netdev - Re: [PATCH] tcp: make urg+gso work for real this time

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Message-Id: <1229689860.12322.13.camel@nathan.suse.cz>
Date:	Fri, 19 Dec 2008 13:31:00 +0100
From:	Petr Tesarik <ptesarik@...e.cz>
To:	Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>
Cc:	David Miller <davem@...emloft.net>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	Netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] tcp: make urg+gso work for real this time

Ilpo Järvinen píše v Čt 18. 12. 2008 v 22:07 +0200:
> On Wed, 17 Dec 2008, David Miller wrote:
> 
> > From: Herbert Xu <herbert@...dor.apana.org.au>
> > Date: Thu, 18 Dec 2008 09:16:37 +1100
> > 
> > And it also shows that our strange scheme, where we don't
> > signal URG until it's within the 16-bit sequence offset
> > limit, at least reports an accurate URG value.
> 
> [...snip...]
> 
> > Given all of this I still think our current compromise is likely the
> > best one.  We never will advertise an URG pointer that is not pointing
> > to where the URG data will be in the sequence space.
> 
> Wholeheartedly agreed, but with added note that if somebody is fool enough 
> to come up complaining about the behavior we've selected (among the palette 
> of broken ways we had available) we might actually succeed in convincing 
> him to come up with something that has more change in working than urg 
> altogether. Sadly, urg is ABI-in-stone that must everyone must keep 
> supporting in some crippled-form. ...But no worries, I've a solution below 
> which should satisfy everybody... :-)
> 
> 
> -- 
>  i.
> 
> 
> [PATCH] tcp: fix all urg troubles for now
> 
> Return to stone age with 64k is enough for everybody attitude
> (or was it 640k, I keep forgetting). Urg certainly works fine
> if no window scaling is not allowed ;-)
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>
> ---
>  net/ipv4/tcp_input.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> index 99b7ecb..54fe815 100644
> --- a/net/ipv4/tcp_input.c
> +++ b/net/ipv4/tcp_input.c
> @@ -72,7 +72,7 @@
>  #include <net/netdma.h>
>  
>  int sysctl_tcp_timestamps __read_mostly = 1;
> -int sysctl_tcp_window_scaling __read_mostly = 1;
> +int sysctl_tcp_window_scaling __read_mostly = 0;

Yes, nice default, but don't you want to
remove /proc/sys/net/ipv4/sysctl_tcp_window_scaling completely? Let's
not make it possible for the admin to shoot himself in the foot by
accident... ;-))

Petr Tesarik

>  int sysctl_tcp_sack __read_mostly = 1;
>  int sysctl_tcp_fack __read_mostly = 1;
>  int sysctl_tcp_reordering __read_mostly = TCP_FASTRETRANS_THRESH;b

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