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author | Josh Blum <josh@joshknows.com> | 2010-12-22 19:19:14 -0800 |
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committer | Josh Blum <josh@joshknows.com> | 2010-12-22 19:19:14 -0800 |
commit | 22ed61f97815856bf74cec25ae6bca88bfbe5f44 (patch) | |
tree | 7d87d49b46f9507ff10486097e6d79e4bee4cb81 /firmware/microblaze/lwip/lwip-1.3.1/doc/rawapi.txt | |
parent | 71fc99d006f2347a356c5339905593f64ff902ec (diff) | |
download | uhd-22ed61f97815856bf74cec25ae6bca88bfbe5f44.tar.gz uhd-22ed61f97815856bf74cec25ae6bca88bfbe5f44.tar.bz2 uhd-22ed61f97815856bf74cec25ae6bca88bfbe5f44.zip |
zpu: renamed the directory for the usrp2 fw to zpu to reflect the cpu type
Diffstat (limited to 'firmware/microblaze/lwip/lwip-1.3.1/doc/rawapi.txt')
-rw-r--r-- | firmware/microblaze/lwip/lwip-1.3.1/doc/rawapi.txt | 478 |
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diff --git a/firmware/microblaze/lwip/lwip-1.3.1/doc/rawapi.txt b/firmware/microblaze/lwip/lwip-1.3.1/doc/rawapi.txt deleted file mode 100644 index 8eec6e786..000000000 --- a/firmware/microblaze/lwip/lwip-1.3.1/doc/rawapi.txt +++ /dev/null @@ -1,478 +0,0 @@ -Raw TCP/IP interface for lwIP - -Authors: Adam Dunkels, Leon Woestenberg, Christiaan Simons - -lwIP provides three Application Program's Interfaces (APIs) for programs -to use for communication with the TCP/IP code: -* low-level "core" / "callback" or "raw" API. -* higher-level "sequential" API. -* BSD-style socket API. - -The sequential API provides a way for ordinary, sequential, programs -to use the lwIP stack. It is quite similar to the BSD socket API. The -model of execution is based on the blocking open-read-write-close -paradigm. Since the TCP/IP stack is event based by nature, the TCP/IP -code and the application program must reside in different execution -contexts (threads). - -The socket API is a compatibility API for existing applications, -currently it is built on top of the sequential API. It is meant to -provide all functions needed to run socket API applications running -on other platforms (e.g. unix / windows etc.). However, due to limitations -in the specification of this API, there might be incompatibilities -that require small modifications of existing programs. - -** Threading - -lwIP started targeting single-threaded environments. When adding multi- -threading support, instead of making the core thread-safe, another -approach was chosen: there is one main thread running the lwIP core -(also known as the "tcpip_thread"). The raw API may only be used from -this thread! Application threads using the sequential- or socket API -communicate with this main thread through message passing. - - As such, the list of functions that may be called from - other threads or an ISR is very limited! Only functions - from these API header files are thread-safe: - - api.h - - netbuf.h - - netdb.h - - netifapi.h - - sockets.h - - sys.h - - Additionaly, memory (de-)allocation functions may be - called from multiple threads (not ISR!) with NO_SYS=0 - since they are protected by SYS_LIGHTWEIGHT_PROT and/or - semaphores. - - Only since 1.3.0, if SYS_LIGHTWEIGHT_PROT is set to 1 - and LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT is set to 1, - pbuf_free() may also be called from another thread or - an ISR (since only then, mem_free - for PBUF_RAM - may - be called from an ISR: otherwise, the HEAP is only - protected by semaphores). - - -** The remainder of this document discusses the "raw" API. ** - -The raw TCP/IP interface allows the application program to integrate -better with the TCP/IP code. Program execution is event based by -having callback functions being called from within the TCP/IP -code. The TCP/IP code and the application program both run in the same -thread. The sequential API has a much higher overhead and is not very -well suited for small systems since it forces a multithreaded paradigm -on the application. - -The raw TCP/IP interface is not only faster in terms of code execution -time but is also less memory intensive. The drawback is that program -development is somewhat harder and application programs written for -the raw TCP/IP interface are more difficult to understand. Still, this -is the preferred way of writing applications that should be small in -code size and memory usage. - -Both APIs can be used simultaneously by different application -programs. In fact, the sequential API is implemented as an application -program using the raw TCP/IP interface. - ---- Callbacks - -Program execution is driven by callbacks. Each callback is an ordinary -C function that is called from within the TCP/IP code. Every callback -function is passed the current TCP or UDP connection state as an -argument. Also, in order to be able to keep program specific state, -the callback functions are called with a program specified argument -that is independent of the TCP/IP state. - -The function for setting the application