From: Eric Dumazet <eric.dumazet@gmail.com>
To: dsahern@kernel.org, netdev@vger.kernel.org
Cc: David Ahern <dsahern@gmail.com>
Subject: Re: [PATCH v2 net] net/ipv6: Do not allow device only routes via the multipath API
Date: Mon, 16 Jul 2018 09:09:44 -0700 [thread overview]
Message-ID: <5d9122fa-8f9a-b11a-3496-06976c96a08b@gmail.com> (raw)
In-Reply-To: <20180715163519.12917-1-dsahern@kernel.org>
On 07/15/2018 09:35 AM, dsahern@kernel.org wrote:
> From: David Ahern <dsahern@gmail.com>
>
> Eric reported that reverting the patch that fixed and simplified IPv6
> multipath routes means reverting back to invalid userspace notifications.
> eg.,
> $ ip -6 route add 2001:db8:1::/64 nexthop dev eth0 nexthop dev eth1
>
> only generates a single notification:
> 2001:db8:1::/64 dev eth0 metric 1024 pref medium
>
> While working on a fix for this problem I found another case that is just
> broken completely - a multipath route with a gateway followed by device
> followed by gateway:
> $ ip -6 ro add 2001:db8:103::/64
> nexthop via 2001:db8:1::64
> nexthop dev dummy2
> nexthop via 2001:db8:3::64
>
> In this case the device only route is dropped completely - no notification
> to userpsace but no addition to the FIB either:
>
> $ ip -6 ro ls
> 2001:db8:1::/64 dev dummy1 proto kernel metric 256 pref medium
> 2001:db8:2::/64 dev dummy2 proto kernel metric 256 pref medium
> 2001:db8:3::/64 dev dummy3 proto kernel metric 256 pref medium
> 2001:db8:103::/64 metric 1024
> nexthop via 2001:db8:1::64 dev dummy1 weight 1
> nexthop via 2001:db8:3::64 dev dummy3 weight 1 pref medium
> fe80::/64 dev dummy1 proto kernel metric 256 pref medium
> fe80::/64 dev dummy2 proto kernel metric 256 pref medium
> fe80::/64 dev dummy3 proto kernel metric 256 pref medium
>
> Really, IPv6 multipath is just FUBAR'ed beyond repair when it comes to
> device only routes, so do not allow it all.
>
> This change will break any scripts relying on the mpath api for insert,
> but I don't see any other way to handle the permutations. Besides, since
> the routes are added to the FIB as standalone (non-multipath) routes the
> kernel is not doing what the user requested, so it might as well tell the
> user that.
Yes, I guess we have no real choice for the moment.
Thanks David
Reviewed-by: Eric Dumazet <edumazet@google.com>
next prev parent reply other threads:[~2018-07-16 16:37 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-15 16:35 [PATCH v2 net] net/ipv6: Do not allow device only routes via the multipath API dsahern
2018-07-16 16:09 ` Eric Dumazet [this message]
2018-07-16 17:14 ` David Ahern
2018-07-16 21:09 ` David Miller
2018-07-17 12:13 ` David Ahern
2018-07-18 20:45 ` David Miller
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=5d9122fa-8f9a-b11a-3496-06976c96a08b@gmail.com \
--to=eric.dumazet@gmail.com \
--cc=dsahern@gmail.com \
--cc=dsahern@kernel.org \
--cc=netdev@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
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;
as well as URLs for NNTP newsgroup(s).