This used to be the previous behavior in older kernels but became broken in
a263b3093641f (ipv4: Make neigh lookups directly in output packet path)
and then later removed because it was broken in 0bb4087cbec0 (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
Jim Westfall (2):
net: Allow neigh contructor functions ability to modify the
primary_key
ipv4: Make neigh lookup keys for loopback/point-to-point devices be
INADDR_ANY
include/net/arp.h | 3 +++
net/core/neighbour.c | 4 ++--
net/ipv4/arp.c | 7 ++++++-
3 files changed, 11 insertions(+), 3 deletions(-)
--
2.15.1
