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#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include "dns.h"
flxDnsPacket* flx_dns_packet_new(void) {
flxDnsPacket *p;
p = g_new(flxDnsPacket, 1);
p->size = p->rindex = 2*6;
memset(p->data, 0, p->size);
return p;
}
void flx_dns_packet_free(flxDnsPacket *p) {
g_assert(p);
g_free(p);
}
void flx_dns_packet_set_field(flxDnsPacket *p, guint index, guint16 v) {
g_assert(p);
g_assert(index < 2*6);
((guint16*) p->data)[index] = g_htons(v);
}
guint16 flx_dns_packet_get_field(flxDnsPacket *p, guint index) {
g_assert(p);
g_assert(index < 2*6);
return g_ntohs(((guint16*) p->data)[index]);
}
guint8* flx_dns_packet_append_name(flxDnsPacket *p, const gchar *name) {
guint8 *d, *f = NULL;
g_assert(p);
g_assert(name);
for (;;) {
guint n = strcspn(name, ".");
if (!n || n > 63)
return NULL;
d = flx_dns_packet_extend(p, n+1);
if (!f)
f = d;
d[0] = n;
memcpy(d+1, name, n);
name += n;
/* no trailing dot */
if (!*name)
break;
name ++;
/* trailing dot */
if (!*name)
break;
}
d = flx_dns_packet_extend(p, 1);
d[0] = 0;
return f;
}
guint8* flx_dns_packet_append_uint16(flxDnsPacket *p, guint16 v) {
guint8 *d;
g_assert(p);
d = flx_dns_packet_extend(p, sizeof(guint16));
*((guint16*) d) = g_htons(v);
return d;
}
guint8 *flx_dns_packet_extend(flxDnsPacket *p, guint l) {
guint8 *d;
g_assert(p);
g_assert(p->size+l <= sizeof(p->data));
d = p->data + p->size;
p->size += l;
return d;
}
guint8 *flx_dns_packet_append_name_compressed(flxDnsPacket *p, const gchar *name, guint8 *prev) {
guint16 *d;
signed long k;
g_assert(p);
if (!prev)
return flx_dns_packet_append_name(p, name);
k = prev - p->data;
if (k < 0 || k >= 0x4000 || (guint) k >= p->size)
return flx_dns_packet_append_name(p, name);
d = (guint16*) flx_dns_packet_extend(p, sizeof(guint16));
*d = g_htons((0xC000 | k));
return prev;
}
gint flx_dns_packet_check_valid(flxDnsPacket *p) {
guint16 flags;
g_assert(p);
if (p->size < 12)
return -1;
flags = flx_dns_packet_get_field(p, DNS_FIELD_FLAGS);
if (flags & DNS_FLAG_OPCODE || flags & DNS_FLAG_RCODE)
return -1;
return 0;
}
gint flx_dns_packet_check_valid_response(flxDnsPacket *p) {
guint16 flags;
g_assert(p);
if (flx_dns_packet_check_valid(p) < 0)
return -1;
flags = flx_dns_packet_get_field(p, DNS_FIELD_FLAGS);
if (!(flags & DNS_FLAG_QR))
return -1;
if (flx_dns_packet_get_field(p, DNS_FIELD_QDCOUNT) > 0)
return -1;
return 0;
}
static gint consume_labels(flxDnsPacket *p, guint index, gchar *ret_name, guint l) {
gint ret = 0;
int compressed = 0;
int first_label = 1;
g_assert(p && ret_name && l);
for (;;) {
guint8 n;
if (index+1 > p->size)
return -1;
n = p->data[index];
if (!n) {
index++;
if (!compressed)
ret++;
if (l < 1)
return -1;
*ret_name = 0;
return ret;
} else if (n <= 63) {
/* Uncompressed label */
index++;
if (!compressed)
ret++;
if (index + n > p->size)
return -1;
if ((guint) n + 1 > l)
return -1;
if (!first_label) {
*(ret_name++) = '.';
l--;
} else
first_label = 0;
memcpy(ret_name, p->data + index, n);
index += n;
ret_name += n;
l -= n;
if (!compressed)
ret += n;
} else if ((n & 0xC0) == 0xC0) {
/* Compressed label */
if (index+2 > p->size)
return -1;
index = ((guint) (p->data[index] & ~0xC0)) << 8 | p->data[index+1];
if (!compressed)
ret += 2;
compressed = 1;
} else
return -1;
}
}
gint flx_dns_packet_consume_name(flxDnsPacket *p, gchar *ret_name, guint l) {
gint r;
if ((r = consume_labels(p, p->rindex, ret_name, l)) < 0)
return -1;
p->rindex += r;
return 0;
}
gint flx_dns_packet_consume_uint16(flxDnsPacket *p, guint16 *ret_v) {
g_assert(p);
g_assert(ret_v);
if (p->rindex + sizeof(guint16) > p->size)
return -1;
*ret_v = g_ntohs(*((guint16*) (p->data + p->rindex)));
p->rindex += sizeof(guint16);
return 0;
}
gint flx_dns_packet_consume_uint32(flxDnsPacket *p, guint32 *ret_v) {
g_assert(p);
g_assert(ret_v);
if (p->rindex + sizeof(guint32) > p->size)
return -1;
*ret_v = g_ntohl(*((guint32*) (p->data + p->rindex)));
p->rindex += sizeof(guint32);
return 0;
}
gint flx_dns_packet_consume_bytes(flxDnsPacket *p, gpointer ret_data, guint l) {
g_assert(p);
g_assert(ret_data);
g_assert(l > 0);
if (p->rindex + l > p->size)
return -1;
memcpy(ret_data, p->data + p->rindex, l);
p->rindex += l;
return 0;
}
gint flx_dns_packet_skip(flxDnsPacket *p, guint length) {
g_assert(p);
if (p->rindex + length > p->size)
return -1;
p->rindex += length;
return 0;
}
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