ipv4: Make neigh lookup keys for loopback/point-to-point devices be I…

…NADDR_ANY Map all lookup neigh keys to INADDR_ANY for loopback/point-to-point devices to avoid making an entry for every remote ip the device needs to talk to. This used the be the old behavior but became broken in a263b30 (ipv4: Make neigh lookups directly in output packet path) and later removed in 0bb4087 (ipv4: Fix neigh lookup keying over loopback/point-to-point devices) because it was broken. Signed-off-by: Jim Westfall <[email protected]> Signed-off-by: David S. Miller <[email protected]>
niw · Jan 15, 2018 · cd9ff4d · cd9ff4d
1 parent 096b985
commit cd9ff4d
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Showing 2 changed files with 9 additions and 1 deletion.
diff --git a/include/net/arp.h b/include/net/arp.h
@@ -20,6 +20,9 @@ static inline u32 arp_hashfn(const void *pkey, const struct net_device *dev, u32
 
 static inline struct neighbour *__ipv4_neigh_lookup_noref(struct net_device *dev, u32 key)
 {
+	if (dev->flags & (IFF_LOOPBACK | IFF_POINTOPOINT))
+		key = INADDR_ANY;
+
 	return ___neigh_lookup_noref(&arp_tbl, neigh_key_eq32, arp_hashfn, &key, dev);
 }
 

diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
@@ -223,11 +223,16 @@ static bool arp_key_eq(const struct neighbour *neigh, const void *pkey)
 
 static int arp_constructor(struct neighbour *neigh)
 {
-	__be32 addr = *(__be32 *)neigh->primary_key;
+	__be32 addr;
 	struct net_device *dev = neigh->dev;
 	struct in_device *in_dev;
 	struct neigh_parms *parms;
+	u32 inaddr_any = INADDR_ANY;
 
+	if (dev->flags & (IFF_LOOPBACK | IFF_POINTOPOINT))
+		memcpy(neigh->primary_key, &inaddr_any, arp_tbl.key_len);
+
+	addr = *(__be32 *)neigh->primary_key;
 	rcu_read_lock();
 	in_dev = __in_dev_get_rcu(dev);
 	if (!in_dev) {