netdev - Re: [TCP_CA_CWR] Causes for entering TCP_CA

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 for Android: free password hash cracker in your pocket

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

Date:	Tue, 14 Jul 2009 12:15:28 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	yinglinsun@...pitt.edu
Cc:	netdev@...r.kernel.org
Subject: Re: [TCP_CA_CWR] Causes for entering TCP_CA_CWR state with 0
 retransmissions

From: Yinglin Sun <yinglinsun@...pitt.edu>
Date: Tue, 14 Jul 2009 15:12:16 -0400

> I use the total number of retransmissions reported by tcp_info. The
> field name is tcpi_total_retrans. From the kernel source code, I found
> that this number is for both fast retransmit and timeout
> retransmissions. On the other hand, if fast retransmission happened,
> ca_state should be TCP_CA_Recovery or TCP_CA_Disorder, but it's
> TCP_CA_CWR.

Great, that if you're reading the code you also see that there
are many code paths that invoke tcp_enter_cwr() that can occur
without any retransmissions. :-)

One such case is when ECN congestion notification bits are
seen in an ACK packet.
--
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