From 6c16fa957e84c8b640dadc4e0264ff0d2dae7aa3 Mon Sep 17 00:00:00 2001
From: Jim Westfall <jwestfall@surrealistic.net>
Date: Sun, 14 Jan 2018 04:18:51 -0800
Subject: [PATCH] ipv4: Make neigh lookup keys for loopback/point-to-point
devices be INADDR_ANY
[ 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(-)
diff --git a/include/net/arp.h b/include/net/arp.h
index 73c49864076b3..174014585adea 100644
--- a/include/net/arp.h
+++ b/include/net/arp.h
@@ -37,6 +37,9 @@ static inline struct neighbour *__ipv4_neigh_lookup(struct net_device *dev, u32
{
struct neighbour *n;
+ if (dev->flags & (IFF_LOOPBACK | IFF_POINTOPOINT))
+ key = INADDR_ANY;
+
rcu_read_lock_bh();
n = __ipv4_neigh_lookup_noref(dev, key);
if (n && !atomic_inc_not_zero(&n->refcnt))
diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index 16acb59d665e3..263729dea5328 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -221,11 +221,16 @@ static u32 arp_hash(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 == NULL) {