Resolve hosts with getaddrinfo so hosts-file IPv6 entries are found

Guard::resolve() combined gethostbynamel(), which is IPv4 only, with a
DNS AAAA query, which skips the hosts file. IPv6 addresses from the
hosts file, such as ::1 for localhost, were never found, so safe mode
couldn't reach a server listening only on them. Use getaddrinfo via
socket_addrinfo_lookup() when ext-sockets is available, falling back to
the previous lookups otherwise.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/p3k/HTTP/Guard.php

@@ -91,6 +91,18 @@ class Guard {
 
   /** Every IPv4 and IPv6 address the system resolver knows for a host. */
   public static function resolve($host) {
+    // getaddrinfo, as curl itself uses, sees both address families and the
+    // hosts file. Without ext-sockets, fall back to asking for each family
+    // separately, which misses IPv6 entries in the hosts file such as ::1.
+    if(function_exists('socket_addrinfo_lookup')) {
+      $addresses = [];
+      foreach(@socket_addrinfo_lookup($host, null, ['ai_socktype' => SOCK_STREAM]) ?: [] as $info) {
+        $address = socket_addrinfo_explain($info)['ai_addr'];
+        $addresses[] = $address['sin6_addr'] ?? $address['sin_addr'];
+      }
+      return array_values(array_unique($addresses));
+    }
+
     $addresses = gethostbynamel($host) ?: [];
     $records = @dns_get_record($host, DNS_AAAA);
     foreach($records ?: [] as $record) {

tests/GuardTest.php

@@ -64,6 +64,25 @@ class GuardTest extends TestCase {
     $this->assertSame(8080, $result['port']);
   }
 
+  // Uses the real system resolver: localhost is in every hosts file, and the
+  // IPv6 entry is only found through getaddrinfo, not a DNS AAAA query.
+  public function testSystemResolverReadsTheHostsFile() {
+    if(!function_exists('socket_addrinfo_lookup'))
+      $this->markTestSkipped('ext-sockets is not available');
+
+    $expected = [];
+    foreach(socket_addrinfo_lookup('localhost', null, ['ai_socktype' => SOCK_STREAM]) as $info) {
+      $address = socket_addrinfo_explain($info)['ai_addr'];
+      $expected[] = $address['sin6_addr'] ?? $address['sin_addr'];
+    }
+
+    $addresses = Guard::resolve('localhost');
+    $this->assertContains('127.0.0.1', $addresses);
+    foreach(array_unique($expected) as $address)
+      $this->assertContains($address, $addresses);
+    $this->assertSame([], Guard::resolve('nonexistent.invalid'));
+  }
+
   public function testUnresolvableHost() {
     $this->assertSame('dns_error', self::guard()->check('https://nowhere.example/')['error']);
   }