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neighbor: Call __ipv4_neigh_lookup_noref in neigh_xmit 

Commit cd9ff4de01 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: cd9ff4de01 ("ipv4: Make neigh lookup keys for loopback/point-to-point devices be INADDR_ANY")
Reported-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: David Ahern <dsahern@gmail.com>
Tested-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David Ahern 2019-05-01 18:18:42 -07:00 committed by David S. Miller
parent 64c6f4bbca
commit 4b2a2bfeb3
1 changed files with 8 additions and 1 deletions
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9
net/core/neighbour.c
View File

@ -31,6 +31,7 @@
#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>
@ -2984,7 +2985,13 @@ int neigh_xmit(int index, struct net_device *dev,
if (!tbl)
goto out;
rcu_read_lock_bh();
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);