connection state is: - -- void tcp_arg(struct tcp_pcb *pcb, void *arg) - - Specifies the program specific state that should be passed to all - other callback functions. The "pcb" argument is the current TCP - connection control block, and the "arg" argument is the argument - that will be passed to the callbacks. - - ---- TCP connection setup - -The functions used for setting up connections is similar to that of -the sequential API and of the BSD socket API. A new TCP connection -identifier (i.e., a protocol control block - PCB) is created with the -tcp_new() function. This PCB can then be either set to listen for new -incoming connections or be explicitly connected to another host. - -- struct tcp_pcb *tcp_new(void) - - Creates a new connection identifier (PCB). If memory is not - available for creating the new pcb, NULL is returned. - -- err_t tcp_bind(struct tcp_pcb *pcb, struct ip_addr *ipaddr, - u16_t port) - - Binds the pcb to a local IP address and port number. The IP address - can be specified as IP_ADDR_ANY in order to bind the connection to - all local IP addresses. - - If another connection is bound to the same port, the function will - return ERR_USE, otherwise ERR_OK is returned. - -- struct tcp_pcb *tcp_listen(struct tcp_pcb *pcb) - - Commands a pcb to start listening for incoming connections. When an - incoming connection is accepted, the function specified with the - tcp_accept() function will be called. The pcb will have to be bound - to a local port with the tcp_bind() function. - - The tcp_listen() function returns a new connection identifier, and - the one passed as an argument to the function will be - deallocated. The reason for this behavior is that less memory is - needed for a connection that is listening, so tcp_listen() will - reclaim the memory needed for the original connection and allocate a - new smaller memory block for the listening connection. - - tcp_listen() may return NULL if no memory was available for the - listening connection. If so, the memory associated with the pcb - passed as an argument to tcp_listen() will not be deallocated. - -- struct tcp_pcb *tcp_listen_with_backlog(struct tcp_pcb *pcb, u8_t backlog) - - Same as tcp_listen, but limits the number of outstanding connections - in the listen queue to the value specified by the backlog argument. - To use it, your need to set TCP_LISTEN_BACKLOG=1 in your lwipopts.h. - -- void tcp_accepted(struct tcp_pcb *pcb) - - Inform lwIP that an incoming connection has been accepted. This would - usually be called from the accept callback. This allows lwIP to perform - housekeeping tasks, such as allowing further incoming connections to be - queued in the listen backlog. - -- void tcp_accept(struct tcp_pcb *pcb, - err_t (* accept)(void *arg, struct tcp_pcb *newpcb, - err_t err)) - - Specified the callback function that should be called when a new - connection arrives on a listening connection. - -- err_t tcp_connect(struct tcp_pcb *pcb, struct ip_addr *ipaddr, - u16_t port, err_t (* connected)(void *arg, - struct tcp_pcb *tpcb, - err_t err)); - - Sets up the pcb to connect to the remote host and sends the - initial SYN segment which opens the connection. - - The tcp_connect() function returns immediately; it does not wait for - the connection to be properly setup. Instead, it will call the - function specified as the fourth argument (the "connected" argument) - when the connection is established. If the connection could not be - properly established, either because the other host refused the - connection or because the other host didn't answer, the "err" - callback function of this pcb (registered with tcp_err, see below) - will be called. - - The tcp_connect() function can return ERR_MEM if no memory is - available for enqueueing the SYN segment. If the SYN indeed was - enqueued successfully, the tcp_connect() function returns ERR_OK. - - ---- Sending TCP data - -TCP data is sent by enqueueing the data with a call to -tcp_write(). When the data is successfully transmitted to the remote -host, the application will be notified with a call to a specified -callback function. - -- err_t tcp_write(struct tcp_pcb *pcb, void *dataptr, u16_t len, - u8_t copy) - - Enqueues the data pointed to by the argument dataptr. The length of - the data is passed as the len parameter. The copy argument is either - 0 or 1 and indicates whether the new memory should be allocated for - the data to be copied into. If the argument is 0, no new memory - should be allocated and the data should only be referenced by - pointer. - - The tcp_write() function will fail and return ERR_MEM if the length - of the data exceeds the current send buffer size or if the length of - the queue of outgoing segment is larger than the upper limit defined - in lwipopts.h. The number of bytes available in the output queue can - be retrieved with the tcp_sndbuf() function. - - The proper way to use this function is to call the function with