Discarding a Packet | Compaq AA-RNG2A-TE specification

eh = *(mtod(m, struct ether_header *)); 2

eh.ether_type = ntohs((unsigned short)eh.ether_type); m->m_data += sizeof(struct ether_header); 4

ADD_RECV_PACKET(ifp, sc, m->m_pkthdr.len); 5 if (eh.ether_dhost[0] & 0x1) {

ADD_RECV_MPACKET(ifp, sc, m->m_pkthdr.len);

}

i = READ_RXS(sc); 6 if (i &= 0x7ff) {

if ((i & 0x400) == 0) { m_freem(m);

goto scrap;

}

}

ether_input(ifp, &eh, m); 7

}

}

3

1Calls the io_blockread( ) routine to perform the data transfer from the FIFO buffer on the adapter to the mbuf in host memory.

2Makes a copy of the ether_header data structure for the ether_input( ) routine.

3Converts the 2-byte ether_type field from network byte order to host byte order and saves it in the ether_header data structure.

4Adjusts the pointer to the received data to point past the MAC header (skips past the destination address, source address, and ether_type fields).

5Calls the ADD_RECV_PACKET macro to increment the receive packet (block) count. If this packet was destined for a broadcast or multicast address, calls the ADD_RECV_MPACKET macro to increment those statistics as well.

6Calls the READ_RXS macro to read the receive status. If the packet just received was not fully received, scraps the packet.

7Calls the ether_input( ) routine to process the received Ethernet packet. The packet is in the mbuf chain without the ether_header data structure, which is provided separately.

13.2.5Discarding a Packet

The following code shows how the el_rint( ) routine discards a packet. Some receive interrupt handlers perform a copy of a few bytes of the packet to determine if the packet is actually destined for the device. Thus, this task is an optional optimization.

scrap:

WRITE_CMD(sc, CMD_RXDTP); status = READ_RXS(sc);

