Commit cc475966 authored by David Ahern's avatar David Ahern Committed by Greg Kroah-Hartman

neighbor: Call __ipv4_neigh_lookup_noref in neigh_xmit

[ Upstream commit 4b2a2bfeb3f056461a90bd621e8bd7d03fa47f60 ]

Commit cd9ff4de changed the key for IFF_POINTOPOINT devices to
INADDR_ANY but neigh_xmit which is used for MPLS encapsulations was not
updated to use the altered key. The result is that every packet Tx does
a lookup on the gateway address which does not find an entry, a new one
is created only to find the existing one in the table right before the
insert since arp_constructor was updated to reset the primary key. This
is seen in the allocs and destroys counters:
    ip -s -4 ntable show | head -10 | grep alloc

which increase for each packet showing the unnecessary overhread.

Fix by having neigh_xmit use __ipv4_neigh_lookup_noref for NEIGH_ARP_TABLE.

Fixes: cd9ff4de ("ipv4: Make neigh lookup keys for loopback/point-to-point devices be INADDR_ANY")
Reported-by: default avatarAlan Maguire <>
Signed-off-by: default avatarDavid Ahern <>
Tested-by: default avatarAlan Maguire <>
Signed-off-by: default avatarDavid S. Miller <>
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent e5c6de66
......@@ -30,6 +30,7 @@
#include <linux/times.h>
#include <net/net_namespace.h>
#include <net/neighbour.h>
#include <net/arp.h>
#include <net/dst.h>
#include <net/sock.h>
#include <net/netevent.h>
......@@ -2490,7 +2491,13 @@ int neigh_xmit(int index, struct net_device *dev,
if (!tbl)
goto out;
neigh = __neigh_lookup_noref(tbl, addr, dev);
if (index == NEIGH_ARP_TABLE) {
u32 key = *((u32 *)addr);
neigh = __ipv4_neigh_lookup_noref(dev, key);
} else {
neigh = __neigh_lookup_noref(tbl, addr, dev);
if (!neigh)
neigh = __neigh_create(tbl, addr, dev, false);
err = PTR_ERR(neigh);
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