From: Justin Mayfield <jmayfield@cradlepoint.com>
Date: Fri, 17 Aug 2012 01:03:48 +0000 (-0600)
Subject: single nexthop flags bug
X-Git-Tag: libnl3_2_12~11
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=b62e019afad652748bcda0205f96611640bcd6d5;p=libnl

single nexthop flags bug

I ran into a bug today related to how Linux handles a route's nexthop
flags when there is just one nexthop.  Namely Linux expects the flags
to be OR'd into the rtm_flags field when there is only one nexthop and
so rtnl_route_build_msg needs to check the number of nexthops and
store the nexthops flags into this field prior to calling
nlmsg_append(...&rtmsg).

Conversely the rtnl_route_parse function needs to pull these lower
0xff bits when a single nexthop is detected.

Attached is my patch.  I don't like the slight duplication of doing
the rtnl_route_get_nnexthops check twice but it seemed to be the least
turmoil of any solution I thought of.
---

diff --git a/lib/route/route_obj.c b/lib/route/route_obj.c
index 62669a9..7ea4fff 100644
--- a/lib/route/route_obj.c
+++ b/lib/route/route_obj.c
@@ -986,6 +986,7 @@ int rtnl_route_parse(struct nlmsghdr *nlh, struct rtnl_route **result)
 	}
 
 	if (old_nh) {
+		rtnl_route_nh_set_flags(old_nh, rtm->rtm_flags & 0xff);
 		if (route->rt_nr_nh == 0) {
 			/* If no nexthops have been provided via RTA_MULTIPATH
 			 * we add it as regular nexthop to maintain backwards
@@ -1045,10 +1046,15 @@ int rtnl_route_build_msg(struct nl_msg *msg, struct rtnl_route *route)
 	if (route->rt_src)
 		rtmsg.rtm_src_len = nl_addr_get_prefixlen(route->rt_src);
 
-
 	if (rtmsg.rtm_scope == RT_SCOPE_NOWHERE)
 		rtmsg.rtm_scope = rtnl_route_guess_scope(route);
 
+	if (rtnl_route_get_nnexthops(route) == 1) {
+		struct rtnl_nexthop *nh;
+		nh = rtnl_route_nexthop_n(route, 0);
+		rtmsg.rtm_flags |= nh->rtnh_flags;
+	}
+
 	if (nlmsg_append(msg, &rtmsg, sizeof(rtmsg), NLMSG_ALIGNTO) < 0)
 		goto nla_put_failure;