}

1

Implementing the Interrupt Section 13–9

Image 147

Compaq AA-RNG2A-TE manual Discarding a Packet

Contents

Compaq Computer Corporation Houston, Texas December Product VersionPage Contents Implementing the Autoconfiguration Support Section probe Implementing the Configure Section Implementing the unattach Routine Implementing the Autoconfiguration Support Section attach Implementing the Start Section Implementing the Initialization Section Implementing the Reset Section Implementing a Watchdog SectionImplementing the ioctl Section Implementing the Interrupt Section Network Device Driver Configuration Index Tables Page Audience About This Manual Scope of this Manual Organization New and Changed Features Examples Related Documentation Reference Pages Reader’s Comments Conventions That are used in driver configuration, these brackets Page Network Device Driver Environment Network Device Driver Include Files Section for a Network Driver Declarations Section for a Network Driver External and Forward Declarations Declaring softc and controller Data Structure Arrays Defining Driver-Specific Macros Declaring and Initializing the driver Data Structure 8Network Device Driver Environment MacroDescription Driver-Specific Macros Start Section for a Network Driver Configure Section for a Network DriverAutoconfiguration Support Section for a Network Driver Initialization Section for a Network Driver Interrupt Section for a Network Driver Reset Section for a Network DriverWatchdog Section for a Network Driver Ioctl Section for a Network Driver 12Network Device Driver Environment Interrupt and Status Register Offset Definitions Defining Device Register Offsets Command Port Register Offset Definitions Defining Device Register Offsets Window 0 Configuration Register Offset Definitions W0CCR Register Constant Defines the offset for the resource configuration register Window 3 Configuration Register Offset Definitions Window 3 Configuration Registers Window 1 Operational Registers Window 1 Operational Register Offset Definitions 10Defining Device Register Offsets Mdncrc Window 4 Diagnostic Register Offset Definitions 12Defining Device Register Offsets Eeprom Data Structure Definition Page Shows a typical softc data structure Defining the softc Data Structure 2Defining the softc Data Structure Defining Common Information Defining the softc Data Structure Defining Media State Information Enabling Support for Enhanced Hardware Management Media state has been determined Defining CSR Pointer Information Defining the Base RegisterDefining Multicast Table Information Defining the Interrupt Handler ID Defining Bus-Specific Information Defining Fifo Maintenance Information Defining Interrupt and Timeout Statistics Defining the Broadcast FlagDefining the Debug Flag Defining the Polling Context Flag Defining Autosense Kernel Thread Context Information Declaring the Simple Lock Data Structure Defining a Copy of the w3eeprom Data Structure Implementing the Configure Section Etc/sysconfigtab database Following code shows how to set up the elconfigure routine Setting Up the elconfigure Routine 4Implementing the Configure Section Implementing the elprobe Routine Implementing the Autoconfiguration Support Section probe Following code shows how to set up the elprobe routine Setting Up the elprobe Routine Implementing the Autoconfiguration Support Section probe Performing Bus-Specific Tasks 4Implementing the Autoconfiguration Support Section probe Implementing the Autoconfiguration Support Section probe Allocating Memory for the softc Data Structure 6Implementing the Autoconfiguration Support Section probe Allocating the etherdriver Data Structure Computing the CSR Addresses Setting Bus-Specific Data Structure Members Implementing the Autoconfiguration Support Section probe Handling First-Time Probe Operations 10Implementing the Autoconfiguration Support Section probe Implementing the Autoconfiguration Support Section probe Handling Subsequent Probe Operations 12Implementing the Autoconfiguration Support Section probe Implementing the Autoconfiguration Support Section probe Registering the Interrupt Handler Implementing the Autoconfiguration Support Section probe Trying to Allocate Another controller Data Structure Saving the controller and softc Data Structure Pointers Implementing the elshutdown Routine Implementing the elautosensethread RoutineRegistering the shutdown Routine 18Implementing the Autoconfiguration Support Section probe Blocking Until Awakened Setting Up the elautosensethread Routine Testing for the Termination Flag Starting Up StatisticsEntering the Packet Transmit Loop Using the Default from the ROM Saving Counters Prior to the Transmit OperationAllocating Memory for a Test Packet Setting the Media in the Hardware Building the Test PacketTransmitting the Test Packet Testing for Loss of Carrier Setting a Timer for the Current Kernel Thread Setting Up New Media Determining Whether Packets Were Transmitted SuccessfullyPrinting Debug Information Establishing the Media 26Implementing the Autoconfiguration Support Section probe Setting Up the elattach Routine Implementing the Autoconfiguration Support Section attach Initializing the Media Address and Media Header Lengths Setting Up the Media 4Implementing the Autoconfiguration Support Section attach Initializing Simple Lock Information Specifying the Network Driver Interfaces Printing a Success Message Signifies that the network interface supports Attaching to the Packet Filter and the Network Layer Setting the Baud Rate Handling the Reinsert Operation Setting Network Attributes and Registering the Adapter Starting the Polling Process Enabling the Interrupt Handler Implementing the unattach Routine Setting Up the elunattach Routine Obtaining the Simple Lock and Shutting Down the Device Verifying That the Interface Has Shut Down Terminating the Autosense Kernel Thread Disabling the Interrupt Handler Terminating the Simple Lock Unregistering the Pcmcia Event Callback RoutineStopping the Polling Process Unregistering the Shutdown Routine Freeing Resources Unregistering the Card from the Hardware Management DatabasePage Setting Up the elinit Routine Implementing the Initialization SectionImplementing the elinit Routine Determining Whether the Pcmcia Card Is Present Setting the IPL and Obtaining the Simple Lock Returning the Status from the elinitlocked Routine Releasing the Simple Lock and Resetting the IPLImplementing the elinitlocked Routine Calling the elinitlocked Routine Clearing Interrupts Resetting the Transmitter and Receiver Ensuring That the 10Base2 Transceiver Is Off Starting the Device Setting the LAN Media Setting a LAN Attribute Resetting the Transmitter and Receiver AgainSelecting Memory Mapping Processing Special Flags Setting the LAN Address Enabling TX and RX Setting the Debug Flag Setting the Operational Window Enabling InterruptsMarking the Device as Running Starting the Transmit of Pending Packets Starting the Autosense Kernel ThreadPage Implementing the elstart Routine Implementing the Start Section Calling the elstartlocked Routine Implementing the elstartlocked Routine 4Implementing the Start Section Implementing the Start Section Handlelongword Transmitting the Buffer Accounting for Outgoing Bytes Indicating When to Start the Watchdog Routine Implementing a Watchdog Section Setting the IPL and Obtaining the Simple Lock Releasing the Simple Lock and Resetting the IPL Implementing the elreset Routine Implementing the Reset Section Implementing the elresetlocked Routine Implementing the ioctl Section Ioctl Command Required Description For More Information Following code shows how to set up the elioctl routine Setting Up the elioctl Routine Setting the IPL and Obtaining the Simple Lock Disabling Loopback Mode Siocdisablback ioctl Command Enabling Loopback Mode Siocenablback ioctl Command Setting the Local MAC Address Siocsphysaddr ioctl Command 12-6Implementing the ioctl Section Implementing the ioctl Section Determines whether the cmd argument is Siocrdctrs or Network Interface Counter Types Bringing Up the Device Siocsifaddr ioctl Command Using Currently Set Flags Siocsifflags ioctl Command Setting the IP MTU Siocsipmtu ioctl CommandSetting the Media Speed Siocsmacspeed ioctl Command Setting Device Characteristics Siocifsetchar ioctl Command Resetting the Device Siocifreset ioctl Command 12-12Implementing the ioctl Section If lockon 1 simpleunlock&sc-elsoftclock splxs Return status Page Implementing the elintr Routine Implementing the Interrupt Section Rearming the Next Timeout Processing Completed Receive and Transmit Operations Reading the Interrupt Status Transmitting Pending Frames Acknowledging the Interrupt Implementing the elrint Routine Indicating That the Interrupt Was Serviced Pulling the Packets from the Fifo Buffer Examining the First Part of the Packet 13-8Implementing the Interrupt Section Copying the Received Packet into the mbuf Discarding a Packet Counting the Transmit Interrupt Implementing the eltint Routine Writing to the Status Register to Obtain the Next Value Managing Excessive Data Collisions Queuing Other Transmits Implementing the elerror Routine Network Device Driver Configuration Page Index-1 Index Index-2 Declarations section, 1-4devdriver.h header file, 1-4device Index-3 Interrupt Index-4 Interrupt handler Index-5 Packet Index-6 ROM Index-7 Transmit