This code is written. and has changes to the following files:
I sent an "atomic patch", and it got stuck in moderation because it is 350k+, that is too big.
My rules to myself were:
All interfaces, function calls, to be preserved. However, This results in an ugly "re-purposing" of variables in the packet-in calls to wget.
Advice and suggestions welcome for the best implementation.
Following is a phased approach to get from here to there.
1. tcp headers, constants and procedure calls. This could be split into a net.h and a new tcp.h, or be added to net.h
module: include net.h
There are many lines of code for TCP header structures, and readily inspected
2. cmd.net, cmd/Kcongif, net/Kconfig and net/Makefile (I don't know if net/Makefile will be built automagically at some point.)
Small changes in a number of places.
3. net.c interfaces. and ping.c, and procedure definitions in include/net.
Body of code. tcp could be a separate module, tcp.c Or integrated into the net.c source code.
As an aside at some point I'd suggest deleting the ip fragmentation reassembly code and second checksum calculating routine in net.c. 3a) IP fragment reassembly does not provide any mechanism to retrieve "lost packets", and should never be use where a complete data stream is necessary. Kernels require a complete data stream, movies do not.
3b) 2 pieces of code to perform the same task, checksum, seems redundant.
4. tpc.c either as a new module, tcp.c, or included in net/net.c, 400-500 lines of code.
5. wget.c and wget.h as a new command, 300+ lines of code.
From 1 to 3 would be "it's not broken" regression testing, and relatively low risk.
4 & 5 would be the new function testing, and would have to include a significant amount of stress testing, because I'm anal retentive and it's too much new code not to have bugs.
Here's the cover letter, for background:
wget and enough TCP stack for fast netboot
September 29, 2017
Boot with udp is relatively slow on a local net, and very slow over a WAN. TCP is a very effective protocol for fast file, or stream, transfers. http (used by wget) is a very efficient protocol, there is one message to retrieve the file, and acks from u-boot to server TCP thereafter.
The code was built & tested on a raspberry pi, LAN and WAN with the Jan 2017 version of u-boot. This code is an update for the current master, September 2017 version of u-boot, and cleaned up to pass clearpatch standards, but not tested.
This is a limited TCP implementation for the wget command only. And all the code newly written, without viewing any copyrighted source.
Complied binary size: When using wget, tftp and nfs can be omitted from the build. This has not been measured. When not using wget, the TCP code is eliminated from the build.
All interfaces, function calls, in use are preserved. This results in an ugly "re-purposing" of variables in the packet-in calls to wget. This requires advice on the best implementation.
Kconfig is used in ./cmd and ./net to control wget and tcp respectively. Makefile in ./net appears to have to be configured by hand.
Duncan Hare
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