[PATCH maint] batman-adv: Fix DAT candidate selection on little endian systems

* [PATCH maint] batman-adv: Fix DAT candidate selection on little endian systems
@ 2019-11-28 11:43 Sven Eckelmann
  2019-11-28 13:19 ` Antonio Quartulli
  0 siblings, 1 reply; 2+ messages in thread
From: Sven Eckelmann @ 2019-11-28 11:43 UTC (permalink / raw)
  To: b.a.t.m.a.n

The distributed arp table is using a DHT to store and retrieve MAC address
information for an IP address. This is done using unicast messages to
selected peers. The potential peers are looked up using the IP address and
the VID.

While the IP address is always stored in big endian byte order, it is not
the case of the VID. It can (depending on the host system) either be big
endian or little endian. The host must therefore always convert it to big
endian to ensure that all devices calculate the same peers for the same
lookup data.

Fixes: 3e26722bc9f2 ("batman-adv: make the Distributed ARP Table vlan aware")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
 net/batman-adv/distributed-arp-table.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/batman-adv/distributed-arp-table.c b/net/batman-adv/distributed-arp-table.c
index 5004e38f..581b3181 100644
--- a/net/batman-adv/distributed-arp-table.c
+++ b/net/batman-adv/distributed-arp-table.c
@@ -287,6 +287,7 @@ static u32 batadv_hash_dat(const void *data, u32 size)
 	u32 hash = 0;
 	const struct batadv_dat_entry *dat = data;
 	const unsigned char *key;
+	__be16 vid;
 	u32 i;
 
 	key = (__force const unsigned char *)&dat->ip;
@@ -296,7 +297,8 @@ static u32 batadv_hash_dat(const void *data, u32 size)
 		hash ^= (hash >> 6);
 	}
 
-	key = (const unsigned char *)&dat->vid;
+	vid = htons(dat->vid);
+	key = (__force const unsigned char *)&vid;
 	for (i = 0; i < sizeof(dat->vid); i++) {
 		hash += key[i];
 		hash += (hash << 10);
-- 
2.20.1


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