IPv4: Don't discard from unspecified src addresses

[bjoernQ]

IPv4 packets from 0.0.0.0 get discarded early. This makes it impossible to create a DHCP server.

Not sure if this is the right location or even the right approach for this fix.

Maybe there is also a way to make this work without modifying the code?

[codecov]

Codecov Report

Merging #787 (7199ad3) into master (e4e39ac) will increase coverage by 0.24%.
The diff coverage is 50.00%.

❗ Current head 7199ad3 differs from pull request most recent head 74fd2ae. Consider uploading reports for the commit 74fd2ae to get more accurate results

@@            Coverage Diff             @@
##           master     #787      +/-   ##
==========================================
+ Coverage   80.08%   80.33%   +0.24%     
==========================================
  Files          69       65       -4     
  Lines       28730    26871    -1859     
==========================================
- Hits        23009    21586    -1423     
+ Misses       5721     5285     -436     

Impacted Files	Coverage Δ
src/iface/interface/ipv4.rs	71.46% <50.00%> (ø)

... and 15 files with indirect coverage changes

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[thvdveld]

I think this is fine. We just need to make sure that we don't transmit to the unspecified address. Which we check here:

https://github.com/smoltcp-rs/smoltcp/blob/master/src/iface/interface/mod.rs#L1647

[bjoernQ]

Thanks! That's good news
Any pointer at where to add tests to make codecov happy? (Sorry, first contribution here)

[thvdveld]

I think it's fine. I think the codecov setup is not yet complete. It should not fail CI in this case. I made some changes to CI in #789. Maybe if you can rebase on master, then we can check if CI still fails or not.

[bjoernQ]

I think it's fine. I think the codecov setup is not yet complete. It should not fail CI in this case. I made some changes to CI in #789. Maybe if you can rebase on master, then we can check if CI still fails or not.

Awesome, that worked! Thanks a lot

[Dirbaio]

thanks!

bors r+

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