;;; hostinfo extension to Chicken Scheme
;;; Description: Look up host, service, and protocol information

;; Copyright (c) 2005-2008, Jim Ursetto.  All rights reserved.
;;
;; Redistribution and use in source and binary forms, with or without
;; modification, are permitted provided that the following conditions are met:
;;
;;   Redistributions of source code must retain the above copyright notice,
;;   this list of conditions and the following disclaimer. Redistributions in
;;   binary form must reproduce the above copyright notice, this list of
;;   conditions and the following disclaimer in the documentation and/or
;;   other materials provided with the distribution. Neither the name of the
;;   author nor the names of its contributors may be used to endorse or
;;   promote products derived from this software without specific prior
;;   written permission.
;;
;; THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
;; IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
;; THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
;; PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR
;; CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
;; EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
;; PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
;; PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
;; LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
;; NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
;; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

;;;

;; This extension performs host, protocol and service information lookups
;; via underlying calls to gethostbyname(3), getprotobyname(3), and
;; getservbyname(3).  Depending on your system, this may consult DNS,
;; NIS, /etc/hosts, /etc/services, /etc/protocols, and so on.

;; A simple interface is provided for the most commmon queries. Also
;; provided is a more comprehensive interface using records, which
;; contain all data available in a lookup.

;; IP addresses are represented by 4 (IPv4) or 16 (IPv6) byte
;; u8vectors. The interface requires, and returns, addresses in this
;; format; functions are provided to convert between the string and
;; u8vector representations. However, the "do what I want" procedures
;; (e.g. host-information) will do the conversion for you.

;; Caveats:
;; - IPv6 addresses can be converted to and from strings, and the underlying structure
;;   supports IPv6, but lookup of IPv6 addresses and records is not currently implemented.
;; - array0->string-vector and array0->bytevector-vector contain redundant code.
;; - host, services, and protocol-information check their argument types, even
;;   though the underlying code already does it.

(declare
 (fixnum))

(cond-expand [paranoia]
             [else
              (declare (no-bound-checks))])

#> #include "hostinfo.h" <#

(require-extension srfi-4 lolevel posix)

(module hostinfo
;;; Short and sweet lookups
  (current-hostname
   hostname->ip ip->hostname
   protocol-name->number protocol-number->name
   service-port->name service-name->port
;;; Entire host, protocol or service record lookup
   hostname->hostinfo ip->hostinfo
   protocol-name->protoinfo protocol-number->protoinfo
   service-port->servinfo service-name->servinfo
;;; Record accessors and predicates
   hostinfo? hostinfo-name hostinfo-aliases hostinfo-addresses
   hostinfo-address hostinfo-type hostinfo-length
   protoinfo? protoinfo-name protoinfo-aliases protoinfo-number
   servinfo? servinfo-name servinfo-aliases servinfo-port servinfo-protocol
;;; One-stop shops -- does what you want
   host-information protocol-information service-information
;;; Utilities
   string->ip ip->string)

  (import scheme chicken
          extras srfi-4 lolevel posix foreign
	  data-structures
          foreigners)

  (define (vector-map p v0)   ; to avoid linking in vector-lib
    (let* ((len (vector-length v0))
           (v (make-vector len)))
      (do ((i 0 (+ i 1)))
          ((>= i len) v)
        (vector-set! v i
                     (p i (vector-ref v0 i))))))

  (cond-expand [unsafe
                (eval-when (compile)
                           (define-inline (##sys#check-string . r)
                             (##core#undefined))) ]
               [else])

;;; C data structure conversions

  (define (c-pointer->blob ptr len)
    (let ((bv (make-blob len))
          (memcpy (foreign-lambda bool "C_memcpy" blob c-pointer integer)))
      (memcpy bv ptr len)
      bv))

