experiment5.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <unistd.h>
   4 #include <string.h>
   5
   6 typedef struct line LINE;
   7
   8 struct line {
   9     unsigned long int mac;
  10     unsigned long int ip;
  11     char *fqdn;
  12     LINE *next;
  13 };
  14
  15 LINE *first = NULL;
  16 LINE *last  = NULL;
  17 LINE *array   = NULL;
  18
  19 int listlen = 0;
  20
  21 /* Removes an entry from our linked list */
  22
  23 static int remove_entry(unsigned long int mac) {
  24     LINE *step = first;
  25     LINE *prev = NULL;
  26     while (step) {
  27         LINE *next = step->next;
  28
  29         if (step->mac == mac) {
  30             if (step->fqdn)
  31                 free(step->fqdn);
  32
  33             if (prev)
  34                 prev->next = next;
  35             free(step);
  36         }
  37
  38         prev = step;
  39         step = next;
  40     }
  41
  42     return 0;
  43 }
  44
  45 /* Adds an entry to the linked list */
  46
  47 static int add_entry(unsigned long int mac, unsigned long int ip, char *fqdn) {
  48     LINE *new = malloc(sizeof(LINE));
  49     new->mac = mac;
  50     new->ip  = ip;
  51     new->fqdn = strdup(fqdn);
  52     new->next = NULL;
  53
  54     if (!first)
  55         first = new;
  56     else
  57         last->next = new;
  58
  59     last = new;
  60
  61     return 0;
  62 }
  63
  64 /* Converts a MA:CA:DD:RE:SS:00 to an unsigned long int */
  65
  66 static unsigned long int macstrtoul(char *mac) {
  67     char macstring[4];
  68     macstring[2] = '\0';
  69     macstring[3] = '\0';
  70
  71     unsigned long int newmac = 0;
  72     strncpy(macstring, &mac[9], 2);
  73     newmac += (strtoul(macstring, NULL, 16) * (unsigned long int)(256 * 256));
  74     strncpy(macstring, &mac[12], 2);
  75     newmac += (strtoul(macstring, NULL, 16) * (unsigned long int)(256));
  76     strncpy(macstring, &mac[15], 2);
  77     newmac += (strtoul(macstring, NULL, 16));
  78
  79     return newmac;
  80 }
  81
  82 /* Parses a line from the file and adds it to the linked list */
  83
  84 static int add_line(char *line) {
  85     if (strncmp(line, "dhcp-host=", 10) == 0 &&
  86                 line[12] == ':' && line[15] == ':' && line[18] == ':' && line[21] == ':' && line[24] == ':' &&
  87                 line[27] == ',') {
  88         char *ip, *nextip;
  89         char macstring[4];
  90         LINE *new = malloc(sizeof(LINE));
  91
  92         if (new == NULL) return -1;
  93
  94         listlen++;
  95         macstring[2] = '\0';
  96         macstring[3] = '\0';
  97
  98         new->mac = 0;
  99         new->ip  = 0;
 100         new->next= NULL;
 101
 102         new->mac = macstrtoul(&line[10]);
 103
 104         ip = strchr(&line[28], ',');
 105         new->fqdn = strndup(&line[28], ip - &line[28]);
 106         ip++;
 107
 108         macstring[1] = '\0'; macstring[2] = '\0';
 109         strncpy(macstring, ip, (nextip = strchr(ip, '.')) - ip);
 110         new->ip += (strtoul(macstring, NULL, 10) * (unsigned long int)(256 * 256 * 256));
 111         ip = nextip + 1;
 112
 113         macstring[1] = '\0'; macstring[2] = '\0';
 114         strncpy(macstring, ip, (nextip = strchr(ip, '.')) - ip);
 115         new->ip += (strtoul(macstring, NULL, 10) * (unsigned long int)(256 * 256));
 116         ip = nextip + 1;
 117
 118         macstring[1] = '\0'; macstring[2] = '\0';
 119         strncpy(macstring, ip, (nextip = strchr(ip, '.')) - ip);
 120         new->ip += (strtoul(macstring, NULL, 10) * (unsigned long int)(256));
 121         ip = nextip + 1;
 122
 123         macstring[1] = '\0'; macstring[2] = '\0';
 124         strncpy(macstring, ip, (nextip = strchr(ip, ',')) - ip);
 125         new->ip += (strtoul(macstring, NULL, 10));
 126
 127         if (!first)
 128             first = new;
 129         else
 130             last->next = new;
 131
 132         last = new;
 133
 134         return 0;
 135     }
 136
 137     return -1;
 138 }
 139
 140 /* Prints out our mac range */
 141
 142 static char * print_mac(unsigned long int mac) {
 143     char *macstring = (char *) malloc(sizeof(char*) * 18);
 144     strcpy(macstring, "00:16:3E:");
 145     snprintf(&macstring[9], 8, "%06lX", mac);
 146     strncpy(&macstring[15], &macstring[13], 2);
 147     macstring[13] = macstring[12];
 148     macstring[12] = macstring[11];
 149     macstring[11] = ':';
 150     macstring[14] = ':';
 151     macstring[17] = '\0';
 152     return macstring;
 153 }
 154
 155 /* And prints out an ip address */
 156
 157 static char * print_ip(unsigned long int ipaddress) {
 158     char *dest = (char *) malloc(sizeof(char*) * 16);
 159     int a, b, c, d;
