From:   Josua Mayer <josua.mayer@jm0.eu>
To:     linux-bluetooth@vger.kernel.org
Cc:     Josua Mayer <josua.mayer@jm0.eu>,
        Marcel Holtmann <marcel@holtmann.org>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 2/3] bluetooth: 6lowpan: check neighbour table for SLAAC
Date:   Fri,  8 Feb 2019 16:25:18 +0100
Message-Id: <20190208152519.16181-3-josua.mayer@jm0.eu>
In-Reply-To: <20190208152519.16181-1-josua.mayer@jm0.eu>
References: <20190208152519.16181-1-josua.mayer@jm0.eu>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-bluetooth-owner@vger.kernel.org
Precedence: bulk

Like any IPv6 capable device, 6LNs can have multiple addresses assigned
using SLAAC and made known through neighbour advertisements.
After checking the destination address against all peers link-local
addresses, consult the neighbour cache for additional known addresses.

RFC7668 defines the scope of Neighbor Advertisements in Section 3.2.3:
1. "A Bluetooth LE 6LN MUST NOT register its link-local address"
2. "A Bluetooth LE 6LN MUST register its non-link-local addresses with
the 6LBR by sending Neighbor Solicitation (NS) messages ..."

Due to these constranits both the link-local addresses tracked in the
list of 6lowpan peers, and the neighbour cache have to be used when
identifying the 6lowpan peer for a destination address.

Signed-off-by: Josua Mayer <josua.mayer@jm0.eu>
---
 net/bluetooth/6lowpan.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/net/bluetooth/6lowpan.c b/net/bluetooth/6lowpan.c
index 553dc719afde..4e14db230793 100644
--- a/net/bluetooth/6lowpan.c
+++ b/net/bluetooth/6lowpan.c
@@ -171,6 +171,7 @@ static inline struct lowpan_peer *peer_lookup_dst(struct lowpan_btle_dev *dev,
 	struct in6_addr *nexthop;
 	struct rt6_info *rt = (struct rt6_info *)skb_dst(skb);
 	int count = atomic_read(&dev->peer_count);
+	struct neighbour *neigh;
 
 	BT_DBG("peers %d addr %pI6c rt %p", count, daddr, rt);
 
@@ -222,6 +223,19 @@ static inline struct lowpan_peer *peer_lookup_dst(struct lowpan_btle_dev *dev,
 		}
 	}
 
+	// use the neighbout cache for matching addresses assigned by SLAAC
+	neigh = __ipv6_neigh_lookup(dev->netdev, nexthop);
+	if (neigh) {
+		list_for_each_entry_rcu(peer, &dev->peers, list) {
+			if (!memcmp(neigh->ha, peer->lladdr, ETH_ALEN)) {
+				neigh_release(neigh);
+				rcu_read_unlock();
+				return peer;
+			}
+		}
+		neigh_release(neigh);
+	}
+
 	rcu_read_unlock();
 
 	return NULL;
-- 
2.20.1