CMakeLists.txt

@@ -1,7 +1,6 @@
 cmake_minimum_required(VERSION 4.0)
 set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
-set(CMAKE_BUILD_TYPE Debug)
 
 project(pupdns VERSION 0.1)
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)

include/dns_packet_buffer.h

@@ -1,14 +1,13 @@
 #pragma once
 #include <stddef.h>
 
-#define PB_SIZE 512
-#define PB_OUT_OF_BOUNDS 9999;
+#define PACKET_BUFFER_SIZE 512
 
 struct DNSPacketBuffer {
-    unsigned char buf[PB_SIZE];
+    char buf[PACKET_BUFFER_SIZE];
     size_t pos;
 };
 
 struct DNSPacketBuffer *new_dns_packet_buffer();
 
-unsigned char pb_read_byte(struct DNSPacketBuffer *);
+struct DNSPacketHeader *dns_header(struct DNSPacketBuffer);

include/dns_packets.h

@@ -1,7 +1,6 @@
 #pragma once
 #include <stddef.h>
 
-#define DNS_HEADER_BYTES 12
 
 struct DNSPacketHeader {
     /*
@@ -9,34 +8,14 @@ struct DNSPacketHeader {
      * a random ID is assigned to query packets.
      * Response packets must contain the same ID as the query.
      */
-    unsigned int packet_id : 16;
-    
-    /*
-     * RD (Recursion Desired)
-     * if set by the client, the server should
-     * attempt to resolve the query recursively
-     * 
-     * the server may not allow recursive resolution.
-     * (see RA / Recursion Available)
-     */
-    unsigned int recursion_desired : 1;
+    size_t packet_id : 16;
 
     /*
-     * TC (Truncated)
-     * if true, this message was truncated.
-     * usually happens when the response payload
-     * is larger than the max UDP packet size
-     *
-     * if set, the query may be re-issued over TCP for the full payload.
+     * QR (Query/Response)
+     * 0 if the packet is a query
+     * 1 if the packet is a response
      */
-    unsigned int is_truncated : 1;
-
-    /*
-     * AA (Authoritative Answer)
-     * 
-     * 1 if the responding server is authoritative for the queried domain
-     */
-    unsigned int is_authoritative : 1;
+    size_t is_response : 1;
 
     /*
      * OPCODE (Operation Code)
@@ -48,14 +27,51 @@ struct DNSPacketHeader {
      *
      * almost always will be 0
      */
-    unsigned int opcode : 4;
+    size_t opcode : 4;
 
     /*
-     * QR (Query/Response)
-     * 0 if the packet is a query
-     * 1 if the packet is a response
+     * AA (Authoritative Answer)
+     * 
+     * 1 if the responding server is authoritative for the queried domain
      */
-    unsigned int is_response : 1;
+    size_t is_authoritative : 1;
+
+    /*
+     * TC (Truncated)
+     * if true, this message was truncated.
+     * usually happens when the response payload
+     * is larger than the max UDP packet size
+     *
+     * if set, the query may be re-issued over TCP for the full payload.
+     */
+    size_t is_truncated : 1;
+
+    /*
+     * RD (Recursion Desired)
+     * if set by the client, the server should
+     * attempt to resolve the query recursively
+     * 
+     * the server may not allow recursive resolution.
+     * (see RA / Recursion Available)
+     */
+    size_t recursion_desired : 1;
+
+
+    /*
+     * RA (Recursion Available)
+     * if set by the server, incicates that the server allows
+     * recursive queries.
+     */
+    size_t recursion_available : 1;   
+
+    /*
+     * Z (Reserved)
+     * in the original spec, this is reserved for future use.
+     *
+     * in later RFCs, it is used for DNSSEC queries.
+     * (to be implemented)
+     */
+    size_t z : 3;
 
     /*
      * RCODE (Response Code)
@@ -70,47 +86,31 @@ struct DNSPacketHeader {
      * 5    - Refused - the nameserver refuses to perform the requested operation. for example, it may refuse a zone transfer.
      * 6-15 - Reserved for future use
      */
-    unsigned int response_code : 4;
-
-    /*
-     * Z (Reserved)
-     * in the original spec, this is reserved for future use.
-     *
-     * in later RFCs, it is used for DNSSEC queries.
-     * (to be implemented)
-     */
-    unsigned int z : 3;
-
-    /*
-     * RA (Recursion Available)
-     * if set by the server, incicates that the server allows
-     * recursive queries.
-     */
-    unsigned int recursion_available : 1;   
+    size_t response_code : 4;
 
     /*
      * QDCOUNT (Question Count)
      * the number of entries in the question section
      */
-    unsigned int question_count : 16;
+    size_t question_count : 16;
 
     /*
      * ANCOUNT (Answer Count)
      * the number of entries in the answer section
      */
-    unsigned int answer_count : 16;
+    size_t answer_count : 16;
 
     /*
      * NSCOUNT (Nameserver Count)
      * the number of entries in the authority records section
      */
-    unsigned int ns_count : 16;
+    size_t ns_count : 16;
 
     /*
      * ARCOUNT (Additional Records Count)
      * the number of entries in the additional records section
      */
-    unsigned int ar_count : 16;
+    size_t ar_count : 16;
 };
 
 
@@ -125,26 +125,26 @@ struct RecordPreamble {
      * TYPE
      * the record type
      */
-    unsigned int type : 16;
+    size_t type : 16;
 
     /*
      * CLASS
      * specifies the class of the data in the RDATA field.
      * in practice, always set to 1
      */
-    unsigned int class : 16;
+    size_t class : 16;
 
