2 files changed, 68 insertions, 46 deletions
diff --git a/ext/socket/ipsocket.c b/ext/socket/ipsocket.c
index e69c8b0a53..24d21a5899 100644
--- a/ext/socket/ipsocket.c
+++ b/ext/socket/ipsocket.c
@@ -574,7 +574,7 @@ init_fast_fallback_inetsock_internal(VALUE v)
     struct wait_fast_fallback_arg wait_arg;
     struct timeval *ends_at = NULL;
     struct timeval delay = (struct timeval){ -1, -1 };
-    wait_arg.writefds = NULL;
+    wait_arg.writefds = &writefds;
     wait_arg.status = 0;
 
     struct hostname_resolution_store resolution_store;
@@ -859,7 +859,6 @@ init_fast_fallback_inetsock_internal(VALUE v)
                     }
                     arg->connection_attempt_fds[arg->connection_attempt_fds_size] = fd;
                     (arg->connection_attempt_fds_size)++;
-                    wait_arg.writefds = &writefds;
 
                     set_timeout_tv(&connection_attempt_delay_strage, 250, now);
                     connection_attempt_delay_expires_at = &connection_attempt_delay_strage;
@@ -922,8 +921,8 @@ init_fast_fallback_inetsock_internal(VALUE v)
         }
 
         wait_arg.nfds = 0;
-        if (arg->connection_attempt_fds_size) {
-            FD_ZERO(wait_arg.writefds);
+        FD_ZERO(wait_arg.writefds);
+        if (in_progress_fds(arg->connection_attempt_fds_size)) {
             int n = 0;
             for (int i = 0; i < arg->connection_attempt_fds_size; i++) {
                 int cfd = arg->connection_attempt_fds[i];
@@ -933,8 +932,6 @@ init_fast_fallback_inetsock_internal(VALUE v)
             }
             if (n > 0) n++;
             wait_arg.nfds = n;
-        } else {
-            wait_arg.writefds = NULL;
         }
 
         FD_ZERO(wait_arg.readfds);
@@ -967,14 +964,39 @@ init_fast_fallback_inetsock_internal(VALUE v)
 
         if (status > 0) {
             /* check for connection */
-            for (int i = 0; i < arg->connection_attempt_fds_size; i++) {
-                int fd = arg->connection_attempt_fds[i];
-                if (fd < 0 || !FD_ISSET(fd, wait_arg.writefds)) continue;
+            if (in_progress_fds(arg->connection_attempt_fds_size)) {
+                for (int i = 0; i < arg->connection_attempt_fds_size; i++) {
+                    int fd = arg->connection_attempt_fds[i];
+                    if (fd < 0 || !FD_ISSET(fd, wait_arg.writefds)) continue;
+
+                    int err;
+                    socklen_t len = sizeof(err);
+
+                    status = getsockopt(fd, SOL_SOCKET, SO_ERROR, &err, &len);
+
+                    if (status < 0) {
+                        last_error.type = SYSCALL_ERROR;
+                        last_error.ecode = errno;
+                        close(fd);
 
-                int err;
-                socklen_t len = sizeof(err);
+                        if (any_addrinfos(&resolution_store)) continue;
+                        if (in_progress_fds(arg->connection_attempt_fds_size)) break;
+                        if (!resolution_store.is_all_finised) break;
+
+                        if (local_status < 0) {
+                            host = arg->local.host;
+                            serv = arg->local.serv;
+                        } else {
+                            host = arg->remote.host;
+                            serv = arg->remote.serv;
+                        }
+                        if (last_error.type == RESOLUTION_ERROR) {
+                            rsock_raise_resolution_error(syscall, last_error.ecode);
+                        } else {
+                            rsock_syserr_fail_host_port(last_error.ecode, syscall, host, serv);
+                        }
+                    }
 
-                if (getsockopt(fd, SOL_SOCKET, SO_ERROR, &err, &len) == 0) {
                     if (err == 0) { /* success */
                         remove_connection_attempt_fd(
                             arg->connection_attempt_fds,
@@ -983,42 +1005,39 @@ init_fast_fallback_inetsock_internal(VALUE v)
                         );
                         connected_fd = fd;
                         break;
-                    };
-
-                    /* fail */
-                    errno = err;
-                    close(fd);
-                    remove_connection_attempt_fd(
-                        arg->connection_attempt_fds,
-                        &arg->connection_attempt_fds_size,
-                        fd
-                    );
-                    continue;
+                    } else { /* fail */
+                        close(fd);
+                        remove_connection_attempt_fd(
+                            arg->connection_attempt_fds,
+                            &arg->connection_attempt_fds_size,
+                            fd
+                        );
+                        last_error.type = SYSCALL_ERROR;
+                        last_error.ecode = err;
+                    }
                 }
-            }
 
