tcp: Don't accept RST packets on listening sockets

[jnkr-ifx]

I ran into the following sequence of events:

• Two TCP sockets are open to a remote host.
• The remote host closes its end of both connections.
• The application tries to write some data to socket 1.
  • The remote host replies with an RST.
  • Socket 1 closes.
  • The application places Socket 1 in listening mode so it can accept a new connection.
• The application tries to write some data to socket 2.
  • The remote host replies with an RST.
  • Socket 1 accepts and discards the RST, because:
    • The packet's destination address and port matches.
    • Socket 1 is in listening mode, so it has no source address and port to compare.
    • The RST packet does not have the ACK flag set, because the remote host does not consider the data packets it recieved to be associated with an open connection.
  • Since socket 1 accepted the RST, it is not delivered to socket 2.
  • Socket 2 eventually retransmits its data packet, and the remote host replies with another RST which is again eaten by socket 1. This repeats indefinitely.

To fix this: a listening socket should not accept a RST packet that is just going to be ignored anyway. This allows the packet to be delivered to the correct socket, or discarded at the iface level if the RST packet does not match any active connection.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.17%. Comparing base (242e02c) to head (e73621d).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1058      +/-   ##
==========================================
- Coverage   81.17%   81.17%   -0.01%     
==========================================
  Files          81       81              
  Lines       28956    28955       -1     
==========================================
- Hits        23505    23503       -2     
- Misses       5451     5452       +1     

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[Dirbaio]

thanks!