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Subject[PATCH 4.9 48/66] ipv4: Make neigh lookup keys for loopback/point-to-point devices be INADDR_ANY
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jim Westfall <jwestfall@surrealistic.net>


[ Upstream commit cd9ff4de0107c65d69d02253bb25d6db93c3dbc1 ]

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 a263b3093641f
(ipv4: Make neigh lookups directly in output packet path) and later removed
in 0bb4087cbec0 (ipv4: Fix neigh lookup keying over loopback/point-to-point
devices) because it was broken.

Signed-off-by: Jim Westfall <jwestfall@surrealistic.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/net/arp.h | 3 +++
net/ipv4/arp.c | 7 ++++++-
2 files changed, 9 insertions(+), 1 deletion(-)

--- a/include/net/arp.h
+++ b/include/net/arp.h
@@ -19,6 +19,9 @@ static inline u32 arp_hashfn(const void

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);
}

--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -223,11 +223,16 @@ static bool arp_key_eq(const struct neig

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) {

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