;;;; Copyright (C) 2021 Julien Lepiller <julien@lepiller.eu>

;;;;

;;;; This library is free software; you can redistribute it and/or

;;;; modify it under the terms of the GNU Lesser General Public

;;;; License as published by the Free Software Foundation; either

;;;; version 3 of the License, or (at your option) any later version.

;;;;

;;;; This library is distributed in the hope that it will be useful,

;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of

;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

;;;; Lesser General Public License for more details.

;;;;

;;;; You should have received a copy of the GNU Lesser General Public

;;;; License along with this library; if not, write to the Free Software

;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

;;;;

(define-module (ip utils)

  #:use-module (ice-9 match)

  #:use-module (netlink constant)

  #:use-module (netlink data)

  #:use-module (netlink message)

  #:use-module (netlink route attrs)

  #:use-module (netlink standard)

  #:export (answer-ok?

            get-attr

            split-flags

            cidr->addr

            cidr->prefix))

(define (answer-ok? answer)

  (cond

    ((equal? (message-kind answer) NLMSG_DONE)

     #t)

    ((equal? (message-kind answer) NLMSG_ERROR)

     (let ((data (message-data answer)))

       (if (nl-data-data data)

           (let ((err (error-message-err data)))

             (if (equal? err 0)

                 #t

                 (begin

                   (format #t "RTNETLINK answers: ~a~%" (strerror (- err)))

                   #f)))

           #f)))))

(define (get-attr attrs type)

  (let ((attrs (filter (lambda (attr) (equal? (route-attr-kind attr) type)) attrs)))

    (match attrs

      (() #f)

      ((attr) (nl-data-data (route-attr-data attr))))))

(define (split-flags flags)

  (let loop ((max-flag 262144) (flags flags) (result '()))

    (cond

      ((equal? max-flag 1)

       (if (equal? flags 1)

           (cons 1 result)

           result))

      ((< flags max-flag)

       (loop (/ max-flag 2) flags result))

      (else

        (loop (/ max-flag 2) (- flags max-flag)

              (cons max-flag result))))))

(define (cidr->addr str)

  (match (string-split str #\/)

    ((addr) addr)

    ((addr prefix) addr)

    (_ (throw 'incorrect-cidr-notation str))))

(define (cidr->prefix str)

  (match (string-split str #\/)

    ((addr) #f)

    ((addr prefix) (string->number prefix))

    (_ (throw 'incorrect-cidr-notation str))))