From: Colin Watson Date: Mon, 26 Aug 2024 01:30:07 +0100 Subject: Deduplicate results from getaddrinfo In certain configurations it's possible to get duplicate results back from getaddrinfo: for example, if you accidentally have more than one line in /etc/hosts mapping the same name to the same IP address, then Linux/glibc systems will return multiple identical entries. This minor misconfiguration is normally harmless, but it caused this program to fail with `EADDRINUSE`: require 'socket' Socket.tcp_server_sockets('localhost', 0) Prior to https://github.com/ruby/net-http/pull/180, this caused a number of `TestNetHTTP*` tests to fail, as seen in these Debian bugs: https://bugs.debian.org/1069399 (Ruby 3.1) https://bugs.debian.org/1064685 (Ruby 3.2) https://bugs.debian.org/1077462 (Ruby 3.3) It's easy enough to deduplicate these. --- ext/socket/lib/socket.rb | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/ext/socket/lib/socket.rb b/ext/socket/lib/socket.rb index de54222..12955e2 100644 --- a/ext/socket/lib/socket.rb +++ b/ext/socket/lib/socket.rb @@ -673,10 +673,16 @@ class Socket < BasicSocket # :stopdoc: def self.ip_sockets_port0(ai_list, reuseaddr) sockets = [] + ai_seen = {} begin sockets.clear port = nil ai_list.each {|ai| + ai_id = [ai.pfamily, ai.socktype, ai.protocol, ai.ip_address] + if ai_seen.include?(ai_id) + next + end + ai_seen[ai_id] = nil begin s = Socket.new(ai.pfamily, ai.socktype, ai.protocol) rescue SystemCallError