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+These extensions can be used if `--protocol tcp' is specified. It
+provides the following options:
+.TP
+.BR "--source-port " "[!] \fIport\fP[:\fIport\fP]"
+Source port or port range specification. This can either be a service
+name or a port number. An inclusive range can also be specified,
+using the format
+.IR port : port .
+If the first port is omitted, "0" is assumed; if the last is omitted,
+"65535" is assumed.
+If the second port greater then the first they will be swapped.
+The flag
+.B --sport
+is a convenient alias for this option.
+.TP
+.BR "--destination-port " "[!] \fIport\fP[:\fIport\fP]"
+Destination port or port range specification.  The flag
+.B --dport
+is a convenient alias for this option.
+.TP
+.BR "--tcp-flags " "[!] \fImask\fP \fIcomp\fP"
+Match when the TCP flags are as specified.  The first argument is the
+flags which we should examine, written as a comma-separated list, and
+the second argument is a comma-separated list of flags which must be
+set.  Flags are:
+.BR "SYN ACK FIN RST URG PSH ALL NONE" .
+Hence the command
+.nf
+ iptables -A FORWARD -p tcp --tcp-flags SYN,ACK,FIN,RST SYN
+.fi
+will only match packets with the SYN flag set, and the ACK, FIN and
+RST flags unset.
+.TP
+.B "[!] --syn"
+Only match TCP packets with the SYN bit set and the ACK,RST and FIN bits
+cleared.  Such packets are used to request TCP connection initiation;
+for example, blocking such packets coming in an interface will prevent
+incoming TCP connections, but outgoing TCP connections will be
+unaffected.
+It is equivalent to \fB--tcp-flags SYN,RST,ACK,FIN SYN\fP.
+If the "!" flag precedes the "--syn", the sense of the
+option is inverted.
+.TP
+.BR "--tcp-option " "[!] \fInumber\fP"
+Match if TCP option set.