date and time created 85/03/01 10:42:09 by ralph

[unix-history] / usr / src / lib / libc / net / res_comp.c

#ifndef lint
static char sccsid[] = "@(#)res_comp.c  4.1 (Berkeley) %G%";
#endif

#include <sys/types.h>
#include <stdio.h>
#include <ctype.h>
#include <nameser.h>


/*
* Expand compressed domain name format to full domain name.
* Return size of compressed name or -1 if there was an error.
*/
dn_expand(msg, comp_dn, exp_dn, length)
       char *msg, *comp_dn, *exp_dn;
       int length;
{
       register char *cp, *dn;
       register int n, c;
       char *eom;
       int len = 0;

       dn = exp_dn;
       cp = comp_dn;
       eom = exp_dn + length - 1;
       /*
        * fetch next label in domain name
        */
       while (n = *cp++) {
               /*
                * Check for indirection
                */
               switch (n & INDIR_MASK) {
               case 0:
                       if (dn != exp_dn)
                               *dn++ = '.';
                       if (dn+n >= eom)
                               return (-1);
                       while (--n >= 0)
                               if (islower(c = *cp++))
                                       *dn++ = toupper(c);
                               else
                                       *dn++ = c;
                       break;

               case INDIR_MASK:
                       if (len == 0)
                               len = cp - comp_dn + 1;
                       cp = msg + (((n & 0x3f) << 8) | (*cp & 0xff));
                       break;

               default:
                       return (-1);                    /* flag error */
               }
       }
       *dn = '\0';
       if (len == 0)
               len = cp - comp_dn;
       return (len);
}

/*
* Compress domain name. Return the size of the compressed name or -1.
* Dnptrs is a list of pointers to previous compressed names. dnptrs[0]
* is a pointer to the beginning of the message. The list ends with NULL.
*/
dn_comp(exp_dn, comp_dn, length, dnptrs, lastdnptr)
       char *exp_dn, *comp_dn;
       int length;
       char **dnptrs, **lastdnptr;
{
       register char *cp, *dn;
       register int c, l;
       char **cpp, **lpp, *sp, *eob;
       char *msg;

       dn = exp_dn;
       cp = comp_dn;
       eob = comp_dn + length;
       if (dnptrs != NULL) {
               if ((msg = *dnptrs++) != NULL) {
                       for (cpp = dnptrs; *cpp != NULL; cpp++)
                               ;
                       lpp = cpp;      /* end of list to search */
               }
       } else
               msg = NULL;
       for (c = *dn++; c != '\0'; ) {
               /* look to see if we can use pointers */
               if (msg != NULL) {
                       if ((l = dn_find(dn-1, msg, dnptrs, lpp)) >= 0) {
                               if (cp+1 >= eob)
                                       return (-1);
                               *cp++ = (l >> 8) | INDIR_MASK;
                               *cp++ = l;
                               return (cp - comp_dn);
                       }
                       /* not found, save it */
                       if (lastdnptr != NULL && cpp < lastdnptr-1) {
                               *cpp++ = cp;
                               *cpp = NULL;
                       }
               }
               sp = cp++;      /* save ptr to length byte */
               do {
                       if (c == '.') {
                               c = *dn++;
                               break;
                       }
                       if (cp >= eob)
                               return (-1);
                       *cp++ = c;
               } while ((c = *dn++) != '\0');
               if ((l = cp - sp - 1) <= 0 || l > MAXLABEL)
                       return (-1);
               *sp = l;
       }
       if (cp >= eob)
               return (-1);
       *cp++ = '\0';
       return (cp - comp_dn);
}

/*
* Skip over a compressed domain name. Return the size.
*/
dn_skip(buf)
       char *buf;
{
       register char *cp;
       register int n;

       cp = buf;
       while (n = *cp++) {
               /*
                * check for indirection
                */
               switch (n & INDIR_MASK) {
               case 0:         /* normal case, n == len */
                       cp += n;
                       continue;
               default:        /* illegal type */
                       return (-1);
               case INDIR_MASK:        /* indirection */
                       cp++;
               }
               break;
       }
       return (cp - buf);
}

/*
* Search for expanded name from a list of previously compressed names.
* Return the offset from msg if found or -1.
*/
dn_find(exp_dn, msg, dnptrs, lastdnptr)
       char *exp_dn, *msg;
       char **dnptrs, **lastdnptr;
{
       register char *dn, *cp, **cpp;
       register int n;
       char *sp;

       for (cpp = dnptrs; cpp < lastdnptr; cpp++) {
               dn = exp_dn;
               sp = cp = *cpp;
               while (n = *cp++) {
                       /*
                        * check for indirection
                        */
                       switch (n & INDIR_MASK) {
                       case 0:         /* normal case, n == len */
                               while (--n >= 0)
                                       if (*dn++ != *cp++)
                                               goto next;
                               if ((n = *dn++) == '\0' && *cp == '\0')
                                       return (sp - msg);
                               if (n == '.')
                                       continue;
                               goto next;

                       default:        /* illegal type */
                               return (-1);

                       case INDIR_MASK:        /* indirection */
                               cp = msg + (((n & 0x3f) << 8) | (*cp & 0xff));
                       }
               }
               if (*dn == '\0')
                       return (sp - msg);
       next:   ;
       }
       return (-1);
}