Code that relies on `resend_count` was added in 7ea4a03 and 247a1eb, but never worked.
This was fixed in #11607 which caused the problem to surface.
Hence undo the first commit entirely and change the logic of the second.
A Minetest peer initiates a connection by sending a packet with an invalid peer_id, for whatever reason the code for doing this ran on both the client and the server meaning you could connect to a client if you knew what the address:port tuple it was listening on.
* Optimize packet construction functions
Some of the functions that construct packets in
connection.cpp are using a const reference to get the raw
packet data to package and others use a value passed
parameter to do that. The ones that use the value passed
parameter suffer from performance hit as the rather bulky
packet data gets a temporary copy when the parameter is
passed before it lands at its final destination inside the
newly constructed packet. The unnecessary temporary copy
hurts quite badly as the underlying class (SharedBuffer)
actually allocates the space for the data in the heap.
Fix the performance hit by converting all of these value
passed parameters to const references. I believe that this
is what the author of the relevant code actually intended
to do as there is a couple of packet construction helper
functions that already use a const reference to get the
raw data.
* Optimize packet sender thread class
Most of the data sending methods of the packet sender thread
class use a value passed parameter for the packet data to be
sent. This causes the rather bulky data to be allocated on
the heap and copied, slowing the packet sending down. Convert
these parameters to const references to avoid the performance
hit.
* Optimize packet receiver thread class
The packet receiver and processor thread class has many
methods (mostly packet handlers) that receive the packed data
by value. This causes a performance hit that is actually
worse than the one caused by the packet sender methods
because the packet is first handed to the processPacket
method which looks at the packet type stored in the header
and then delegates the actual handling to one of the
handlers. Both, processPacket and all the handlers get the
packet data by value, leading to at least two unnecessary
copies of the data (with malloc and all the slow bells and
whistles of bulky classes).
As there already is a few methods that use a const reference
parameter for the packet data, convert all this value passed
packets to const references.
The reverted commit 968ce9af598024ec71e9ffb2d15c3997a13ad754
is suspected (through the use of bisection) of causing network slowdowns.
Revert for now as we are close to release.
* Few code updates
* Do not show average RTT before timing out
* Fix unwanted integer division in RTTStatistics
* Fix float format, prettier jitter calculation
* Use +=, 0.1f -> 100.0f for stronger average updates
* Add session_t typedef + remove unused functions
u16 peer_id is used everywhere, to be more consistent and permit some evolutions on this type in the future (i'm working on a PoC), uniformize u16 peer_id to SessionId peer_id
* Move Connection threads to dedicated files + various cleanups
* ConnectionReceiveThread::processPacket now uses function pointer table to route MT packet types
* Various code style fixes
* Code style with clang-format
* Various SharedBuffer copy removal
* SharedBuffer cannot be copied anymore using Buffer
* Fix many SharedBuffer copy (thanks to delete operator)
