(in-package :sb-bsd-sockets) #| getsockopt(socket, level, int optname, void *optval, socklen_t *optlen) setsockopt(socket, level, int optname, void *optval, socklen_t optlen)              ^ SOL_SOCKET or a protocol number In terms of providing a useful interface, we have to face up to the fact that most of these take different data types - some are integers, some are booleans, some are foreign struct instances, etc etc  (define-socket-option lisp-name doc level number mangle-arg size mangle-return) macro-expands to two functions that define lisp-name and (setf ,lisp-name) and calls the functions mangle-arg and mangle-return on outgoing and incoming data resp. Parameters passed to the function thus defined (lisp-name) are all passed directly into mangle-arg.  mangle-arg should return an alien pointer  - this is passed unscathed to the foreign routine, so wants to have type (* t).  Note that even for options that have integer arguments, this is still a pointer to said integer. size is the size of the buffer that the return of mangle-arg points to, and also of the buffer that we should allocate for getsockopt to write into. mangle-return is called with an alien buffer and should turn it into something that the caller will want. Code for options that not every system has should be conditionalised:  (if (boundp 'sockint::IP_RECVIF)      (define-socket-option so-receive-interface nil (getprotobyname "ip")        sockint::IP_RECVIF  ...  )) |# (defmacro define-socket-option     (lisp-name documentation      level number buffer-type mangle-arg mangle-return mangle-setf-buffer      &optional features info)   (let ((find-level          (if (numberp (eval level))              level              `(get-protocol-by-name ,(string-downcase (symbol-name level)))))         (supportedp (or (null features) (sb-int:featurep features))))     `(progn       (export ',lisp-name)       (defun ,lisp-name (socket)         ,@(when documentation (list (concatenate 'string documentation " " info)))         ,(if supportedp              `(sb-alien:with-alien ((size sb-alien:int)                                       (buffer ,buffer-type))                   (setf size (sb-alien:alien-size ,buffer-type :bytes))                   (if (= -1 (sockint::getsockopt (socket-file-descriptor socket)                                                  ,find-level ,number                                                  (sb-alien:addr buffer)                                                  (sb-alien:addr size)))                       (socket-error "getsockopt")                       (,mangle-return buffer size)))              `(error 'unsupported-operator                :format-control "Socket option ~S is not supported in this platform."                :format-arguments (list ',lisp-name))))       (defun (setf ,lisp-name) (new-val socket)         ,(if supportedp              `(sb-alien:with-alien ((buffer ,buffer-type))                   (setf buffer ,(if mangle-arg                                     `(,mangle-arg new-val)                                     `new-val))                   (when (= -1 (sockint::setsockopt (socket-file-descriptor socket)                                                    ,find-level ,number                                                    (,mangle-setf-buffer buffer)                                                    ,(if (eql buffer-type 'sb-alien:c-string)                                                         `(length new-val)                                                         `(sb-alien:alien-size ,buffer-type :bytes))))                     (socket-error "setsockopt")))              `(error 'unsupported-operator                :format-control "Socket option ~S is not supported on this platform."                :format-arguments (list ',lisp-name))))))) ;;; sockopts that have integer arguments (defun foreign-int-to-integer (buffer size)   (assert (= size (sb-alien:alien-size sb-alien:int :bytes)))   buffer) (defmacro define-socket-option-int (name level number &optional features (info ""))   `(define-socket-option ,name nil ,level ,number      sb-alien:int nil foreign-int-to-integer sb-alien:addr ,features ,info)) (define-socket-option-int   sockopt-receive-low-water sockint::sol-socket sockint::so-rcvlowat) (define-socket-option-int   sockopt-send-low-water sockint::sol-socket sockint::so-sndlowat) (define-socket-option-int   sockopt-type sockint::sol-socket sockint::so-type) (define-socket-option-int   sockopt-send-buffer sockint::sol-socket sockint::so-sndbuf) (define-socket-option-int   sockopt-receive-buffer sockint::sol-socket sockint::so-rcvbuf) (define-socket-option-int   sockopt-priority sockint::sol-socket sockint::so-priority :linux   "Available only on Linux.") ;;; boolean options are integers really (defun foreign-int-to-bool (x size)   (if (zerop (foreign-int-to-integer x size))       nil       t)) (defun bool-to-foreign-int (val)   (if val 1 0)) (defmacro define-socket-option-bool (name level c-name &optional features (info ""))   `(define-socket-option ,name     ,(format nil "~@<Return the value of the ~A socket option for SOCKET. ~                  This can also be updated with SETF.~:@>"              (symbol-name c-name))     ,level ,c-name     sb-alien:int bool-to-foreign-int foreign-int-to-bool sb-alien:addr     ,features ,info)) (define-socket-option-bool   sockopt-reuse-address sockint::sol-socket sockint::so-reuseaddr) (define-socket-option-bool   sockopt-keep-alive sockint::sol-socket sockint::so-keepalive) (define-socket-option-bool   sockopt-oob-inline sockint::sol-socket sockint::so-oobinline) (define-socket-option-bool   sockopt-bsd-compatible sockint::sol-socket sockint::so-bsdcompat :linux   "Available only on Linux.") (define-socket-option-bool   sockopt-pass-credentials sockint::sol-socket sockint::so-passcred :linux   "Available only on Linux.") (define-socket-option-bool   sockopt-debug sockint::sol-socket sockint::so-debug) (define-socket-option-bool   sockopt-dont-route sockint::sol-socket sockint::so-dontroute) (define-socket-option-bool   sockopt-broadcast sockint::sol-socket sockint::so-broadcast) (define-socket-option-bool sockopt-tcp-nodelay :tcp sockint::tcp-nodelay) (defun identity-1 (x &rest args)   (declare (ignore args))   x) (define-socket-option sockopt-bind-to-device nil sockint::sol-socket   sockint::so-bindtodevice sb-alien:c-string identity identity-1 identity   :linux "Available only on Linux") ;;; other kinds of socket option ;;; so_peercred takes a ucre structure ;;; so_linger struct linger { ;                  int   l_onoff;    /* linger active */ ;                  int   l_linger;   /* how many seconds to linger for */ ;              }; #| (sockopt-reuse-address 2) (defun echo-server ()   (let ((s (make-inet-socket :stream (get-protocol-by-name "tcp"))))     (setf (sockopt-reuse-address s) t)     (setf (sockopt-bind-to-device s) "lo")     (socket-bind s (make-inet-address "127.0.0.1") 3459)     (socket-listen s 5)     (dotimes (i 10)       (let* ((s1 (socket-accept s))              (stream (socket-make-stream s1 :input t :output t :buffering :none)))         (let ((line (read-line stream)))           (format t "got one ~A ~%" line)           (format stream "~A~%" line))         (close stream))))) NIL |#