404 lines
17 KiB
C
404 lines
17 KiB
C
/**
|
||
* @defgroup lwip lwIP
|
||
*
|
||
* @defgroup infrastructure Infrastructure
|
||
*
|
||
* @defgroup api APIs
|
||
* lwIP provides three Application Program's Interfaces (APIs) for programs
|
||
* to use for communication with the TCP/IP code:
|
||
* - low-level "core" / "callback" or @ref callbackstyle_api.
|
||
* - higher-level @ref sequential_api.
|
||
* - BSD-style @ref socket.
|
||
*
|
||
* 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.
|
||
*
|
||
* All 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.
|
||
*
|
||
* Do not confuse the lwIP raw API with raw Ethernet or IP sockets.
|
||
* The former is a way of interfacing the lwIP network stack (including
|
||
* TCP and UDP), the latter refers to processing raw Ethernet or IP data
|
||
* instead of TCP connections or UDP packets.
|
||
*
|
||
* Raw API applications may never block since all packet processing
|
||
* (input and output) as well as timer processing (TCP mainly) is done
|
||
* in a single execution context.
|
||
*
|
||
* @defgroup callbackstyle_api "raw" APIs
|
||
* @ingroup api
|
||
* Non thread-safe APIs, callback style for maximum performance and minimum
|
||
* memory footprint.
|
||
* Program execution is driven by callbacks functions, which are then
|
||
* invoked by the lwIP core when activity related to that application
|
||
* occurs. A particular application may register to be notified via a
|
||
* callback function for events such as incoming data available, outgoing
|
||
* data sent, error notifications, poll timer expiration, connection
|
||
* closed, etc. An application can provide a callback function to perform
|
||
* processing for any or all of these events. 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 raw API (sometimes called native API) is an event-driven API designed
|
||
* to be used without an operating system that implements zero-copy send and
|
||
* receive. This API is also used by the core stack for interaction between
|
||
* the various protocols. It is the only API available when running lwIP
|
||
* without an operating system.
|
||
*
|
||
* @defgroup sequential_api Sequential-style APIs
|
||
* @ingroup api
|
||
* Sequential-style APIs, blocking functions. More overhead, but can be called
|
||
* from any thread except TCPIP thread.
|
||
* 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).
|
||
*
|
||
* @defgroup socket Socket API
|
||
* @ingroup api
|
||
* BSD-style socket API.\n
|
||
* Thread-safe, to be called from non-TCPIP threads only.\n
|
||
* Can be activated by defining @ref LWIP_SOCKET to 1.\n
|
||
* Header is in posix/sys/socket.h\n
|
||
* 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.
|
||
*
|
||
* @defgroup netifs NETIFs
|
||
*
|
||
* @defgroup apps Applications
|
||
*/
|
||
|
||
/**
|
||
* @mainpage Overview
|
||
* @verbinclude "README"
|
||
*/
|
||
|
||
/**
|
||
* @page upgrading Upgrading
|
||
* @verbinclude "UPGRADING"
|
||
*/
|
||
|
||
/**
|
||
* @page changelog Changelog
|
||
*
|
||
* 2.1.0
|
||
* -----
|
||
* * Support TLS via new @ref altcp_api connection API (https, smtps, mqtt over TLS)
|
||
* * Switch to cmake as the main build system (Makefile file lists are still
|
||
* maintained for now)
|
||
* * Improve IPv6 support: support address scopes, support stateless DHCPv6, bugfixes
|
||
* * Add debug helper asserts to ensure threading/locking requirements are met
|
||
* * Add sys_mbox_trypost_fromisr() and tcpip_callbackmsg_trycallback_fromisr()
|
||
* (for FreeRTOS, mainly)
|
||
* * socket API: support poll(), sendmsg() and recvmsg(); fix problems on close
|
||
*
|
||
* Detailed Changelog
|
||
* ------------------
|
||
* @verbinclude "CHANGELOG"
|
||
*/
|
||
|
||
/**
|
||
* @page contrib How to contribute to lwIP
|
||
* @verbinclude "contrib.txt"
|
||
*/
|
||
|
||
/**
|
||
* @page pitfalls Common pitfalls
|
||
*
|
||
* Multiple Execution Contexts in lwIP code
|
||
* ========================================
|
||
*
|
||
* The most common source of lwIP problems is to have multiple execution contexts
|
||
* inside the lwIP code.
|
||
*
|
||
* lwIP can be used in two basic modes: @ref lwip_nosys (no OS/RTOS
|
||
* running on target system) or @ref lwip_os (there is an OS running
|
||
* on the target system).
|
||
*
|
||
* See also: @ref multithreading (especially the part about @ref LWIP_ASSERT_CORE_LOCKED()!)
