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authorYuchung Cheng <ycheng@google.com>2012-01-19 14:42:21 +0000
committerDavid S. Miller <davem@davemloft.net>2012-01-22 15:08:44 -0500
commit974c12360dfe6ab01201fe9e708e7755c413f8b6 (patch)
tree8cdf87f44c8be550af2ec1530f8cb271fb1a2e1f /include
parentd0249e44432aa0ffcf710b64449b8eaa3722547e (diff)
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 'include')
-rw-r--r--include/linux/snmp.h1
1 files changed, 0 insertions, 1 deletions
diff --git a/include/linux/snmp.h b/include/linux/snmp.h
index e16557a357e..c1241c42817 100644
--- a/include/linux/snmp.h
+++ b/include/linux/snmp.h
@@ -192,7 +192,6 @@ enum
LINUX_MIB_TCPPARTIALUNDO, /* TCPPartialUndo */
LINUX_MIB_TCPDSACKUNDO, /* TCPDSACKUndo */
LINUX_MIB_TCPLOSSUNDO, /* TCPLossUndo */
- LINUX_MIB_TCPLOSS, /* TCPLoss */
LINUX_MIB_TCPLOSTRETRANSMIT, /* TCPLostRetransmit */
LINUX_MIB_TCPRENOFAILURES, /* TCPRenoFailures */
LINUX_MIB_TCPSACKFAILURES, /* TCPSackFailures */