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dccp ccid-2: Share TCP's minimum RTO code

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Using a fixed RTO_MIN of 0.2 seconds was found to cause problems for CCID-2
over 802.11g: at least once per session there was 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 CCID-2:

> 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.

Documentation also updated (plus minor whitespace fixes).

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Gerrit Renker
2010-08-29 19:23:13 +00:00
committed by David S. Miller
parent 22b71c8f4f
commit 4886fcad6e
2 changed files with 23 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
net/dccp/ccids/ccid2.c
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@ -325,8 +325,9 @@ 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) */
@ -367,7 +368,7 @@ 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);
}
}