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single nexthop flags bug

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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.
This commit is contained in:
Justin Mayfield 2012-08-16 19:03:48 -06:00 • committed by Thomas Graf
parent de28daf226
commit b62e019afa
1 changed files with 7 additions and 1 deletions
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8
lib/route/route_obj.c
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@ -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;