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Bind the random UDP source port exclusively on Windows - #158
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TestResolvDNS#test_query_ipv4_address occasionally fails on Windows CI: 1) Failure: TestResolvDNS#test_query_ipv4_address [C:/a/ruby/ruby/src/test/resolv/test_dns.rb:236]: <1> expected but was <0>. On Windows, Resolv picks a random source port by itself and binds 0.0.0.0 to it. Windows allows this even when another socket has already bound 127.0.0.1 to the same port, and then delivers datagrams sent to 127.0.0.1 to that other socket. When the chosen port collides like this, the reply from the nameserver on 127.0.0.1 never reaches the resolver, which waits out every timeout and returns no resources. This commit sets SO_EXCLUSIVEADDRUSE before binding so that bind fails on a port another socket already uses, and retries with another port. Ruby does not define Socket::SO_EXCLUSIVEADDRUSE, so its value, ~SO_REUSEADDR, is used directly. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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TestResolvDNS#test_query_ipv4_address occasionally fails on Windows CI:
On Windows, Resolv picks a random source port by itself and binds 0.0.0.0 to it. Windows allows this even when another socket has already bound 127.0.0.1 to the same port, and then delivers datagrams sent to 127.0.0.1 to that other socket. When the chosen port collides like this, the reply from the nameserver on 127.0.0.1 never reaches the resolver, which waits out every timeout and returns no resources.
This commit sets SO_EXCLUSIVEADDRUSE before binding so that bind fails on a port another socket already uses, and retries with another port. Ruby does not define Socket::SO_EXCLUSIVEADDRUSE, so its value, ~SO_REUSEADDR, is used directly.