Issue #21104 has been updated by shioimm (Misaki Shioi). Thank you for the additional reports. Based on the information shared so far, it seems that the host machines experiencing the issue have a common factor: they are running macOS version 15.3 on Apple Silicon. (However, it does not appear that the problem occurs on all machines with version 15.3. Considering the timing when the issue was first reported on rubygems, it is also possible that it was already happening on versions earlier than 15.3.) (Since the problem also occurs in Safe Mode, it seems unlikely that third-party software or network extensions are involved.) For reference, I am using an M2 Mac running macOS 15.4.1, and I have not encountered this issue. That said, I find it hard to believe that changes affecting networking behavior would have been introduced in such a minor version update, and indeed, there is no mention of such changes in the macOS Release Notes: https://developer.apple.com/documentation/macos-release-notes?utm_source=cha... I have contacted the authors of RFC 8305 (some of whom have email addresses under the `@apple.com` domain) to inquire whether they have any relevant information regarding this matter, but I have not received a response so far. If anyone has experienced this issue and was able to resolve it by upgrading to macOS 15.4, I would greatly appreciate it if you could share that information. ---------------------------------------- Bug #21104: Net::HTTP connections failing in Ruby >= 3.4.0 on macOS with Happy Eyeballs enabled https://bugs.ruby-lang.org/issues/21104#change-112796 * Author: mjt58 (Mike Thompson) * Status: Open * ruby -v: ruby 3.4.1 (2024-12-25 revision 48d4efcb85) +PRISM [arm64-darwin24] * Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- A project I work on recently upgraded Ruby to 3.4.1 from 3.3.5. Following the upgrade, and when running locally on my Mac, all attempts to connect to an external service within the project over http(s) fail. We use `mise` for managing development tool dependencies, including Ruby, and I am using macOS 15.3. For example running something as simple as: ``` require 'net/http' puts Net::HTTP.get(URI('https://bbc.co.uk')) ``` Will fail with the following stack trace: ``` /path/to/.local/share/mise/installs/ruby/3.4.1/lib/ruby/3.4.0/net/protocol.rb:46:in 'OpenSSL::SSL::SSLSocket#connect_nonblock': Connection reset by peer - SSL_connect (Errno::ECONNRESET) from /path/to/.local/share/mise/installs/ruby/3.4.1/lib/ruby/3.4.0/net/protocol.rb:46:in 'Net::Protocol#ssl_socket_connect' from /path/to/.local/share/mise/installs/ruby/3.4.1/lib/ruby/3.4.0/net/http.rb:1736:in 'Net::HTTP#connect' from /path/to/.local/share/mise/installs/ruby/3.4.1/lib/ruby/3.4.0/net/http.rb:1636:in 'Net::HTTP#do_start' from /path/to/.local/share/mise/installs/ruby/3.4.1/lib/ruby/3.4.0/net/http.rb:1625:in 'Net::HTTP#start' from /path/to/.local/share/mise/installs/ruby/3.4.1/lib/ruby/3.4.0/net/http.rb:1064:in 'Net::HTTP.start' from /path/to/.local/share/mise/installs/ruby/3.4.1/lib/ruby/3.4.0/net/http.rb:824:in 'Net::HTTP.get_response' from /path/to/.local/share/mise/installs/ruby/3.4.1/lib/ruby/3.4.0/net/http.rb:805:in 'Net::HTTP.get' from request.rb:2:in '<main>' ``` I tried different versions of Ruby and confirmed that the issue appears with 3.4.0. After reading the release notes for this version, I tried setting `RUBY_TCP_NO_FAST_FALLBACK=1` and this worked, allowing me to work around the problem. This issue has also been encountered by others, please see: https://github.com/rubygems/rubygems/issues/8390 -- https://bugs.ruby-lang.org/