add HTTP streaming support

[jluebbe]

This adds support for rauc install https://update-server.example/update.rauc for verity format bundles without needing temporary space. Internally, it is based on mounting the bundle using NBD and a unprivileged helper process.

• better configure.ac error handling
• documentation
• improved tests
• release notes

[zyga]

Quick first pass. I'll do a separate review of the nbd code.

[codecov]

Codecov Report

Merging #755 (3a0ce3e) into master (15f3f9b) will decrease coverage by 2.87%.
The diff coverage is 41.30%.

❗ Current head 3a0ce3e differs from pull request most recent head e573033. Consider uploading reports for the commit e573033 to get more accurate results

@@            Coverage Diff             @@
##           master     #755      +/-   ##
==========================================
- Coverage   72.45%   69.58%   -2.88%     
==========================================
  Files          28       30       +2     
  Lines        9109    10070     +961     
==========================================
+ Hits         6600     7007     +407     
- Misses       2509     3063     +554     

Impacted Files	Coverage Δ
include/bundle.h	100.00% <ø> (ø)
include/config_file.h	100.00% <ø> (ø)
include/utils.h	100.00% <ø> (+50.00%)	⬆️
src/stats.c	0.00% <0.00%> (ø)
src/nbd.c	35.78% <35.78%> (ø)
src/main.c	74.98% <52.63%> (-0.41%)	⬇️
src/service.c	74.17% <54.54%> (-0.83%)	⬇️
src/utils.c	72.68% <61.76%> (-2.18%)	⬇️
src/bundle.c	66.21% <72.22%> (+1.67%)	⬆️
src/config_file.c	84.02% <76.92%> (-0.14%)	⬇️
... and 4 more

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[mschwan-phytec]

Many thanks for adding this feature! I gave this a quick try using a simple webserver built with nginx to serve the bundle and installation of the bundle succeeded just fine. As I am building RAUC with Yocto, the corresponding changes in meta-rauc to support this feature were easily added. @jluebbe If you like, I could already open a PR to add these changes. Apart from trying this out and adding Yocto build support, is there anything in particular that I can help with to get this PR merged a little faster?

[jluebbe]

Many thanks for adding this feature! I gave this a quick try using a simple webserver built with nginx to serve the bundle and installation of the bundle succeeded just fine.

Thanks for the feedback!

As I am building RAUC with Yocto, the corresponding changes in meta-rauc to support this feature were easily added. @jluebbe If you like, I could already open a PR to add these changes.

You could just open a WIP PR there as well. Due to the new dependency, we should probably have a PACKAGECONFIG option.

Apart from trying this out and adding Yocto build support, is there anything in particular that I can help with to get this PR merged a little faster?

More testing feedback is definitely appreciated. If you don't want to go through the code, feedback on the documentation is also very useful. Are there any aspects which are not yet documented enough?

[ejoerns]

This is my first review round and includes everything I've found so far. Most things found are just minor issues, refactoring requests or error handling quirks.

All in all my tests on actual hardware looked very promising and did not reveal any major show stopper yet. After verity support, this is another well done and important milestone for RAUC 👍

I have a bunch of method documentation and in-code comments that I used for making the code more parsable for my poor human eyes. Maybe I can drop some of them in the second round as they might also help others or at least give a more comprehensive and cleaner internal API documentation.

[jluebbe]

@ejoerns You should be able to use git range-diff 98f14cdfa9ea..32cec8f21879 15f3f9b0d86c..4918dd51d71e to review the changes. I intend to split off the proxy part of nbd.c into a new nbd-proxy.c, but that should be a separate PR to avoid making my fixes more difficult to follow during review. I've fixed the typo in the docs locally.

[jluebbe]

@ejoerns I've updated the PR as discussed.

[jluebbe]

@ejoerns I've fixed the uncrustify failure.