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

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Date:	Thu, 12 Mar 2015 10:45:09 +0100
From:	Ulf samuelsson <netdev@...gii.com>
To:	YOSHIFUJI Hideaki/吉藤英明 
	<hideaki.yoshifuji@...aclelinux.com>
Cc:	yzhu1 <Yanjun.Zhu@...driver.com>,
	"brian.haley@...com" <brian.haley@...com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"alexandre.dietsch@...driver.com" <alexandre.dietsch@...driver.com>,
	"clinton.slabbert@...driver.com" <clinton.slabbert@...driver.com>,
	"kuznet@....inr.ac.ru" <kuznet@....inr.ac.ru>,
	"jmorris@...ei.org" <jmorris@...ei.org>,
	"kaber@...sh.net" <kaber@...sh.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"ulf.samuelsson@...csson.com" <ulf.samuelsson@...csson.com>,
	"YOSHIFUJI Hideaki (USAGI Project)" <yoshfuji@...ux-ipv6.org>
Subject: Re: [PATCH V2 0/1] neighbour: Support broadcast ARP in neighbor PROPE state

If you want to send 3 unicasts followed by 3 broadcast,
you have to set mcast_solicit to 6.
This means you will send 6 broadcasts in incomplete state.

I think the following configuration is wanted:

Incomplete state: send 3 broadcast
Probe state: send 3 unicast, followed by 3 broadcast then goto STALE OR
                     Send 3 unicast, then go to STALE

Best Regards
Ulf Samuelsson
ulf@...gii.com
+46  (722) 427 437


> 12 mar 2015 kl. 10:28 skrev YOSHIFUJI Hideaki/吉藤英明  <hideaki.yoshifuji@...aclelinux.com>:
> 
> Hi,
> 
> Ulf samuelsson wrote:
>> That also means that you increase the number of broadcasts in incomplete state.
>> Is that really desirable?
> 
> In NUD_INCOMPLETE state, neighbour subsystem *skips* sending unicast probes
> and send multicast probes mcast_solicit times. If you do not increase
> the number of mcast_solicit, the number of multicast probes in
> NUD_INCOMPLETE will not increased.
> 
> --yoshfuji
> 
>> 
>> Best Regards
>> Ulf Samuelsson
>> ulf@...gii.com
>> +46  (722) 427 437
>> 
>> 
>>> 12 mar 2015 kl. 09:42 skrev YOSHIFUJI Hideaki <hideaki.yoshifuji@...aclelinux.com>:
>>> 
>>> 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 <hideaki.yoshifuji@...aclelinux.com>
>>> Technical Division, MIRACLE LINUX CORPORATION
>>> --
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> 
> -- 
> 吉藤英明 <hideaki.yoshifuji@...aclelinux.com>
> ミラクル・リナックス株式会社 技術本部 サポート部
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