3Com 4007, Implementation Manual, Page: 325 / 684

The Packet Filtering Language 325
pushTop (continued) 1 byte Rather than use multiple
pushField .w 12
commands to look at the 12th offset where the
Ethernet type field resides, use multiple
pushTop
commands, as shown here:
Original Filter:
pushField.w 12
pushLiteral.w 0x6004
eq
reject
pushField.w 12
pushLiteral.w 0x0800
eq
reject
pushField.w 12
pushLiteral.w 0x0806
ne
Shortened Filter:
PushField.w 12
pushTop
pushTop
pushLiteral.w 0x6004
eq
reject
pushLiteral.w 0x0800
eq
reject
pushLiteral.w 0x0806
ne
pushSPGM 1 byte Pushes the source port group mask (SPGM) onto the
top of the stack. The SPGM is a bitmap representing
the groups to which the source port of a packet
belongs. This instruction pushes 4 bytes on to the
stack.
Each port group mask is represented by a single bit in
the SPGM bitmap. Port group masks are assigned to
the bitmap in sequence, starting with port group mask
1 as the least significant bit through port group mask
32 as the most significant bit.
Use
pushSPGM
to filter by port groups. See “Using
Port Groups in Custom Packet Filters” for more
information.
Table 66 Packet Filtering Opcodes (continued)
Opcode
Memory
Requirements
Description