Update code

dns.c

@@ -51,6 +51,100 @@ unsigned int dns_read_int(unsigned char **buffer)
     return ntohs(value);
 }
 
+struct dns_rrs *dns_rr_get_start(struct dns_packet *packet, int type, int *count)
+{
+    unsigned short start;
+    struct dns_head *head = &packet->head;
+
+    switch (type) {
+    case DNS_RR_QD:
+        *count = head->qdcount;
+        start = packet->questions;
+        break;
+    case DNS_RR_AN:
+        *count = head->ancount;
+        start = packet->answers;
+        break;
+    case DNS_RR_NS:
+        *count = head->nscount;
+        start = packet->nameservers;
+        break;
+    case DNS_RR_NR:
+        *count = head->nrcount;
+        start = packet->additional;
+        break;
+    default:
+        return NULL;
+        break;
+    }
+
+    return (struct dns_rrs *)(packet->data + start);
+}
+
+struct dns_rrs *dns_rr_get_next(struct dns_packet *packet, struct dns_rrs *rrs)
+{
+    if (rrs->next == 0) {
+        return NULL;
+    }
+
+    return (struct dns_rrs *)(packet->data + rrs->next);
+}
+
+unsigned char *dns_rr_add_start(struct dns_packet *packet, int *maxlen)
+{
+    struct dns_rrs *rrs;
+    unsigned char *end = packet->data + packet->len;
+    rrs = (struct dns_rrs *)end;
+    *maxlen = packet->size - packet->len - sizeof(*packet);
+    if (packet->len >= packet->size - sizeof(*packet)) {
+        return NULL;
+    }
+    return rrs->data;
+}
+
+int dns_rr_add_end(struct dns_packet *packet, int type, int len)
+{
+    struct dns_rrs *rrs;
+    struct dns_head *head = &packet->head;
+    unsigned char *end = packet->data + packet->len;
+    rrs = (struct dns_rrs *)end;
+    unsigned short *count;
+    unsigned short *start;
+
+    if (packet->len + len > packet->size - sizeof(*packet)) {
+        return -1;
+    }
+
+    switch (type) {
+    case DNS_RR_QD:
+        count = &head->qdcount;
+        start = &packet->questions;
+        break;
+    case DNS_RR_AN:
+        count = &head->ancount;
+        start = &packet->answers;
+        break;
+    case DNS_RR_NS:
+        count = &head->nscount;
+        start = &packet->nameservers;
+        break;
+    case DNS_RR_NR:
+        count = &head->nrcount;
+        start = &packet->additional;
+        break;
+    default:
+        return -1;
+        break;
+    }
+
+    *count += 1;
+    rrs->next = *start;
+    rrs->len = len;
+    *start = packet->len;
+    packet->len += len;
+    return 0;
+}
+
 int dns_decode_head(struct dns_head *head, unsigned char **data)
 {
     unsigned int fields;
@@ -91,7 +185,7 @@ int dns_encode_head(unsigned char **data, struct dns_head *head)
     return 0;
 }
 
-int dns_get_domain(char *output, int size, unsigned char *data)
+int dns_decode_domain(char *output, int size, unsigned char *data)
 {
     int i = 0;
     int output_len = 0;
@@ -155,7 +249,7 @@ int dns_encode_domain(unsigned char *output, int size, char *domain)
 int dns_decode_qd(unsigned char *data, int size, char *domain, int domain_size, int *qtype, int *qclass)
 {
     int len = 0;
-	len = dns_get_domain(domain, domain_size, data);
+    len = dns_decode_domain(domain, domain_size, data);
     data += len;
     *qtype = dns_read_short(&data);
     *qclass = dns_read_short(&data);
@@ -163,6 +257,94 @@ int dns_decode_qd(unsigned char *data, int size, char *domain, int domain_size,
     return len;
 }
 
