Network Driver in Linux 2.4 潘仁義 CCU COMM. Overview Bus DeviceOperating System Auto...

Network Driver in Linux 2.4Network Driver in Linux 2.4

潘仁義CCU COMM

OverviewOverview

Bus

DeviceOperating System

Auto Configuration

Direct Memory AccessPower management

I/O accessByte ordering

Address translation

Interrupt handling

Bus cycles

Driver frameworkTimer management

Memory managementRace condition handling (SMP)

CPU/Memory cache consistency

Device operations

OutlineOutline

Driver frameworkLinux network drivers

Device operationRTL8139 programming

Driver exampleA piece of code for 93C46 series

EEPROM, 93C46 64 x 16 bits, 93C66 256 x 16 bits

pci_skeleton.c (for RTL8139)

Linux network driver frameworkLinux network driver frameworkConnecting to the Kernel (1/2)Connecting to the Kernel (1/2)

Module_loadingstruct net_device snull_dev = { init : snull_init, }; // 初始化函式if((result = register_netdev(snull_dev)))) printk(“error”);

呼叫前 , 先設定 name 為“ eth%d”, 以便其配置 “ ethX”函式內部會呼叫 devinit()

snull_init( )Probe functionCalled when register_netdev()Usually avoid registering I/O and IRQ, delay until devopen() timeTo fill in the “dev” strcutureether_setup(dev), 會將正確的 ARP 相關作業方法設定好設定私有資料結構 “ priv”; 網路介面生命期與系統一樣長 , 可放統計資料

Module_unloadingkfree(priv); unregister_netdev (snull_dev);

Linux network driver frameworkLinux network driver frameworkConnecting to the Kernel (2/2)Connecting to the Kernel (2/2)

struct net_device {char name[IFNAMSIZ]; // eth%d

unsigned long base_addr, unsigned char irq;

unsigned char broadcast[], dev_addr[MAX_ADDR_LEN];

unsigned short flags; // IFF_UP, IFF_PROMISC, IFF_ALLMULTI

Function pointers:(*init) 初始化(*open) 開啟介面(*stop) 停用介面 (*do_ioctl)()

(*tx_timeout) 逾時處理(*get_stats) 結算統計資訊(*hard_start_xmit) 送出封包(*set_multicast_list) 群播及 flag 變動處理

unsigned long trans_start, last_rx; // for watchdog and power management

struct dev_mc_list *mc_list; // multicast address list

Linux network driver frameworkLinux network driver frameworkOpening and closingOpening and closing

在介面傳輸封包之前，必須先以 ifconfig 開啟介面，並賦予 IP 位址ifconfig 設定 IP 位址給介面時：

ioctl(SIOCSIFADDR) 設定軟體位址給介面ioctl(SIOCSIFFLAGS) 要求驅動程式開啟、關閉介面觸動 open 及 stop

open() 設法取得必要的系統資源 ( 佔領 IRQ, IObase, buffer)

要求介面硬體起動讀出 MAC, 複製到 devdev_addr ( 也可作在 init 或 probe 時 )

將 devdev_addr 設定至介面 MAC 暫存器中stop()

停止介面硬體歸還系統資源

Linux network driver frameworkLinux network driver framework Packet transmission: Packet transmission: 當核心需要送出資料封包時當核心需要送出資料封包時

將資料排入出境封包佇列 (outgoing queue)

呼叫作業方法hard_start_transmit(struct sk_buff *skb, struct net_device *dev)僅將封包交付網卡。網卡後續會再將封包傳送至網路 ( 例如 RTL8139)

Spinlock_t xmit_lock; 只有在返回後才有可能再被呼叫實務上，於返回之後，網路卡仍忙著傳輸剛交付的封包。網卡緩衝區小，滿了必須讓核心知道，不接收新的傳輸要求。netif_stop_queue() 與 netif_wake_queue(),netif_start_queue()

註 : 還有 Carrier loss detection/Watchdog 的 netif_carrier_on/off()跟 Hot-plugging/power management 的 netif_device_attach/detach()

核心經手的每一封包，都是包裝成一個 struct sk_buff socket buffer

指向 sk_buff 的指標，通常取名為 skb

skbdata 指向即將被送出的封包skblen 是該封包的長度，單位是 octet

Linux network driver frameworkLinux network driver frameworkTransmission queuing modelTransmission queuing model

netif_start_queue()netif_wake_queue() netif_stop_queue() netif_carrer_on()

netif_carrer_off()

netif_device_attach()netif_device_detach()

If ( present && carrier_ok && queue_stopped &&

( jiffies – trans_start ) > watchdog_timeo ) Then

Call tx_timeout( )更新統計，並設定使能繼續送封包

Present?

