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lwIP mirror from http://git.savannah.gnu.org/cgit/lwip.git
7cedf7ae71
This patch aims to fix three closely related issues. o The implementation of IPV6_FRAG_COPYHEADER was fundamentally incompatible with the presence of extension headers between the IPv6 header and the Fragment Header. This patch changes the implementation to support such extension headers as well, with pretty much the same memory requirements. As a result, we can remove the check that prevented such packets from being reassembled in all cases, even with IPV6_FRAG_COPYHEADER off. o Given that temporary data is stored in the Fragment Header of packets saved for the purpose of reassembly, but ICMPv6 "Fragment Reassembly Time Exceeded" packets contain part of the original packet, such ICMPv6 packets could actually end up containing part of the temporary data, which may even include a pointer value. The ICMPv6 packet should contain the original, unchanged packet, so save the original header data before overwriting it even if IPV6_FRAG_COPYHEADER is disabled. This does add some extra memory consumption. o Previously, the reassembly would leave the fragment header in the reassembled packet, which is not permitted by RFC 2460 and prevents reassembly of particularly large packets (close to 65535 bytes after reassembly). This patch gets rid of the fragment header. It does require an implementation of memmove() for that purpose. Note that this patch aims to improve correctness. Future changes might restore some of the previous functionality in order to regain optimal performance for certain cases (at the cost of more code). |
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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, IPv4 and IPv6) 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
* MLD (Multicast listener discovery for IPv6). Aims to be compliant with
RFC 2710. No support for MLDv2
* ND (Neighbor discovery and stateless address autoconfiguration for IPv6).
Aims to be compliant with RFC 4861 (Neighbor discovery) and RFC 4862
(Address autoconfiguration)
* UDP (User Datagram Protocol) including experimental UDP-lite extensions
* TCP (Transmission Control Protocol) with congestion control, RTT estimation
and fast recovery/fast retransmit
* raw/native API for enhanced performance
* Optional Berkeley-like socket API
* DNS (Domain names resolver)
APPLICATIONS
* HTTP server with SSI and CGI
* SNMPv2c agent with MIB compiler (Simple Network Management Protocol)
* SNTP (Simple network time protocol)
* NetBIOS name service responder
* MDNS (Multicast DNS) responder
* iPerf server implementation
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, Git and the
mailing list. A core team of developers will commit changes to the
Git source tree.
The lwIP TCP/IP stack is maintained in the 'lwip' Git module and
contributions (such as platform ports) are in the 'contrib' Git module.
See doc/savannah.txt for details on Git server access for users and
developers.
The current Git trees are web-browsable:
http://git.savannah.gnu.org/cgit/lwip.git
http://git.savannah.gnu.org/cgit/lwip/lwip-contrib.git
Submit patches and bugs via the lwIP project page:
http://savannah.nongnu.org/projects/lwip/
Continuous integration builds (GCC, clang):
https://travis-ci.org/yarrick/lwip-merged
DOCUMENTATION
Self documentation of the source code is regularly extracted from the current
Git sources and is available from this web page:
http://www.nongnu.org/lwip/
There is now a constantly growing 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/
lwIP was originally written by Adam Dunkels:
http://dunkels.com/adam/
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>