experiment5.c

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