From fcb9d0e3b063dff19de405bceccf7b4ba891d944 Mon Sep 17 00:00:00 2001
From: FoxyHunter <fox@foxyhunter.be>
Date: Mon, 1 Jun 2026 20:38:27 +0200
Subject: [PATCH] Feat: main application logic

---
 src/main.c | 143 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 143 insertions(+)
 create mode 100644 src/main.c

diff --git a/src/main.c b/src/main.c
new file mode 100644
index 0000000..ee03956
--- /dev/null
+++ b/src/main.c
@@ -0,0 +1,143 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <signal.h>
+#include <unistd.h>
+#include <curl/curl.h>
+#include "config.h"
+#include "gandi.h"
+#include "ipcheck.h"
+#include "log.h"
+#include "selfcheck.h"
+
+static volatile sig_atomic_t g_running = 1;
+
+static void handle_signal(int sig) {
+    (void)sig;
+    g_running = 0;
+}
+
+int main(void) {
+    struct sigaction sa = {0};
+    sa.sa_handler = handle_signal;
+    sigaction(SIGINT, &sa, NULL);
+    sigaction(SIGTERM, &sa, NULL);
+
+    Config cfg = {0};
+    if (config_load(&cfg) != 0) return EXIT_FAILURE;
+
+    log_init();
+    curl_global_init(CURL_GLOBAL_DEFAULT);
+
+    int ret = EXIT_SUCCESS;
+
+    if (gandi_init(cfg.api_token) != 0) {
+        log_error("gandi_init failed");
+        ret = EXIT_FAILURE;
+        goto cleanup;
+    }
+
+    char cached_ip[GANDI_MAX_IP_LEN] = {0};
+    if (gandi_get_self_ip(cfg.dns_keeper_domain, cfg.dns_keeper_record, cached_ip) != 0) {
+        log_error("Failed to fetch initial IP from self record %s.%s",
+                cfg.dns_keeper_record, cfg.dns_keeper_domain);
+        ret = EXIT_FAILURE;
+        goto cleanup;
+    }
+    log_info("Self record points to %s", cached_ip);
+
+    char self_fqdn[256];
+    snprintf(self_fqdn, sizeof(self_fqdn), "%s.%s", cfg.dns_keeper_record, cfg.dns_keeper_domain);
+
+    if (selfcheck_start_listener(cfg.dns_keeper_port) != 0) {
+        log_error("Failed to start self-check listener on port %d", cfg.dns_keeper_port);
+        ret = EXIT_FAILURE;
+        goto cleanup;
+    }
+    log_info("Listening on UDP port %d", cfg.dns_keeper_port);
+
+    int fail_count = 0; /* consecutive self-check failures */
+    int drift_count = 0; /* when external IP matches cache but self-check fails */
+
+    while (g_running) {
+        if (selfcheck_domain(self_fqdn, cfg.dns_keeper_port) == 0) {
+            fail_count  = 0;
+            drift_count = 0;
+            sleep(cfg.poll_interval);
+            continue;
+        }
+
+        fail_count++;
+        if (fail_count < SELFCHECK_FAIL_THRESHOLD) {
+            sleep(cfg.poll_interval);
+            continue;
+        }
+
+        fail_count = 0;
+        char public_ip[IPCHECK_MAX_IP_LEN] = {0};
+        if (ipcheck_get_public_ip(public_ip) != 0) {
+            log_warn("ipcheck: failed to determine public IP, skipping cycle");
+            sleep(cfg.poll_interval);
+            continue;
+        }
+
+        if (strcmp(public_ip, cached_ip) == 0) {
+            drift_count++;
+            if (drift_count >= SELFCHECK_DRIFT_THRESHOLD) {
+                char gandi_ip[GANDI_MAX_IP_LEN] = {0};
+                if (gandi_get_self_ip(cfg.dns_keeper_domain, cfg.dns_keeper_record, gandi_ip) == 0
+                        && strcmp(gandi_ip, cached_ip) != 0) {
+                    log_info("Cache drift: cached %s but Gandi has %s, resyncing",
+                            cached_ip, gandi_ip);
+                    strncpy(cached_ip, gandi_ip, GANDI_MAX_IP_LEN - 1);
+                    cached_ip[GANDI_MAX_IP_LEN - 1] = '\0';
+                }
+                drift_count = 0;
+            }
+            sleep(SELFCHECK_COOLDOWN_S);
+            continue;
+        }
+
+        drift_count = 0;
+        log_info("IP change detected: %s -> %s", cached_ip, public_ip);
+
+        if (selfcheck_ip_str(public_ip, cfg.dns_keeper_port) != 0) {
+            log_warn("Direct check of %s failed, deferring update", public_ip);
+            sleep(SELFCHECK_COOLDOWN_S);
+            continue;
+        }
+
+        int failed_updates = 0;
+        for (int i = 0; i < cfg.domain_count; i++) {
+            if (strcmp(cfg.domains[i], cfg.dns_keeper_domain) == 0) continue;
+
+            int gret = gandi_update_domains(cfg.domains[i], cached_ip, public_ip);
+            if (gret == -3) {
+                log_info("gandi: [%s] no matching A records for %s, skipping",
+                        cfg.domains[i], cached_ip);
+            } else if (gret != 0) {
+                failed_updates = 1;
+            }
+        }
+
+        int sret = gandi_update_record(cfg.dns_keeper_domain, cfg.dns_keeper_record,
+                                       cached_ip, public_ip);
+        if (sret == 0) {
+            strncpy(cached_ip, public_ip, GANDI_MAX_IP_LEN - 1);
+            cached_ip[GANDI_MAX_IP_LEN - 1] = '\0';
+        } else {
+            log_error("Failed to update self record, cached IP not advanced");
+            failed_updates = 1;
+        }
+
+        if (failed_updates) log_error("One or more updates failed this cycle");
+
+        sleep(SELFCHECK_COOLDOWN_S);
+    }
+
+    log_info("Shutting down");
+cleanup:
+    curl_global_cleanup();
+    config_free(&cfg);
+    return ret;
+}