netdev - Re: [PATCH iproute 2/2] utils: fix get_rtnl_link_stats

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Message-ID: <20181011080922.43508083@xeon-e3>
Date:   Thu, 11 Oct 2018 08:09:22 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH iproute 2/2] utils: fix get_rtnl_link_stats_rta stats
 parsing

On Thu, 11 Oct 2018 14:24:03 +0200
Lorenzo Bianconi <lorenzo.bianconi@...hat.com> wrote:

> > > iproute2 walks through the list of available tunnels using netlink
> > > protocol in order to get device info instead of reading
> > > them from proc filesystem. However the kernel reports device statistics
> > > using IFLA_INET6_STATS/IFLA_INET6_ICMP6STATS attributes nested in
> > > IFLA_PROTINFO one but iproutes expects these info in
> > > IFLA_STATS64/IFLA_STATS attributes.
> > > The issue can be triggered with the following reproducer:
> > > 
> > > $ip link add ip6d0 type ip6tnl mode ip6ip6 local 1111::1 remote 2222::1
> > > $ip -6 -d -s tunnel show ip6d0
> > > ip6d0: ipv6/ipv6 remote 2222::1 local 1111::1 encaplimit 4 hoplimit 64
> > > tclass 0x00 flowlabel 0x00000 (flowinfo 0x00000000)
> > > Dump terminated
> > > 
> > > Fix the issue introducing IFLA_INET6_STATS attribute parsing
> > > 
> > > Fixes: 3e953938717f ("iptunnel/ip6tunnel: Use netlink to walk through
> > > tunnels list")
> > > 
> > > Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@...hat.com>  
> > 
> > Can't we fix the kernel to report statistics properly, rather than
> > starting iproute2 doing more /proc interfaces.
> >   
> 
> Hi Stephen,

> sorry, I did not get what you mean. Current iproute implementation
> walks through tunnels list using netlink protocol and parses device
> statistics in the kernel netlink message. However it does not take
> into account the actual netlink message layout since the statistic
> attribute is nested in IFLA_PROTINFO one.
> Moreover AFAIU the related kernel code has not changed since iproute
> commit 3e953938717f, so I guess we should fix the issue in iproute code
> instead in the kernel one. Do you agree?
> 
> Regards,
> Lorenzo

Sorry, I was confused and the stats code is really about parsing existing
pile of statistics in netlink.  I thought it was doing /proc version
like nstat already does.

I will reset these patches to under review.