netdev - Re: [RFC] gre: conform to RFC6040 ECN progogation

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Message-ID: <1349110181.2577.16.camel@bwh-desktop.uk.solarflarecom.com>
Date:	Mon, 1 Oct 2012 17:49:41 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Stephen Hemminger <shemminger@...tta.com>
CC:	Chris Wright <chrisw@...hat.com>,
	David Miller <davem@...emloft.net>, <netdev@...r.kernel.org>
Subject: Re: [RFC] gre: conform to RFC6040 ECN progogation

On Mon, 2012-10-01 at 08:56 -0700, Stephen Hemminger wrote:
> On Mon, 1 Oct 2012 16:55:19 +0100
> Ben Hutchings <bhutchings@...arflare.com> wrote:
> 
> > On Mon, 2012-09-24 at 14:44 -0700, Stephen Hemminger wrote:
> > [...]
> > > --- a/net/ipv4/ip_gre.c	2012-09-21 08:45:55.948772761 -0700
> > > +++ b/net/ipv4/ip_gre.c	2012-09-24 14:35:54.666185603 -0700
> > [...]
> > > @@ -703,17 +704,18 @@ static int ipgre_rcv(struct sk_buff *skb
> > >  			skb_postpull_rcsum(skb, eth_hdr(skb), ETH_HLEN);
> > >  		}
> > >  
> > > +		__skb_tunnel_rx(skb, tunnel->dev);
> > > +
> > > +		skb_reset_network_header(skb);
> > > +		if (!ipgre_ecn_decapsulate(iph, skb))
> > > +			goto drop;
> > > +
> > >  		tstats = this_cpu_ptr(tunnel->dev->tstats);
> > >  		u64_stats_update_begin(&tstats->syncp);
> > >  		tstats->rx_packets++;
> > >  		tstats->rx_bytes += skb->len;
> > >  		u64_stats_update_end(&tstats->syncp);
> > 
> > I don't know why you're moving this code above the stats update;
> > rx_packets/rx_bytes should include dropped packets.
> > 
> > Ben.
> > 
> > > -		__skb_tunnel_rx(skb, tunnel->dev);
> > > -
> > > -		skb_reset_network_header(skb);
> > > -		ipgre_ecn_decapsulate(iph, skb);
> > > -
> > >  		netif_rx(skb);
> > >  
> > >  		rcu_read_unlock();
> > 
> 
> Is that true? I thought they were accounted for by rx_dropped.

I don't think rx_dropped is appropriate for counting invalid packets,
but maybe actual practice is already different.

As for whether packets counted in rx_dropped should also be counted in
rx_packets/rx_bytes, I really don't know.  The current comments on
rtnl_link_stats (inherited from net_device_stats) are totally inadequate
as a specification.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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