refactor initial code and accept a UDP request

include/dns_packet_buffer.h

@@ -0,0 +1,13 @@
+#pragma once
+#include <stddef.h>
+
+#define PACKET_BUFFER_SIZE 512
+
+struct DNSPacketBuffer {
+    char buf[PACKET_BUFFER_SIZE];
+    size_t pos;
+};
+
+struct DNSPacketBuffer *new_dns_packet_buffer();
+
+struct DNSPacketHeader *dns_header(struct DNSPacketBuffer);

include/dns_packets.h

@@ -2,7 +2,7 @@
 #include <stddef.h>
 
 
-struct Header {
+struct DNSPacketHeader {
     /*
      * ID (Packet Identifier)
      * a random ID is assigned to query packets.

include/dns_request.h

@@ -0,0 +1,7 @@
+#pragma once
+
+#include "dns_packets.h"
+
+struct DNSRequest {
+    struct DNSPacketHeader header;
+};

include/packet_buffer.h

@@ -1,11 +0,0 @@
-#pragma once
-#include <stddef.h>
-
-#define PACKET_BUFFER_SIZE 512
-
-struct PacketBuffer {
-    char buf[PACKET_BUFFER_SIZE];
-    size_t pos;
-};
-
-struct PacketBuffer *new_packet_buffer();

include/udp_server.h

@@ -0,0 +1,5 @@
+#pragma once
+
+#define UDP_PORT 53
+
+int start_server();

src/dns_packet_buffer.c

@@ -0,0 +1,14 @@
+#include "dns_packet_buffer.h"
+#include <stdlib.h>
+
+struct DNSPacketBuffer *new_dns_packet_buffer()
+{
+    struct DNSPacketBuffer *buf;
+    buf = malloc(sizeof(struct DNSPacketBuffer));
+    return buf;
+}
+
+struct DNSPacketHeader *dns_header(struct DNSPacketBuffer)
+{
+
+}

src/dns_request.c

@@ -0,0 +1,3 @@
+#include "dns_request.h"
+
+

src/main.c

@@ -1,11 +1,13 @@
 #include <stdio.h>
-#include "packet_buffer.h"
+
+#include "udp_server.h"
 
 int main()
 {
-    struct PacketBuffer *buf = new_packet_buffer();
+    if (start_server() != 0) {
-
+        perror("couldn't start UDP server");
-    printf("size: %ld\n", sizeof(buf->buf));
+        return 1;
+    }
 
     return 0;
 }

src/packet_buffer.c

@@ -1,9 +0,0 @@
-#include "packet_buffer.h"
-#include <stdlib.h>
-
-struct PacketBuffer *new_packet_buffer()
-{
-    struct PacketBuffer *buf;
-    buf = malloc(sizeof(struct PacketBuffer));
-    return buf;
-}

src/udp_server.c

@@ -0,0 +1,47 @@
+#include "udp_server.h"
+#include "dns_packet_buffer.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>
+
+int start_server()
+{
+    struct DNSPacketBuffer *pb = new_dns_packet_buffer();
+
+    struct sockaddr_in servaddr = {0};
+
+    int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
+
+    if (sockfd == -1)
+    {
+        perror("failed to create socket");
+        return -1;
+    }
+
+    servaddr.sin_family = AF_INET; 
+    servaddr.sin_port = htons(UDP_PORT);
+    servaddr.sin_addr.s_addr = INADDR_ANY;
+
+    int rc = bind(sockfd, (const struct sockaddr *)&servaddr, sizeof(servaddr));
+
+    if (rc == -1)
+    {
+        perror("failed to bind");
+        close(sockfd);
+        return -1;
+    }
+
+    socklen_t len = 0;
+
+    int n = recvfrom(sockfd, (char *)pb->buf, sizeof(pb->buf), MSG_WAITALL, 0, &len);
+
+    printf("%s", pb->buf);
+
+    close(sockfd);
+    return 0;
+}