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-rw-r--r--src/network/dn_comp.c103
1 files changed, 102 insertions, 1 deletions
diff --git a/src/network/dn_comp.c b/src/network/dn_comp.c
index 4f4452aa..a17d434d 100644
--- a/src/network/dn_comp.c
+++ b/src/network/dn_comp.c
@@ -1,9 +1,110 @@
+#include <string.h>
#include <resolv.h>
#include "libc.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)
{
- return -1;
+ int i, j, n, m=0, offset, bestlen=0, bestoff;
+ 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);