From: rubybugs@... Date: 2014-02-22T12:52:00+00:00 Subject: [ruby-core:61013] [ruby-trunk - Bug #9544] Ruby resolver not using autoport Issue #9544 has been updated by Jakub Szafranski. 
# ruby -rsocket -e '10.times { p Addrinfo.udp("0.0.0.0", 0).bind.local_address }'
#<Addrinfo: 0.0.0.0:65533 UDP>
#<Addrinfo: 0.0.0.0:65532 UDP>
#<Addrinfo: 0.0.0.0:65531 UDP>
#<Addrinfo: 0.0.0.0:65530 UDP>
#<Addrinfo: 0.0.0.0:65529 UDP>
#<Addrinfo: 0.0.0.0:65528 UDP>
#<Addrinfo: 0.0.0.0:65527 UDP>
#<Addrinfo: 0.0.0.0:65526 UDP>
#<Addrinfo: 0.0.0.0:65525 UDP>
#<Addrinfo: 0.0.0.0:65524 UDP>
BUT: 
# sysctl -w net.inet.udp.rfc6056.selected=random_pick
net.inet.udp.rfc6056.selected: bsd -> random_pick
# ruby -rsocket -e '10.times { p Addrinfo.udp("0.0.0.0", 0).bind.local_address }'
#<Addrinfo: 0.0.0.0:56358 UDP>
#<Addrinfo: 0.0.0.0:52365 UDP>
#<Addrinfo: 0.0.0.0:58857 UDP>
#<Addrinfo: 0.0.0.0:53113 UDP>
#<Addrinfo: 0.0.0.0:49585 UDP>
#<Addrinfo: 0.0.0.0:62833 UDP>
#<Addrinfo: 0.0.0.0:65299 UDP>
#<Addrinfo: 0.0.0.0:53542 UDP>
#<Addrinfo: 0.0.0.0:60367 UDP>
#<Addrinfo: 0.0.0.0:52945 UDP>
# uname -mrsv
NetBSD 6.1.3 NetBSD 6.1.3 (GENERIC) amd64
So basically, the system admin can change the random port alghoritm, and he can choose from a variety of alghoritms: 
# sysctl net.inet.udp.rfc6056.available
net.inet.udp.rfc6056.available = bsd random_start random_pick hash doublehash randinc
Once again - I really think that it's not ruby case to randomize the port - in my opinion, this should always rely on the underlying system, and such thing shouldn't be forced by the language itself. ---------------------------------------- Bug #9544: Ruby resolver not using autoport https://bugs.ruby-lang.org/issues/9544#change-45419 * Author: Jakub Szafranski * Status: Feedback * Priority: Normal * Assignee: * Category: core * Target version: current: 2.2.0 * ruby -v: ruby 2.1.0p0 (2013-12-25 revision 44422) [x86_64-freebsd9.1] * Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN, 2.1: UNKNOWN ---------------------------------------- ### Problem On one of my production servers I've noticed that customers were failing to install anything using gem and the latest ruby. After a bit of debugging we've found out, that it's related to ruby resolve module: 
> p Resolv.getaddress "google.com"
Errno::EPERM: Operation not permitted - bind(2) for "0.0.0.0" port 62374
        from /home/pudlobe/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/resolv.rb:654:in `bind'
        from /home/pudlobe/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/resolv.rb:654:in `bind_random_port'
        from /home/pudlobe/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/resolv.rb:747:in `block in initialize'
        from /home/pudlobe/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/resolv.rb:735:in `each'
        ...
The interesting part is _bind_random_port_ function. What for? The standard way of binding to a random port for udp connection is to use port 0. And on that particular machine it fails because it's using a mac_portacl module to filter which user can bind to what ports. **However, port 0 is excepted from this rule, because it's the AUTOPORT** - practically every system that allows such port filtering also allows to set an exception for the autoport. ### Docs 
Purpose:

Port 0 is officially a reserved port in TCP/IP networking, meaning that it should not be used for any TCP or UDP network communications. However, port 0 sometimes takes on a special meaning in network programming, particularly Unix socket programming. In that environment, port 0 is a programming technique for specifying system-allocated (dynamic) ports.
Description:

Configuring a new socket connection requires assigning a TCP or UDP port number. Instead of hard-coding a particular port number, or writing code that searches for an available port on the local system, network programmers can instead specify port 0 as a connection parameter. That triggers the operating system to automatically search for and return the next available port in the dynamic port number range.
### Impact This bug affects every system that has a restricted port-binding policy, making ruby unavailable for security-freak admins ;) ### Suggested fix: Either use port 0 to bind to the port, or at least make an option for the system admin/end user to specify the port by himself. -- http://bugs.ruby-lang.org/