|
||
*
|
||
* Mainloop Mode
|
||
* -------------
|
||
* In mainloop mode, only @ref callbackstyle_api can be used.
|
||
* The user has two possibilities to ensure there is only one
|
||
* exection context at a time in lwIP:
|
||
*
|
||
* 1) Deliver RX ethernet packets directly in interrupt context to lwIP
|
||
* by calling netif->input directly in interrupt. This implies all lwIP
|
||
* callback functions are called in IRQ context, which may cause further
|
||
* problems in application code: IRQ is blocked for a long time, multiple
|
||
* execution contexts in application code etc. When the application wants
|
||
* to call lwIP, it only needs to disable interrupts during the call.
|
||
* If timers are involved, even more locking code is needed to lock out
|
||
* timer IRQ and ethernet IRQ from each other, assuming these may be nested.
|
||
*
|
||
* 2) Run lwIP in a mainloop. There is example code here: @ref lwip_nosys.
|
||
* lwIP is _ONLY_ called from mainloop callstacks here. The ethernet IRQ
|
||
* has to put received telegrams into a queue which is polled in the
|
||
* mainloop. Ensure lwIP is _NEVER_ called from an interrupt, e.g.
|
||
* some SPI IRQ wants to forward data to udp_send() or tcp_write()!
|
||
*
|
||
* OS Mode
|
||
* -------
|
||
* In OS mode, @ref callbackstyle_api AND @ref sequential_api can be used.
|
||
* @ref sequential_api are designed to be called from threads other than
|
||
* the TCPIP thread, so there is nothing to consider here.
|
||
* But @ref callbackstyle_api functions must _ONLY_ be called from
|
||
* TCPIP thread. It is a common error to call these from other threads
|
||
* or from IRQ contexts. Ethernet RX needs to deliver incoming packets
|
||
* in the correct way by sending a message to TCPIP thread, this is
|
||
* implemented in tcpip_input().
|
||
* Again, ensure lwIP is _NEVER_ called from an interrupt, e.g.
|
||
* some SPI IRQ wants to forward data to udp_send() or tcp_write()!
|
||
*
|
||
* 1) tcpip_callback() can be used get called back from TCPIP thread,
|
||
* it is safe to call any @ref callbackstyle_api from there.
|
||
*
|
||
* 2) Use @ref LWIP_TCPIP_CORE_LOCKING. All @ref callbackstyle_api
|
||
* functions can be called when lwIP core lock is aquired, see
|
||
* @ref LOCK_TCPIP_CORE() and @ref UNLOCK_TCPIP_CORE().
|
||
* These macros cannot be used in an interrupt context!
|
||
* Note the OS must correctly handle priority inversion for this.
|
||
*
|
||
* Cache / DMA issues
|
||
* ==================
|
||
*
|
||
* DMA-capable ethernet hardware and zero-copy RX
|
||
* ----------------------------------------------
|
||
*
|
||
* lwIP changes the content of RECEIVED pbufs in the TCP code path.
|
||
* This implies one or more cacheline(s) of the RX pbuf become dirty
|
||
* and need to be flushed before the memory is handed over to the
|
||
* DMA ethernet hardware for the next telegram to be received.
|
||
* See http://lists.nongnu.org/archive/html/lwip-devel/2017-12/msg00070.html
|
||
* for a more detailed explanation.
|
||
* Also keep in mind the user application may also write into pbufs,
|
||
* so it is generally a bug not to flush the data cache before handing
|
||
* a buffer to DMA hardware.
|
||
*
|
||
* DMA-capable ethernet hardware and cacheline alignment
|
||
* -----------------------------------------------------
|
||
* Nice description about DMA capable hardware and buffer handling:
|
||
* http://www.pebblebay.com/a-guide-to-using-direct-memory-access-in-embedded-systems-part-two/
|
||
* Read especially sections "Cache coherency" and "Buffer alignment".
|
||
*/
|
||
|
||
/**
|
||
* @page bugs Reporting bugs
|
||
* Please report bugs in the lwIP bug tracker at savannah.\n
|
||
* BEFORE submitting, please check if the bug has already been reported!\n
|
||
* https://savannah.nongnu.org/bugs/?group=lwip
|
||
*/
|
||
|
||
/**
|
||
* @page zerocopyrx Zero-copy RX
|
||
* The following code is an example for zero-copy RX ethernet driver:
|
||
* @include ZeroCopyRx.c
|
||
*/
|
||
|
||
/**
|
||
* @defgroup lwip_nosys Mainloop mode ("NO_SYS")
|
||
* @ingroup lwip
|
||
* Use this mode if you do not run an OS on your system. \#define NO_SYS to 1.
