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Bug #21790 » ruby_dns_fork_bug.rb

Reproduction Script - adamoffat (Adam Moffat), 12/17/2025 06:02 PM

 
#!/usr/bin/env ruby
# Reproduction script for macOS 26.x DNS fork bug
# Run with: ruby ruby_dns_fork_bug.rb
#
# Note: Remove the Timeout.timeout(90) wrapper to observe the hang
# indefinitely. The timeout is included only to allow the script to
# exit for testing purposes.

require "socket"
require "timeout"

puts "Ruby #{RUBY_VERSION} on #{RUBY_PLATFORM}"
puts "Testing DNS resolution after fork..."

# Parent performs DNS lookup for IPv4-only host
Socket.getaddrinfo("api.segment.io", 443, nil, :STREAM)
puts "Parent: DNS completed"

# Fork and try DNS in child
pid = fork do
puts "Child: Attempting DNS resolution..."
begin
Timeout.timeout(90) do
Socket.getaddrinfo("api.segment.io", 443, nil, :STREAM)
end
puts "Child: SUCCESS"
exit 0
rescue Timeout::Error
puts "Child: FAILED - hung for 90 seconds"
exit 1
end
end

Process.wait(pid)
exit_code = $?.exitstatus

if exit_code == 0
puts "PASS: Bug not present"
else
puts "FAIL: Bug reproduced - DNS resolution hung after fork"
end

exit exit_code
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