;; Convert from null-terminated array of c-strings to vector of strings.
;; These functions use C_alloc and so are not suitable for large datasets.
;; Note: get_argv_2 of runtime.c shows how to build a list instead of a vector (in reverse).
  (define array0->string-vector
    (foreign-primitive scheme-object (((pointer "char *") list)) "
    char **p; int len = 0;
    C_word *a, vec, *elt;

    for (p = list; *p; ++p, ++len);

    a = C_alloc(C_SIZEOF_VECTOR(len));
    vec = (C_word)a;
    *a++ = C_make_header(C_VECTOR_TYPE, len);

    for (p = list; *p; ++p) {
       len = strlen(*p);
       elt = C_alloc(C_SIZEOF_STRING(len));
       /* Both C_mutate and *a++ =  seem to work fine here. */
       C_mutate(a++, C_string(&elt, len, *p));
    }
    return(vec);"
                       ))

  ;; Convert from null-terminated array of IP addresses to vector of strings.
  (define array0->bytevector-vector
    (foreign-primitive scheme-object (((pointer "char *") list) (integer addrlen)) "
    char **p; int len = 0;
    C_word *a, vec, *elt;

    for (p = list; *p; ++p, ++len);

    a = C_alloc(C_SIZEOF_VECTOR(len));
    vec = (C_word)a;
    *a++ = C_make_header(C_VECTOR_TYPE, len);

    for (p = list; *p; ++p) {
       elt = C_alloc(C_SIZEOF_STRING(addrlen));
       C_mutate(a++, C_bytevector(&elt, addrlen, *p));
    }
    return(vec);"
                       ))

  ;; Not currently used.  Could make the array0-> stuff somewhat cleaner.
  ;; (define array0-length
  ;;   (foreign-lambda* integer (((pointer "void *") list)) #<<EOF
  ;;     void **p; int len = 0;
  ;;     for (p = list; *p; ++p, ++len);
  ;;     return(len);
  ;; EOF
  ;; ))

;;; string->ip conversion

  ;; inet_pton does not like "127.1", nor "0", nor any other non-standard
  ;; representation of IP addresses.  This is specified by RFC2553.
  ;; inet_aton resolves these addresses.  We use inet_pton here.

  (define-foreign-variable inet4-addrstrlen integer "INET_ADDRSTRLEN")
  (define-foreign-variable inet6-addrstrlen integer "INET6_ADDRSTRLEN")
  (define-foreign-variable af-inet  integer "AF_INET")
  (define-foreign-variable af-inet6 integer "AF_INET6")

  (define inet-ntop (foreign-lambda c-string "inet_ntop" integer u8vector c-string integer))
  (define inet-pton (foreign-lambda* bool ((integer type) (c-string src) (blob dest))
                                     "return(inet_pton(type, src, dest) == 1);"))

  (define (string->ip4 str)
    (##sys#check-string str 'string->ip4)
    (let ((bv (make-blob 4)))
      (and (inet-pton af-inet str bv)
           (blob->u8vector bv))))

  (define (string->ip6 str)
    (##sys#check-string str 'string->ip6)
    (let ((bv (make-blob 16)))
      (and (inet-pton af-inet6 str bv)
           (blob->u8vector bv))))

  (define (string->ip str)
    (or (string->ip4 str)
        (string->ip6 str)))

;;; ip->string conversion

  (define (ip4->string addr)
    (let ((len inet4-addrstrlen))
      (inet-ntop af-inet addr (make-string len) len)))

  (define (ip6->string addr)
    (let ((len inet6-addrstrlen))
      (inet-ntop af-inet6 addr (make-string len) len)))

  ;; Take an IPv4 or IPv6 u8vector and convert it into the
  ;; appropriate string representation, via inet_ntop.
  (define (ip->string addr)
    (let ((len (u8vector-length addr)))
      (cond ((fx= len 4)  (ip4->string addr))
            ((fx= len 16) (ip6->string addr))
            (else
             (error "Invalid IP address length" addr)))))