Queue stopped ?

Carrier ok ?

Packets from OS

Packets from OS

Packets go to the LAN

Packets go to the LAN

Linux network driver frameworkLinux network driver frameworkPacket receptionPacket reception

封包接收事件通常是從網路硬體觸發中斷開始多半寫在 interrupt handler

配置一個 sk_buff ，並交給核心內部的網路子系統Interrupt-based 較 polling 方式有效率

Example: snull_rx()skb = dev_alloc_skb(len+2); // 採用 GFP_ATOMIC, 可在 ISR 中用skb_reserve(skb, 2); // 16 byte align the IP field

memcpy(skb_put(skb, len), receive_packet, len); //skb_put() 參考 sk_buff

填寫相關資訊skbdev = dev;

skbprotocol = eth_type_trans(skb, dev);

skbip_summed = CHECKSUM_UNNECESSARY; /* 不必檢查 */

CHECKSUM_HW( 硬體算了 )/NONE( 待算 , 預設 )/UNNECESSARY( 不算 )

netif_rx(skb); // 交給核心內部的網路子系統

Linux network driver frameworkLinux network driver frameworkThe interrupt handlerThe interrupt handler

Interrupt happen whenA new packet has arrived

Transmission of an outgoing packet is completed

Something happened: PCI bus error, cable length change, time out

Interrupt status register (ISR)Packet reception

Pass to the kernel

Packet transmission is completedReset the transmit buffer of the interface

Statistics

Linux network driver frameworkLinux network driver frameworkThe socket buffers (struct sk_buff)The socket buffers (struct sk_buff)

payloadheadroom tailroom

head data tail endlen

struct sk_buff *dev_alloc_skb(len) 配置

void dev_kfree_skb(struct sk_buff *) 釋放An empty sk_buff

void skb_reserve(skb, len) 保留前頭空間

unsigned char *skb_put(skb, len) 附加資料

unsigned char*skb_push(skb, len) 前置資料

unsigned char *skb_pull(skb, len) 前抽資料

Linux network driver frameworkLinux network driver frameworkSetup receive mode and multicast accept listSetup receive mode and multicast accept list

Unicast, broadcast (all 1), multicast (bit0==1)Receive all, receive all multicast, receive a list of multicast address

Transmit multicast framesis the same as unicast

Receive multicast framesHardware filtering for a list of multicast addresses

void (*set_multicast_list)(dev)要接收的群播位址清單或是 dev->flags 有改變 , 會被核心呼叫

struct dev_mc_list *mc_list; // int mc_count串列所有 dev 必須接收的所有群播位址

IFF_PROMISC設立則進入『混雜模式』 ( 全收 )

IFF_ALLMULTI收進所有群播封包

OutlineOutline






RTL8139 block diagramRTL8139 block diagram

Device operationDevice operationRTL8139(A/B) programmingRTL8139(A/B) programming

Packet transmission4 transmit descriptors in round-robinTransmit FIFO and Early Transmit

Packet receptionRing buffer in a physical continuous memoryReceive FIFO and FIFO Threshold

Hardware initializationCommand register (0x37)

Reset (4) / Transmit Enable (2) / Receive Enable (3) / Buffer empty (0)

Transmit (Tx) Configuration Register (0x40~0x43)Interframe Gap time ( 螃蟹卡 ) (25~24)

Receive (Rx) Configuration Register (0x44~0x47)Rx FIFO threshold (15~13)Accept Broadcast (3) / Multicast (2) / All (0, Promiscuous mode) packetRx buffer length (12~11)

Interrupt Mask Register (0x3C~0x3D)

Software initialization (TxDescriptor and Ring buffer)

RTL8139 RTL8139 Packet transmissionPacket transmissionTransmit descriptorTransmit descriptor

Transmit start address (TSAD0-3)The physical address of packet

The packet must be in a continuous physical memory

Transmit status(TSD0-3)TOK(15R)

Set to 1 indicates packet transmission was completed successfully and no transmit underrun (14R) has occurred

OWN(13R/W)Set to 1 when the Tx DMA operation of this descriptor was completed

The driver must set this bit to 0 when the “Size” is written

Size(12~0R/W)The total size in bytes of the data in this descriptor

Early Tx Threshold(21~16R/W)When the byte count in the Tx FIFO reaches this, the transmit happens.

