netdev - Re: possible bug in latest network tree

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Message-ID: <1459372663.6473.211.camel@edumazet-glaptop3.roam.corp.google.com>
Date:	Wed, 30 Mar 2016 14:17:43 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	"Light, John J" <john.j.light@...el.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: possible bug in latest network tree

On Wed, 2016-03-30 at 21:05 +0000, Light, John J wrote:
> David,
> 
> I see a recent change in inet_connection_sock.c that uses
> sysctl_tcp_synack_retries suspiciously.
> 
> Previously, sysctl_tcp_synack_retries was a global variable, and now
> it has been moved into the fragment (really netns_ipv4).

You mean the network namespace ?
> 
> In reqsk_timer_handler (inet_connection_sock.c) near line 563 it is
> used as the default max_retries value in case icsk->icsk_syn_retries
> is not set.
> 
> Previously, other transports (dccp?) would use the TCP global variable
> as a default.  Now that the defaults come from the fragment, I suspect
> the fragment variable is not set for other transports.  (I can't find
> where it's set for dccp.)
> 
> Of course, this will only show in non-TCP transport protocols when the
> icsk retries value is not set, so it's a rare case.  Perhaps it's an
> unreachable case, since I don't know all the kernel paths.
> 
> Maybe the problem is that the default shouldn't be to a TCP value, but
> should be a 'transport' value.
> 
> This code is somewhat convoluted, so I am not sure of my analysis, but
> I wanted you to consider it.
> 

No idea why you ask David instead of patch author ?

I don't see any problem here.

Do we really want to spend time on this minor issue ?