[398] | 1 | #include <string.h>
|
---|
| 2 | #include <resolv.h>
|
---|
| 3 | #include "libc.h"
|
---|
| 4 |
|
---|
| 5 | /* RFC 1035 message compression */
|
---|
| 6 |
|
---|
| 7 | /* label start offsets of a compressed domain name s */
|
---|
| 8 | static int getoffs(short *offs, const unsigned char *base, const unsigned char *s)
|
---|
| 9 | {
|
---|
| 10 | int i=0;
|
---|
| 11 | for (;;) {
|
---|
| 12 | while (*s & 0xc0) {
|
---|
| 13 | if ((*s & 0xc0) != 0xc0) return 0;
|
---|
| 14 | s = base + ((s[0]&0x3f)<<8 | s[1]);
|
---|
| 15 | }
|
---|
| 16 | if (!*s) return i;
|
---|
| 17 | if (s-base >= 0x4000) return 0;
|
---|
| 18 | offs[i++] = s-base;
|
---|
| 19 | s += *s + 1;
|
---|
| 20 | }
|
---|
| 21 | }
|
---|
| 22 |
|
---|
| 23 | /* label lengths of an ascii domain name s */
|
---|
| 24 | static int getlens(unsigned char *lens, const char *s, int l)
|
---|
| 25 | {
|
---|
| 26 | int i=0,j=0,k=0;
|
---|
| 27 | for (;;) {
|
---|
| 28 | for (; j<l && s[j]!='.'; j++);
|
---|
| 29 | if (j-k-1u > 62) return 0;
|
---|
| 30 | lens[i++] = j-k;
|
---|
| 31 | if (j==l) return i;
|
---|
| 32 | k = ++j;
|
---|
| 33 | }
|
---|
| 34 | }
|
---|
| 35 |
|
---|
| 36 | /* longest suffix match of an ascii domain with a compressed domain name dn */
|
---|
| 37 | static int match(int *offset, const unsigned char *base, const unsigned char *dn,
|
---|
| 38 | const char *end, const unsigned char *lens, int nlen)
|
---|
| 39 | {
|
---|
| 40 | int l, o, m=0;
|
---|
| 41 | short offs[128];
|
---|
| 42 | int noff = getoffs(offs, base, dn);
|
---|
| 43 | if (!noff) return 0;
|
---|
| 44 | for (;;) {
|
---|
| 45 | l = lens[--nlen];
|
---|
| 46 | o = offs[--noff];
|
---|
| 47 | end -= l;
|
---|
| 48 | if (l != base[o] || memcmp(base+o+1, end, l))
|
---|
| 49 | return m;
|
---|
| 50 | *offset = o;
|
---|
| 51 | m += l;
|
---|
| 52 | if (nlen) m++;
|
---|
| 53 | if (!nlen || !noff) return m;
|
---|
| 54 | end--;
|
---|
| 55 | }
|
---|
| 56 | }
|
---|
| 57 |
|
---|
| 58 | int __dn_comp(const char *src, unsigned char *dst, int space, unsigned char **dnptrs, unsigned char **lastdnptr)
|
---|
| 59 | {
|
---|
| 60 | int i, j, n, m=0, offset, bestlen=0, bestoff;
|
---|
| 61 | unsigned char lens[127];
|
---|
| 62 | unsigned char **p;
|
---|
| 63 | const char *end;
|
---|
| 64 | size_t l = strnlen(src, 255);
|
---|
| 65 | if (l && src[l-1] == '.') l--;
|
---|
| 66 | if (l>253 || space<=0) return -1;
|
---|
| 67 | if (!l) {
|
---|
| 68 | *dst = 0;
|
---|
| 69 | return 1;
|
---|
| 70 | }
|
---|
| 71 | end = src+l;
|
---|
| 72 | n = getlens(lens, src, l);
|
---|
| 73 | if (!n) return -1;
|
---|
| 74 |
|
---|
| 75 | p = dnptrs;
|
---|
| 76 | if (p && *p) for (p++; *p; p++) {
|
---|
| 77 | m = match(&offset, *dnptrs, *p, end, lens, n);
|
---|
| 78 | if (m > bestlen) {
|
---|
| 79 | bestlen = m;
|
---|
| 80 | bestoff = offset;
|
---|
| 81 | if (m == l)
|
---|
| 82 | break;
|
---|
| 83 | }
|
---|
| 84 | }
|
---|
| 85 |
|
---|
| 86 | /* encode unmatched part */
|
---|
| 87 | if (space < l-bestlen+2+(bestlen-1 < l-1)) return -1;
|
---|
| 88 | memcpy(dst+1, src, l-bestlen);
|
---|
| 89 | for (i=j=0; i<l-bestlen; i+=lens[j++]+1)
|
---|
| 90 | dst[i] = lens[j];
|
---|
| 91 |
|
---|
| 92 | /* add tail */
|
---|
| 93 | if (bestlen) {
|
---|
| 94 | dst[i++] = 0xc0 | bestoff>>8;
|
---|
| 95 | dst[i++] = bestoff;
|
---|
| 96 | } else
|
---|
| 97 | dst[i++] = 0;
|
---|
| 98 |
|
---|
| 99 | /* save dst pointer */
|
---|
| 100 | if (i>2 && lastdnptr && dnptrs && *dnptrs) {
|
---|
| 101 | while (*p) p++;
|
---|
| 102 | if (p+1 < lastdnptr) {
|
---|
| 103 | *p++ = dst;
|
---|
| 104 | *p=0;
|
---|
| 105 | }
|
---|
| 106 | }
|
---|
| 107 | return i;
|
---|
| 108 | }
|
---|
| 109 |
|
---|
| 110 | weak_alias(__dn_comp, dn_comp);
|
---|