lib/libminlib/dhcp_settag.c

   1 /*      dhcp_init(), dhcp_settag()                      Author: Kees J. Bot
   2  *                                                              1 Dec 2000
   3  */
   4 #define nil ((void*)0)
   5 #include <stddef.h>
   6 #include <string.h>
   7 #include <sys/types.h>
   8 #include <net/hton.h>
   9 #include <net/gen/in.h>
  10 #include <net/gen/dhcp.h>
  11
  12 #define arraysize(a)    (sizeof(a) / sizeof((a)[0]))
  13 #define arraylimit(a)   ((a) + arraysize(a))
  14
  15 void dhcp_init(dhcp_t *dp)
  16 {
  17     /* Initialize a DHCP packet. */
  18     memset(dp, 0, offsetof(dhcp_t, magic));
  19     dp->magic= DHCP_MAGIC;
  20     memset(dp->options, 255, sizeof(dp->options));
  21 }
  22
  23 int dhcp_settag(dhcp_t *dp, int tag, void *data, size_t len)
  24 {
  25     /* Add a tag to a DHCP packet.  No padding.  Only do the options field.
  26      * (This is Minix, we don't need megabytes of silly bits of data.)
  27      * The length may be zero to delete a tag.
  28      */
  29     u8_t *p;
  30     int n;
  31
  32     if (tag <= 0 || tag >= 255) return 0;
  33
  34     for (p= dp->options; p < arraylimit(dp->options) && *p != 255; p += n) {
  35         n= 1 + 1 + p[1];
  36         if (*p == tag) {
  37             /* The tag is already there, remove it so it gets replaced. */
  38             memmove(p, p + n, arraylimit(dp->options) - (p + n));
  39             memset(arraylimit(dp->options) - n, 255, n);
  40             n= 0;
  41         }
  42     }
  43
  44     /* Add tag. */
  45     if (len == 0) {
  46         /* We're merely deleting a tag. */
  47     } else
  48     if (p + 1 + 1 + len <= arraylimit(dp->options)) {
  49         *p++ = tag;
  50         *p++ = len;
  51         memcpy(p, data, len);
  52     } else {
  53         /* Oops, it didn't fit?  Is this really Minix??? */
  54         return 0;
  55     }
  56     return 1;
  57 }