| #include "libc.h" |
| #include <resolv.h> |
| #include <string.h> |
| |
| /* RFC 1035 message compression */ |
| |
| /* label start offsets of a compressed domain name s */ |
| static int getoffs(short* offs, const unsigned char* base, const unsigned char* s) { |
| int i = 0; |
| for (;;) { |
| while (*s & 0xc0) { |
| if ((*s & 0xc0) != 0xc0) |
| return 0; |
| s = base + ((s[0] & 0x3f) << 8 | s[1]); |
| } |
| if (!*s) |
| return i; |
| if (s - base >= 0x4000) |
| return 0; |
| offs[i++] = s - base; |
| s += *s + 1; |
| } |
| } |
| |
| /* label lengths of an ascii domain name s */ |
| static int getlens(unsigned char* lens, const char* s, int l) { |
| int i = 0, j = 0, k = 0; |
| for (;;) { |
| for (; j < l && s[j] != '.'; j++) |
| ; |
| if (j - k - 1u > 62) |
| return 0; |
| lens[i++] = j - k; |
| if (j == l) |
| return i; |
| k = ++j; |
| } |
| } |
| |
| /* longest suffix match of an ascii domain with a compressed domain name dn */ |
| static int match(int* offset, const unsigned char* base, const unsigned char* dn, const char* end, |
| const unsigned char* lens, int nlen) { |
| int l, o, m = 0; |
| short offs[128]; |
| int noff = getoffs(offs, base, dn); |
| if (!noff) |
| return 0; |
| for (;;) { |
| l = lens[--nlen]; |
| o = offs[--noff]; |
| end -= l; |
| if (l != base[o] || memcmp(base + o + 1, end, l)) |
| return m; |
| *offset = o; |
| m += l; |
| if (nlen) |
| m++; |
| if (!nlen || !noff) |
| return m; |
| end--; |
| } |
| } |
| |
| int __dn_comp(const char* src, unsigned char* dst, int space, unsigned char** dnptrs, |
| unsigned char** lastdnptr) { |
| int i, j, n, m = 0, offset = 0, bestlen = 0, bestoff = 0; |
| unsigned char lens[127]; |
| unsigned char** p; |
| const char* end; |
| size_t l = strnlen(src, 255); |
| if (l && src[l - 1] == '.') |
| l--; |
| if (l > 253 || space <= 0) |
| return -1; |
| if (!l) { |
| *dst = 0; |
| return 1; |
| } |
| end = src + l; |
| n = getlens(lens, src, l); |
| if (!n) |
| return -1; |
| |
| p = dnptrs; |
| if (p && *p) |
| for (p++; *p; p++) { |
| m = match(&offset, *dnptrs, *p, end, lens, n); |
| if (m > bestlen) { |
| bestlen = m; |
| bestoff = offset; |
| if (m == l) |
| break; |
| } |
| } |
| |
| /* encode unmatched part */ |
| if (space < l - bestlen + 2 + (bestlen - 1 < l - 1)) |
| return -1; |
| memcpy(dst + 1, src, l - bestlen); |
| for (i = j = 0; i < l - bestlen; i += lens[j++] + 1) |
| dst[i] = lens[j]; |
| |
| /* add tail */ |
| if (bestlen) { |
| dst[i++] = 0xc0 | bestoff >> 8; |
| dst[i++] = bestoff; |
| } else |
| dst[i++] = 0; |
| |
| /* save dst pointer */ |
| if (i > 2 && lastdnptr && dnptrs && *dnptrs) { |
| while (*p) |
| p++; |
| if (p + 1 < lastdnptr) { |
| *p++ = dst; |
| *p = 0; |
| } |
| } |
| return i; |
| } |
| |
| weak_alias(__dn_comp, dn_comp); |
