This module matches the parameters in Authentication header of IPsec packets.
.TP
[\fB!\fP] \fB\-\-ahspi\fP \fIspi\fP[\fB:\fP\fIspi\fP]
Matches SPI.
.TP
[\fB!\fP] \fB\-\-ahlen\fP \fIlength\fP
Total length of this header in octets.
.TP
\fB\-\-ahres\fP
Matches if the reserved field is filled with zero.
