mongoose/examples/captive_dns_server/captive_dns_server.c

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/*
* Copyright (c) 2014 Cesanta Software Limited
* All rights reserved
*/
/*
* Try it out with:
* $ dig -t A www.google.com -4 @localhost -p 5533
*/
#include "../../mongoose.h"
#include <stdio.h>
static int s_exit_flag = 0;
static in_addr_t s_our_ip_addr;
static const char *s_listening_addr = "udp://:5533";
static void ev_handler(struct mg_connection *nc, int ev, void *ev_data) {
struct mg_dmg_message *msg;
struct mg_dmg_resource_record *rr;
struct mg_dmg_reply reply;
int i;
switch (ev) {
case MG_DNS_MESSAGE:
msg = (struct mg_dmg_message *) ev_data;
reply = mg_dmg_create_reply(&nc->send_mbuf, msg);
for (i = 0; i < msg->num_questions; i++) {
rr = &msg->questions[i];
if (rr->rtype == MG_DNS_A_RECORD) {
mg_dmg_reply_record(&reply, rr, NULL, rr->rtype, 3600,
&s_our_ip_addr, 4);
}
}
/*
* We don't set the error flag even if there were no answers
* maching the MG_DNS_A_RECORD query type.
* This indicates that we have (syntetic) answers for MG_DNS_A_RECORD.
* See http://goo.gl/QWvufr for a distinction between NXDOMAIN and NODATA.
*/
mg_dmg_send_reply(nc, &reply);
break;
}
}
int main(int argc, char *argv[]) {
struct mg_mgr mgr;
struct mg_connection *nc;
int i;
mg_mgr_init(&mgr, NULL);
s_our_ip_addr = inet_addr("127.0.0.1");
/* Parse command line arguments */
for (i = 1; i < argc; i++) {
if (strcmp(argv[i], "-D") == 0) {
mgr.hexdump_file = argv[++i];
} else if (strcmp(argv[i], "-l") == 0 && i + 1 < argc) {
s_listening_addr = argv[++i];
} else {
s_our_ip_addr = inet_addr(argv[i]);
}
}
fprintf(stderr, "Listening on '%s'\n", s_listening_addr);
if ((nc = mg_bind(&mgr, s_listening_addr, ev_handler)) == NULL) {
fprintf(stderr, "cannot bind to socket\n");
exit(1);
}
mg_set_protocol_dns(nc);
while (s_exit_flag == 0) {
mg_mgr_poll(&mgr, 1000);
}
mg_mgr_free(&mgr);
return 0;
}