From 000001 to 111111 in unit of 32 bytes (000000 = 8 bytes)

RTL8139 RTL8139 Packet transmissionPacket transmissionProcess of transmitting a packetProcess of transmitting a packet

1. copy the packet to a physically continuous buffer in memory

2. Write the functioning descriptorAddress, Size, Early transmit threshold, Clear OWN bit (this starts PCI operation)

3. As TxFIFO meet threshold, the chip start to move from FIFO to line

4. When the whole packet is moved to FIFO, the OWN bit is set to 1

5. When the whole packet is moved to line, the TOK(TSD) is set to 1

6. If TOK(IMR) is set, then TOK(ISR) is set and a interrupt is triggered

7. Interrupt service routine called, driver should clear TOK(ISR)

Packet receptionPacket receptionRing bufferRing buffer

1. Data goes to RxFIFOcoming from line

2. Move to the buffer when early receive threshold is meet.

Ring bufferphysical continuous

CBR (0x3A~3B R)the Current address of data moved to Buffer

CAPR (0x38~39 R/W)the pointer keeps Current Address of Pkt having been read

Status of receiving a packet

stored in front of the packet (packet header)

Packet receptionPacket receptionThe Packet Header (32 bits, i.e. 4 bytes)The Packet Header (32 bits, i.e. 4 bytes)

Bit 31~16: rx_size, including 4 bytes CRC in the tailpkt_size = rx_size - 4

Packet receptionPacket receptionPProcess of packet receive in detail

Data received from line is stored in the receive FIFO

When Early Receive Threshold is meet, data is moved from FIFO to Receive Buffer

After the whole packet is moved from FIFO to Receive Buffer, the receive packet header (receive status and packet length) is written in front of the packet.

CBA is updated to the end of the packet. 4 byte alignment

CMD (BufferEmpty) is clear and ISR(ROK) is set.

ISR routine called and then driver clear ISR(ROK) and update CAPR

cur_rx = (cur_rx + rx_size + 4 + 3) & ~3;

NETDRV_W16_F (RxBufPtr, cur_rx - 16);

Packet header

Avoid overflow

OutlineOutline






EEPROM 93C46 operationsEEPROM 93C46 operations

93C46 Command Register (0x50 R/W)

A piece code for EEPROM 93C46 A piece code for EEPROM 93C46

11. /* Shift the read command bits out. */12. for (i = 4 + addr_len; i >= 0; i--) {13. int dataval = (read_cmd & (1 << i))

? EE_DATA_WRITE : 0;14. writeb (EE_ENB | dataval, ee_addr);15. eeprom_delay ();16. writeb (EE_ENB | dataval | EE_SHIFT_C

LK, ee_addr);17. eeprom_delay ();18. }19. writeb (EE_ENB, ee_addr);20. eeprom_delay ();

21. for (i = 16; i > 0; i--) {22. writeb (EE_ENB | EE_SHIFT_CLK, ee_a

ddr);23. eeprom_delay ();24. retval = (retval << 1) | ((readb (ee_addr)

& EE_DATA_READ) ? 1 : 0);25. writeb (EE_ENB, ee_addr);26. eeprom_delay ();27. }28. /* Terminate the EEPROM access. */29. writeb (~EE_CS, ee_addr);30. eeprom_delay ();31. return retval;32. }

#define EE_SHIFT_CLK 0x04 /* EEPROM shift clock. */#define EE_CS 0x08 /* EEPROM chip select.

