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Network Devices

Network Devices. Reading: Chapter 5. Network devices. Interface between network adapters and software protocols Asynchronous input/output point of protocol stack. (Network) Hardware Properties. I/O ports (base address) Address of the hardware (in I/O address space) Interrupt ReQuest (IRQ)

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Network Devices

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  1. Network Devices Reading: Chapter 5 FSU CIS 5930 Internet Protocols

  2. Network devices • Interface between network adapters and software protocols • Asynchronous input/output point of protocol stack FSU CIS 5930 Internet Protocols

  3. (Network) Hardware Properties • I/O ports (base address) • Address of the hardware (in I/O address space) • Interrupt ReQuest (IRQ) • Informing kernel something happens at hardware • DMA channel • Direct Memory Access FSU CIS 5930 Internet Protocols

  4. Network device interface • Abstract from technical details of network adapters • Uniform interface for access by protocol instances • dev.c (net/core/dev.c) • Providing interface/functions for upper layer • net_device structure (include/linux/netdevice.h) • Hiding specific details in network drivers • xxx_driver.c (drivers/net/xxx_driver.c) • Implementation of specific network drivers FSU CIS 5930 Internet Protocols

  5. Higher protocol instances dev.c Network devices (Adapter-independent) dev_open dev_close netif_rx dev_queue_xmit Network-devices interface net_device Abstraction from Adapter specfics dev->hard_start_xmit dev->open dev->stop driver.c net_start_xmit net_rx net_tx Network driver(Adapter-specifics) net_open net_stop skb skb net_interrupt skb Network device interface (Cont’d) FSU CIS 5930 Internet Protocols

  6. net_device structure • Defined in include/linux/netdevice.h • Abtract from network adapter specifics • Containing network adapter information • Configuration data of the adapter • General fields of a network device • Hardware-specific fields • Data on physical layer • Data on network layer • Device-driver methods/functions FSU CIS 5930 Internet Protocols

  7. General fields of a network device • Name • For example, eth0, lo • ifindex • State • For example, if the adapter is up • qdisc • Queue discipline • How packets are served • And other fields FSU CIS 5930 Internet Protocols

  8. Hardware-specific fields • rmem_start, rmem_end, mem_start, mem_end • Memory for sending/receiving packets • base_addr • I/O base address • irq • Interrupt ReQuest • DMA channel • And other fields FSU CIS 5930 Internet Protocols

  9. Data on physical layer • hard_header_length • Layer-2 packet header length • mtu • Maximum transfer unit • addr_len, dev_addr[MAX_ADDR_LEN] • Layer-2 address length and address • And other fields FSU CIS 5930 Internet Protocols

  10. Data on network layer • ip_ptr, ip6_ptr, etc • Corresponding layer-3 pointers • family • Address family, e.g., AF_INET for IP • pa_alen • Address length for the family, e.g, 4 for IP • pa_addr, pa_mask • Address and mask • And other fields FSU CIS 5930 Internet Protocols

  11. Device-driver methods • They are function pointers. Adapter drivers need to implement and map to them • Initialization/activation/de-activation • init(), destructor(), open(), close() • Transmission of data • hard_start_xmit() • Control functions • do_ioctl(), set_config() • Helpful functions • dard_header(), hard_header_parse(), etc • Other functions FSU CIS 5930 Internet Protocols

  12. net_device name: eth1 dev_base state net_device next priv net_device ... name: eth0 Hardware state local2private driver structure next MAC Layer priv ... Network layer Hardware open MAC Layer adapter2_open() stop adapter2_stop() hard_start_xmit Network layer adapter2_start_xmit() ... open adapter_open() stop adapter_stop() hard_start_xmit adapter_start_xmit() ... local1private driver structure Managing Network Devices FSU CIS 5930 Internet Protocols

  13. Functions to manage devices • Registering/unregistering devices • Opening/closing devices • Creating/finding devices • Transmitting over devices • Provided in the following two files • net/core/dev.c • drivers/net/net_init.c FSU CIS 5930 Internet Protocols

  14. Registering/unregistering devices • init_netdev(dev, sizeof_priv, mask, setup) • init_etherdev(dev, priv_size) • ether_setup(dev) • register_netdevice(dev) • unregister_netdevice(dev) FSU CIS 5930 Internet Protocols

  15. Opening/closing devices • dev_open(dev) • dev_close(dev) FSU CIS 5930 Internet Protocols

  16. Creating/finding devices • dev_alloc_name(dev, name) • dev_alloc(name, err) • dev_get_by_name(name) • dev_get(name) • dev_getbyhwaddr(type, ha) • dev_load(name) FSU CIS 5930 Internet Protocols

  17. Transmitting over network devices • dev_queue_xmit(skb) FSU CIS 5930 Internet Protocols

  18. Network drivers • They implement adapter specific functions • Initializing adapters • Opening and closing network adapters • Transmitting/receiving data • We use sample driver isa_skeleton.c to discuss functions (drivers/net/isa_skeleton.c) FSU CIS 5930 Internet Protocols

  19. Initializing adapters • net_init()/net_probe() • netcard_probe(dev) • netcard_probe1(dev, ioaddr) • Helper functions to allocate system resources • Request_region(), release_region(), check_region() • Request_irq(), free_irq() • Request_dma(), free_dma() FSU CIS 5930 Internet Protocols

  20. Opening/closing adapters • net_open(dev) • net_stop(dev) FSU CIS 5930 Internet Protocols

  21. dev.c netif_rx driver.c net_error net_tx net_rx Completing A transmission process Receiving a packet Errow situation net_interrupt Transmitting data • net_send_packet(skb, dev) • net_interrupt(irq, dev_id, regs) • net_tx(dev) • net_rx(dev) FSU CIS 5930 Internet Protocols

  22. About the project • Progress, problems encountered FSU CIS 5930 Internet Protocols

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