Add openssl_overrides to conduit context

src/conduit-lwt-unix/conduit_lwt_unix.ml

@@ -108,6 +108,7 @@ type ctx = {
   src : Unix.sockaddr option;
   tls_own_key : tls_own_key;
   tls_authenticator : Conduit_lwt_tls.X509.authenticator;
+  openssl_overrides : Conduit_lwt_unix_ssl.Overrides.t option;
 }
 
 let string_of_unix_sockaddr sa =
@@ -154,19 +155,28 @@ let default_ctx =
       src = None;
       tls_own_key = `None;
       tls_authenticator = Lazy.force Conduit_lwt_tls.X509.default_authenticator;
+      openssl_overrides = None;
     }
 
 let init ?src ?(tls_own_key = `None)
     ?(tls_authenticator = Lazy.force Conduit_lwt_tls.X509.default_authenticator)
-    () =
+    ?openssl_overrides () =
   match src with
-  | None -> Lwt.return { src = None; tls_own_key; tls_authenticator }
+  | None ->
+      Lwt.return
+        { src = None; tls_own_key; tls_authenticator; openssl_overrides }
   | Some host -> (
       let open Unix in
       Lwt_unix.getaddrinfo host "0" [ AI_PASSIVE; AI_SOCKTYPE SOCK_STREAM ]
       >>= function
       | { ai_addr; _ } :: _ ->
-          Lwt.return { src = Some ai_addr; tls_own_key; tls_authenticator }
+          Lwt.return
+            {
+              src = Some ai_addr;
+              tls_own_key;
+              tls_authenticator;
+              openssl_overrides;
+            }
       | [] -> Lwt.fail_with "Invalid conduit source address specified")
 
 module Sockaddr_io = struct
@@ -284,6 +294,18 @@ let connect_with_openssl ~ctx (`Hostname hostname, `IP ip, `Port port) =
         in
         Some ctx_ssl
   in
+  let hostname, ctx_ssl =
+    match ctx.openssl_overrides with
+    | None | Some { client = None } -> (hostname, ctx_ssl)
+    | Some { client = Some overrides } ->
+        let hostname =
+          match overrides.hostname with Some x -> x | None -> hostname
+        in
+        let ctx_ssl =
+          match overrides.ctx with Some x -> Some x | None -> ctx_ssl
+        in
+        (hostname, ctx_ssl)
+  in
   Conduit_lwt_unix_ssl.Client.connect ?ctx:ctx_ssl ?src:ctx.src ~hostname sa
   >>= fun (fd, ic, oc) ->
   let flow = TCP { fd; ip; port } in

src/conduit-lwt-unix/conduit_lwt_unix.mli

@@ -161,6 +161,7 @@ val init :
   ?src:string ->
   ?tls_own_key:tls_own_key ->
   ?tls_authenticator:Conduit_lwt_tls.X509.authenticator ->
+  ?openssl_overrides:Conduit_lwt_unix_ssl.Overrides.t ->
   unit ->
   ctx io
 (** [init ?src ?tls_own_key ()] will initialize a Unix conduit that binds to the

src/conduit-lwt-unix/conduit_lwt_unix_ssl.dummy.ml

@@ -15,6 +15,15 @@
  *
  *)
 
+module Overrides = struct
+  module Client = struct
+    type t = { ctx : [ `Ssl_not_available ] option; hostname : string option }
+  end
+
+  type t = { client : Client.t option }
+end
+
+
 module Client = struct
   let default_ctx = `Ssl_not_available
   let create_ctx ?certfile:_ ?keyfile:_ ?password:_ () = default_ctx

src/conduit-lwt-unix/conduit_lwt_unix_ssl.dummy.mli

@@ -17,6 +17,14 @@
 
 (** TLS/SSL connections via {{:http://www.openssl.org} OpenSSL} C bindings *)
 
+module Overrides : sig
+  module Client : sig
+    type t = { ctx : [ `Ssl_not_available ] option; hostname : string option }
+  end
+
+  type t = { client : Client.t option }
+end
+
 module Client : sig
   val default_ctx : [ `Ssl_not_available ]
 

src/conduit-lwt-unix/conduit_lwt_unix_ssl.real.ml

@@ -34,6 +34,14 @@ let chans_of_fd sock =
   let ic = Lwt_io.make ~mode:Lwt_io.input ~close (Lwt_ssl.read_bytes sock) in
   (Lwt_ssl.get_fd sock, ic, oc)
 
+module Overrides = struct
+  module Client = struct
+    type t = { ctx : Ssl.context option; hostname : string option }
+  end
+
+  type t = { client : Client.t option }
+end
+
 module Client = struct
   let create_ctx ?certfile ?keyfile ?password () =
     let ctx = Ssl.create_context Ssl.SSLv23 Ssl.Client_context in

src/conduit-lwt-unix/conduit_lwt_unix_ssl.real.mli

@@ -17,6 +17,14 @@
 
 (** TLS/SSL connections via {{:http://www.openssl.org} OpenSSL} C bindings *)
 
+module Overrides : sig
+  module Client : sig
+    type t = { ctx : Ssl.context option; hostname : string option }
+  end
+
+  type t = { client : Client.t option }
+end
+
 module Client : sig
   val default_ctx : Ssl.context