asyncnet, net: call SSL_shutdown only when connection established

This commit prevents "SSL_shutdown while in init" errors from happening.

See https://github.com/openssl/openssl/issues/710#issuecomment-253897666

lib/wrappers/openssl.nim

@@ -201,6 +201,9 @@ const
   SSL_OP_ALL* = 0x000FFFFF
   SSL_VERIFY_NONE* = 0x00000000
   SSL_VERIFY_PEER* = 0x00000001
+  SSL_ST_CONNECT* = 0x1000
+  SSL_ST_ACCEPT* = 0x2000
+  SSL_ST_INIT* = SSL_ST_CONNECT or SSL_ST_ACCEPT
   OPENSSL_DES_DECRYPT* = 0
   OPENSSL_DES_ENCRYPT* = 1
   X509_V_OK* = 0
@@ -282,6 +285,13 @@ when compileOption("dynlibOverride", "ssl") or defined(noOpenSSLHacks):
       # Static linking against OpenSSL < 1.1.0 is not supported
       discard
 
+  when defined(libressl) or defined(openssl10):
+    proc SSL_state(ssl: SslPtr): cint {.cdecl, dynlib: DLLSSLName, importc.}
+    proc SSL_in_init*(ssl: SslPtr): cint {.inline.} =
+      SSl_state(ssl) and SSL_ST_INIT
+  else:
+    proc SSL_in_init*(ssl: SslPtr): cint {.cdecl, dynlib: DLLSSLName, importc.}
+
   template OpenSSL_add_all_algorithms*() = discard
 
   proc SSLv23_client_method*(): PSSL_METHOD {.cdecl, dynlib: DLLSSLName, importc.}
@@ -382,6 +392,24 @@ else:
       if theProc.isNil: 0.culong
       else: theProc()
 
+  proc SSL_in_init*(ssl: SslPtr): cint =
+    # A compatibility wrapper for `SSL_in_init()` for OpenSSL 1.0, 1.1 and LibreSSL
+    const MainProc = "SSL_in_init"
+    let
+      theProc {.global.} = cast[proc(ssl: SslPtr): cint {.cdecl.}](sslSymNullable(MainProc))
+      # Fallback
+      sslState {.global.} = cast[proc(ssl: SslPtr): cint {.cdecl.}](sslSymNullable("SSL_state"))
+
+    # FIXME: This shouldn't be needed, but the compiler is complaining about
+    #        `sslState` being GC-ed memory???
+    {.gcsafe.}:
+      if not theProc.isNil:
+        theProc(ssl)
+      elif not sslState.isNil:
+        sslState(ssl) and SSL_ST_INIT
+      else:
+        raiseInvalidLibrary MainProc
+
 proc ERR_load_BIO_strings*(){.cdecl, dynlib: DLLUtilName, importc.}
 
 proc SSL_new*(context: SslCtx): SslPtr{.cdecl, dynlib: DLLSSLName, importc.}