DNS (Linux): add systemd-resolved support; add verbose logs

Author: CarterLi

src/detection/dns/dns_linux.c

@@ -3,18 +3,32 @@
 #include "common/io/io.h"
 #include "util/mallocHelper.h"
 #include "util/stringUtils.h"
+#include "util/debug.h"
 
 #ifdef __HAIKU__
 #define RESOLV_CONF "/system/settings/network/resolv.conf"
 #else
 #define RESOLV_CONF "/etc/resolv.conf"
 #endif
 
-const char* ffDetectDNS(FFDNSOptions* options, FFlist* results)
+static const char* detectDnsFromConf(const char* path, FFDNSOptions* options, FFlist* results)
 {
-    FF_AUTO_CLOSE_FILE FILE* file = fopen(FASTFETCH_TARGET_DIR_ROOT RESOLV_CONF, "r");
+    FF_DEBUG("Attempting to read DNS config from %s", path);
+
+    FF_AUTO_CLOSE_FILE FILE* file = fopen(path, "r");
     if (!file)
-        return "fopen (" FASTFETCH_TARGET_DIR_ROOT RESOLV_CONF ") failed";
+    {
+        FF_DEBUG("Failed to open %s: %m", path);
+        return "fopen(path, r) failed";
+    }
+
+    if (results->length > 0)
+    {
+        FF_DEBUG("Clearing existing DNS entries (%u entries)", results->length);
+        FF_LIST_FOR_EACH(FFstrbuf, item, *results)
+            ffStrbufDestroy(item);
+        ffListClear(results);
+    }
 
     FF_AUTO_FREE char* line = NULL;
     size_t len = 0;
@@ -38,7 +52,90 @@ const char* ffDetectDNS(FFDNSOptions* options, FFlist* results)
             FFstrbuf* item = (FFstrbuf*) ffListAdd(results);
             ffStrbufInitS(item, nameserver);
             ffStrbufTrimRightSpace(item);
+            FF_DEBUG("Found DNS server: %s", item->chars);
+        }
+    }
+
+    FF_DEBUG("Found %u DNS servers in %s", results->length, path);
+    return NULL;
+}
+
+const char* ffDetectDNS(FFDNSOptions* options, FFlist* results)
+{
+    FF_DEBUG("Starting DNS detection");
+
+    const char* error = detectDnsFromConf(FASTFETCH_TARGET_DIR_ROOT RESOLV_CONF, options, results);
+    if (error != NULL)
+    {
+        FF_DEBUG("Error detecting DNS: %s", error);
+        return error;
+    }
+
+    #if __linux__ && !__ANDROID__
+    // Handle different DNS management services
+    if (results->length == 1)
+    {
+        const FFstrbuf* firstEntry = FF_LIST_GET(FFstrbuf, *results, 0);
+
+        if (ffStrbufEqualS(firstEntry, "127.0.0.53"))
+        {
+            FF_DEBUG("Detected systemd-resolved (127.0.0.53), checking actual DNS servers");
+            // Managed by systemd-resolved
+            if (detectDnsFromConf("/run/systemd/resolve/resolv.conf", options, results) == NULL)
+                return NULL;
         }
+        else if (ffStrbufEqualS(firstEntry, "127.0.0.1"))
+        {
+            FF_DEBUG("Detected possible NetworkManager (127.0.0.1), checking actual DNS servers");
+            // Managed by NetworkManager
+            if (detectDnsFromConf("/var/run/NetworkManager/resolv.conf", options, results) == NULL)
+                return NULL;
+        }
+    }
+
+    // Check other possible DNS configuration files
+    if (results->length == 0)
+    {
+        FF_DEBUG("No DNS servers found, trying alternative config files");
+
+        // Try resolvconf
+        FF_DEBUG("Trying resolvconf configuration");
+        if (detectDnsFromConf(FASTFETCH_TARGET_DIR_ROOT "/run/resolvconf/resolv.conf", options, results) == NULL && results->length > 0)
+            return NULL;
+
+        // Try dnsmasq
+        FF_DEBUG("Trying dnsmasq configuration");
+        if (detectDnsFromConf(FASTFETCH_TARGET_DIR_ROOT "/var/run/dnsmasq/resolv.conf", options, results) == NULL && results->length > 0)
+            return NULL;
+
+        // Try openresolv
+        FF_DEBUG("Trying openresolv configuration");
+        if (detectDnsFromConf(FASTFETCH_TARGET_DIR_ROOT "/etc/resolv.conf.openresolv", options, results) == NULL && results->length > 0)
+            return NULL;
     }
+    #elif defined(__FreeBSD__) || defined(__DragonFly__) || defined(__NetBSD__) || defined(__OpenBSD__)
+    // Handle BSD-specific DNS configurations
+    if (results->length == 0)
+    {
+        FF_DEBUG("No DNS servers found, trying BSD-specific config files");
+
+        // FreeBSD and other BSDs may use resolvconf service
+        FF_DEBUG("Trying BSD resolvconf configuration");
+        if (detectDnsFromConf(FASTFETCH_TARGET_DIR_ROOT "/var/run/resolvconf/resolv.conf", options, results) == NULL && results->length > 0)
+            return NULL;
+
+        // Some BSDs store DNS configuration here
+        FF_DEBUG("Trying BSD nameserver configuration");
+        if (detectDnsFromConf(FASTFETCH_TARGET_DIR_ROOT "/var/run/nameserver", options, results) == NULL && results->length > 0)
+            return NULL;
+
+        // Try common BSD paths
+        FF_DEBUG("Trying BSD common paths");
+        if (detectDnsFromConf(FASTFETCH_TARGET_DIR_ROOT "/etc/nameserver", options, results) == NULL && results->length > 0)
+            return NULL;
+    }
+    #endif
+
+    FF_DEBUG("DNS detection completed with %u servers found", results->length);
     return NULL;
 }