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Merge branch 'ipv4-Make-neigh-lookup-keys-for-loopback-point-to-point-devices-be-INADDR_ANY'

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Jim Westfall says:

====================
ipv4: Make neigh lookup keys for loopback/point-to-point devices be INADDR_ANY

This used to be the previous behavior in older kernels but became broken in
a263b30936 (ipv4: Make neigh lookups directly in output packet path)
and then later removed because it was broken in 0bb4087cbe (ipv4: Fix neigh
lookup keying over loopback/point-to-point devices)

Not having this results in there being an arp entry for every remote ip
address that the device talks to.  Given a fairly active device it can
cause the arp table to become huge and/or having to add/purge large number
of entires to keep within table size thresholds.

$ ip -4 neigh show nud noarp | grep tun | wc -l
55850

$ lnstat -k arp_cache:entries,arp_cache:allocs,arp_cache:destroys -c 10
arp_cach|arp_cach|arp_cach|
 entries|  allocs|destroys|
   81493|620166816|620126069|
  101867|   10186|       0|
  113854|    5993|       0|
  118773|    2459|       0|
   27937|   18579|   63998|
   39256|    5659|       0|
   56231|    8487|       0|
   65602|    4685|       0|
   79697|    7047|       0|
   90733|    5517|       0|

v2:
 - fixes coding style issues
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2018-01-15 14:53:44 -05:00
commit db9ca5cacb
3 changed files with 11 additions and 3 deletions
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3
include/net/arp.h
View File

@ -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);
}

4
net/core/neighbour.c
View File

@ -532,7 +532,7 @@ struct neighbour *__neigh_create(struct neigh_table *tbl, const void *pkey,
if (atomic_read(&tbl->entries) > (1 << nht->hash_shift))
nht = neigh_hash_grow(tbl, nht->hash_shift + 1);
hash_val = tbl->hash(pkey, dev, nht->hash_rnd) >> (32 - nht->hash_shift);
hash_val = tbl->hash(n->primary_key, dev, nht->hash_rnd) >> (32 - nht->hash_shift);
if (n->parms->dead) {
rc = ERR_PTR(-EINVAL);
@ -544,7 +544,7 @@ struct neighbour *__neigh_create(struct neigh_table *tbl, const void *pkey,
n1 != NULL;
n1 = rcu_dereference_protected(n1->next,
lockdep_is_held(&tbl->lock))) {
if (dev == n1->dev && !memcmp(n1->primary_key, pkey, key_len)) {
if (dev == n1->dev && !memcmp(n1->primary_key, n->primary_key, key_len)) {
if (want_ref)
neigh_hold(n1);
rc = n1;

7
net/ipv4/arp.c
View File

@ -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) {