*/#define EE_DATA_WRITE 0x02 /* EEPROM chip data in. */#define EE_DATA_READ 0x01 /* EEPROM chip data out. */#define EE_ENB (0x80 | EE_CS)

#define eeprom_delay() readl(ee_addr)

/* EEPROM commands include the alway-set leading bit */#define EE_WRITE_CMD (5)#define EE_READ_CMD (6)#define EE_ERASE_CMD (7)

1. static int __devinit read_eeprom (2. void *ioaddr, int location, int addr_len)3. {4. int i;5. unsigned retval = 0;6. void *ee_addr = ioaddr + Cfg9346;7. int read_cmd = location |

(EE_READ_CMD << addr_len);

8. writeb (EE_ENB & ~EE_CS, ee_addr);9. writeb (EE_ENB, ee_addr);10. eeprom_delay ();

addr_len = read_eeprom (ioaddr, 0, 8) == 0x8129 ? 8 : 6;for (i = 0; i < 3; i++) ((u16 *) (dev->dev_addr))[i] = le16_to_cpu (read_eeprom (ioaddr, i + 7, addr_len));

OutlineOutline






#include<> of the RTL8139#include<> of the RTL8139

pci-skeleton.c

module.h kernel.h

pci.h

init.h

netdevice.hetherdevice.h

delay.h

mii.h

asm/io.h

skbuff.h

Definitions for Ethernet eth_type_trans()

alloc_ethdev()

Definitions for struct net_devic

eregister_netdev

()netif_*()skbuff.h

Definitions of I/O port read/write an

dioremap()

PCI defines and prototypes

pci_alloc_consistent()pci_resource_*()

pci_request_regions()pci_set_master()

pci_read_config_word()(err)Definitions for MII_ADVERTISE,

MII_LPAADVERTISE_FULL, LPA_100FULL…

barrier()printk()

byteorder.h

udelay() definition

給 multicast 算 ether_crc()

module_init()

module_exit()spinlock.h

config.hMOD_*

MODULE_*()

crc32.h

被間接引入sched.h (irq,jiffies,capabl

e)slab.htime.h

spinlock.hasm/atomic.

h

PCI BUS

Network Device

Operating System

Driver structure of the RTL8139Driver structure of the RTL8139

pci_module_init() / pci_unregister_driver()static struct pci_driver netdrv_pci_driver = {

name: "netdrv",

id_table: netdrv_pci_tbl,

probe: netdrv_init_one,

remove: netdrv_remove_one,

#ifdef CONFIG_PM

suspend: netdrv_suspend,

resume: netdrv_resume,

static struct pci_device_id netdrv_pci_tbl[] __devinitdata = {{0x10ec, 0x8139, PCI_ANY_ID, PCI_ANY_ID, 0, 0, RTL8139 },

MODULE_DEVICE_TABLE (pci, netdrv_pci_tbl);

pci_device_id

driver_data(Private, Sq# here)

PCI device probe functionPCI device probe functionnetdrv_init_one()netdrv_init_one()

netdrv_init_one()

call netdrv_init_board()

to get net_device dev, void *ioaddr

Initial net_device devSet up dev_addr[], irq, base_addrSet up method:

dev->open,dev->hard_start_transmit,dev->stop, dev->get_stats, dev->set_multicast_list, dev->do_ioctl, dev->tx_timeout

struct pci_dev *pdev, struct pci_device_id *ent

Linux invoke when probing

netdrv_init_board()

dev = alloc_etherdev(sizeof())

pci_enable_device (pdev);pci_request_regions (pdev, “pci-sk");pci_set_master (pdev);

mmio_start = pci_resource_start (pdev, 1);

ioaddr = ioremap (mmio_start, len);

Soft reset the chip.NETDRV_W8 (ChipCmd, (NETDRV_R8 (ChipCmd)

& ChipCmdClear) | CmdReset);

identify chip attached to board

register_netdev (dev); // ethX登記 I/O port and memory

NETDRV_W?()NETDRV_W?()

