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| author | Yuchung Cheng <ycheng@google.com> | 2012-01-19 14:42:21 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2012-01-22 15:08:44 -0500 |
| commit | 974c12360dfe6ab01201fe9e708e7755c413f8b6 (patch) | |
| tree | 8cdf87f44c8be550af2ec1530f8cb271fb1a2e1f /net/ipv4/proc.c | |
| parent | d0249e44432aa0ffcf710b64449b8eaa3722547e (diff) | |
| download | linux-974c12360dfe6ab01201fe9e708e7755c413f8b6.tar.bz2 | |
tcp: detect loss above high_seq in recovery
Correctly implement a loss detection heuristic: New sequences (above
high_seq) sent during the fast recovery are deemed lost when higher
sequences are SACKed.
Current code does not catch these losses, because tcp_mark_head_lost()
does not check packets beyond high_seq. The fix is straight-forward by
checking packets until the highest sacked packet. In addition, all the
FLAG_DATA_LOST logic are in-effective and redundant and can be removed.
Update the loss heuristic comments. The algorithm above is documented
as heuristic B, but it is redundant too because heuristic A already
covers B.
Note that this change only marks some forward-retransmitted packets LOST.
It does NOT forbid TCP performing further CWR on new losses. A potential
follow-up patch under preparation is to perform another CWR on "new"
losses such as
1) sequence above high_seq is lost (by resetting high_seq to snd_nxt)
2) retransmission is lost.
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/proc.c')
| -rw-r--r-- | net/ipv4/proc.c | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c index 3569d8ecaeac..6afc807ee2ad 100644 --- a/net/ipv4/proc.c +++ b/net/ipv4/proc.c @@ -216,7 +216,6 @@ static const struct snmp_mib snmp4_net_list[] = { SNMP_MIB_ITEM("TCPPartialUndo", LINUX_MIB_TCPPARTIALUNDO), SNMP_MIB_ITEM("TCPDSACKUndo", LINUX_MIB_TCPDSACKUNDO), SNMP_MIB_ITEM("TCPLossUndo", LINUX_MIB_TCPLOSSUNDO), - SNMP_MIB_ITEM("TCPLoss", LINUX_MIB_TCPLOSS), SNMP_MIB_ITEM("TCPLostRetransmit", LINUX_MIB_TCPLOSTRETRANSMIT), SNMP_MIB_ITEM("TCPRenoFailures", LINUX_MIB_TCPRENOFAILURES), SNMP_MIB_ITEM("TCPSackFailures", LINUX_MIB_TCPSACKFAILURES), |