show capative portal on connect

Signed-off-by: Peter Siegmund <developer@mars3142.org>

firmware/components/connectivity-manager/src/dns_hijack.c

@@ -0,0 +1,80 @@
+// Minimaler DNS-Server für Captive Portal (alle Anfragen auf AP-IP)
+// Quelle: https://github.com/espressif/esp-idf/blob/master/examples/protocols/sntp/main/dns_server.c (angepasst)
+#include <arpa/inet.h>
+#include <esp_log.h>
+#include <freertos/FreeRTOS.h>
+#include <freertos/task.h>
+#include <lwip/inet.h>
+#include <lwip/sockets.h>
+#include <netinet/in.h>
+#include <string.h>
+#include <sys/socket.h>
+
+#define DNS_PORT 53
+#define DNS_MAX_LEN 512
+static const char *TAG = "dns_hijack";
+
+static char s_ap_ip[16] = "192.168.4.1"; // Default AP-IP, ggf. dynamisch setzen
+
+void dns_set_ap_ip(const char *ip)
+{
+    strncpy(s_ap_ip, ip, sizeof(s_ap_ip) - 1);
+    s_ap_ip[sizeof(s_ap_ip) - 1] = 0;
+}
+
+static void dns_server_task(void *pvParameters)
+{
+    int sock = socket(AF_INET, SOCK_DGRAM, 0);
+    if (sock < 0)
+    {
+        ESP_LOGE(TAG, "Failed to create socket");
+        vTaskDelete(NULL);
+        return;
+    }
+    struct sockaddr_in server_addr = {0};
+    server_addr.sin_family = AF_INET;
+    server_addr.sin_port = htons(DNS_PORT);
+    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
+    bind(sock, (struct sockaddr *)&server_addr, sizeof(server_addr));
+
+    uint8_t buf[DNS_MAX_LEN];
+    while (1)
+    {
+        struct sockaddr_in from;
+        socklen_t fromlen = sizeof(from);
+        int len = recvfrom(sock, buf, sizeof(buf), 0, (struct sockaddr *)&from, &fromlen);
+        if (len < 0)
+            continue;
+        // DNS Header: 12 bytes, Antwort-Flag setzen
+        buf[2] |= 0x80; // QR=1 (Antwort)
+        buf[3] = 0x80;  // RA=1, RCODE=0
+        // Fragen: 1, Antworten: 1
+        buf[7] = 1;
+        // Antwort anhängen (Name Pointer auf Frage)
+        int qlen = len - 12;
+        int pos = len;
+        buf[pos++] = 0xC0;
+        buf[pos++] = 0x0C; // Name pointer
+        buf[pos++] = 0x00;
+        buf[pos++] = 0x01; // Type A
+        buf[pos++] = 0x00;
+        buf[pos++] = 0x01; // Class IN
+        buf[pos++] = 0x00;
+        buf[pos++] = 0x00;
+        buf[pos++] = 0x00;
+        buf[pos++] = 0x3C; // TTL 60s
+        buf[pos++] = 0x00;
+        buf[pos++] = 0x04; // Data length
+        inet_pton(AF_INET, s_ap_ip, &buf[pos]);
+        pos += 4;
+        sendto(sock, buf, pos, 0, (struct sockaddr *)&from, fromlen);
+    }
+    close(sock);
+    vTaskDelete(NULL);
+}
+
+void dns_server_start(const char *ap_ip)
+{
+    dns_set_ap_ip(ap_ip);
+    xTaskCreate(dns_server_task, "dns_server", 4096, NULL, 3, NULL);
+}