external/bsd/ntp/dist/libntp/numtohost.c

   1 /*      $NetBSD$        */
   2
   3 /*
   4  * numtohost - convert network number to host name.
   5  */
   6 #include <config.h>
   7
   8 #include <sys/types.h>
   9 #ifdef HAVE_NETINET_IN_H
  10 #include <netinet/in.h>         /* ntohl */
  11 #endif
  12
  13 #include "ntp_fp.h"
  14 #include "ntp_stdlib.h"
  15 #include "lib_strbuf.h"
  16
  17 #define LOOPBACKNET     0x7f000000
  18 #define LOOPBACKHOST    0x7f000001
  19 #define LOOPBACKNETMASK 0xff000000
  20
  21 char *
  22 numtohost(
  23         u_int32 netnum
  24         )
  25 {
  26         char *bp;
  27         struct hostent *hp;
  28
  29         /*
  30          * This is really gross, but saves lots of hanging looking for
  31          * hostnames for the radio clocks.  Don't bother looking up
  32          * addresses on the loopback network except for the loopback
  33          * host itself.
  34          */
  35         if ((((ntohl(netnum) & LOOPBACKNETMASK) == LOOPBACKNET)
  36              && (ntohl(netnum) != LOOPBACKHOST))
  37             || ((hp = gethostbyaddr((char *)&netnum, sizeof netnum, AF_INET))
  38                 == 0))
  39             return numtoa(netnum);
  40
  41         LIB_GETBUF(bp);
  42
  43         bp[LIB_BUFLENGTH-1] = '\0';
  44         (void) strncpy(bp, hp->h_name, LIB_BUFLENGTH-1);
  45         return bp;
  46 }