/* write MMIO register, with flush *//* Flush avoids rtl8139 bug w/ posted MMIO writes */#define NETDRV_W8_F(reg, val8)do { writeb ((val8), ioaddr + (reg)); readb (ioaddr + (reg)); } while (0)#define NETDRV_W16_F(reg, val16)do { writew ((val16), ioaddr + (reg)); readw (ioaddr + (reg)); } while (0)#define NETDRV_W32_F(reg, val32)do { writel ((val32), ioaddr + (reg)); readl (ioaddr + (reg)); } while (0)#define NETDRV_W8 NETDRV_W8_F#define NETDRV_W16 NETDRV_W16_F#define NETDRV_W32 NETDRV_W32_F#define NETDRV_R8(reg) readb (ioaddr + (reg))#define NETDRV_R16(reg) readw (ioaddr + (reg))#define NETDRV_R32(reg) ((unsigned long) readl (ioaddr + (reg)))

Device methodsDevice methods

dev->openint netdrv_open (struct net_device *dev);dev->hard_start_transmitint netdrv_start_xmit (struct sk_buff *skb, struct net_device *dev);dev->stopint netdrv_close (…);dev->get_statsstruct net_device_stats * netdrv_get_stats (struct net_device *);dev->set_multicast_listvoid netdrv_set_rx_mode (…);dev->do_ioctlint netdrv_ioctl (struct net_device *dev, struct ifreq *rq, int cmd);dev->tx_timeoutvoid netdrv_tx_timeout (struct net_device *dev);

Up up……Up up……netdrv_opennetdrv_open()()

request_irq (dev->irq, netdrv_interrupt, SA_SHIRQ, dev->name, dev)

tx_bufs = pci_alloc_consistent(pdev, TXBUFLEN, &tx_bufs_dma);rx_ring = pci_alloc_consistent(pdev, RXBUFLEN, &rx_ring_dma);

netdrv_init_ring (dev);

netdrv_hw_start (dev);

Set the timer to check for link beat

netdrv_open()Soft reset the chip

/* Restore our idea of the MAC address. */NETDRV_W32_F (MAC0 + 0, cpu_to_le32 (*(u32 *) (dev->dev_addr + 0)));NETDRV_W32_F (MAC0 + 4, cpu_to_le32 (*(u32 *) (dev->dev_addr + 4)));

NETDRV_W8_F (ChipCmd, (NETDRV_R8 (ChipCmd) & ChipCmdClear) | CmdRxEnb | CmdTxEnb);

Setting RxConfig and TxConfig

NETDRV_W32_F (RxBuf, tp->rx_ring_dma);

init Tx buffer DMA addresses

netdrv_set_rx_mode (dev);

NETDRV_W16_F (IntrMask, netdrv_intr_mask);

netif_start_queue (dev);

netdrv_hw_start (dev)

Setup receive mode and multicast Setup receive mode and multicast hashtablehashtable(*set_multicast_list)()(*set_multicast_list)()netdrv_set_rx_mode()netdrv_set_rx_mode()

if (flags & IFF_PROMISC) AcceptBroadcast | AcceptMulticast | AcceptMyPhys | AcceptAllPhy

mc_filter[1] = mc_filter[0] = 0xffffffff

else if ((mc_count > multicast_filter_limit) || (flags & IFF_ALLMULTI))

AcceptBroadcast | AcceptMulticast | AcceptMyPhys

mc_filter[1] = mc_filter[0] = 0xffffffff

elseAcceptBroadcast | AcceptMulticast | AcceptMyPhys

mclist[0].dmi_addr

mclist[1].dmi_addr

mclist[2].dmi_addr

ether_crc()31 30 29 28 27 26 25...0

63 62 1 0

Transmit a packetTransmit a packetnetdrv_start_xmit()netdrv_start_xmit()

if (skb->len < ETH_ZLEN) skb = skb_padto(skb, ETH_ZLEN);

entry = atomic_read (&cur_tx) % NUM_TX_DESC;

tx_info[entry].skb = skb;

memcpy (tx_buf[entry], skb->data, skb->len);

NETDRV_W32 (TxStatus[entry], tx_flag | skb->len);

dev->trans_start = jiffies;

atomic_inc (&cur_tx);if ((atomic_read (&cur_tx) - atomic_read (&dirty_tx)) >= NUM_TX_DESC)

netif_stop_queue (dev);

netdrv_start_xmit()

dirty_tx

0 1 2 3 0 1 2

cur_tx

Interrupt handlingInterrupt handlingnetdrv_interrupt()netdrv_interrupt()

spin_lock (&tp->lock);status = NETDRV_R16 (IntrStatus);NETDRV_W16_F (IntrStatus, status); // Acknowledge

