Allowed Metric Names

Name Description
SyncookiesSent An application wasn’t able to accept a connection fast enough, so the kernel couldn’t store an entry in the queue for this connection. Instead of dropping it, it sent a cookie to the client.
SyncookiesRecv After sending a cookie, it came back to us and passed the check.
SyncookiesFailed After sending a cookie, it came back to us but looked invalid.
EmbryonicRsts
PruneCalled
RcvPruned If the kernel is really really desperate and cannot give more memory to this socket even after dropping the ofo queue, it will simply discard the packet it received. This is Really Bad.
OfoPruned When a socket is using too much memory (rmem), the kernel will first discard any out-of-order packet that has been queued (with SACK).
OutOfWindowIcmps
LockDroppedIcmps
ArpFilter
TW
TWRecycled
TWKilled
PAWSPassive
PAWSActive
PAWSEstab
DelayedACKs We waited for another packet to send an ACK, but didn’t see any, so a timer ended up sending a delayed ACK.
DelayedACKLocked We wanted to send a delayed ACK but failed because the socket was locked. So the timer was reset.
DelayedACKLost We sent a delayed and duplicated ACK because the remote peer retransmitted a packet, thinking that it didn’t get to us.
ListenOverflows We completed a 3WHS but couldn’t put the socket on the accept queue, so we had to discard the connection.
ListenDrops We couldn’t accept a connection because one of: we had no route to the destination, we failed to allocate a socket, we failed to allocate a new local port bind bucket. Note: this counter also include all the increments made to ListenOverflows
TCPPrequeued
TCPDirectCopyFromBacklog
TCPDirectCopyFromPrequeue
TCPPrequeueDropped
TCPHPHits
TCPHPHitsToUser
TCPPureAcks
TCPHPAcks
TCPRenoRecovery A packet was lost and we recovered after a fast retransmit.
TCPSackRecovery A packet was lost and we recovered by using selective acknowledgements.
TCPSACKReneging
TCPFACKReorder We detected re-ordering using FACK (Forward ACK — the highest sequence number known to have been received by the peer when using SACK — FACK is used during congestion control).
TCPSACKReorder We detected re-ordering using SACK.
TCPRenoReorder We detected re-ordering using fast retransmit.
TCPTSReorder We detected re-ordering using the timestamp option.
TCPFullUndo We detected some erroneous retransmits and undid our CWND reduction.
TCPPartialUndo We detected some erroneous retransmits, a partial ACK arrived while we were fast retransmitting, so we were able to partially undo some of our CWND reduction.
TCPDSACKUndo We detected some erroneous retransmits, a D-SACK arrived and ACK’ed all the retransmitted data, so we undid our CWND reduction.
TCPLossUndo We detected some erroneous retransmits, a partial ACK arrived, so we undid our CWND reduction.
TCPLoss
TCPLostRetransmit
TCPRenoFailures
TCPSackFailures
TCPLossFailures
TCPFastRetrans
TCPForwardRetrans
TCPSlowStartRetrans
TCPTimeouts
TCPRenoRecoveryFail
TCPSackRecoveryFail
TCPSchedulerFailed
TCPRcvCollapsed
TCPDSACKOldSent
TCPDSACKOfoSent
TCPDSACKRecv
TCPDSACKOfoRecv
TCPSACKDiscard We got a completely invalid SACK block and discarded it.
TCPDSACKIgnoredOld We got a duplicate SACK while retransmitting so we discarded it.
TCPDSACKIgnoredNoUndo We got a duplicate SACK and discarded it.
TCPAbortOnSyn We received an unexpected SYN so we sent a RST to the peer.
TCPAbortOnData We were in FIN_WAIT1 yet we received a data packet with a sequence number that’s beyond the last one for this connection, so we RST’ed.
TCPAbortOnClose We received data but the user has closed the socket, so we have no wait of handing it to them, so we RST’ed.
TCPAbortOnMemory This is Really Bad. It happens when there are too many orphaned sockets (not attached a FD) and the kernel has to drop a connection. Sometimes it will send a reset to the peer, sometimes it wont.
TCPAbortOnTimeout The connection timed out really hard.
TCPAbortOnLinger We killed a socket that was closed by the application and lingered around for long enough.
TCPAbortFailed We tried to send a reset, probably during one of teh TCPABort* situations above, but we failed e.g. because we couldn’t allocate enough memory (very bad).
TCPMemoryPressures Number of times a socket was put in “memory pressure” due to a non fatal memory allocation failure (reduces the send buffer size etc).
TCPBacklogDrop We received something but had to drop it because the socket’s receive queue was full.
RtoAlgorithm The algorithm used to determine the timeout value used for retransmitting unacknowledged octets.
RtoMin The minimum value permitted by a TCP implementation for the retransmission timeout, measured in milliseconds. More refined semantics for objects of this type depend upon the algorithm used to determine the retransmission timeout. In particular, when the timeout algorithm is “rsre ” (3), an object of this type has the semantics of the LBOUND quantity described in RFC 793.
RtoMax The maximum value permitted by a TCP implementation for the retransmission timeout, measured in milliseconds. More refined semantics for objects of this type depend upon the algorithm used to determine the retransmission timeout. In particular, when the timeout algorithm is “rsre” (3), an object of this type has the semantics of the UBOUND quantity described in RFC 793.
MaxConn The limit on the total number of TCP connections theentity can support. In entities where the maximum number of connections isdynamic, this object should contain the value -1.
ActiveOpens The number of times TCP connections have made a direct transition to the SYN-SENT state from the CLOSED state.
PassiveOpens The number of times TCP connections have made a direct transition to the SYN-RCVD state from the LISTEN state.
AttemptFails The number of times TCP connections have made a direct transition to the CLOSED state from either the SYN-SENT state or the SYN-RCVD state, plus the number of times TCP connections have made a direct transition to the LISTEN state from the SYN-RCVD state.
EstabResets The number of times TCP connections have made a direct transition to the CLOSED state from either the ESTABLISHED state or the CLOSE-WAIT state.
CurrEstab The number of TCP connections for which the current state is either ESTABLISHED or CLOSE- WAIT.
InSegs The total number of segments received, including those received in error. This count includes segments received on currently established connections.
OutSegs The total number of segments sent, including those on current connections but excluding those containing only retransmitted octets.
RetransSegs The total number of segments retransmitted – that is, the number of TCP segments transmitted containing one or more previously transmitted octets.
InErrs The total number of segments received in error (for example, bad TCP checksums).
OutRsts The number of TCP segments sent containing the RST flag.