From: Nicolas Dichtel <nicolas.dichtel@6wind•com>
To: Roopa Prabhu <roopa@cumulusnetworks•com>, davem@davemloft•net
Cc: 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: Fri, 4 Sep 2015 10:12:53 +0200 [thread overview]
Message-ID: <55E95285.6020102@6wind.com> (raw)
In-Reply-To: <1441237466-22302-1-git-send-email-roopa@cumulusnetworks.com>
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)")
> 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 ;-)).
> +
> + list_for_each_entry(nh, rt6_nh_list, next) {
> + printk(KERN_WARNING "%s: %pI6 nexthop %pI6 ifi %d\n",
pr_warn() or pr_err()?
> + errstr, &nh->r_cfg.fc_dst, &nh->r_cfg.fc_gateway,
> + nh->r_cfg.fc_ifindex);
> + }
> +}
next prev parent reply other threads:[~2015-09-04 8:12 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 [this message]
2015-09-06 20:46 ` roopa
2015-09-07 12:03 ` Nicolas Dichtel
2015-09-08 0:01 ` roopa
2015-09-08 9:33 ` Nicolas Dichtel
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=55E95285.6020102@6wind.com \
--to=nicolas.dichtel@6wind$(echo .)com \
--cc=Mazziesaccount@gmail$(echo .)com \
--cc=davem@davemloft$(echo .)net \
--cc=hannes@stressinduktion$(echo .)org \
--cc=jmorris@namei$(echo .)org \
--cc=kuznet@ms2$(echo .)inr.ac.ru \
--cc=netdev@vger$(echo .)kernel.org \
--cc=roopa@cumulusnetworks$(echo .)com \
--cc=yoshfuji@linux-ipv6$(echo .)org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox