From: roopa <roopa@cumulusnetworks•com>
To: nicolas.dichtel@6wind•com
Cc: davem@davemloft•net, Mazziesaccount@gmail•com,
hannes@stressinduktion•org, kuznet@ms2•inr.ac.ru,
jmorris@namei•org, yoshfuji@linux-ipv6•org,
netdev@vger•kernel.org
Subject: Re: [PATCH net-next v2] ipv6: fix multipath route replace error recovery
Date: Sun, 06 Sep 2015 13:46:39 -0700 [thread overview]
Message-ID: <55ECA62F.9070905@cumulusnetworks.com> (raw)
In-Reply-To: <55E95285.6020102@6wind.com>
On 9/4/15, 1:12 AM, Nicolas Dichtel wrote:
> Le 03/09/2015 01:44, Roopa Prabhu a écrit :
>> From: Roopa Prabhu <roopa@cumulusnetworks•com>
>>
>> Problem:
>> The ecmp route replace support for ipv6 in the kernel, deletes the
>> existing ecmp route too early, ie when it installs the first nexthop.
>> If there is an error in installing the subsequent nexthops, its too late
>> to recover the already deleted existing route
>>
>> This patch fixes the problem with the following:
>> a) Changes the existing multipath route add code to a two stage process:
>> build rt6_infos + insert them
>> ip6_route_add rt6_info creation code is moved into
>> ip6_route_info_create.
>> b) This ensures that all errors are caught during building rt6_infos
>> and we fail early
>> c) Separates multipath add and del code. Because add needs the special
>> two stage mode in a) and delete essentially does not care.
>> d) In any event if the code fails during inserting a route again, a
>> warning is printed (This should be unlikely)
>>
>> Before the patch:
>> $ip -6 route show
>> 3000:1000:1000:1000::2 via fe80::202:ff:fe00:b dev swp49s0 metric 1024
>> 3000:1000:1000:1000::2 via fe80::202:ff:fe00:d dev swp49s1 metric 1024
>> 3000:1000:1000:1000::2 via fe80::202:ff:fe00:f dev swp49s2 metric 1024
>>
>> /* Try replacing the route with a duplicate nexthop */
>> $ip -6 route change 3000:1000:1000:1000::2/128 nexthop via
>> fe80::202:ff:fe00:b dev swp49s0 nexthop via fe80::202:ff:fe00:d dev
>> swp49s1 nexthop via fe80::202:ff:fe00:d dev swp49s1
>> RTNETLINK answers: File exists
>>
>> $ip -6 route show
>> /* previously added ecmp route 3000:1000:1000:1000::2 dissappears from
>> * kernel */
>>
>> After the patch:
>> $ip -6 route show
>> 3000:1000:1000:1000::2 via fe80::202:ff:fe00:b dev swp49s0 metric 1024
>> 3000:1000:1000:1000::2 via fe80::202:ff:fe00:d dev swp49s1 metric 1024
>> 3000:1000:1000:1000::2 via fe80::202:ff:fe00:f dev swp49s2 metric 1024
>>
>> /* Try replacing the route with a duplicate nexthop */
>> $ip -6 route change 3000:1000:1000:1000::2/128 nexthop via
>> fe80::202:ff:fe00:b dev swp49s0 nexthop via fe80::202:ff:fe00:d dev
>> swp49s1 nexthop via fe80::202:ff:fe00:d dev swp49s1
>> RTNETLINK answers: File exists
>>
>> $ip -6 route show
>> 3000:1000:1000:1000::2 via fe80::202:ff:fe00:b dev swp49s0 metric 1024
>> 3000:1000:1000:1000::2 via fe80::202:ff:fe00:d dev swp49s1 metric 1024
>> 3000:1000:1000:1000::2 via fe80::202:ff:fe00:f dev swp49s2 metric 1024
>>
>> Fixes: 4a287eba2de3 ("IPv6 routing, NLM_F_* flag support: REPLACE and
>> EXCL flags support, warn about missing CREATE flag")
> ECMP was added one year after this patch. The right tag is:
> Fixes: 51ebd3181572 ("ipv6: add support of equal cost multipath (ECMP)")
I went back and looked again. It is a recent one 27596472473a ("ipv6:
fix ECMP route replacement").
>
>> Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks•com>
>> ---
>> v2 - fix a rt6_info leak in cleanup on error
>>
>> This bug is present in 4.1 kernel and 4.2 too.
>> Since 4.2 is out or almost out, I am submitting the patch against
>> net-next.
>> I can respin against net if needed. I have tried to keep the changes
>> local
>> to route.c closer to the netlink message handling. Most of the
>> changes move
>> code into separate functions.
>>
>> net/ipv6/route.c | 209
>> ++++++++++++++++++++++++++++++++++++++++++++++++-------
>> 1 file changed, 183 insertions(+), 26 deletions(-)
>>
>> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> [snip]
>> +static void ip6_print_replace_route_err(struct list_head *rt6_nh_list)
>> +{
>> + struct rt6_nh *nh;
>> + char *errstr = "IPV6: unexpected error replacing route";
> Generally, it's better to not break log. It eases grep.
> Something shorter may be enough: "ECMPv6", the log level already
> indicates
> that it's an error (which is always unexpected ;-)).
correct. What i was trying to really say is 'replace failed but it
deleted already existing route'.
I have tried to reword it in v3. posting soon.
>
>> +
>> + list_for_each_entry(nh, rt6_nh_list, next) {
>> + printk(KERN_WARNING "%s: %pI6 nexthop %pI6 ifi %d\n",
> pr_warn() or pr_err()?
I will use pr_warn.
next prev parent reply other threads:[~2015-09-06 20:46 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-02 23:44 [PATCH net-next v2] ipv6: fix multipath route replace error recovery Roopa Prabhu
2015-09-04 8:12 ` Nicolas Dichtel
2015-09-06 20:46 ` roopa [this message]
2015-09-07 12:03 ` Nicolas Dichtel
2015-09-08 0:01 ` roopa
2015-09-08 9:33 ` Nicolas Dichtel
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