Spec says, “The ISR bits are always set to 1 if the condition is present. ”Spec says, “Reading the ISR clears all. Writing to the ISR has no effect.”

if (status & (PCIErr | PCSTimeout | RxUnderrun | RxOverflow |RxFIFOOver | TxErr | RxErr))

netdrv_weird_interrupt (dev, tp, ioaddr, status, link_changed);

if (RxOK | RxUnderrun | RxOverflow | RxFIFOOver)netdrv_rx_interrupt (dev, tp, ioaddr);

if (status & (TxOK | TxErr))netdrv_tx_interrupt (dev, tp, ioaddr);

spin_unlock (&tp->lock);

0 1 1 1 0 0 1 1

0 0 1 1 0 0 1 0

Interrupt

ISR

IMR

Interrupt handlingInterrupt handlingnetdrv_tx_interrupt(dev, tp, ioaddr)netdrv_tx_interrupt(dev, tp, ioaddr)

1. dirty_tx = atomic_read (&tp->dirty_tx); 2. cur_tx = atomic_read (&tp->cur_tx); 3. tx_left = cur_tx - dirty_tx;4. while (tx_left > 0) {5. int entry = dirty_tx % NUM_TX_DESC;6. int txstatus = NETDRV_R32 (TxStatus[entry]);7. if (!(txstatus & (TxStatOK | TxUnderrun | TxAborted))) break; /* It still hasn't been Txed

*/8. if (txstatus & (TxOutOfWindow | TxAborted)) { /* There was an major error, log it. */9. tp->stats.tx_errors++;10. } else {11. if (txstatus & TxUnderrun) /* Add 64 to the Tx FIFO threshold. */12. tp->tx_flag += 0x00020000; 13. tp->stats.tx_bytes += txstatus & 0x7ff;14. tp->stats.tx_packets++;15. }16. dev_kfree_skb_irq (tp->tx_info[entry].skb);17. tp->tx_info[entry].skb = NULL;18. dirty_tx++;19. if (netif_queue_stopped (dev))20. netif_wake_queue (dev);21. cur_tx = atomic_read (&tp->cur_tx);22. tx_left = cur_tx - dirty_tx;23. }24. atomic_set (&tp->dirty_tx, dirty_tx);

Interrupt handling Interrupt handling Packet receptionPacket receptionnetdrv_rx_interrupt (dev,tp, ioaddr)netdrv_rx_interrupt (dev,tp, ioaddr)

1. rx_ring = tp->rx_ring;2. cur_rx = tp->cur_rx;3. while ((NETDRV_R8 (ChipCmd) & RxBufEmpty) == 0) {4. ring_offset = cur_rx % RX_BUF_LEN;5. rx_status = le32_to_cpu (*(u32 *) (rx_ring + ring_offset));6. rx_size = rx_status >> 16;7. pkt_size = rx_size - 4;8. skb = dev_alloc_skb (pkt_size + 2);9. skb->dev = dev;10. skb_reserve (skb, 2); /* 16 byte align the IP fields. */11. eth_copy_and_sum (skb, &rx_ring[ring_offset + 4], pkt_size, 0);12. skb_put (skb, pkt_size);13. skb->protocol = eth_type_trans (skb, dev);14. netif_rx (skb);15. dev->last_rx = jiffies;16. tp->stats.rx_bytes += pkt_size;17. tp->stats.rx_packets++;18. cur_rx = (cur_rx + rx_size + 4 + 3) & ~3;19. NETDRV_W16_F (RxBufPtr, cur_rx - 16);20. }21. tp->cur_rx = cur_rx; Status packet CRC

Backup slideBackup slide

How snull is designed ?How snull is designed ?

Ping 看看…

14.3 14.3 詳解詳解 net_devicenet_device 結構結構

初次研究網路驅動程式的讀者可以略過本節 ,因為就算不了解它 ,也不會妨礙你的入門學習 .逐一描述每個欄位的意義與用途 , 參考性質 , 不需強記 .此結構可分為兩大部分 :開放與隱藏 .開放 - 此結構宣告為靜態結構 ,可以預先設定初值的欄位 .隱藏 -剩餘欄位 ,主要提供核心內部的網路層使用 .