;;; hostent raw structure

  (define-foreign-record-type (hostent "struct hostent")
    (c-string h_name hostent-name)
    (c-pointer h_aliases hostent-h_aliases)
    (integer h_addrtype hostent-addrtype)
    (integer h_length hostent-length)
    (c-pointer h_addr_list hostent-addr-list))

  ;; Some convenient accessors for the raw hostent structure--with raw c pointers
  ;; converted to the appropriate scheme objects.  We only use these once or twice
  ;; below, so their main advantage is clarity.
  (define (hostent-aliases h)
    (array0->string-vector (hostent-h_aliases h)))
  (define (hostent-address h)
    (let* ((get-addr (foreign-lambda* c-pointer ((hostent h)) "return(h->h_addr_list[0]);"))
           (addr (get-addr h)))
      (blob->u8vector
       (c-pointer->blob addr (hostent-length h)))))
  (define (hostent-addresses h)
    (vector-map (lambda (i x) (blob->u8vector x))
                (array0->bytevector-vector (hostent-addr-list h)
                                           (hostent-length h))))
  ;; The IPv6 equivalents of these are getipnodebyname and
  ;; getipnodebyaddr.
  (define gethostent/name (foreign-lambda hostent "gethostbyname" c-string))

  (define (gethostent/addr addr)
    (if (fx= (u8vector-length addr) 4)
        (gethostent/addr/bv (u8vector->blob addr))
        (error "invalid IP address length; only IPv4 supported" addr)))

  ;; Warning: handle IPv6!!
  (define gethostent/addr/bv (foreign-lambda* hostent ((blob addr))
                                              "return(gethostbyaddr((const char *)addr, 4, AF_INET));"))

  ;; This was originally made a macro so we could easily return multiple
  ;; values -- but we're now returning a hostinfo structure.  Eh.
  (define (hostent->hostinfo h)
    (make-hostinfo (hostent-name h)
                   (hostent-addresses h)
                   (hostent-aliases h)))

;;; hostinfo and host information

  ;; The standard host name for the current processor.
  ;; Gets & Sets, error otherwise.

  (define set-host-name!
    (foreign-lambda* int ((c-string name))
                     "return(sethostname(name, strlen(name)));"))

  (define (current-hostname . args)
    (if (null? args)
        (get-host-name)
        (and (zero? (set-host-name! (->string (car args))))
             (error 'current-hostname "cannot set hostname"))))

  ;; Structure accessors created by define-foreign-record do not intercept
  ;; NULL pointer input, including #f.
  (define (hostname->ip host)
    (and-let* ((h (gethostent/name host)))
      (hostent-address h)))

  (define (hostname->hostinfo host)
    (and-let* ((h (gethostent/name host)))
      (hostent->hostinfo h)))

  (define (ip->hostname addr)
    (and-let* ((h (gethostent/addr addr)))
      (hostent-name h)))

  (define (ip->hostinfo addr)
    (and-let* ((h (gethostent/addr addr)))
      (hostent->hostinfo h)))

  ;; A simple hostinfo structure.
  (define-record-type hostinfo
    (make-hostinfo name addresses aliases)
    hostinfo?
    (name hostinfo-name)
    (addresses hostinfo-addresses)
    (aliases hostinfo-aliases))

  ;; "Accessors" for phantom fields.
  ;; We don't need to store length or type, as these are artifacts
  ;; of the C implementation, and can be derived from the address itself.
  (define (hostinfo-address h) (vector-ref (hostinfo-addresses h) 0))
  (define (hostinfo-length h) (u8vector-length (hostinfo-address h)))
  (define (hostinfo-type h)
    (let ((len (u8vector-length (hostinfo-address h))))
      (cond ((fx= len 4)  'AF_INET)   ;; Kind of a dummy implementation--
            ((fx= len 16) 'AF_INET6)  ;; not sure what value would be appropriate
            (else
             (error "Invalid IP address length" (hostinfo-address h))))))