-            if (connected_fd >= 0) break;
-            last_error.type = SYSCALL_ERROR;
-            last_error.ecode = errno;
+                if (connected_fd >= 0) break;
 
-            if (!in_progress_fds(arg->connection_attempt_fds_size)) {
-                if (any_addrinfos(&resolution_store)) {
-                    connection_attempt_delay_expires_at = NULL;
-                } else if (resolution_store.is_all_finised) {
-                    if (local_status < 0) {
-                        host = arg->local.host;
-                        serv = arg->local.serv;
-                    } else {
-                        host = arg->remote.host;
-                        serv = arg->remote.serv;
-                    }
-                    if (last_error.type == RESOLUTION_ERROR) {
-                        rsock_raise_resolution_error(syscall, last_error.ecode);
-                    } else {
-                        rsock_syserr_fail_host_port(last_error.ecode, syscall, host, serv);
+                if (!in_progress_fds(arg->connection_attempt_fds_size)) {
+                    if (any_addrinfos(&resolution_store)) {
+                        connection_attempt_delay_expires_at = NULL;
+                    } else if (resolution_store.is_all_finised) {
+                        if (local_status < 0) {
+                            host = arg->local.host;
+                            serv = arg->local.serv;
+                        } else {
+                            host = arg->remote.host;
+                            serv = arg->remote.serv;
+                        }
+                        if (last_error.type == RESOLUTION_ERROR) {
+                            rsock_raise_resolution_error(syscall, last_error.ecode);
+                        } else {
+                            rsock_syserr_fail_host_port(last_error.ecode, syscall, host, serv);
+                        }
                     }
+                    user_specified_connect_timeout_at = NULL;
                 }
-                user_specified_connect_timeout_at = NULL;
             }
 
             /* check for hostname resolution */
diff --git a/ext/socket/tcpsocket.c b/ext/socket/tcpsocket.c
index 10b4810869..3c03e89e0d 100644
--- a/ext/socket/tcpsocket.c
+++ b/ext/socket/tcpsocket.c
@@ -20,14 +20,17 @@
  *
  * Starting from Ruby 3.4, this method operates according to the
  * Happy Eyeballs Version 2 ({RFC 8305}[https://datatracker.ietf.org/doc/html/rfc8305])
- * algorithm with *fast_fallback:true+, except on Windows.
+ * algorithm by default, except on Windows.
+ *
+ * To make it behave the same as in Ruby 3.3 and earlier,
+ * explicitly specify the option +fast_fallback:false+.
  *
  * Happy Eyeballs Version 2 is not provided on Windows,
  * and it behaves the same as in Ruby 3.3 and earlier.
  *
  * [:resolv_timeout] Specifies the timeout in seconds from when the hostname resolution starts.
  * [:connect_timeout] This method sequentially attempts connecting to all candidate destination addresses.<br>The +connect_timeout+ specifies the timeout in seconds from the start of the connection attempt to the last candidate.<br>By default, all connection attempts continue until the timeout occurs.<br>When +fast_fallback:false+ is explicitly specified,<br>a timeout is set for each connection attempt and any connection attempt that exceeds its timeout will be canceled.
- * [:fast_fallback] Enables the Happy Eyeballs Version 2 algorithm (disabled by default).
+ * [:fast_fallback] Enables the Happy Eyeballs Version 2 algorithm (enabled by default).
  *
  * === Happy Eyeballs Version 2
  * Happy Eyeballs Version 2 ({RFC 8305}[https://datatracker.ietf.org/doc/html/rfc8305])
@@ -57,7 +60,7 @@ tcp_init(int argc, VALUE *argv, VALUE sock)
     VALUE kwargs[4];
     VALUE resolv_timeout = Qnil;
     VALUE connect_timeout = Qnil;
-    VALUE fast_fallback = Qfalse;
+    VALUE fast_fallback = Qtrue;
     VALUE test_mode_settings = Qnil;
 
     if (!keyword_ids[0]) {