netdev - Re: [PATCH net-next 2/2] tcp: add TCP_CC

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Date:	Wed, 29 Apr 2015 04:07:05 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Daniel Borkmann <daniel@...earbox.net>
Cc:	Eric Dumazet <edumazet@...gle.com>,
	"David S. Miller" <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Yuchung Cheng <ycheng@...gle.com>,
	Neal Cardwell <ncardwell@...gle.com>
Subject: Re: [PATCH net-next 2/2] tcp: add TCP_CC_INFO socket option

On Wed, 2015-04-29 at 10:17 +0200, Daniel Borkmann wrote:
> On 04/29/2015 01:23 AM, Eric Dumazet wrote:
> > Some Congestion Control modules can provide per flow information,
> > but current way to get this information is to use netlink.
> >
> > Like TCP_INFO, let's add TCP_CC_INFO so that applications can
> > issue a getsockopt() if they have a socket file descriptor,
> > instead of playing complex netlink games.
> >
> > Sample usage would be :
> >
> >    union tcp_cc_info info;
> >    socklen_t len = sizeof(info);
> >
> >    if (getsockopt(fd, SOL_TCP, TCP_CC_INFO, &info, &len) == -1)
> >
> > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> > Cc: Yuchung Cheng <ycheng@...gle.com>
> > Cc: Neal Cardwell <ncardwell@...gle.com>
> 
> Presuming other cc algorithms would in future also export
> internal information through this interface, would it make
> sense to put tcp_cc_info into a container structure so we
> don't miss out attr (vegas, dctcp, ...), like:
> 
>    struct tcp_cc_exp {
>      u32               kind;
>      union tcp_cc_info info;
>    };
> 
> Otherwise looks good:
> 
> Acked-by: Daniel Borkmann <daniel@...earbox.net>

I thought of this, but I really believe this is not needed, as the
application can already fetch CC name (if really its does not know yet)

And I also wanted to get same layout for info provided by netlink and
getsockopt()

Thanks !


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