Remove useless select() calls in Analysisd decoders

[chemamartinez]

Description

As @vikman90 states here. There exists a known bug with the select() call when handling file descriptors higher than 1024.

We noticed the select() calls in the SCA, Syscollector, and Syscheck decoders are not needed since OS_RecvSecureTCP() waits for the response from Wazuh DB.

Tests

• Compilation without warnings in every supported platform
  • Linux
• Source installation
• Review logs syntax and correct language
• Tested queries from the three issued decoders.

Analysisd stats after restarting:

# Syscheck events decoded
syscheck_events_decoded='431'
syscheck_edps='86'

# Syscollector events decoded
syscollector_events_decoded='472'
syscollector_edps='94'

# Security configuration assessment events decoded
sca_events_decoded='101'
sca_edps='20'

• Memory tests for Linux
  • Scan-build report
  • Valgrind (memcheck and descriptor leaks check)

Valgrind report of ossec-analysisd stressed with Syscheck, Syscollector and SCA events:

==46889== LEAK SUMMARY:
==46889==    definitely lost: 100 bytes in 9 blocks
==46889==    indirectly lost: 0 bytes in 0 blocks
==46889==      possibly lost: 7,072 bytes in 26 blocks
==46889==    still reachable: 14,881,769 bytes in 68,750 blocks
==46889==         suppressed: 0 bytes in 0 blocks
==46889== Reachable blocks (those to which a pointer was found) are not shown.
==46889== To see them, rerun with: --leak-check=full --show-leak-kinds=all

• 100 bytes lost correspond to the rules load fixed at Fix bugs reported by Clang analyzer #3887
• No descriptor leaks

Scan-build report

Done building server

scan-build: Removing directory '/tmp/scan-build-2019-09-12-103908-47512-1' because it contains no reports.
scan-build: No bugs found.

[JuantAldea]

Changes are correct.

Given that:

• recv, on its own, waits, and
• the only purpose of those selects is to wait on a single descriptor,

connectwill return:

• -1: failure and return. But if there's no select there's no error,
• >=0: number of descriptors with activity
  • 0: No descriptors with activity -> timeout -> recv will wait
  • >0: recv will do whatever it has to.

As shown, recv will wait if needed, rendering the wait performed by connect redundant.

Q.E.D