+int dns_add_domain(struct dns_packet *packet, char *domain, int qtype, int qclass)
+{
+    int maxlen = 0;
+    int i;
+    int len = 0;
+    unsigned char *data = dns_rr_add_start(packet, &maxlen);
+    unsigned char *data_ptr = data;
+    if (data == NULL) {
+        return -1;
+    }
+
+    for (i = 0; i < maxlen - 4; i++) {
+        *data = *domain;
+        if (*domain == '\0') {
+            data++;
+            i++;
+            break;
+        }
+        data++;
+        domain++;
+    }
+    len += i;
+    *((unsigned short *)(data)) = qtype;
+    data += 2;
+    len += 2;
+
+    *((unsigned short *)(data)) = qclass;
+    data += 2;
+    len += 2;
+
+    return dns_rr_add_end(packet, DNS_RR_QD, len);
+}
+
+int dns_add_A(struct dns_packet *packet, char *domain, int qtype, int qclass)
+{
+    int maxlen = 0;
+    int i;
+    int len = 0;
+    unsigned char *data = dns_rr_add_start(packet, &maxlen);
+    unsigned char *data_ptr = data;
+    if (data == NULL) {
+        return -1;
+    }
+
+
+    return dns_rr_add_end(packet, DNS_RR_AN, len);
+}
+
+int dns_add_AAAA(struct dns_packet *packet, char *domain, int qtype, int qclass)
+{
+    int maxlen = 0;
+    int i;
+    int len = 0;
+    unsigned char *data = dns_rr_add_start(packet, &maxlen);
+    unsigned char *data_ptr = data;
+    if (data == NULL) {
+        return -1;
+    }
+
+
+    return dns_rr_add_end(packet, DNS_RR_AN, len);
+}
+
+int dns_get_domain(struct dns_rrs *rrs, char *domain, int maxsize, int *qtype, int *qclass)
+{
+    int i = 0;
+    unsigned char *data = rrs->data;
+    for (i = 0; i < maxsize; i++) {
+        *domain = *data;
+        if (*data == '\0') {
+            domain++;
+            data++;
+            break;
+        }
+        *domain = *data;
+        domain++;
+        data++;
+    }
+
+    *qtype = *((unsigned short *)(data));
+    data += 2;
+
+    *qclass = *((unsigned short *)(data));
+    data += 2;
+
+    return 0;
+}
+
 int dns_decode_body(struct dns_packet *packet, unsigned char *data, int size)
 {
     struct dns_head *head = &packet->head;
@@ -179,7 +361,10 @@ int dns_decode_body(struct dns_packet *packet, unsigned char *data, int size)
 
     for (i = 0; i < head->qdcount; i++) {
         len = dns_decode_qd(data, size - decode_len, name, DNS_MAX_CNAME_LEN, &qtype, &qclass);
-		printf("QR: %d, domain: %s, qtype = %d, qclass = %d\n", head->qr, name, qtype, qclass);
+        if (dns_add_domain(packet, name, qtype, qclass) != 0) {
+            return -1;
+        }
+        head->qdcount--;
         decode_len += len;
         data += len;
     }
@@ -195,9 +380,32 @@ int dns_decode(struct dns_packet *packet, unsigned char *data, int size)
 
     decode_len = dns_decode_head(head, &data);
     ret = dns_decode_body(packet, data, size - decode_len);
+
+    struct dns_rrs *rrs;
+    int count = 0;
+    int i = 0;
+
+    rrs = dns_rr_get_start(packet, DNS_RR_QD, &count);
+    for (i = 0; i < count && rrs; i++, rrs = dns_rr_get_next(packet, rrs)) {
+        char name[128];
+        int qclass = 0;
+        int qtype = 0;
+
+        dns_get_domain(rrs, name, 128, &qtype, &qclass);
+
+        printf("QR: %d, domain: %s, qtype = %d, qclass = %d\n", head->qr, name, qtype, qclass);
+    }
+
     return ret;
 }
 
+int dns_packet_init(struct dns_packet *packet, int size)
+{
+    memset(packet, 0, size);
+    packet->size = size;
+
+    return 0;
+}
 
 int dns_encode(unsigned char *data, int size, struct dns_packet *packet)
 {
@@ -209,7 +417,7 @@ int dns_encode(unsigned char *data, int size, struct dns_packet *packet)
     while (1) {
         len = dns_encode_domain(data, size, "www.baidu.com");
         data += len;
-		dns_write_short(&data, /*qType*/12);
+        dns_write_short(&data, /*qType*/ 12);
         dns_write_short(&data, /*qClass*/ 1);
     }
 

dns.h

@@ -79,14 +79,6 @@ struct dns_qds {
 	unsigned short classes;
 };
 
-struct dns_rrs {
-	unsigned short type;
-	unsigned short classes;
-	unsigned int ttl;
-	unsigned short rd_length;
-	char rd_data[0];
-};
-
 typedef uint32_t TTL;
 
 typedef struct dns_question_t /* RFC-1035 */
@@ -148,12 +140,26 @@ typedef union dns_answer_t {
 	dns_aaaa_t aaaa;
 } dns_answer_t;
 
+#define DNS_RR_QD 0
+#define DNS_RR_AN 1
+#define DNS_RR_NS 2
+#define DNS_RR_NR 3
+
+struct dns_rrs {
+	unsigned short next;
+	unsigned short len;
+	unsigned char data[0];
+};
+
 struct dns_packet {
 	struct dns_head head;
-	dns_question_t *questions;
+	unsigned short questions;
-	dns_answer_t *answers;
+	unsigned short answers;
-	dns_answer_t *nameservers;
+	unsigned short nameservers;
-	dns_answer_t *additional;
+	unsigned short additional;
+	int size;
+	int len;
+	unsigned char data[0];
 };
 
 int dns_decode(struct dns_packet *packet, unsigned char *data, int size);

dns_server.c

@@ -63,6 +63,7 @@ static int _dns_server_process(struct timeval *now)
         goto errout;
     }
 
+    dns_packet_init(packet, sizeof(rsppacket));
 	dns_decode(packet, inpacket, len);
 
 	printf("head.id = %d\n", packet->head.id);