libipt_icmp.man

This extension can be used if `\-\-protocol icmp' is specified. It
provides the following option:
.TP
[\fB!\fP] \fB\-\-icmp\-type\fP {\fItype\fP[\fB/\fP\fIcode\fP]|\fItypename\fP}
This allows specification of the ICMP type, which can be a numeric
ICMP type, type/code pair, or one of the ICMP type names shown by the command
.nf
 iptables \-p icmp \-h
.fi