at - most tcp_sndbuf() bytes of data. If the function returns ERR_MEM, - the application should wait until some of the currently enqueued - data has been successfully received by the other host and try again. - -- void tcp_sent(struct tcp_pcb *pcb, - err_t (* sent)(void *arg, struct tcp_pcb *tpcb, - u16_t len)) - - Specifies the callback function that should be called when data has - successfully been received (i.e., acknowledged) by the remote - host. The len argument passed to the callback function gives the - amount bytes that was acknowledged by the last acknowledgment. - - ---- Receiving TCP data - -TCP data reception is callback based - an application specified -callback function is called when new data arrives. When the -application has taken the data, it has to call the tcp_recved() -function to indicate that TCP can advertise increase the receive -window. - -- void tcp_recv(struct tcp_pcb *pcb, - err_t (* recv)(void *arg, struct tcp_pcb *tpcb, - struct pbuf *p, err_t err)) - - Sets the callback function that will be called when new data - arrives. The callback function will be passed a NULL pbuf to - indicate that the remote host has closed the connection. If - there are no errors and the callback function is to return - ERR_OK, then it must free the pbuf. Otherwise, it must not - free the pbuf so that lwIP core code can store it. - -- void tcp_recved(struct tcp_pcb *pcb, u16_t len) - - Must be called when the application has received the data. The len - argument indicates the length of the received data. - - ---- Application polling - -When a connection is idle (i.e., no data is either transmitted or -received), lwIP will repeatedly poll the application by calling a -specified callback function. This can be used either as a watchdog -timer for killing connections that have stayed idle for too long, or -as a method of waiting for memory to become available. For instance, -if a call to tcp_write() has failed because memory wasn't available, -the application may use the polling functionality to call tcp_write() -again when the connection has been idle for a while. - -- void tcp_poll(struct tcp_pcb *pcb, u8_t interval, - err_t (* poll)(void *arg, struct tcp_pcb *tpcb)) - - Specifies the polling interval and the callback function that should - be called to poll the application. The interval is specified in - number of TCP coarse grained timer shots, which typically occurs - twice a second. An interval of 10 means that the application would - be polled every 5 seconds. - - ---- Closing and aborting connections - -- err_t tcp_close(struct tcp_pcb *pcb) - - Closes the connection. The function may return ERR_MEM if no memory - was available for closing the connection. If so, the application - should wait and try again either by using the acknowledgment - callback or the polling functionality. If the close succeeds, the - function returns ERR_OK. - - The pcb is deallocated by the TCP code after a call to tcp_close(). - -- void tcp_abort(struct tcp_pcb *pcb) - - Aborts the connection by sending a RST (reset) segment to the remote - host. The pcb is deallocated. This function never fails. - -If a connection is aborted because of an error, the application is -alerted of this event by the err callback. Errors that might abort a -connection are when there is a shortage of memory. The callback -function to be called is set using the tcp_err() function. - -- void tcp_err(struct tcp_pcb *pcb, void (* err)(void *arg, - err_t err)) - - The error callback function does not get the pcb passed to it as a - parameter since the pcb may already have been deallocated. - - ---- Lower layer TCP interface - -TCP provides a simple interface to the lower layers of the -system. During system initialization, the function tcp_init() has -to be called before any other TCP function is called. When the system -is running, the two timer functions tcp_fasttmr() and tcp_slowtmr() -must be called with regular intervals. The tcp_fasttmr() should be -called every TCP_FAST_INTERVAL milliseconds (defined in tcp.h) and -tcp_slowtmr() should be called every TCP_SLOW_INTERVAL milliseconds. - - ---- UDP interface - -The UDP interface is similar to that of TCP, but due to the lower -level of complexity of UDP, the interface is significantly simpler. - -- struct udp_pcb *udp_new(void) - - Creates a new UDP pcb which can be used for UDP communication. The - pcb is not active until it has either been bound to a local address - or connected to a remote address. - -- void udp_remove(struct udp_pcb *pcb) - - Removes and deallocates the pcb. - -- err_t udp_bind(struct udp_pcb *pcb, struct ip_addr *ipaddr, - u16_t port) - - Binds the pcb to a local address. The IP-address argument "ipaddr" - can be IP_ADDR_ANY to indicate that it should listen to any local IP - address. The function currently always return ERR_OK. - -- err_t udp_connect(struct udp_pcb *pcb, struct ip_addr *ipaddr, - u16_t port) - - Sets the remote end of