  ;; Format the structure for easy interactive viewing--should be possible to
  ;; add a ctor for this representation, though it's not clear why you'd want to.
  (define-record-printer (hostinfo h port)
    (fprintf port "#,(hostinfo name: ~S addresses: ~S aliases: ~S)"
             (hostinfo-name h) (hostinfo-addresses h) (hostinfo-aliases h)))

  ;; Warning:  lookup of an IP address which is invalid yet numeric will
  ;; return a false positive.  Bug in gethostbyname?
  ;; E.g.  (hostname->hostinfo "1") => #,(hostinfo name: "1" addresses: (#u8(0 0 0 1)))
  ;; ** If we used inet_aton for string->ip, then these cases would
  ;; be transformed into u8vector IPs, and the lookup would correctly fail.

  ;; Return a hostinfo record.  HOST is a u8vector IP address, a string
  ;; hostname, or a string numeric IP address.
  (define (host-information host)
    (if (u8vector? host)
        (ip->hostinfo host)
        (begin
          (##sys#check-string host 'host-information)
          (cond ((string->ip host) => ip->hostinfo)
                (else (hostname->hostinfo host))))))

;;; protocols

  (define-foreign-record-type (protoent "struct protoent")
    (c-string p_name protoent-name)
    (c-pointer p_aliases protoent-p_aliases)
    (integer p_proto protoent-proto))

  (define getprotoent/name   (foreign-lambda protoent "getprotobyname" c-string))
  (define getprotoent/number (foreign-lambda protoent "getprotobynumber" integer))

  ;; Raw structure -> scheme-object accessors
  (define (protoent-aliases p)
    (array0->string-vector (protoent-p_aliases p)))

  (define-record-type protoinfo
    (make-protoinfo name number aliases)
    protoinfo?
    (name protoinfo-name)
    (number protoinfo-number)
    (aliases protoinfo-aliases))

  (define-record-printer (protoinfo p port)
    (fprintf port "#,(protoinfo name: ~S number: ~S aliases: ~S)"
             (protoinfo-name p) (protoinfo-number p) (protoinfo-aliases p)))

  (define (protocol-name->number name)
    (and-let* ((p (getprotoent/name name)))
      (protoent-proto p)))
  (define (protocol-number->name nr)
    (and-let* ((p (getprotoent/number nr)))
      (protoent-name p)))

  (define (protoent->protoinfo p)
    (make-protoinfo (protoent-name p)
                    (protoent-proto p)
                    (protoent-aliases p)))

  (define (protocol-name->protoinfo name)
    (and-let* ((p (getprotoent/name name)))
      (protoent->protoinfo p)))
  (define (protocol-number->protoinfo nr)
    (and-let* ((p (getprotoent/number nr)))
      (protoent->protoinfo p)))

  (define (protocol-information proto)
    (if (fixnum? proto)
        (protocol-number->protoinfo proto)
        (begin
          (##sys#check-string proto 'protocol-information)
          (protocol-name->protoinfo proto))))

;;; services

  (define-foreign-type port-number int
    (foreign-lambda int "htons" int)
    (foreign-lambda int "ntohs" int) )

  (define-foreign-record-type (servent "struct servent")
    (c-string s_name servent-name)
    (c-pointer s_aliases servent-s_aliases)
    (port-number s_port servent-port)
    (c-string s_proto servent-proto))

  (define (servent->servinfo s)
    (make-servinfo (servent-name s)
                   (servent-port s)
                   (array0->string-vector
                    (servent-s_aliases s))
                   (servent-proto s)))

  (define getservent/name (foreign-lambda servent "getservbyname" c-string c-string))
  (define getservent/port (foreign-lambda servent "getservbyport" port-number c-string))

  (define-record-type servinfo
    (make-servinfo name port aliases protocol)
    servinfo?
    (name servinfo-name)
    (port servinfo-port)
    (aliases servinfo-aliases)
    (protocol servinfo-protocol))

