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112 lines
4.0 KiB
Plaintext
112 lines
4.0 KiB
Plaintext
Raw TCP/IP interface for lwIP
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Authors: Adam Dunkels, Leon Woestenberg, Christiaan Simons
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--- System initalization
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A truly complete and generic sequence for initializing the lwIP stack
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cannot be given because it depends on additional initializations for
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your runtime environment (e.g. timers).
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We can give you some idea on how to proceed when using the raw API.
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We assume a configuration using a single Ethernet netif and the
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UDP and TCP transport layers, IPv4 and the DHCP client.
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Call these functions in the order of appearance:
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- lwip_init()
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Initialize the lwIP stack and all of its subsystems.
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- netif_add(struct netif *netif, const ip4_addr_t *ipaddr,
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const ip4_addr_t *netmask, const ip4_addr_t *gw,
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void *state, netif_init_fn init, netif_input_fn input)
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Adds your network interface to the netif_list. Allocate a struct
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netif and pass a pointer to this structure as the first argument.
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Give pointers to cleared ip_addr structures when using DHCP,
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or fill them with sane numbers otherwise. The state pointer may be NULL.
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The init function pointer must point to a initialization function for
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your Ethernet netif interface. The following code illustrates its use.
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err_t netif_if_init(struct netif *netif)
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{
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u8_t i;
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for (i = 0; i < ETHARP_HWADDR_LEN; i++) {
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netif->hwaddr[i] = some_eth_addr[i];
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}
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init_my_eth_device();
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return ERR_OK;
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}
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For Ethernet drivers, the input function pointer must point to the lwIP
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function ethernet_input() declared in "netif/etharp.h". Other drivers
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must use ip_input() declared in "lwip/ip.h".
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- netif_set_default(struct netif *netif)
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Registers the default network interface.
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- netif_set_link_up(struct netif *netif)
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This is the hardware link state; e.g. whether cable is plugged for wired
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Ethernet interface. This function must be called even if you don't know
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the current state. Having link up and link down events is optional but
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DHCP and IPv6 discover benefit well from those events.
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- netif_set_up(struct netif *netif)
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This is the administrative (= software) state of the netif, when the
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netif is fully configured this function must be called.
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- dhcp_start(struct netif *netif)
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Creates a new DHCP client for this interface on the first call.
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You can peek in the netif->dhcp struct for the actual DHCP status.
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- sys_check_timeouts()
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When the system is running, you have to periodically call
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sys_check_timeouts() which will handle all timers for all protocols in
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the stack; add this to your main loop or equivalent.
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--- Optimization hints
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The first thing you want to optimize is the lwip_standard_checksum()
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routine from src/core/inet.c. You can override this standard
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function with the #define LWIP_CHKSUM <your_checksum_routine>.
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There are C examples given in inet.c or you might want to
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craft an assembly function for this. RFC1071 is a good
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introduction to this subject.
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Other significant improvements can be made by supplying
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assembly or inline replacements for htons() and htonl()
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if you're using a little-endian architecture.
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#define lwip_htons(x) <your_htons>
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#define lwip_htonl(x) <your_htonl>
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If you #define them to htons() and htonl(), you should
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#define LWIP_DONT_PROVIDE_BYTEORDER_FUNCTIONS to prevent lwIP from
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defining hton*/ntoh* compatibility macros.
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Check your network interface driver if it reads at
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a higher speed than the maximum wire-speed. If the
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hardware isn't serviced frequently and fast enough
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buffer overflows are likely to occur.
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E.g. when using the cs8900 driver, call cs8900if_service(ethif)
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as frequently as possible. When using an RTOS let the cs8900 interrupt
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wake a high priority task that services your driver using a binary
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semaphore or event flag. Some drivers might allow additional tuning
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to match your application and network.
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For a production release it is recommended to set LWIP_STATS to 0.
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Note that speed performance isn't influenced much by simply setting
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high values to the memory options.
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For more optimization hints take a look at the lwIP wiki.
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