doc: escape minus sign in manpages

groff formats '-' as a hyphen, and '\-' is needed for a minus.

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>
diff --git a/extensions/libxt_tcp.man b/extensions/libxt_tcp.man
index 9b4ed59..8f39cdb 100644
--- a/extensions/libxt_tcp.man
+++ b/extensions/libxt_tcp.man
@@ -1,7 +1,7 @@
-These extensions can be used if `--protocol tcp' is specified. It
+These extensions can be used if `\-\-protocol tcp' is specified. It
 provides the following options:
 .TP
-[\fB!\fP] \fB--source-port\fP,\fB--sport\fP \fIport\fP[\fB:\fP\fIport\fP]
+[\fB!\fP] \fB\-\-source\-port\fP,\fB\-\-sport\fP \fIport\fP[\fB:\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 \fIport\fP\fB:\fP\fIport\fP.
@@ -9,15 +9,15 @@
 "65535" is assumed.
 If the second port is greater than the first they will be swapped.
 The flag
-.B --sport
+\fB\-\-sport\fP
 is a convenient alias for this option.
 .TP
-[\fB!\fP] \fB--destination-port\fP,\fB--dport\fP \fIport\fP[\fB,\fP\fIport\fP]
+[\fB!\fP] \fB\-\-destination\-port\fP,\fB\-\-dport\fP \fIport\fP[\fB,\fP\fIport\fP]
 Destination port or port range specification.  The flag
-.B --dport
+\fB\-\-dport\fP
 is a convenient alias for this option.
 .TP
-[\fB!\fP] \fB--tcp-flags\fP \fImask\fP \fIcomp\fP
+[\fB!\fP] \fB\-\-tcp\-flags\fP \fImask\fP \fIcomp\fP
 Match when the TCP flags are as specified.  The first argument \fImask\fP is the
 flags which we should examine, written as a comma-separated list, and
 the second argument \fIcomp\fP is a comma-separated list of flags which must be
@@ -25,20 +25,20 @@
 .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
+ 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
-[\fB!\fP] \fB--syn\fP
+[\fB!\fP] \fB\-\-syn\fP
 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
+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
-[\fB!\fP] \fB--tcp-option\fP \fInumber\fP
+[\fB!\fP] \fB\-\-tcp\-option\fP \fInumber\fP
 Match if TCP option set.