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 */
8static 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 */
24static 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 */
37static 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
58int __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
110weak_alias(__dn_comp, dn_comp);
111