TCPServer returning "0:0:0:0:0:0:0:0" as bound ip address

[HoneyryderChuck]

Environment Information

Provide at least:

• JRuby version: jruby 9.4.6.0 (3.1.4) 2024-02-20 576fab2 OpenJDK 64-Bit Server VM 25.402-b06 on 1.8.0_402-b06 +jit [x86_64-linux]
• Operating system and platform: docker image (jruby:9.4)

Expected Behavior

The httpx jruby suite started failing recently, when a certain proxy test would try to bind to the "0:0:0:0:0:0:0:0" address. This address was collected from here, where I confirmed that, after initiating the server with TCPServer.new(0), the call to .addr returns "0:0:0:0:0:0:0:0" in the 3rd and 4th array elements.

This seems to only happen on gitlab CI though, as locally it consistently returns "0:0:0:0"

[headius]

I suspect this is due to differences in that environment relaing to IPv6 and the Java/JDK being run.

You say that locally it's "0:0:0:0" which seems a strange address to me, given that the catch-all address for IPv6 should be "0:0:0:0:0:0:0:0" as you say it does on Gitlab CI. Do you mean "0.0.0.0"?

There are some JVM properties you can set (with -J-D<property> flag to JRuby or JAVA_OPTS=-D<property> env var) that will change how JDK decides to use IPv6 vs IPv4. Perhaps you can give some of these a try and see if it helps?

https://docs.oracle.com/javase/8/docs/technotes/guides/net/ipv6_guide/#ipv6-related