Re: [PATCH 0/3] [v3] Revert Backoff on ICMP destination unreachable

[David Miller <davem@davemloft.net>]

From: Damian Lukowski <damian@tvk.rwth-aachen.de>
Date: Wed, 26 Aug 2009 12:16:22 +0200

> This series of patches implements the TCP improvement of the Internet Draft
> "Make TCP more Robust to Long Connectivity Disruptions"
> (http://tools.ietf.org/html/draft-zimmermann-tcp-lcd).
> 
> Exponential backoff is TCP's standard behaviour during long connectivity
> disruptions, which is a countermeasure against network congestion.
> If congestion can be excluded as the reason for RTO retransmission loss,
> backoff is not desirable, as it yields longer TCP recovery times, when
> the communication path is repaired shortly after an unsuccessful
> retransmission probe.
> 
> 1) This patch renames the skb in tcp_v4_err() in preparation for patch 2.
> 2) Contains the main reversion logic.
>    Reintroduces tcp_bound_rto() and __tcp_set_rto()
> 3) This patch modifies the interpretation of the tcp_retries{1,2} sysctls.
>    It became necessary because with patch2 the assumption that the number
>    of retransmits corresponds to an specific timeout value is not accurate
>    anymore. With this patch tcp_retries{1,2} specifies a timeout value,
>    equivalent to the time a connection with an rto value of MIN_RTO (200ms)
>    would need to retransmit N segments. IOW: The meaning (in sense of time)
>    is mostly preserved, but the actual connection timeout does not depend
>    on the calculated rto of the connection, anymore.
> 
> Signed-off-by: Damian Lukowski <damian@tvk.rwth-aachen.de>

Ilpo can you please review this new version of Damian's changes?

Thanks.