add: dns lookup

src/main.c

@@ -4,6 +4,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <netinet/in.h>
@@ -14,6 +15,8 @@
 #include <fcntl.h>
 #include <sys/time.h>
 #include <stdbool.h>
+#include <sys/socket.h>
+#include <netdb.h>
 
 bool loop = true;
 
@@ -144,6 +147,36 @@ void signal_handler(int code)
     loop = false;
 }
 
+char *dns_lookup(const char *hostname)
+{
+    printf("%s\n",hostname);
+    char *ipstr = malloc(sizeof(char) * INET_ADDRSTRLEN);
+    if (ipstr == NULL)
+        return NULL;
+
+    struct addrinfo filter;
+
+    bzero(&filter, sizeof(filter));
+    filter.ai_family = AF_INET; 
+
+    struct addrinfo *responses;
+    if (getaddrinfo(hostname, NULL, &filter, &responses) != 0)
+    {
+        print_err("dns lookup failed");
+        free(ipstr);
+        return NULL;
+    }
+
+    struct addrinfo *first = responses;
+    struct in_addr *addr = &(((struct sockaddr_in *) responses->ai_addr)->sin_addr);
+    
+    inet_ntop(first->ai_family, addr, ipstr, sizeof(char) * INET_ADDRSTRLEN);
+
+    freeaddrinfo(responses);
+
+    return ipstr;
+}
+
 int main(int ac, char **av)
 {
     (void) ac;
@@ -153,6 +186,17 @@ int main(int ac, char **av)
 
     signal(SIGINT, signal_handler);
 
+    char *ipstr = dns_lookup("google.com");
+    if (ipstr == NULL)
+        return 5;
+
+    struct sockaddr_in dest;
+
+    dest.sin_family = AF_INET;
+    dest.sin_port = htons(0);       
+    inet_pton(AF_INET, ipstr, &dest.sin_addr);
+    free(ipstr);
+
     int sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
 
     if (sockfd == -1)
@@ -161,12 +205,6 @@ int main(int ac, char **av)
         return 1;
     }
 
-    struct sockaddr_in dest;
-
-    dest.sin_family = AF_INET;
-    dest.sin_port = htons(0);       
-    inet_pton(AF_INET, "8.8.8.8", &dest.sin_addr);
-
     char *packet = create_packet(payload_size);
     if (packet == NULL)
     {
@@ -198,7 +236,6 @@ int main(int ac, char **av)
             close(sockfd);
             return 2;
         }
-        printf("icmp request sent\n");
 
         do
         {