[PATCH v1 net 3/4] neighbour: Don't render blackhole_netdev via RTM_GETNEIGHTBL.

The cited commits started to initialise blackhole_netdev with
neigh_parms_alloc().

This is visible in init_net as the ifindex==0 entries via
RTM_GETNEIGHTBL:

  # ynl --family rt-neigh --dump getneightbl --output-json \
    | jq '.[] | select(.parms.ifindex == 0)
              | {name: .name, ifindex: .parms.ifindex}'
  {
    "name": "arp_cache",
    "ifindex": 0
  }
  {
    "name": "ndisc_cache",
    "ifindex": 0
  }

For RTM_SETNEIGHTBL, ifindex being 0 means wildcard.

Let's skip blackhole_netdev's parms in neightbl_dump_info().

Note that lookup_neigh_parms() does not need the same change
because the default parms is always the first entry and matches
with ifindex == 0.

Fixes: e5f80fcf869a ("ipv6: give an IPv6 dev to blackhole_netdev")
Fixes: 22600596b675 ("ipv4: give an IPv4 dev to blackhole_netdev")
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
Cc: Xin Long <lucien.xin@gmail.com>
---
 net/core/neighbour.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 454a8b8f3aa0..b90957b630ce 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c

@@ -2625,6 +2625,9 @@ static int neightbl_dump_info(struct sk_buff *skb, struct netlink_callback *cb)
 			if (!net_eq(neigh_parms_net(p), net))
 				continue;
 
+			if (p->dev == blackhole_netdev)
+				continue;
+
 			if (nidx < neigh_skip)
 				goto next;
 

-- 
2.55.0.1003.g10538fe699-goog