netdev - Re: [PATCH net] tcp: fix bogus RTT on special retransmission

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CADVnQynxiJGzHdPisAN+YTYeoWQT1Cp2bJ4=0Zz=evu9cno5-Q@mail.gmail.com>
Date:	Fri, 28 Feb 2014 20:38:57 -0500
From:	Neal Cardwell <ncardwell@...gle.com>
To:	Yuchung Cheng <ycheng@...gle.com>
Cc:	David Miller <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Nandita Dukkipati <nanditad@...gle.com>,
	Netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net] tcp: fix bogus RTT on special retransmission

On Fri, Feb 28, 2014 at 7:42 PM, Yuchung Cheng <ycheng@...gle.com> wrote:
> RTT may be bogus with tall loss probe (TLP) when a packet
> is retransmitted and latter (s)acked without TCPCB_SACKED_RETRANS flag.
>
> For example, TLP calls __tcp_retransmit_skb() instead of
> tcp_retransmit_skb(). The skb timestamps are updated but the sacked
> flag is not marked with TCPCB_SACKED_RETRANS. As a result we'll
> get bogus RTT in tcp_clean_rtx_queue() or in tcp_sacktag_one() on
> spurious retransmission.
>
> The fix is to apply the sticky flag TCP_EVER_RETRANS to enforce Karn's
> check on RTT sampling. However this will disable F-RTO if timeout occurs
> after TLP, by resetting undo_marker in tcp_enter_loss(). We relax this
> check to only if any pending retransmists are still in-flight.
>
> Signed-off-by: Yuchung Cheng <ycheng@...gle.com>

Acked-by: Neal Cardwell <ncardwell@...gle.com>

neal
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html