/usr.bin/talk/get_iface.c

https://bitbucket.org/freebsd/freebsd-head/ · C · 100 lines · 48 code · 16 blank · 36 comment · 10 complexity · 3b75d88d30f7c72fccba9ebde37bda0b MD5 · raw file

  1. /*
  2. * Copyright 1994, 1995 Massachusetts Institute of Technology
  3. *
  4. * Permission to use, copy, modify, and distribute this software and
  5. * its documentation for any purpose and without fee is hereby
  6. * granted, provided that both the above copyright notice and this
  7. * permission notice appear in all copies, that both the above
  8. * copyright notice and this permission notice appear in all
  9. * supporting documentation, and that the name of M.I.T. not be used
  10. * in advertising or publicity pertaining to distribution of the
  11. * software without specific, written prior permission. M.I.T. makes
  12. * no representations about the suitability of this software for any
  13. * purpose. It is provided "as is" without express or implied
  14. * warranty.
  15. *
  16. * THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''. M.I.T. DISCLAIMS
  17. * ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
  18. * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  19. * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
  20. * SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  21. * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  22. * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  23. * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  24. * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  25. * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  26. * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27. * SUCH DAMAGE.
  28. */
  29. #include <sys/cdefs.h>
  30. __FBSDID("$FreeBSD$");
  31. /*
  32. * From:
  33. * Id: find_interface.c,v 1.1 1995/08/14 16:08:39 wollman Exp
  34. */
  35. #include <errno.h>
  36. #include <string.h>
  37. #include <unistd.h>
  38. #include "talk.h"
  39. /*
  40. * Try to find the interface address that is used to route an IP
  41. * packet to a remote peer.
  42. */
  43. int
  44. get_iface(struct in_addr *dst, struct in_addr *iface)
  45. {
  46. static struct sockaddr_in local;
  47. struct sockaddr_in remote;
  48. socklen_t namelen;
  49. int s, rv;
  50. memcpy(&remote.sin_addr, dst, sizeof remote.sin_addr);
  51. remote.sin_port = htons(60000);
  52. remote.sin_family = AF_INET;
  53. remote.sin_len = sizeof remote;
  54. local.sin_addr.s_addr = htonl(INADDR_ANY);
  55. local.sin_port = htons(60000);
  56. local.sin_family = AF_INET;
  57. local.sin_len = sizeof local;
  58. s = socket(PF_INET, SOCK_DGRAM, 0);
  59. if (s < 0)
  60. return -1;
  61. do {
  62. rv = bind(s, (struct sockaddr *)&local, sizeof local);
  63. local.sin_port = htons(ntohs(local.sin_port) + 1);
  64. } while(rv < 0 && errno == EADDRINUSE);
  65. if (rv < 0) {
  66. close(s);
  67. return -1;
  68. }
  69. do {
  70. rv = connect(s, (struct sockaddr *)&remote, sizeof remote);
  71. remote.sin_port = htons(ntohs(remote.sin_port) + 1);
  72. } while(rv < 0 && errno == EADDRINUSE);
  73. if (rv < 0) {
  74. close(s);
  75. return -1;
  76. }
  77. namelen = sizeof local;
  78. rv = getsockname(s, (struct sockaddr *)&local, &namelen);
  79. close(s);
  80. if (rv < 0)
  81. return -1;
  82. memcpy(iface, &local.sin_addr, sizeof local.sin_addr);
  83. return 0;
  84. }