fix: exhaust egress socket state on `poll`

[thomaseizinger]

At present, smoltcp only does a single pass of advancing the egress socket state. This means the layer above has to call poll in a loop to ensure sufficient progress has been made.

We already exhaustively progress the ingress state further up so doing the same thing for the egress state seems appropriate.

[codecov[bot]]

Codecov Report

:x: Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review. :white_check_mark: Project coverage is 80.45%. Comparing base (17012eb) to head (671827b). :warning: Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/iface/interface/mod.rs	66.66%	1 Missing :warning:

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1059   +/-   ##
=======================================
  Coverage   80.45%   80.45%           
=======================================
  Files          81       81           
  Lines       24461    24461           
=======================================
  Hits        19681    19681           
  Misses       4780     4780           

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[thvdveld]

@whitequark @Dirbaio I don't see any reason why not to do this.

[whitequark]

I thought @Dirbaio had a case where this caused an issue?

[thvdveld]

I thought that as well and was digging in old issues and PRs, but I didn't find anything related to the egress. Most of the issues were with ingress resulting in a DoS.

[whitequark]

@thomaseizinger Could you re-run/fix the test please? We'll merge it after.

[thomaseizinger]

@thomaseizinger Could you re-run/fix the test please? We'll merge it after.

I just accepted the new snapshot but I don't really know what it is testing.

[whitequark]

Thanks!