 160     ldiv_t ip = ldiv(ipaddress, (256*256*256));
 161     a = ip.quot;
 162     ip = ldiv(ip.rem, (256*256));
 163     b = ip.quot;
 164     ip = ldiv(ip.rem, (256));
 165     c = ip.quot;
 166     d = ip.rem;
 167
 168     snprintf(dest, 16, "%d.%d.%d.%d", a, b, c, d);
 169     return dest;
 170 }
 171
 172 /* Print out the dnsmasq format and clean up the linked list */
 173
 174 static int print_forget(char *path) {
 175     FILE *fd = fopen(path, "w+");
 176
 177     if (fd)
 178         flock(fd, LOCK_EX);
 179
 180     LINE *step = first;
 181     while (step) {
 182         LINE *this = step;
 183         char *pretty_mac = print_mac(this->mac);
 184         char *pretty_ip  = print_ip(this->ip);
 185
 186         if (fd)
 187             fprintf(fd, "dhcp-host=%s,%s,%s,24h\n", pretty_mac, this->fqdn, pretty_ip);
 188
 189         free(pretty_mac);
 190         free(pretty_ip);
 191
 192         free(this->fqdn);
 193
 194         step = this->next;
 195         free(this);
 196     }
 197
 198     if (fd) {
 199         flock(fd, LOCK_UN);
 200         fclose(fd);
 201     }
 202
 203     return 0;
 204 }
 205
 206 /* Convert the linked list to a more 'defacto' array format */
 207
 208 static int ll_array() {
 209     int i = 0;
 210     array = malloc(sizeof(LINE) * listlen);
 211
 212     LINE *step = first;
 213     while (step) {
 214         array[i].mac  = step->mac;
 215         array[i].ip  = step->ip;
 216         array[i].fqdn = step->fqdn;
 217         step = step->next;
 218         i++;
 219     }
 220
 221     return 0;
 222 }
 223
 224 /* Compare functions */
 225
 226 static int bymac(const void *a, const void *b) {
 227     LINE *temp1 = (LINE *) a;
 228     LINE *temp2 = (LINE *) b;
 229
 230     return temp1->mac - temp2->mac;
 231 }
 232
 233 static int byip(const void *a, const void *b) {
 234     LINE *temp1 = (LINE *) a;
 235     LINE *temp2 = (LINE *) b;
 236
 237     return temp1->ip - temp2->ip;
 238 }
 239
 240 /* Find the first 'free' mac */
 241
 242 static unsigned long int nextmac() {
 243     int i;
 244     for (i = 0; i < (listlen - 1); i++) {
 245         if (array[i+1].mac != 0 && array[i+1].mac != array[i].mac + 1) return array[i].mac + 1;
 246     }
 247     return array[listlen - 1].mac + 1;
 248 }
 249
 250 /* Find the first 'free' ip */
 251 static unsigned long int nextip() {
 252     int i;
 253     for (i = 0; i < (listlen - 1); i++) {
 254         if (array[i+1].ip != array[i].ip + 1) return array[i].ip + 1;
 255     }
 256     return array[listlen - 1].ip + 1;
 257 }
 258
 259 /* Opens the cabinet config */
 260
 261 static char * loader(char *cabinet) {
 262     FILE *fd;
 263     char *pad = malloc(sizeof(char) * 128);
 264
 265     listlen = 0;
 266     first = NULL;
 267     last  = NULL;
 268     array   = NULL;
 269
 270     if (pad == NULL) return NULL;
 271
 272     snprintf(pad, 128, "/mnt/netapp/ipservices/%s.conf", cabinet);
 273
 274     if ((fd = fopen(pad, "r")) != NULL) {
 275         char line[128];
 276         flock(fd, LOCK_EX);
 277         while (!feof(fd)) {
 278             if (fgets(line, 128, fd) > 0)
 279                 add_line(line);
 280         }
 281         flock(fd, LOCK_UN);
 282         fclose(fd);
 283     }
 284
 285     return pad;
 286 }
 287
 288 /* Exported functions */
 289
 290 int removeOldMac(char *cabinet, char *mac) {
 291     char *pad = loader(cabinet);
 292
 293     if (pad == NULL)
 294         return -1;
 295
 296     unsigned long int old_mac = macstrtoul(mac);
 297     remove_entry(old_mac);
 298     print_forget(pad);
 299     free(pad);
 300 }
 301
 302
 303 int getNewMac(char *cabinet, char *fqdn, char **mac, char **ip) {
 304     unsigned long int new_mac, new_ip;
 305     char *pad = loader(cabinet);
 306
 307     if (pad == NULL)
 308         return -1;
 309
 310     if (listlen == 0) {
 311         new_mac = 0;
 312         new_ip = 0;
 313     } else {
 314         ll_array();
 315
 316         qsort(array, listlen, sizeof(LINE), bymac);
 317         new_mac = nextmac();
 318
 319         qsort(array, listlen, sizeof(LINE), byip);
 320         new_ip = nextip();
 321     }
 322
 323     if (mac)
 324         *mac = print_mac(new_mac);
 325
 326     if (ip)
 327         *ip = print_ip(new_ip);
 328
 329     add_entry(new_mac, new_ip, fqdn);
 330
 331     free(array);
 332
 333     print_forget(pad);
 334
 335     free(pad);
 336
 337     return 0;
 338 }
 339
 340 /* Good for unittesting */
 341
 342 #ifdef WITH_MAIN
 343 int main(int argc, char *argv[]) {
 344     if (argc == 4) {
 345         removeOldMac(argv[1], argv[2]);
 346     } else if (argc == 3) {
 347         getNewMac(argv[1], argv[2], NULL, NULL);
 348     }
 349     return 0;
 350 }
 351 #endif