Fall 2004FSU CIS 5930 Internet Protocols1 Network Devices Reading: Chapter 5

Fall 2004FSU CIS 5930 Internet Protocols2 Network devices Interface between network adapters and software protocols Asynchronous input/output point of protocol stack

Fall 2004FSU CIS 5930 Internet Protocols3 (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

Fall 2004FSU CIS 5930 Internet Protocols4 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

Fall 2004FSU CIS 5930 Internet Protocols5 Network device interface (Cont’d) driver.c net_tx net_interrupt net_rx skb net_start_xmit net_opennet_stop net_device dev.c netif_rx dev->hard_start_xmitdev->opendev->stop dev_queue_xmit dev_opendev_close Higher protocol instances Network devices (Adapter-independent) Network-devices interface Network driver (Adapter-specifics) Abstraction from Adapter specfics

Fall 2004FSU CIS 5930 Internet Protocols6 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

Fall 2004FSU CIS 5930 Internet Protocols7 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

Fall 2004FSU CIS 5930 Internet Protocols8 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

Fall 2004FSU CIS 5930 Internet Protocols9 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

Fall 2004FSU CIS 5930 Internet Protocols10 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

Fall 2004FSU CIS 5930 Internet Protocols11 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

Fall 2004FSU CIS 5930 Internet Protocols12 Managing Network Devices dev_base name: eth0 state next priv net_device... Hardware MAC Layer Network layer local1 private driver structure name: eth1 state next priv net_device... Hardware MAC Layer Network layer local2 private driver structure net_device open stop hard_start_xmit... adapter_open() adapter_stop() adapter_start_xmit() open stop hard_start_xmit... adapter2_open() adapter2_stop() adapter2_start_xmit()

Fall 2004FSU CIS 5930 Internet Protocols13 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

Fall 2004FSU CIS 5930 Internet Protocols14 Registering/unregistering devices init_netdev(dev, sizeof_priv, mask, setup) init_etherdev(dev, priv_size) ether_setup(dev) register_netdevice(dev) unregister_netdevice(dev)

Fall 2004FSU CIS 5930 Internet Protocols15 Opening/closing devices dev_open(dev) dev_close(dev)

Fall 2004FSU CIS 5930 Internet Protocols16 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)

Fall 2004FSU CIS 5930 Internet Protocols17 Transmitting over network devices dev_queue_xmit(skb)

Fall 2004FSU CIS 5930 Internet Protocols18 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)

Fall 2004FSU CIS 5930 Internet Protocols19 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()

Fall 2004FSU CIS 5930 Internet Protocols20 Opening/closing adapters net_open(dev) net_stop(dev)

Fall 2004FSU CIS 5930 Internet Protocols21 Transmitting data net_send_packet(skb, dev) net_interrupt(irq, dev_id, regs) –net_tx(dev) –net_rx(dev) dev.c driver.c net_interrupt netif_rx net_rxnet_tx Receiving a packet Completing A transmission process net_error Errow situation

Fall 2004FSU CIS 5930 Internet Protocols22 About the project Progress, problems encountered