data_len > 0; ) {
-		struct rta_mpath_nh *mpnh = &mp->nhops[mp->num_nhops++];
-
-		if (!snl_parse_header(ss, rtnh, rtnh->rtnh_len, &_mpath_nh_parser, mpnh))
-			return (false);
-
-		int len = NL_ITEM_ALIGN(rtnh->rtnh_len);
-		data_len -= len;
-		rtnh = (struct rtnexthop *)(void *)((char *)rtnh + len);
-	}
-	if (data_len != 0 || mp->num_nhops == 0) {
-		return (false);
-	}
-
-	*((struct rta_mpath **)target) = mp;
-	return (true);
+	return (snl_attr_get_parray_sz(ss, nla, start_size, &_mpath_nh_parser, target));
 }
 
 struct snl_parsed_route {
 	struct sockaddr		*rta_dst;
 	struct sockaddr		*rta_gw;
 	struct nlattr		*rta_metrics;
-	struct rta_mpath	*rta_multipath;
+	struct rta_mpath	rta_multipath;
 	uint32_t		rta_expires;
 	uint32_t		rta_oif;
 	uint32_t		rta_expire;
diff --git a/usr.bin/netstat/route_netlink.c b/usr.bin/netstat/route_netlink.c
index 6e7e505c9619..3b1880fb9d90 100644
--- a/usr.bin/netstat/route_netlink.c
+++ b/usr.bin/netstat/route_netlink.c
@@ -237,11 +237,11 @@ p_rtentry_netlink(struct snl_state *ss, const char *name, struct nlmsghdr *hdr)
 	if (rt.rtax_weight == 0)
 		rt.rtax_weight = rt_default_weight;
 
-	if (rt.rta_multipath != NULL) {
+	if (rt.rta_multipath.num_nhops != 0) {
 		uint32_t orig_rtflags = rt.rta_rtflags;
 		uint32_t orig_mtu = rt.rtax_mtu;
-		for (int i = 0; i < rt.rta_multipath->num_nhops; i++) {
-			struct rta_mpath_nh *nhop = &rt.rta_multipath->nhops[i];
+		for (uint32_t i = 0; i < rt.rta_multipath.num_nhops; i++) {
+			struct rta_mpath_nh *nhop = rt.rta_multipath.nhops[i];
 
 			rt.rta_gw = nhop->gw;
 			rt.rta_oif = nhop->ifindex;