patches Blockstore::is_shred_duplicate for resigned chained Merkle shreds

[behzadnouri]

Problem

With chained Merkle shreds which are signed by the retransmitter, different retransmitter signatures does not make a shred duplicate.

Summary of Changes

patched Blockstore::is_shred_duplicate for resigned chained Merkle shreds

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 53.65854% with 38 lines in your changes are missing coverage. Please review.

Project coverage is 82.1%. Comparing base (ad12ea3) to head (9282e6f).
Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##           master    #1271     +/-   ##
=========================================
- Coverage    82.1%    82.1%   -0.1%     
=========================================
  Files         893      893             
  Lines      236936   237008     +72     
=========================================
+ Hits       194705   194717     +12     
- Misses      42231    42291     +60     

[AshwinSekar]

LGTM, for my understanding: in the absence of malicious activity this could only happen if we repaired during slow turbine propagation and received the shred twice?

[behzadnouri]

LGTM, for my understanding: in the absence of malicious activity this could only happen if we repaired during slow turbine propagation and received the shred twice?

That is one possibility but also with 32:32 erasure encoding you can recover the whole batch as soon as you receive half of the batch. But at least some of the shreds you have already recovered from erasure encoding will be received from turbine later on as well.

[AshwinSekar]

got it, so the retransmitter signature is not erasure coded, and recovered shreds will be missing the signature causing this duplicate check to fail when the shred is received through turbine

[behzadnouri]

got it, so the retransmitter signature is not erasure coded, and recovered shreds will be missing the signature causing this duplicate check to fail when the shred is received through turbine

right