+.IP \fBpush_vlan\fR:\fIethertype\fR
+Push a new VLAN tag onto the packet. Ethertype is used as the the Ethertype
+for the tag. Only ethertype 0x8100 should be used. (0x88a8 which the spec
+allows isn't supported at the moment.)
+A priority of zero and the tag of zero are used for the new tag.
+.
+.IP \fBpush_mpls\fR:\fIethertype\fR
+If the packet does not already contain any MPLS labels, changes the
+packet's Ethertype to \fIethertype\fR, which must be either the MPLS
+unicast Ethertype \fB0x8847\fR or the MPLS multicast Ethertype
+\fB0x8848\fR, and then pushes an initial label stack entry. The label
+stack entry's default label is 2 if the packet contains IPv6 and 0
+otherwise, its default traffic control value is the low 3 bits of the
+packet's DSCP value (0 if the packet is not IP), and its TTL is copied
+from the IP TTL (64 if the packet is not IP).
+.IP
+If the packet does already contain an MPLS label, pushes a new
+outermost label as a copy of the existing outermost label.
+.IP
+There are some limitations in the implementation. \fBpush_mpls\fR
+followed by another \fBpush_mpls\fR will result in the first
+\fBpush_mpls\fR being discarded.
+.
+.IP \fBpop_mpls\fR:\fIethertype\fR
+Strips the outermost MPLS label stack entry.
+Currently the implementation restricts \fIethertype\fR to a non-MPLS Ethertype
+and thus \fBpop_mpls\fR should only be applied to packets with
+an MPLS label stack depth of one.
+.
+.IP
+There are some limitations in the implementation. \fBpop_mpls\fR
+followed by another \fBpush_mpls\fR without an intermediate
+\fBpush_mpls\fR will result in the first \fBpush_mpls\fR being
+discarded.
+.