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/*
DNS should have used LZ77 instead of its own sophomoric compression algorithm.
*/
#include <errno.h>
#include "dns.h"
#include "error.h"
unsigned int dns_packet_copy(const char *buf,unsigned int len,unsigned int pos,char *out,unsigned int outlen)
{
while (outlen) {
if (pos >= len) { errno = error_proto; return 0; }
*out = buf[pos++];
++out; --outlen;
}
return pos;
}
unsigned int dns_packet_skipname(const char *buf,unsigned int len,unsigned int pos)
{
unsigned char ch;
for (;;) {
if (pos >= len) break;
ch = buf[pos++];
if (ch >= 192) return pos + 1;
if (ch >= 64) break;
if (!ch) return pos;
pos += ch;
}
errno = error_proto;
return 0;
}
unsigned int dns_packet_getname(const char *buf,unsigned int len,unsigned int pos,char **d)
{
unsigned int loop = 0;
unsigned int state = 0;
unsigned int firstcompress = 0;
unsigned int where;
unsigned char ch;
char name[255];
unsigned int namelen = 0;
for (;;) {
if (pos >= len) goto PROTO; ch = buf[pos++];
if (++loop >= 1000) goto PROTO;
if (state) {
if (namelen + 1 > sizeof name) goto PROTO; name[namelen++] = ch;
--state;
}
else {
while (ch >= 192) {
where = ch; where -= 192; where <<= 8;
if (pos >= len) goto PROTO; ch = buf[pos++];
if (!firstcompress) firstcompress = pos;
pos = where + ch;
if (pos >= len) goto PROTO; ch = buf[pos++];
if (++loop >= 1000) goto PROTO;
}
if (ch >= 64) goto PROTO;
if (namelen + 1 > sizeof name) goto PROTO; name[namelen++] = ch;
if (!ch) break;
state = ch;
}
}
if (!dns_domain_copy(d,name)) return 0;
if (firstcompress) return firstcompress;
return pos;
PROTO:
errno = error_proto;
return 0;
}
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