01_DCCP_shutdown-unnecessary.diff

01_DCCP_shutdown-unnecessary.diff

This calls shutdown(2) for unused communication paths in the DCCP sender/receiver:
 * the sender does not read data from the client and so calls shutdown(SHUT_RD);
 * the client does not send data to the server and so calls shutdown(SHUT_WR).
The advantage that this buys is a performance optimisation: using shutdown(2) in
DCCP means disabling the corresponding CCID kernel modules, which reduces the
processing costs, i.e.
 * when using SHUT_RD, the receiver congestion-control module is de-activated;
 * when using SHUT_WR, the sender congestion-control module is de-activated.

More information can be found on
http://www.erg.abdn.ac.uk/users/gerrit/dccp/notes/shutdown/