the pcb. This function does not generate any - network traffic, but only set the remote address of the pcb. - -- err_t udp_disconnect(struct udp_pcb *pcb) - - Remove the remote end of the pcb. This function does not generate - any network traffic, but only removes the remote address of the pcb. - -- err_t udp_send(struct udp_pcb *pcb, struct pbuf *p) - - Sends the pbuf p. The pbuf is not deallocated. - -- void udp_recv(struct udp_pcb *pcb, - void (* recv)(void *arg, struct udp_pcb *upcb, - struct pbuf *p, - struct ip_addr *addr, - u16_t port), - void *recv_arg) - - Specifies a callback function that should be called when a UDP - datagram is received. - - ---- System initalization - -A truly complete and generic sequence for initializing the lwip stack -cannot be given because it depends on the build configuration (lwipopts.h) -and additional initializations for your runtime environment (e.g. timers). - -We can give you some idea on how to proceed when using the raw API. -We assume a configuration using a single Ethernet netif and the -UDP and TCP transport layers, IPv4 and the DHCP client. - -Call these functions in the order of appearance: - -- stats_init() - - Clears the structure where runtime statistics are gathered. - -- sys_init() - - Not of much use since we set the NO_SYS 1 option in lwipopts.h, - to be called for easy configuration changes. - -- mem_init() - - Initializes the dynamic memory heap defined by MEM_SIZE. - -- memp_init() - - Initializes the memory pools defined by MEMP_NUM_x. - -- pbuf_init() - - Initializes the pbuf memory pool defined by PBUF_POOL_SIZE. - -- etharp_init() - - Initializes the ARP table and queue. - Note: you must call etharp_tmr at a ARP_TMR_INTERVAL (5 seconds) regular interval - after this initialization. - -- ip_init() - - Doesn't do much, it should be called to handle future changes. - -- udp_init() - - Clears the UDP PCB list. - -- tcp_init() - - Clears the TCP PCB list and clears some internal TCP timers. - Note: you must call tcp_fasttmr() and tcp_slowtmr() at the - predefined regular intervals after this initialization. - -- netif_add(struct netif *netif, struct ip_addr *ipaddr, - struct ip_addr *netmask, struct ip_addr *gw, - void *state, err_t (* init)(struct netif *netif), - err_t (* input)(struct pbuf *p, struct netif *netif)) - - Adds your network interface to the netif_list. Allocate a struct - netif and pass a pointer to this structure as the first argument. - Give pointers to cleared ip_addr structures when using DHCP, - or fill them with sane numbers otherwise. The state pointer may be NULL. - - The init function pointer must point to a initialization function for - your ethernet netif interface. The following code illustrates it's use. - - err_t netif_if_init(struct netif *netif) - { - u8_t i; - - for(i = 0; i < ETHARP_HWADDR_LEN; i++) netif->hwaddr[i] = some_eth_addr[i]; - init_my_eth_device(); - return ERR_OK; - } - - For ethernet drivers, the input function pointer must point to the lwip - function ethernet_input() declared in "netif/etharp.h". Other drivers - must use ip_input() declared in "lwip/ip.h". - -- netif_set_default(struct netif *netif) - - Registers the default network interface. - -- netif_set_up(struct netif *netif) - - When the netif is fully configured this function must be called. - -- dhcp_start(struct netif *netif) - - Creates a new DHCP client for this interface on the first call. - Note: you must call dhcp_fine_tmr() and dhcp_coarse_tmr() at - the predefined regular intervals after starting the client. - - You can peek in the netif->dhcp struct for the actual DHCP status. - - ---- Optimalization hints - -The first thing you want to optimize is the lwip_standard_checksum() -routine from src/core/inet.c. You can override this standard -function with the #define LWIP_CHKSUM <your_checksum_routine>. - -There are C examples given in inet.c or you might want to -craft an assembly function for this. RFC1071 is a good -introduction to this subject. - -Other significant improvements can be made by supplying -assembly or inline replacements for htons() and htonl() -if you're using a little-endian architecture. -#define LWIP_PLATFORM_BYTESWAP 1 -#define LWIP_PLATFORM_HTONS(x) <your_htons> -#define LWIP_PLATFORM_HTONL(x) <your_htonl> - -Check your network interface driver if it reads at -a higher speed than the maximum wire-speed. If the -hardware isn't serviced frequently and fast enough -buffer overflows are likely to occur. - -E.g. when using the cs8900 driver, call cs8900if_service(ethif) -as frequently as possible. When using an RTOS let the cs8900 interrupt -wake a high priority task that services your driver using a binary -semaphore or event flag. Some drivers might allow additional tuning -to match your application and network. - -For a production release it is recommended to set LWIP_STATS to 0. -Note that speed performance isn't influenced much by simply setting -high values to the memory options. |