Subject: Re: [PATCH V2 0/1] neighbour: Support broadcast ARP in neighbor PROPE state

From: YOSHIFUJI Hideaki <[email-masked]>
Date: Thu, 12 Mar 2015 17:42:53 +0900

Hello.

yzhu1 wrote:
> The state machine is in the attachment.
>
> Best Regards!
> Zhu Yanjun
> On 03/12/2015 02:58 PM, Zhu Yanjun wrote:
>> V2:
>>    set ARP_PROBE_BCAST default N.
>>
>> V1:
>>    Have a problem with an HP router at a certain location, which
>>    is configured to only answer to broadcast ARP requests.
>>    That cannot be changed.
>>
>>    The first ARP request the kernel sends out, is a broadcast request,
>>    which is fine, but after the reply, the kernel sends unicast requests,
>>    which will not get any replies.
>>
>>    The ARP entry will after some time enter STALE state,
>>    and if nothing is done it will time out, and be removed.
>>    This process takes to long, and I have been told that it is
>>    difficult to makes changes that will eventually remove it.
>>
>>    Have tried to change the state from STALE to INCOMPLETE, which failed,
>>    and then tried to change the state to PROBE which also failed.
>>
>>    The stack is only sending out unicasts, and never broadcast.
>>    Is there any way to get the stack to send out a broadcast ARP
>>    without having to wait for the entry to be removed?

Neighbour subsystem will send multicast probes after unicast
probes in NUD_PROBE state if mcast_solicit is more than
ucast_solicit.  Try setting net.ipv4.neigh.*.ucast_solicit to
the value less than net.ipv4.neigh.*.mcast_solicit, please?
e.g.

net.ipv4.neigh.eth0.mcast_solicit = 3
net.ipv4.neigh.eth0.ucast_solicit = 1

--yoshfuji

>>
>>    I think the recommended behaviour in IPv6 is to send out 3 unicasts
>>    and if all fails, to send out broadcasts.
>>
>> Zhu Yanjun (1):
>>    neighbour: Support broadcast ARP in neighbor PROPE state
>>
>>   include/net/neighbour.h        |  7 ++++++
>>   include/uapi/linux/neighbour.h |  6 +++++
>>   include/uapi/linux/sysctl.h    |  3 +++
>>   kernel/sysctl_binary.c         |  3 +++
>>   net/core/neighbour.c           | 44 +++++++++++++++++++++++++++++---
>>   net/ipv4/Kconfig               | 57 ++++++++++++++++++++++++++++++++++++++++++
>>   net/ipv4/arp.c                 |  7 ++++--
>>   7 files changed, 121 insertions(+), 6 deletions(-)
>>
>

-- 
Hideaki Yoshifuji <[email-masked]>
Technical Division, MIRACLE LINUX CORPORATION