This commit also fixes a bug which caused the server to initialize all boolean options to false.
It was caused by SiLoadProtoCfg() not checking whether the item exists in the configuration file.
CfgGetBool() always returns false if the item doesn't exist.
The WireGuard implementation will have two options that should not have a fixed default value, because they represent two keys (one is preshared, the other is private).
Instead of handling these two options differently in ProtoNewContainer(), this commit adds a new function to PROTO_IMPL: ProtoOptionString().
ProtoOptionString() takes the option's name as argument and returns a heap-allocated string that will be used as value. The function returns NULL when the option doesn't need a randomized value.
PROTO_OPTION is a structure that describes an option (who would've guessed?).
It's designed in a way that allows it to occupy as low memory as possible, while providing great flexibility.
The idea is similar to the one implemented in LIST for trivial types, with the difference that PROTO_OPTION doesn't require casting due to the use of union.
When a datagram is received, the matching session is looked up in a hash list; if it's not found, a new session is created.
This method allows to use a single UDP port for multiple protocols, as we do with TCP.
Also, each session has its own dedicated thread, used to process the received datagrams and generate the ones that are then sent through the UDP listener.
In addition to guaranteeing constant performance, separate threads also prevent a single one from blocking all sessions.
- An additional parameter is added to IsPacketForMe(), used to specify the protocol type (currently either TCP or UDP).
- SupportedModes() is dropped because it's now redundant.
- IsOk() and EstablishedSessions() are dropped because error checking should be handled by the implementation.
- ProtoImplDetect() now takes a buffer and its size rather than a SOCK, so that it can be used to detect UDP protocols.
- The OpenVPN toggle check is moved to ProtoImplDetect(), so that we don't have to duplicate it once UDP support is implemented.
The PROTO structure is now used to identify the system as a whole, rather than a single protocol. It's stored and initialized in Server.
ProtoCompare(), ProtoAdd() and ProtoDetected() are renamed to make the difference between PROTO and PROTO_IMPL more clear.
ProtoGet() and ProtoNum() are removed because the related list can now be accessed directly by Server.
This commit adds a protocol interface to the server, its purpose is to manage TCP connections and the various third-party protocols.
More specifically, ProtoHandleConnection() takes care of exchanging the packets between the local and remote endpoint; the protocol implementation only has to parse them and act accordingly.
The interface knows which protocol is the connection for by calling IsPacketForMe(), a function implemented for each protocol.
