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Inside Macintosh: Networking /

Chapter 11 - Ethernet, Token Ring, and Fiber Distributed Data Interface / Ethernet, Token Ring, and FDDI Reference

Routines / Adding and Removing Ethernet Multicast Addresses

EDelMulti

The EDelMulti function decrements the counter kept by the hardware device driver for a particular multicast address for Ethernet or FDDI or a particular functional address for token ring.

FUNCTION EDelMulti (thePBptr: EParamBlkPtr; 
                     async: Boolean): OSErr;

thePBptr

A pointer to a parameter block of type EParamBlock.

async

A Boolean value that specifies whether the function should be
executed asynchronously or synchronously. Specify TRUE for asynchronous execution.

-->	ioCompletion	ProcPtr	A pointer to completion routine.
<--	ioResult	OSErr	The result code.
-->	ioRefNum	Integer	The driver reference number.
-->	csCode	Integer	Always ENetDelMulti for this function.
-->	eMultiAddr	6-byte array	A multicast address.

Field Description

eMultiAddr

The multicast address that you no longer want to use.

DESCRIPTION

Each time a client of either the Ethernet or FDDI hardware device driver calls the EAddMulti function, the driver increments a counter for the multicast address specified by the eMultiAddr parameter. Each time a client of either the Ethernet or FDDI hardware device driver calls the EDelMulti function, the driver decrements the counter for the address specified by the eMultiAddr parameter.

As long as the count for a multicast address is equal to or greater than 1, the hardware device driver accepts packets directed to that multicast address. When the count for an address equals 0, the driver removes that address from the list of multicast addresses that it accepts. For token ring, the same process applies to functional addresses.

SPECIAL CONSIDERATIONS

Because more than one client of the .ENET driver might be using a particular multicast address, you should call the EDelMulti function only once for each time you called the EAddMulti function.

TOKEN RING AND FDDI CONSIDERATIONS

If your application added a multicast address for FDDI, you use this function to delete the address when you no longer need it. If your application added a functional address for token ring, use this function to delete the address when you no longer need it. Functional addresses are the token ring equivalent of Ethernet and FDDI multicast addresses. Be careful not to use the broadcast address as either a multicast or a functional address. (For information on all three types of addresses, see Inside AppleTalk, second edition.)

ASSEMBLY-LANGUAGE INFORMATION

To execute the EDelMulti function from assembly language, call the _Control
trap macro with a value of ENetDelMulti in the csCode field of the parameter
block. To execute the _Control trap asynchronously, include the value ,ASYNC in
the operand field.

RESULT CODES

noErr	0	No error
eMultiErr	-91	Address not found