netdev - [PATCH net] net/ipv6: do not copy DST

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Message-Id: <20180913203814.189698-1-posk@google.com>
Date:   Thu, 13 Sep 2018 13:38:14 -0700
From:   Peter Oskolkov <posk@...gle.com>
To:     David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Cc:     Peter Oskolkov <posk@...gle.com>, David Ahern <dsahern@...il.com>
Subject: [PATCH net] net/ipv6: do not copy DST_NOCOUNT flag on rt init

DST_NOCOUNT in dst_entry::flags tracks whether the entry counts
toward route cache size (net->ipv6.sysctl.ip6_rt_max_size).

If the flag is NOT set, dst_ops::pcpuc_entries counter is incremented
in dist_init() and decremented in dst_destroy().

This flag is tied to allocation/deallocation of dst_entry and
should not be copied from another dst/route. Otherwise it can happen
that dst_ops::pcpuc_entries counter grows until no new routes can
be allocated because the counter reached ip6_rt_max_size due to
DST_NOCOUNT not set and thus no counter decrements on gc-ed routes.

Fixes: 3b6761d18bc1 ("net/ipv6: Move dst flags to booleans in fib entries")
Cc: David Ahern <dsahern@...il.com>
Acked-by: Wei Wang <weiwan@...gle.com>
Signed-off-by: Peter Oskolkov <posk@...gle.com>
---
 net/ipv6/route.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 3eed045c65a5..a3902f805305 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -946,7 +946,7 @@ static void ip6_rt_init_dst_reject(struct rt6_info *rt, struct fib6_info *ort)

 static void ip6_rt_init_dst(struct rt6_info *rt, struct fib6_info *ort)
 {
-	rt->dst.flags |= fib6_info_dst_flags(ort);
+	rt->dst.flags |= fib6_info_dst_flags(ort) & ~DST_NOCOUNT;

 	if (ort->fib6_flags & RTF_REJECT) {
 		ip6_rt_init_dst_reject(rt, ort);
-- 
2.19.0.397.gdd90340f6a-goog