mirror of
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lwIP mirror from http://git.savannah.gnu.org/cgit/lwip.git
25f9f55878
I consider to remove the PPP_INPROC_OWNTHREAD crap in ppp-new, as said in bugs #37278 and #37353. 1. It requires the ppp_input_thread() function to be modified to match user system, like some did by adding the vTaskDelete(NULL); FreeRTOS call at the end of the function, for example. This is a tiny-tiny fonction that should be, in my opinion, on the user port, like the Ethernet input thread we see in many Ethernet port. 2. It is actually not that thread safe. 2.1. pcb->phase IS modified by the lwIP core thread so it should at least be set to volatile, otherwise the pcb->phase copy may live indefinitely in CPU register. It works because of the sio_read() function call which without doubt flush pcb->phase copy from CPU register. I dont want to set ppp_pcb struct to volatile for obvious performance reasons. 2.2. This function assume PCB still exists whatever is happening, which is not the case after you called ppp_delete() function outside of this thread. If sio_read() is blocking waiting data and pcb destroyed, it is going to read a deallocated pcb which luckily should still have pcb->phase set to 0 (=PHASE_DEAD) due to preallocated "control block" structures of lwIP. Even with sio_read_abort(), there might be timings issue due to a lack of a synchronization mechanism. 3. I dislike the sys_msleep(1), it means that systems should have at least a 11 chr buffer at 115200/10 byte/s, and bigger with higher serial speed, for example with 3G/HSDPA modems accessed through SPI, at 20 Mbits/s this is a ~2000 bytes buffer required to keep incoming data during this sleep, I don't see why we require systems to do so, sio_read() should obviously be a blocking call. I cannot easily remove this sleep because some systems might have wrongfully used this call as a CPU idle feature with a non blocking sio_read() call. |
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INTRODUCTION
lwIP is a small independent implementation of the TCP/IP protocol
suite that has been developed by Adam Dunkels at the Computer and
Networks Architectures (CNA) lab at the Swedish Institute of Computer
Science (SICS).
The focus of the lwIP TCP/IP implementation is to reduce the RAM usage
while still having a full scale TCP. This making lwIP suitable for use
in embedded systems with tens of kilobytes of free RAM and room for
around 40 kilobytes of code ROM.
FEATURES
* IP (Internet Protocol) including packet forwarding over multiple network
interfaces
* ICMP (Internet Control Message Protocol) for network maintenance and debugging
* IGMP (Internet Group Management Protocol) for multicast traffic management
* UDP (User Datagram Protocol) including experimental UDP-lite extensions
* TCP (Transmission Control Protocol) with congestion control, RTT estimation
and fast recovery/fast retransmit
* Specialized raw/native API for enhanced performance
* Optional Berkeley-like socket API
* DNS (Domain names resolver)
* SNMP (Simple Network Management Protocol)
* DHCP (Dynamic Host Configuration Protocol)
* AUTOIP (for IPv4, conform with RFC 3927)
* PPP (Point-to-Point Protocol)
* ARP (Address Resolution Protocol) for Ethernet
LICENSE
lwIP is freely available under a BSD license.
DEVELOPMENT
lwIP has grown into an excellent TCP/IP stack for embedded devices,
and developers using the stack often submit bug fixes, improvements,
and additions to the stack to further increase its usefulness.
Development of lwIP is hosted on Savannah, a central point for
software development, maintenance and distribution. Everyone can
help improve lwIP by use of Savannah's interface, CVS and the
mailing list. A core team of developers will commit changes to the
CVS source tree.
The lwIP TCP/IP stack is maintained in the 'lwip' CVS module and
contributions (such as platform ports) are in the 'contrib' module.
See doc/savannah.txt for details on CVS server access for users and
developers.
Last night's CVS tar ball can be downloaded from:
http://savannah.gnu.org/cvs.backups/lwip.tar.gz [CHANGED - NEEDS FIXING]
The current CVS trees are web-browsable:
http://savannah.nongnu.org/cgi-bin/viewcvs/lwip/lwip/
http://savannah.nongnu.org/cgi-bin/viewcvs/lwip/contrib/
Submit patches and bugs via the lwIP project page:
http://savannah.nongnu.org/projects/lwip/
DOCUMENTATION
The original out-dated homepage of lwIP and Adam Dunkels' papers on
lwIP are at the official lwIP home page:
http://www.sics.se/~adam/lwip/
Self documentation of the source code is regularly extracted from the
current CVS sources and is available from this web page:
http://www.nongnu.org/lwip/
There is now a constantly growin wiki about lwIP at
http://lwip.wikia.com/wiki/LwIP_Wiki
Also, there are mailing lists you can subscribe at
http://savannah.nongnu.org/mail/?group=lwip
plus searchable archives:
http://lists.nongnu.org/archive/html/lwip-users/
http://lists.nongnu.org/archive/html/lwip-devel/
Reading Adam's papers, the files in docs/, browsing the source code
documentation and browsing the mailing list archives is a good way to
become familiar with the design of lwIP.
Adam Dunkels <adam@sics.se>
Leon Woestenberg <leon.woestenberg@gmx.net>