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diff --git a/ssl/statem/README b/ssl/statem/README deleted file mode 100644 index bafe33060c92..000000000000 --- a/ssl/statem/README +++ /dev/null @@ -1,63 +0,0 @@ -State Machine Design -==================== - -This file provides some guidance on the thinking behind the design of the -state machine code to aid future maintenance. - -The state machine code replaces an older state machine present in OpenSSL -versions 1.0.2 and below. The new state machine has the following objectives: - - Remove duplication of state code between client and server - - Remove duplication of state code between TLS and DTLS - - Simplify transitions and bring the logic together in a single location - so that it is easier to validate - - Remove duplication of code between each of the message handling functions - - Receive a message first and then work out whether that is a valid - transition - not the other way around (the other way causes lots of issues - where we are expecting one type of message next but actually get something - else) - - Separate message flow state from handshake state (in order to better - understand each) - - message flow state = when to flush buffers; handling restarts in the - event of NBIO events; handling the common flow of steps for reading a - message and the common flow of steps for writing a message etc - - handshake state = what handshake message are we working on now - - Control complexity: only the state machine can change state: keep all - the state changes local to the state machine component - -The message flow state machine is divided into a reading sub-state machine and a -writing sub-state machine. See the source comments in statem.c for a more -detailed description of the various states and transitions possible. - -Conceptually the state machine component is designed as follows: - - libssl - | ----------------------------|-----statem.h-------------------------------------- - | - _______V____________________ - | | - | statem.c | - | | - | Core state machine code | - |____________________________| - statem_local.h ^ ^ - _________| |_______ - | | - _____________|____________ _____________|____________ - | | | | - | statem_clnt.c | | statem_srvr.c | - | | | | - | TLS/DTLS client specific | | TLS/DTLS server specific | - | state machine code | | state machine code | - |__________________________| |__________________________| - | |_______________|__ | - | ________________| | | - | | | | - ____________V_______V________ ________V______V_______________ - | | | | - | statem_lib.c | | statem_dtls.c | - | | | | - | Non core functions common | | Non core functions common to | - | to both servers and clients | | both DTLS servers and clients | - |_____________________________| |_______________________________| - |