diff --git a/src/stack-unix/tcpv4_socket.ml b/src/stack-unix/tcpv4_socket.ml
index 9f150c9e1..f1a0ae7fa 100644
--- a/src/stack-unix/tcpv4_socket.ml
+++ b/src/stack-unix/tcpv4_socket.ml
@@ -14,7 +14,7 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  *)
 
-open Lwt
+open Lwt.Infix
 
 type ipaddr = Ipaddr.V4.t
 type flow = Lwt_unix.file_descr
@@ -26,13 +26,13 @@ type t = {
 
 include Tcp_socket
 
-let connect id =
+let connect addr =
   let t =
-    match id with
+    match addr with
     | None -> { interface=None }
     | Some ip -> { interface=Some (Ipaddr_unix.V4.to_inet_addr ip) }
   in
-  return t
+  Lwt.return t
 
 let dst fd =
   match Lwt_unix.getpeername fd with
@@ -54,7 +54,7 @@ let create_connection ?keepalive _t (dst,dst_port) =
         | None -> ()
         | Some { Mirage_protocols.Keepalive.after; interval; probes } ->
           Tcp_socket_options.enable_keepalive ~fd ~after ~interval ~probes );
-      return (Ok fd))
+      Lwt.return (Ok fd))
     (fun exn ->
        Lwt.catch (fun () -> Lwt_unix.close fd) (fun _ -> Lwt.return_unit) >>= fun () ->
-       return (Error (`Exn exn)))
+       Lwt.return (Error (`Exn exn)))
diff --git a/src/stack-unix/tcpv6_socket.ml b/src/stack-unix/tcpv6_socket.ml
index 45f40c440..498e591fd 100644
--- a/src/stack-unix/tcpv6_socket.ml
+++ b/src/stack-unix/tcpv6_socket.ml
@@ -25,6 +25,8 @@ type t = {
   interface: Unix.inet_addr option;    (* source ip to bind to *)
 }
 
+include Tcp_socket
+
 let connect addr =
   let t =
     match addr with
@@ -50,12 +52,10 @@ let create_connection ?keepalive _t (dst,dst_port) =
         (Lwt_unix.ADDR_INET ((Ipaddr_unix.V6.to_inet_addr dst), dst_port))
       >>= fun () ->
       ( match keepalive with
-      | None -> ()
-      | Some { Mirage_protocols.Keepalive.after; interval; probes } ->
-        Tcp_socket_options.enable_keepalive ~fd ~after ~interval ~probes );
+        | None -> ()
+        | Some { Mirage_protocols.Keepalive.after; interval; probes } ->
+          Tcp_socket_options.enable_keepalive ~fd ~after ~interval ~probes );
       Lwt.return (Ok fd))
     (fun exn ->
        Lwt.catch (fun () -> Lwt_unix.close fd) (fun _ -> Lwt.return_unit) >>= fun () ->
        Lwt.return (Error (`Exn exn)))
-
-include Tcp_socket
diff --git a/src/stack-unix/udpv6_socket.ml b/src/stack-unix/udpv6_socket.ml
index 922f31f30..5b392c925 100644
--- a/src/stack-unix/udpv6_socket.ml
+++ b/src/stack-unix/udpv6_socket.ml
@@ -15,15 +15,13 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  *)
 
-open Lwt
+open Lwt.Infix
 
-type buffer = Cstruct.t
 type ipaddr = Ipaddr.V6.t
 type flow = Lwt_unix.file_descr
-type +'a io = 'a Lwt.t
 type ip = Ipaddr.V6.t option (* source ip and port *)
 type ipinput = unit Lwt.t
-type callback = src:ipaddr -> dst:ipaddr -> src_port:int -> buffer -> unit io
+type callback = src:ipaddr -> dst:ipaddr -> src_port:int -> Cstruct.t -> unit Lwt.t
 
 type t = {
   interface: Unix.inet_addr; (* source ip to bind to *)
@@ -35,12 +33,12 @@ let get_udpv6_listening_fd {listen_fds;interface} port =
     Lwt.return @@ Hashtbl.find listen_fds (interface,port)
   with Not_found ->
     let fd = Lwt_unix.(socket PF_INET6 SOCK_DGRAM 0) in
-    Lwt_unix.bind fd (Lwt_unix.ADDR_INET (interface,port))
+    Lwt_unix.bind fd (Lwt_unix.ADDR_INET (interface, port))
     >>= fun () ->
-    Hashtbl.add listen_fds (interface,port) fd;
+    Hashtbl.add listen_fds (interface, port) fd;
     Lwt.return fd
 
-(** IO operation errors *)
+
 type error = [`Sendto_failed]
 
 let pp_error ppf = function
@@ -54,10 +52,9 @@ let connect (id:ip) =
       | None -> Ipaddr_unix.V6.to_inet_addr Ipaddr.V6.unspecified
       | Some ip -> Ipaddr_unix.V6.to_inet_addr ip
     in { interface; listen_fds }
-  in return t
+  in Lwt.return t
 
-let disconnect _ =
-  return_unit
+let disconnect _ = Lwt.return_unit
 
 let id { interface; _ } =
   Some (Ipaddr_unix.V6.of_inet_addr_exn interface)