netdev - Re: [PATCH net-next 3/3] ipv4: Create probe timer for tcp PMTU as per RFC4821

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Message-ID: <1424089194.4942.56.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Mon, 16 Feb 2015 04:19:54 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Fan Du <fengyuleidian0615@...il.com>
Cc:	Fan Du <fan.du@...el.com>, davem@...emloft.net,
	netdev@...r.kernel.org
Subject: Re: [PATCH net-next 3/3] ipv4: Create probe timer for tcp PMTU as
 per RFC4821

On Mon, 2015-02-16 at 13:38 +0800, Fan Du wrote:
> 于 2015年02月13日 20:31, Eric Dumazet 写道:

> > We certainly wont add yet another timer in tcp socket for such usage.
> >
> > And a buggy one, since you forgot all the refcounting associated with
> > such timers.
> 
> oh, embarrassing...
> Will place probe timer aside with icsk_delack_timer in struct inet_connection_sock,
> and manipulate through sk_reset_timer.

No : I said we would _not_ accept yet another timer (ie a big structure)
for such very rare event.

You can implement a pseudo timer, using a simple u32 field, that you
test in tcp_mtu_probe() to clear icsk->icsk_mtup.probe_size when enough
time has elapsed.

(tcp_time_stamp is u32, so are tp->lsndtime, tp->snd_cwnd_stamp, 
tp->rcv_tstamp, tp->retrans_stamp, tp->tso_deferred, ...)



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