int handleRequest(struct dnsServer *srv, int len)
{
struct DNSHeader head;
struct DNSQuestion question;
struct DNSAnswer answer;
int8_t *ptr = srv->buffer;
char *addr, *buf = NULL;
uint16_t size;
uint8_t found = 0;
ptr = readDNSHeader(&head, ptr);
ptr = readDNSQuestion(&question, ptr);
if (question.qtype == TYPE_A)
addr = resolveHost(question.qname);
else if (question.qtype = TYPE_PTR)
addr = resolveAddress(question.qname);
#if DEBUG == 1
printf("Received packet from %s:%d\tID: %04x\n",
inet_ntoa(srv->client.sin_addr), ntohs(srv->client.sin_port), head.id);
printf("NAME TO RESOLVE: %s\t%s\n", question.qname, addr);
#endif
if ((question.qtype != TYPE_A && question.qtype != TYPE_PTR || question.qclass != CLASS_IN) ||
addr == NULL)
{
passthrough(srv, len);
}
else
{
answer = createDNSAnswer(&question, addr, question.qtype == TYPE_A);
createDNSResponse(&head, &question, &answer, (void **)&buf, &size);
sendto(srv->sock, buf, size, 0, (struct sockaddr*)&srv->client, sizeof(srv->client));
}
return 0; //packet sent
}
int main(int argc, char *argv[])
{
// set working directory
char path[128];
int lenPath = 0;
char *tmp = argv[0], *pos;
while (1)
{
pos = strchr(tmp, '/');
if (pos == NULL)
break;
lenPath += pos - tmp + 1;
tmp = pos + 1;
}
strcpy(path, argv[0]);
path[lenPath] = '\0';
int d = open(path, O_RDONLY);
fchdir(d);
// read config.txt
char str[64];
FILE *fp;
if ((fp = fopen("../config/config.txt", "r")) == NULL)
{
printf("Read config error\n");
return -1;
}
// read and bulid hashtable
initHashTable();
while (!feof(fp))
{
fgets(str, 64, fp);
char name[64], ip[64];
char *ptr;
int lenIP = strchr(str, ' ') - str;
int lenName;
if (strchr(str, '\n') != NULL)
{
lenName = strchr(str, '\n') - strchr(str, ' ') - 1;
}
else
{
lenName = strlen(str) - lenIP - 1;
}
ptr = str;
for (int i = 0; i < lenIP; i++, ptr++)
{
ip[i] = *ptr;
}
ip[lenIP] = '\0';
ptr += 1;
for (int i = 0; i < lenName; i++, ptr++)
{
name[i] = *ptr;
}
name[lenName] = '\0';
// printf ("%s --> %s\n", name, ip);
add(name, ip);
}
fclose(fp);
dispalyTable();
// bulid socket
int sockfd;
struct sockaddr_in serverAddr, clientAddr;
sockfd = socket(AF_INET, SOCK_DGRAM, 0);
bzero(&serverAddr, sizeof(struct sockaddr_in));
serverAddr.sin_family = AF_INET;
serverAddr.sin_addr.s_addr = htonl(INADDR_ANY);
serverAddr.sin_port = htons(PORT);
if (bind(sockfd, (struct sockaddr *)(&serverAddr), sizeof(serverAddr)) == -1)
{
printf("Bind Fail\n");
printf("%s\n", strerror(errno));
return -1;
}
printf("***************************************\n");
printf("Bind Success!\n");
printf("***************************************\n");
printf("listening port %d\n", PORT);
// recive message from clients
char message[1024];
while (1)
{
socklen_t len;
len = sizeof(clientAddr);
recvfrom(sockfd, message, sizeof(message), 0, (struct sockaddr *)(&clientAddr), &len);
//handle message from clients
char name[64];
memset(name, 0, sizeof(name));
printDNSQuery(message, name);
HashNode* ans = search(name);
if (ans)
{
printf("%s\n", ans->ip);
char dnsAnswer[1024];
createDNSAnswer(ans->ip, dnsAnswer, message);
sendto(sockfd, dnsAnswer, sizeof(dnsAnswer), 0, (struct sockaddr *)&clientAddr, sizeof(clientAddr));
}
else
{
printf("DNS request timed out.\n");
}
}
return 0;
}
