fix: client rpcserver subscriber hang

[jim3ma]

Description

1. One remote peer come with StartNum > 0, eg: StartNum = 1
2. Local peer run sendRemainingPieceTasks and s.totalPieces is -1
3. Local peer start to back source or download from other peers with piece 0
4. For piece 0 from local peer, due to s.totalPieces is -1, the following check will be skipped and will be sent to remote peer: if s.totalPieces > -1 && uint32(info.Num) < nextPieceNum, then len(s.sentMap)++
5. s.totalPieces will be updated
6. because the piece 0 which should not be sent in step 4, will hit the following logic to break loop

     if s.totalPieces > -1 && len(s.sentMap)+int(s.skipPieceCount) == int(s.totalPieces) {
        s.Unlock()
        break loop
    }

7. The subscriber will hang until other peers send more pieces.

Solution:

We should not check completeness via fuzzy len(s.sentMap), and check the next piece num is a better method.

Related Issue

Motivation and Context

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation Update (if none of the other choices apply)

Checklist

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 9 lines in your changes are missing coverage. Please review.

Project coverage is 52.83%. Comparing base (22f46b7) to head (53a4880).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3246      +/-   ##
==========================================
- Coverage   52.86%   52.83%   -0.04%     
==========================================
  Files         192      192              
  Lines       20341    20351      +10     
==========================================
- Hits        10754    10753       -1     
- Misses       8788     8796       +8     
- Partials      799      802       +3     

Flag	Coverage Δ
unittests	52.83% <66.66%> (-0.04%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
client/daemon/rpcserver/subscriber.go	56.96% <66.66%> (+2.90%)	⬆️

... and 3 files with indirect coverage changes

[gaius-qi]

LGTM

[xujihui1985]

LTGM