271 lines
7.9 KiB
C
271 lines
7.9 KiB
C
/*
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* Copyright (c) 2017, Peter Haag
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* Copyright (c) 2014, Peter Haag
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* Copyright (c) 2013, Peter Haag
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* * Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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* * Neither the name of the author nor the names of its contributors may be
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* used to endorse or promote products derived from this software without
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* specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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*/
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#include "config.h"
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#ifdef HAVE_FEATURES_H
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#include <features.h>
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#endif
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#include <stdio.h>
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#include <stdlib.h>
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#include <stdarg.h>
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#include <string.h>
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#include <errno.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include <netinet/in.h>
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#ifdef HAVE_ARPA_NAMESER_H
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#include <arpa/nameser.h>
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#endif
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#ifdef HAVE_ARPA_NAMESER_COMPAT_H
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#include <arpa/nameser_compat.h>
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#endif
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#include <resolv.h>
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#include <pthread.h>
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#ifdef HAVE_STDINT_H
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#include <stdint.h>
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#endif
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <netinet/in_systm.h>
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#include <netinet/ip.h>
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#include <netinet/ip6.h>
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#include <netinet/tcp.h>
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#include <netinet/udp.h>
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#include <netinet/ip_icmp.h>
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#include <netinet/icmp6.h>
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#include <arpa/inet.h>
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#include <pcap.h>
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#include "util.h"
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#include "nffile.h"
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#include "bookkeeper.h"
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#include "collector.h"
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#include "flowtree.h"
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#include "content_dns.h"
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#ifndef DEVEL
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# define dbg_printf(...) /* printf(__VA_ARGS__) */
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#else
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# define dbg_printf(...) printf(__VA_ARGS__)
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#endif
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#include "inline.c"
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/*
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* Structure for query header. The order of the fields is machine- and
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* compiler-dependent, depending on the byte/bit order and the layout
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* of bit fields. We use bit fields only in int variables, as this
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* is all ANSI requires. This requires a somewhat confusing rearrangement.
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*/
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typedef struct dns_header_s {
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unsigned id :16; /* query identification number */
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#ifdef WORDS_BIGENDIAN
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/* fields in third byte */
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unsigned qr: 1; /* response flag */
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unsigned opcode: 4; /* purpose of message */
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unsigned aa: 1; /* authoritive answer */
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unsigned tc: 1; /* truncated message */
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unsigned rd: 1; /* recursion desired */
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/* fields in fourth byte */
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unsigned ra: 1; /* recursion available */
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unsigned unused :3; /* unused bits (MBZ as of 4.9.3a3) */
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unsigned rcode :4; /* response code */
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#else
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/* fields in third byte */
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unsigned rd :1; /* recursion desired */
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unsigned tc :1; /* truncated message */
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unsigned aa :1; /* authoritive answer */
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unsigned opcode :4; /* purpose of message */
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unsigned qr :1; /* response flag */
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/* fields in fourth byte */
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unsigned rcode :4; /* response code */
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unsigned unused :3; /* unused bits (MBZ as of 4.9.3a3) */
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unsigned ra :1; /* recursion available */
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#endif
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/* remaining bytes */
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unsigned qdcount :16; /* number of question entries */
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unsigned ancount :16; /* number of answer entries */
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unsigned nscount :16; /* number of authority entries */
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unsigned arcount :16; /* number of resource entries */
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} dns_header_t;
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#define DNS_QUERY_TYPE_A (1)
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#define DNS_QUERY_TYPE_AAAA (2)
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#define DNS_QUERY_TYPE_SRV (3)
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typedef struct dns_host_st {
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struct dns_host_st *next;
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unsigned int type;
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unsigned int class;
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unsigned int ttl;
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void *rr;
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} dns_host_t;
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typedef struct dns_srv_st {
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unsigned int priority;
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unsigned int weight;
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unsigned int port;
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unsigned int rweight;
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char name[256];
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} dns_srv_t;
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static void *_a_rr(void **p) {
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struct in_addr in;
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in.s_addr = ntohl(Get_val32(*p)); *p += 4;
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return strdup(inet_ntoa(in));
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}
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static void *_aaaa_rr(void **p) {
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char addr[INET6_ADDRSTRLEN];
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uint64_t sa6[2];
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memcpy((void *)sa6, *p, 16);
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inet_ntop(AF_INET6, (struct sockaddr_storage *)&sa6, addr, sizeof(addr));
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return strdup(addr);
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}
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void content_decode_dns(struct FlowNode *node, uint8_t *payload, uint32_t payload_size) {
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dns_header_t *dns_header = (dns_header_t *)payload;
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uint32_t qdcount, ancount;
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void *p, *eod;
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#define DN_LENGTH 256
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char dn[DN_LENGTH];
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int i;
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if ( payload_size < sizeof(dns_header_t) ) {
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LogError("Unable to decode short DNS packet");
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return;
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}
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// no of query packets
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qdcount = ntohs(dns_header->qdcount);
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dbg_printf("DNS Queries: %u\n", qdcount);
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// no of answer packets
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ancount = ntohs(dns_header->ancount);
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dbg_printf("DNS Answers: %u\n", ancount);
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// end of dns packet
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eod = (void *)(payload + payload_size);
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// reord pointer
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p = (void *)(payload + sizeof(dns_header_t));
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for (i=0; i<qdcount && p < eod; i++ ) {
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int32_t len = dn_expand(payload, eod, p, dn, DN_LENGTH);
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if (len < 0) {
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LogError("dn_expand() failed: %s", "");
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}
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dbg_printf("DNS Query dn_expand: %s\n", dn);
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p = (void *) (p + len + 4); // + 4 bytes of fixed data in query
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}
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for (i=0; i<ancount && p < eod; i++ ) {
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uint32_t type, class, ttl;
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int32_t len = dn_expand(payload, eod, p, dn, DN_LENGTH);
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// keep compiler happy
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UNUSED(class);
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UNUSED(ttl);
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if(len < 0) {
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LogError("dn_expand() failed: %s", "");
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}
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dbg_printf("DNS Answer %i dn_expand: %s ", i, dn);
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p += len;
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/* extract the various parts of the record */
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type = Get_val16(p); p += 2;
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class = Get_val16(p); p += 2;
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ttl = Get_val32(p); p += 4;
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len = Get_val16(p); p += 2;
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dbg_printf(" Type: %u, class: %u, ttl: %u, len: %u ", type, class, ttl, len);
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/* type-specific processing */
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switch(type) {
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char *s;
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#ifdef T_A
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case T_A:
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#else
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case ns_t_a:
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#endif
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s = _a_rr(&p);
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dbg_printf("A: %s\n", s);
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free(s);
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break;
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#ifdef T_A6
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case T_A6:
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#endif
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#ifdef T_AAAA
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case T_AAAA:
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#else
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case ns_t_a6:
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case ns_t_aaaa:
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#endif
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s = _aaaa_rr(&p);
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dbg_printf("AAAA: %s\n", s);
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free(s);
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break;
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#ifdef T_CNAME
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case T_CNAME: {
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#else
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case ns_t_cname: {
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#endif
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int32_t len = dn_expand(payload, eod, p, dn, DN_LENGTH);
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dbg_printf("CNAME: %s\n", dn);
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p = (void *)(p + len);
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} break;
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default:
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dbg_printf("<unkn>\n");
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p = (void *)(p + len);
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continue;
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}
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}
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} // End of content_decode_dns
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