netdev - [PATCH 1/3] dccp ccid-2: Share TCP's minimum RTO code

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]

Date:	Fri, 13 Aug 2010 07:21:39 +0200
From:	Gerrit Renker <gerrit@....abdn.ac.uk>
To:	dccp@...r.kernel.org
Cc:	netdev@...r.kernel.org, Gerrit Renker <gerrit@....abdn.ac.uk>
Subject: [PATCH 1/3] dccp ccid-2: Share TCP's minimum RTO code

Over the same link, DCCP and TCP face similar problems; and DCCP's
CCID-2 is in fact a restricted form of TCP.

Using the same RTO_MIN of 0.2 seconds was found to cause problems for CCID-2
over 802.11g: at least once per session there is a spurious timeout. It helped
to then increase the the value of RTO_MIN over this link.

Since the problem is the same as in TCP, this patch makes the solution from
commit "05bb1fad1cde025a864a90cfeb98dcbefe78a44a"
       "[TCP]: Allow minimum RTO to be configurable via routing metrics."
available to DCCP.

This avoids reinventing the wheel, so that e.g. the following works in the
expected way now also for DCCP:

> ip route change 10.0.0.2 rto_min 800 dev ath0

Luckily this useful rto_min function was recently moved to net/tcp.h,
which simplifies sharing code originating from TCP.

Signed-off-by: Gerrit Renker <gerrit@....abdn.ac.uk>
---
 net/dccp/ccids/ccid2.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

--- a/net/dccp/ccids/ccid2.c
+++ b/net/dccp/ccids/ccid2.c
@@ -267,8 +267,9 @@ static void ccid2_rtt_estimator(struct sock *sk, const long mrtt)
 		hc->tx_srtt = m << 3;
 		hc->tx_mdev = m << 1;
 
-		hc->tx_mdev_max = max(TCP_RTO_MIN, hc->tx_mdev);
+		hc->tx_mdev_max = max(hc->tx_mdev, tcp_rto_min(sk));
 		hc->tx_rttvar   = hc->tx_mdev_max;
+
 		hc->tx_rtt_seq  = dccp_sk(sk)->dccps_gss;
 	} else {
 		/* Update scaled SRTT as SRTT += 1/8 * (m - SRTT) */
@@ -309,7 +310,7 @@ static void ccid2_rtt_estimator(struct sock *sk, const long mrtt)
 				hc->tx_rttvar -= (hc->tx_rttvar -
 						  hc->tx_mdev_max) >> 2;
 			hc->tx_rtt_seq  = dccp_sk(sk)->dccps_gss;
-			hc->tx_mdev_max = TCP_RTO_MIN;
+			hc->tx_mdev_max = tcp_rto_min(sk);
 		}
 	}
 
--
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