|
||
* Feed incoming packets to netif->input(pbuf, netif) function from mainloop,
|
||
* *not* *from* *interrupt* *context*. You can allocate a @ref pbuf in interrupt
|
||
* context and put them into a queue which is processed from mainloop.\n
|
||
* Call sys_check_timeouts() periodically in the mainloop.\n
|
||
* Porting: implement all functions in @ref sys_time, @ref sys_prot and
|
||
* @ref compiler_abstraction.\n
|
||
* You can only use @ref callbackstyle_api in this mode.\n
|
||
* Sample code:\n
|
||
* @include NO_SYS_SampleCode.c
|
||
*/
|
||
|
||
/**
|
||
* @defgroup lwip_os OS mode (TCPIP thread)
|
||
* @ingroup lwip
|
||
* Use this mode if you run an OS on your system. It is recommended to
|
||
* use an RTOS that correctly handles priority inversion and
|
||
* to use @ref LWIP_TCPIP_CORE_LOCKING.\n
|
||
* Porting: implement all functions in @ref sys_layer.\n
|
||
* You can use @ref callbackstyle_api together with @ref tcpip_callback,
|
||
* and all @ref sequential_api.
|
||
*/
|
||
|
||
/**
|
||
* @page sys_init System initalization
|
||
A truly complete and generic sequence for initializing the lwIP stack
|
||
cannot be given because it depends on 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:
|
||
|
||
- lwip_init(): Initialize the lwIP stack and all of its subsystems.
|
||
|
||
- netif_add(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 its use.
|
||
|
||
@code{.c}
|
||
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;
|
||
}
|
||
@endcode
|
||
|
||
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_link_up(struct netif *netif)
|
||
This is the hardware link state; e.g. whether cable is plugged for wired
|
||
Ethernet interface. This function must be called even if you don't know
|
||
the current state. Having link up and link down events is optional but
|
||
DHCP and IPv6 discover benefit well from those events.
|
||
|
||
- netif_set_up(struct netif *netif)
|
||
This is the administrative (= software) state of the 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.
|
||
You can peek in the netif->dhcp struct for the actual DHCP status.
|
||
|
||
- sys_check_timeouts()
|
||
When the system is running, you have to periodically call
|
||
sys_check_timeouts() which will handle all timers for all protocols in
|
||
the stack; add this to your main loop or equivalent.
|
||
*/
|
||
|
||
/**
|
||
* @page multithreading Multithreading
|
||
* 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"). When running in a multithreaded
|
||
* environment, raw API functions MUST only be called from the core thread
|
||
* since raw API functions are not protected from concurrent access (aside
|
||
* from pbuf- and memory management functions). 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
|
||
* - pppapi.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 @ref SYS_LIGHTWEIGHT_PROT and/or
|
||
* semaphores.
|
||
*
|
||
* Netconn or Socket API functions are thread safe against the
|
||
* core thread but they are not reentrant at the control block
|
||
* granularity level. That is, a UDP or TCP control block must
|
||
* not be shared among multiple threads without proper locking.
|
||
*
|
||
* If @ref SYS_LIGHTWEIGHT_PROT is set to 1 and
|
||
* @ref 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).
|
||
*
|
||
* How to get threading done right
|
||
* -------------------------------
|
||
*
|
||
* It is strongly recommended to implement the LWIP_ASSERT_CORE_LOCKED()
|
||
* macro in an application that uses multithreading. lwIP code has
|
||
* several places where a check for a correct thread context is
|
||
* implemented which greatly helps the user to get threading done right.
|
||
* See the example sys_arch.c files in unix and Win32 port
|
||
* in the contrib repository.
|
||
*
|
||
* In short: Copy the functions sys_mark_tcpip_thread() and
|
||
* sys_check_core_locking() to your port and modify them to work with your OS.
|
||
* Then let @ref LWIP_ASSERT_CORE_LOCKED() and @ref LWIP_MARK_TCPIP_THREAD()
|
||
* point to these functions.
|
||
*
|
||
* If you use @ref LWIP_TCPIP_CORE_LOCKING, you also need to copy and adapt
|
||
* the functions sys_lock_tcpip_core() and sys_unlock_tcpip_core().
|
||
* Let @ref LOCK_TCPIP_CORE() and @ref UNLOCK_TCPIP_CORE() point
|
||
* to these functions.
|
||
*/
|
||
|
||
/**
|
||
* @page optimization Optimization 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_htons(x) your_htons()
|
||
\#define lwip_htonl(x) your_htonl()
|
||
If you \#define them to htons() and htonl(), you should
|
||
\#define LWIP_DONT_PROVIDE_BYTEORDER_FUNCTIONS to prevent lwIP from
|
||
defining htonx / ntohx compatibility macros.
|
||
|
||
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.
|
||
*/
|