  (define-record-printer (servinfo s port)
    (fprintf port "#,(servinfo name: ~S port: ~S aliases: ~S protocol: ~S)"
             (servinfo-name s) (servinfo-port s) (servinfo-aliases s) (servinfo-protocol s)))

  ;; If provided with the optional protocol argument (a string), these will
  ;; restrict their search to that protocol.
  (define (service-name->port name . pr)
    (let-optionals pr ((proto #f))
                   (and-let* ((s (getservent/name name proto)))
                     (servent-port s))))
  (define (service-port->name port . pr)
    (let-optionals pr ((proto #f))
                   (and-let* ((s (getservent/port port proto)))
                     (servent-name s))))
  (define (service-name->servinfo name . pr)
    (let-optionals pr ((proto #f))
                   (and-let* ((s (getservent/name name proto)))
                     (servent->servinfo s))))
  (define (service-port->servinfo port . pr)
    (let-optionals pr ((proto #f))
                   (and-let* ((s (getservent/port port proto)))
                     (servent->servinfo s))))

  ;; Return service information given a service name or port, and an
  ;; optional protocol name or number to restrict the search to.
  ;; Note: if the protocol-number->name lookup fails,
  ;; an error is thrown, as this was probably not intended.
  (define (service-information service . pr)
    (let-optionals pr ((proto #f))
                   (let ((proto (if (fixnum? proto)
                                    (or (protocol-number->name proto)
                                        (error 'service-information "illegal protocol number" proto))
                                    proto)))
                     (if (fixnum? service)
                         (service-port->servinfo service proto)
                         (begin
                           (##sys#check-string service 'service-information)
                           (service-name->servinfo service proto))))))
)   ; end module

;;; Tests
(cond-expand
 [testing
  (import hostinfo)
  (current-hostname)
  (host-information "www.call-with-current-continuation.org")
  (host-information '#u8(194 97 107 133))
  (host-information "194.97.107.133")
                                        ; =>  #,(hostinfo name: "www003.lifemedien.de" addresses: #(#u8(194 97 107 133))
                                        ;        aliases: #("www.call-with-current-continuation.org"))
  (ip->hostname '#u8(194 97 107 133)) ; "www003.lifemedien.de"
  (string->ip "0708::0901")  ;  #u8(7 8 0 0 0 0 0 0 0 0 0 0 0 0 9 1)
  (ip->string '#u8(127 0 0 1))        ;  "127.0.0.1"
  (hostinfo-aliases
   (hostname->hostinfo
    (ip->hostname (hostname->ip
                   (hostinfo-name
                    (host-information "www.call-with-current-continuation.org"))))))
                                        ; => #("www.call-with-current-continuation.org")

  (protocol-information 17) ; => #,(protoinfo name: "udp" number: 17 aliases: #("UDP"))
  (protoinfo-name (protocol-information 2)) ; => "igmp"
  (protoinfo-aliases (protocol-name->protoinfo
                      (protocol-number->name
                       (protoinfo-number
                        (protocol-information "ospf"))))) ; => #("OSPFIGP")
  (protocol-name->number "OSPFIGP") ; 89 (you can look up aliases, too)

  (servinfo-protocol (service-name->servinfo
                      (service-port->name
                       (servinfo-port (service-information "ssh"))))) ; => "udp" (yes, really)
  (service-information "ssh" "tcp") ; => #,(servinfo name: "ssh" port: 22 aliases: #() protocol: "tcp")
  (service-information "ssh" "tco")   ; => #f
  (service-information 512 "tcp") ; #,(servinfo name: "exec" port: 512 aliases: #() protocol: "tcp")
  (service-information 512 "udp") ; #,(servinfo name: "comsat" port: 512 aliases: #("biff") protocol: "udp")
  (service-information 512 17)        ; same as previous
  (service-information 512 170000)   ; Error: (service-information) illegal protocol number: 170000
  ] [else])