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Properties
TCPOptionSizes
Validity of TCP header option sizes. (Default: Valid-
ateLogBad)
TCPMSSMin
Minimum allowed TCP MSS (Maximum Segment
Size). (Default: 100)
TCPMSSOnLow
How to handle too low MSS values. (Default:
DropLog)
TCPMSSMax
Maximum allowed TCP MSS (Maximum Segment
Size). (Default: 1460)
TCPMSSVPNMax
Limits TCP MSS for VPN connections; minimizes
fragmentation. (Default: 1400)
TCPMSSOnHigh
How to handle too high MSS values. (Default: Ad-
just)
TCPMSSLogLevel
When to log regarding too high TCP MSS, if not
logged by "TCP MSS on high". (Default: 7000)
TCPMSSAutoClamping
Automatically clamp TCP MSS according to MTU
of involved interfaces - in addition to "TCP MSS
max". (Default: Yes)
TCPZeroUnusedACK
Force unused ACK fields to zero; helps prevent con-
nection spoofing. (Default: Yes)
TCPZeroUnusedURG
Force unused URG fields to zero; prevents small in-
formation leak. (Default: Yes)
TCPOPT_WSOPT
The WSOPT (Window Scale) option (common).
(Default: ValidateLogBad)
TCPOPT_SACK
The SACK/SACKPERMIT (Selective ACK) options
(common). (Default: ValidateLogBad)
TCPOPT_TSOPT
The
TSOPT
(Timestamp)
option
(common).
(Default: ValidateLogBad)
TCPOPT_ALTCHKREQ
The ALTCHKREQ (Alternate Checksum Request)
option. (Default: StripLog)
TCPOPT_ALTCHKDATA
The ALTCHKDATA (Alternate Checksum Data)
option. (Default: StripLog)
TCPOPT_CC
The CC (Connection Count) option series (semi
common). (Default: StripLogBad)
TCPOPT_OTHER
How to handle TCP options not specified above.
(Default: StripLog)
TCPSynUrg
The TCP URG flag together with SYN; normally in-
valid (strip=strip URG). (Default: DropLog)
TCPSynPsh
The TCP PSH flag together with SYN; normally in-
valid but always used by some IP stacks (strip=strip
PSH). (Default: StripSilent)
TCPSynRst
The TCP RST flag together with SYN; normally in-
3.52.22. TCPSettings
Chapter 3. Configuration Reference
188