14.3.1 14.3.1 開放欄位開放欄位 (1/2)(1/2)

char name[IFNAMESIZ] 裝置名稱unsigned long rmem_end;unsigned long rmem_start;unsigned long mem_end;unsigned long mem_start;

裝置的公共記憶體範圍 ,rmem是接收區的範圍 ,mem是傳送區的範圍 .unsigned long base_addr; 網路卡 I/O基底位址unsigned char irq; 裝置使用的中斷編號

14.3.1 14.3.1 開放欄位開放欄位 (2/2)(2/2)

unsigned char if_port; 若網卡有多個連接埠 ,此欄代表正在使用的的那個連接埠 .

unsigned char dma; 分配給網路裝置的 DMA通道 .unsigned long state;

裝置的狀態 ,驅程不直接操作這些旗標 ,而是透過一組工具函式來改變或取得 .struct net_device *next;

指向全域鏈結串列裡的下一個裝置 ,驅程不應該接觸到 .int (*init)(struct net_device *dev); 指向初始函式的指標 .

14.3.2 14.3.2 隱藏欄位隱藏欄位

這些欄位大致可分成三大類 : 第一類提供網路介面資訊 (ifconfig). 第二類輔助驅動程式 (核心用不到 ). 第三類裝置作業方法 ,是 kernel-driver介面的一部分 .

其後說明上述欄位 ,並非表示在此結構的實際排列順序 .

14.3.2.1 14.3.2.1 界面資訊欄位界面資訊欄位 (1/5)(1/5)

設定網路介面的資訊性欄位 (driver/net/net_init.c)

void ether_setup(struct net_device *dev);

void fddi_setup(struct net_device *dev);

void hippi_setup(struct net_device *dev);

void ltalk_setup(struct net_device *dev);

void tr_setup(struct net_device *dev);

void fc_setup(struct net_device *dev);

這六類已經涵括所有能夠找到的網路技術 ,若有更新奇的玩意兒 ,就只好老老實實自己填寫下面的欄位了 .

14.3.2.1 14.3.2.1 界面資訊欄位界面資訊欄位 (2/5)(2/5)

unsigned short hard_header_len;

硬體標頭長度 ,計算單位是 octet. 對於 Ethernet 值為 14

unsigned mtu;

傳輸單位上限 . 對於 Ethernet 值為 1500 octets

unsigned long tx_queue_len;

傳輸佇列可容納的訊框長度上限 . ether_setup() 設為 100

unsigned short type;

介面硬體型態 . 提供 ARP判斷介面支援何種硬體位址

14.3.2.1 14.3.2.1 界面資訊欄位界面資訊欄位 (3/5)(3/5)

unsigned char addr_len;

硬體位址 (MAC)長度 .unsigned char broadcast[MAX_ADDR_LEN];

廣播位址 .unsigned char dev_addr[MAX_ADDR_LEN];

硬體位址 .以 Ethernet而言 ,硬體位址長度為 6 octets,廣播位址是 6個連續0xff, ether_setup()能正確地填寫這兩值 ,但 MAC位址則須靠驅動程式自己填寫 .

14.3.2.1 14.3.2.1 界面資訊欄位界面資訊欄位 (4/5)(4/5)

unsigned short flags; 介面旗標 .flags是一個位元遮罩 ,<linux/if.h>定義了一系列代表

各種位元值的 IFF_符號 (InterFace Flags),有效的旗標包括 :IFF_UP 介面運作狀態 .對驅程唯讀 ,只有核心能變更 .IFF_BROADCAST 介面是否具備廣播能力 .IFF_DEBUG 除錯模式 . 驅程用此控制 printk 的囉唆程度IFF_LOOPBACK 只有 loopback介面才能設立此旗標 .IFF_POINTOPOINT 點對點介面 .IFF_NOARP 是否支援 ARP.