     /*
      * TTL (Time-To-Live)
      * how long a record can be cached before it should be requeried.
      */
-    unsigned int ttl : 32;
+    size_t ttl : 32;
 
     /*
      * RDLENGTH (Record Data Length)
      * length of the record-type-specific data.
      */
-    unsigned int rd_data_length: 16;
+    size_t rd_data_length: 16;
 };
 
 /*
@@ -153,5 +153,5 @@ struct RecordPreamble {
  */
 struct ARecord {
     struct RecordPreamble preamble;
-    unsigned int ip : 32;
+    size_t ip : 32;
 };

include/dns_request.h

@@ -1,10 +1,7 @@
 #pragma once
 
 #include "dns_packets.h"
-#include "dns_packet_buffer.h"
 
 struct DNSRequest {
-    struct DNSPacketHeader *header;
+    struct DNSPacketHeader header;
 };
-
-struct DNSRequest *parse_dns_query(struct DNSPacketBuffer *pb);

include/udp_server.h

@@ -1,5 +1,5 @@
 #pragma once
 
-#define UDP_PORT 1053
+#define UDP_PORT 53
 
 int start_server();

src/dns_packet_buffer.c

@@ -1,5 +1,4 @@
 #include "dns_packet_buffer.h"
-#include <stdio.h>
 #include <stdlib.h>
 
 struct DNSPacketBuffer *new_dns_packet_buffer()
@@ -8,3 +7,8 @@ struct DNSPacketBuffer *new_dns_packet_buffer()
     buf = malloc(sizeof(struct DNSPacketBuffer));
     return buf;
 }
+
+struct DNSPacketHeader *dns_header(struct DNSPacketBuffer)
+{
+
+}

src/dns_request.c

@@ -1,36 +1,3 @@
-#include <stdlib.h>
-#include <arpa/inet.h>
-
 #include "dns_request.h"
 
-struct DNSRequest *parse_dns_query(struct DNSPacketBuffer *pb)
-{
-    struct DNSRequest *req;
-    req = malloc(sizeof(struct DNSRequest));
-    req->header = (struct DNSPacketHeader *) pb->buf;
 
-    /*
-     * casting the buffer directly into the packet header struct like this
-     * works okay, but because of the nature of the DNS protocol, it needs
-     * a lot of manual tweaking.
-     *
-     * the struct fields are defined in a weird order (compared to the spec)
-     * because C wants to read each byte from right to left,
-     * but DNS fields go left to right.
-     *
-     * so for each set of fields adding up to 8 bits of data, i reversed the
-     * order of the fields in the struct definition so that the fields end up
-     * with the correct bits off the wire.
-     *
-     * DNS also has multi-bit (but less than a byte) fields such as 
-     * opcode and response code. fortunately we can skip these for now,
-     * since opcode is practically always zero for our purposes,
-     * and response_code only makes sense in the server response.
-     *
-     * but we do need to take care of all the network-order 16-bit fields.
-     */
-    req->header->packet_id = ntohs(req->header->packet_id);
-    req->header->question_count = ntohs(req->header->question_count);
-
-    return req;
-}

src/udp_server.c

@@ -2,10 +2,10 @@
 #include "dns_packet_buffer.h"
 #include "dns_request.h"
 
-#include <stdlib.h>
 #include <stdio.h>
 #include <unistd.h>
 #include <fcntl.h>
+#include <string.h>
 #include <arpa/inet.h>
 #include <sys/socket.h>
 #include <netinet/in.h>
@@ -37,37 +37,20 @@ int start_server()
         return -1;
     }
 
-    while (true) {
-        socklen_t len = 0;
+    socklen_t len = 0;
 
-        int n = recvfrom(sockfd, (char *)pb->buf, sizeof(pb->buf), MSG_WAITALL, 0, &len);
+    int n = recvfrom(sockfd, (char *)pb->buf, sizeof(pb->buf), MSG_WAITALL, 0, &len);
 
-        printf("===== NEW REQUEST =====\n");
-        printf("received %d bytes\n", n);
+    printf("received %d bytes\n", n);
 
-        struct DNSRequest *req = parse_dns_query(pb);
+    struct DNSRequest *req = new_dns_request(pb);
 
-        printf("packet_id: %x\n", req->header->packet_id);
-        printf("is_response: %d\n", req->header->is_response);
-        printf("opcode: %d\n", req->header->opcode);
-        printf("is_authoritative: %d\n", req->header->is_authoritative);
-        printf("is_truncated: %d\n", req->header->is_truncated);
-        printf("recursion_desired: %d\n", req->header->recursion_desired);
-        printf("recursion_available: %d\n", req->header->recursion_available);
-        printf("reserved: %d\n", req->header->z);
-        printf("response_code: %d\n", req->header->response_code);
-        printf("question_count: %d\n", req->header->question_count);
-        printf("answer_count: %d\n", req->header->answer_count);
-        printf("ns_count: %d\n", req->header->ns_count);
-        printf("ar_count: %d\n", req->header->ar_count);
-
-        // for (int i=0; i<n; i++) {
-        //     printf("%d = %02X\n", i, (unsigned char)pb->buf[i]);
-        // }
-
-        free(pb);
-        free(req);
-    }
+    printf("packet_id: %x\n", req->header->packet_id);
+    printf("is_response: %d\n", req->header->is_response);
+    printf("opcode: %d\n", req->header->opcode);
+    printf("is_authoritative: %d\n", req->header->is_authoritative);
+    printf("is_truncated: %d\n", req->header->is_truncated);
+    printf("recursion_desired: %d\n", req->header->recursion_desired);
 
     close(sockfd);
     return 0;