netdev - No pmtu probing on retransmits?

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Message-ID: <20080203123719.GA3323@basil.nowhere.org>
Date:	Sun, 3 Feb 2008 13:37:19 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	jheffner@....edu, netdev@...r.kernel.org
Subject: No pmtu probing on retransmits?

Hallo,

While looking for something else in tcp_output.c I noticed that
MTU probing seems to be only done in tcp_write_xmit (when
packets come directly from process context), but not via the timer
driven timer retransmit path (tcp_retransmit_skb). Is that intentional?
It looks quite weird. I would normally assume PMTU blackholes get usually
detected on retransmit timeouts. Or do I miss something? 

You seem to have assumed interrupt context at least
because tcp_mtu_probe() uses GFP_ATOMIC which is only needed for
interrupts. Currently it is only called in process context I think.

-Andi

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