14.3.2.1 14.3.2.1 界面資訊欄位界面資訊欄位 (5/5)(5/5)

IFF_PROMISC 啟動混雜模式 .IFF_MULTICAST 介面是否具備群播能力 .IFF_ALLMULTI 要求介面收下所有群播封包 .IFF_MASTER 負載平衡 . 驅程不需理會 .IFF_SLAVE 負載平衡 . 驅程不需理會 .IFF_PORTSEL 支援具備切換傳媒能力的網卡 .IFF_AUTOMEDIA 同上 ,多了自動 .IFF_DYNAMIC 介面的硬體位址可以被改變 .撥接裝置 .IFF_RUNNING 與 IFF_UP相同 ,只為了保持 BSD相容性 .IFF_NOTRAILERS Linux 並未使用 .為了 BSD相容性

14.3.2.2 14.3.2.2 網路介面的作業方法網路介面的作業方法 (1/4)(1/4)

大致可分成基本與額外兩組 ,你的驅程必須提供基本作業方法 ,網路介面才有用 .額外作業方法是屬於比較高階的功能 ,並不嚴格要求一定要具備 .以下為基本作業方法 :int (*open)(struct net_device *dev); 開啟介面int (*stop)(struct net_device *dev); 停用介面int (*hard_start_xmit) (struct sk_buff *skb, struct net_device *dev); 要求硬體開始送出一個封包int (*hard_header) (struct sk_buff *skb, struct net_device *dev, unsigned short type, void *daddr, void *saddr, unsigned len); 負責建構硬體標頭


int (*rebuild_header)(struct sk_buff *skb); 負責在傳輸封包之前重建硬體標頭 . 2.4 改用 hard_header

void (*tx_timeout)(struct net_device *dev); 若無法在一段合理時間內完成封包傳輸 ,則會呼叫此作業方法 .

struct net_device_stats *(*get_stats)(struct net_device *dev); 每當應用程式需介面統計資訊時 ,就會觸動此作業方法 .

int (*set_config)(struct net_device *dev, struct ifmap *map); 更改介面的硬體組態 .


以下為額外作業方法 :int (*do_ioctl)(struct net_device *dev, struct ifreq *ifr, int cmd);

執行特殊的 ioctl命令 .void (*set_multicast_list)(struct net_device *dev);

每當裝置的群播名單或 flags位元遮罩有任何變動時 ,就會觸發此作業方法 .int (*set_mac_address)(struct net_device *dev, void *addr);

若你的網卡提供改變硬體位址的能力 , 則可以實作此作業方法 .


int (*change_mtu)(struct net_device *dev, int new_mtu); 當介面 MTU有所變更時 ,由此作業方法負責相關動作 .

int (*header_cache) (struct neighbour *neigh, struct hh_cache *hh); 將 ARP查詢的結果填寫到 hh_cache結構 .

int (*header_cache_update) (struct hh_cache *hh, struct net_device *dev, unsigned char *haddr);

MAC位址備改變時 ,修正 hh_cache結構裡的目標位址 .int (*hard_header_parse) (struct sk_buff *skb, unsigned char *haddr);

從 skb取出來源位址 ,然後複製到 haddr所指的緩衝區 .

14.3.2.3 14.3.2.3 工具欄位工具欄位 (1/2)(1/2)

unsigned long trans_start; 開始傳輸的系統時刻 .

unsigned long last_rx; 最近一次收到完整封包的系統時刻 .

int watchdog_timeo; 網路子系統斷定傳輸逾期的最短時間間隔 .

void *priv; 地位相當於 filp->private_data.struct dev_mc_list *mc_list;int mc_count;

這兩個欄位用來處理群播傳輸 . mc_count 是 mc_list 的節點個數 .

14.3.2.3 14.3.2.3 工具欄位工具欄位 (2/2)(2/2)

spinlock_t xmit_lock; 保護驅程的 hard_start_xmit,避免它被同時多次重複呼叫 .

int xmit_lock_owner; 代表目前有多少個 CPU取得了 xmit_lock的擁有權 .

struct module *owner; 擁有本網路裝置結構的模組 .用來維護模組的用量計次 .

14.12 14.12 統計資訊統計資訊Struct net_device_stats 裡面重要欄位

unsigned long tx_packets;unsigned long rx_packets;unsigned long tx_bytes;unsigned long rx_bytes;unsigned long tx_errors;unsigned long rx_errors;unsigned long tx_dropped;unsigned long rx_dropped;unsigned long collisions;unsigned long multicast;

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