netdev - Re: [PATCH iproute2 2/2] ip: remove NLM_F

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Message-ID: <20121025092526.5bb0a7ca@nehalam.linuxnetplumber.net>
Date:	Thu, 25 Oct 2012 09:25:26 -0700
From:	Stephen Hemminger <shemminger@...tta.com>
To:	nicolas.dichtel@...nd.com
Cc:	netdev@...r.kernel.org, joe@...ches.com, bernat@...fy.cx,
	eric.dumazet@...il.com, yoshfuji@...ux-ipv6.org,
	davem@...emloft.net
Subject: Re: [PATCH iproute2 2/2] ip: remove NLM_F_EXCL in case of ECMPv6
 routes

On Thu, 25 Oct 2012 18:20:49 +0200
Nicolas Dichtel <nicolas.dichtel@...nd.com> wrote:

> Le 25/10/2012 18:06, Stephen Hemminger a écrit :
> > On Tue, 23 Oct 2012 14:42:56 +0200
> > Nicolas Dichtel <nicolas.dichtel@...nd.com> wrote:
> >
> >> ECMPv6 routes are added each one after the other by the kernel, so we should
> >> avoid to set the flag NLM_F_EXCL.
> >>
> >> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@...nd.com>
> >> ---
> >>   ip/iproute.c | 5 ++++-
> >>   1 file changed, 4 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/ip/iproute.c b/ip/iproute.c
> >> index c60156f..799a70e 100644
> >> --- a/ip/iproute.c
> >> +++ b/ip/iproute.c
> >> @@ -694,8 +694,11 @@ int parse_nexthops(struct nlmsghdr *n, struct rtmsg *r, int argc, char **argv)
> >>   		rtnh = RTNH_NEXT(rtnh);
> >>   	}
> >>
> >> -	if (rta->rta_len > RTA_LENGTH(0))
> >> +	if (rta->rta_len > RTA_LENGTH(0)) {
> >>   		addattr_l(n, 1024, RTA_MULTIPATH, RTA_DATA(rta), RTA_PAYLOAD(rta));
> >> +		if (r->rtm_family == AF_INET6)
> >> +			n->nlmsg_flags &= ~NLM_F_EXCL;
> >> +	}
> >>   	return 0;
> >>   }
> >>
> >
> > Shouldn't this be true for multipath IPv4 as well?
> >
> In IPv4, the message is treating in one shot, because all nexthops are added in 
> the route. In IPv6, each nexthop is added like a single route and then they are 
> linked together.

So it is a fundamental design flaw in how either v4 or v6 was implemented in
the kernel?
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