143 lines
3.8 KiB
C
143 lines
3.8 KiB
C
#include "simple_dns_server.h"
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#include "lwip/sockets.h"
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#include "lwip/netdb.h"
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#include "esp_log.h"
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#include "freertos/FreeRTOS.h"
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#include "freertos/task.h"
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#include <string.h>
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static const char *TAG = "DNS_SERVER";
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static int dns_socket = -1;
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static TaskHandle_t dns_task_handle = NULL;
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static char dns_ip[16] = {0};
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// DNS header structure
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typedef struct {
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uint16_t id;
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uint16_t flags;
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uint16_t qdcount;
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uint16_t ancount;
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uint16_t nscount;
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uint16_t arcount;
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} dns_header_t;
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static void dns_server_task(void *pvParameters) {
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char rx_buffer[512];
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char tx_buffer[512];
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struct sockaddr_in dest_addr;
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dest_addr.sin_addr.s_addr = htonl(INADDR_ANY);
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dest_addr.sin_family = AF_INET;
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dest_addr.sin_port = htons(53);
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dns_socket = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);
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if (dns_socket < 0) {
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ESP_LOGE(TAG, "Unable to create socket: errno %d", errno);
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vTaskDelete(NULL);
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return;
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}
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int err = bind(dns_socket, (struct sockaddr *)&dest_addr, sizeof(dest_addr));
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if (err < 0) {
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ESP_LOGE(TAG, "Socket bind failed: errno %d", errno);
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close(dns_socket);
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vTaskDelete(NULL);
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return;
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}
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ESP_LOGI(TAG, "DNS server started on port 53");
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while (1) {
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struct sockaddr_in source_addr;
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socklen_t socklen = sizeof(source_addr);
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int len = recvfrom(dns_socket, rx_buffer, sizeof(rx_buffer) - 1, 0,
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(struct sockaddr *)&source_addr, &socklen);
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if (len < 0) {
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ESP_LOGE(TAG, "recvfrom failed: errno %d", errno);
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break;
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}
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if (len < sizeof(dns_header_t)) {
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continue;
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}
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// Parse DNS query (unused)
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// dns_header_t *header = (dns_header_t *)rx_buffer;
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// Build DNS response
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memcpy(tx_buffer, rx_buffer, len);
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dns_header_t *response = (dns_header_t *)tx_buffer;
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// Set response flags
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response->flags = htons(0x8180); // Standard query response, no error
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response->ancount = htons(1); // One answer
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// Add answer section (Type A record)
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int pos = len;
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// Name pointer to question
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tx_buffer[pos++] = 0xC0;
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tx_buffer[pos++] = 0x0C;
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// Type A
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tx_buffer[pos++] = 0x00;
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tx_buffer[pos++] = 0x01;
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// Class IN
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tx_buffer[pos++] = 0x00;
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tx_buffer[pos++] = 0x01;
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// TTL (60 seconds)
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tx_buffer[pos++] = 0x00;
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tx_buffer[pos++] = 0x00;
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tx_buffer[pos++] = 0x00;
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tx_buffer[pos++] = 0x3C;
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// Data length (4 bytes for IPv4)
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tx_buffer[pos++] = 0x00;
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tx_buffer[pos++] = 0x04;
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// IP address
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int a, b, c, d;
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sscanf(dns_ip, "%d.%d.%d.%d", &a, &b, &c, &d);
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tx_buffer[pos++] = a;
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tx_buffer[pos++] = b;
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tx_buffer[pos++] = c;
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tx_buffer[pos++] = d;
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// Send response
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sendto(dns_socket, tx_buffer, pos, 0,
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(struct sockaddr *)&source_addr, sizeof(source_addr));
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}
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close(dns_socket);
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dns_socket = -1;
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vTaskDelete(NULL);
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}
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esp_err_t simple_dns_server_start(const char *ap_ip) {
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if (dns_task_handle != NULL) {
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ESP_LOGW(TAG, "DNS server already running");
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return ESP_ERR_INVALID_STATE;
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}
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strncpy(dns_ip, ap_ip, sizeof(dns_ip) - 1);
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xTaskCreate(dns_server_task, "dns_server", 4096, NULL, 5, &dns_task_handle);
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return ESP_OK;
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}
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void simple_dns_server_stop(void) {
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if (dns_task_handle != NULL) {
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if (dns_socket >= 0) {
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close(dns_socket);
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dns_socket = -1;
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}
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vTaskDelete(dns_task_handle);
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dns_task_handle = NULL;
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ESP_LOGI(TAG, "DNS server stopped");
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}
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} |