feat(ext/net): add reuseAddress option for UDP

[Trolloldem]

This commit adds a reuseAddress option for UDP sockets. When this option is enabled, one can listen on an address even though it is already being listened on from a different process or thread. The new socket will steal the address from the existing socket.

On Windows and Linux this uses the SO_REUSEADDR option, while on other Unixes this is done with SO_REUSEPORT.

This behavior aligns with what libuv does.

TCP sockets still unconditionally set the SO_REUSEADDR flag - this behavior matches Node.js and Go. This PR does not change this behaviour.

[Trolloldem]

I think there is something wrong with this PR. The CI keep failing even after several resets, but when I run the same CI after a merge of the branch on my main branch, which starts from a clean state, they are successful. Am I doing something wrong in the process?

[bartlomieju]

@Trolloldem you are hitting an internal compiler error in Rust. You can (most likely) fix this, by changing cache keys in .github/workflows/ci.yml - 5-cargo-... to 6-cargo-...

[Trolloldem]

Thank you @bartlomieju, it seems fine now. Is it better to also add test for the described behavior in Windows?

[CLAassistant]

All committers have signed the CLA.

[bartlomieju]

Thank you @bartlomieju, it seems fine now. Is it better to also add test for the described behavior in Windows?

That would be great! I'll try to get this landed for 1.20

[Trolloldem]

Thank you @bartlomieju, it seems fine now. Is it better to also add test for the described behavior in Windows?

That would be great! I'll try to get this landed for 1.20

Test for Windows behavior added and CI seem fine. I leave here a quick reference about the tests implemented:

• netTcpReuseAddr opens a socket using the default setting for SO_REUSEADDR of each OS, then the socket is closed,
  putting it in the TIME_WAIT state; a second socket is successfully opened
• netTcpNoReuseAddr performs the same steps of the previous test but SO_REUSEADDR is set to false, in order to test the behavior in OS different from Windows. In this case the test has to fail with an AddrInUse error. This test can fail in two point, proving the same property, the first point being the first listener creation (it can fail since sockets from previous tests that occupied the required port are in the TIME_WAIT state) while the second point is the creation of the second listener (since the first one is in the TIME_WAIT state)
• netTcpTrueReuseAddrWindows set SO_REUSEADDR to true and is run only in Windows. In this case two listeners are bound to the same port, which is usually forbidden for the default setting of SO_REUSEADDR equal to false

The tests listenTlsWithReuseAddr, listenTlsWithNoReuseAddr and listenTlsWithTrueReuseAddrWindows follow the same
logic but are for listenTls

[bartlomieju]

@Trolloldem sorry for the delay, I've got two nitpicks and after that we can land the PR.

[Trolloldem]

@Trolloldem sorry for the delay, I've got two nitpicks and after that we can land the PR.

No problem to me. I've noticed there was a lot of things moving with 1.20, so I took the chance to rearrange the commit history of the PR into a single commit + one commit to change the cache key.

I've addressed the requests concerning the docstrings and merged my branch with the latest version of the main branch of Deno

[ry]

Why default to true? Does Node default to true?

[Trolloldem]

SO_REUSEADDR defaults to true since, as stated in #13808, the previous implementation of TCP socket used the std::net implementation, which sets SO_REUSEADDR to true when binding a TcpListener outside of Windows. In this way it is possible to keep the behavior of existing code that does not explicit use the new reuseAddress argument. Setting this to false as default value could break existing code due to the fact that in Unix system is not possible to bind socket to a combination of address+port occupied by closed sockets in the TIME_WAIT state, as visible in failed tests in #13794. In addition, this seem the same behavior of node: unix tcp, win tcp.

[Trolloldem]

The changes introduced up to now concern only TCP sockets. With the last two commits I have extended the possibility of using the SO_REUSEADDR even for UDP sockets. Since they have a different behavior compared to TCP sockets, I have also updated the docstring of the reuseAddress optional argument. This argument now can be specified through Deno.listenDatagram. In addition to that, 2 new test have been added: netUdpReuseAddr and netUdpNoReuseAddr.

To enable this option, the Socket2 crate has been used, using the same settings of the std::net implementation of UdpSocket.

Similarly to node (win udp, unix udp), the options always defaults to false, and for both Windows and Linux setting SO_REUSEADDR actually uses that option under the hood. For the other *nix systems SO_REUSEPORT is actually used.

[Trolloldem]

The changes introduced up to now concern only TCP sockets. With the last two commits I have extended the possibility of using the SO_REUSEADDR even for UDP sockets. Since they have a different behavior compared to TCP sockets, I have also updated the docstring of the reuseAddress optional argument. This argument now can be specified through Deno.listenDatagram. In addition to that, 2 new test have been added: netUdpReuseAddr and netUdpNoReuseAddr.

To enable this option, the Socket2 crate has been used, using the same settings of the std::net implementation of UdpSocket.

Similarly to node (win udp, unix udp), the options always defaults to false, and for both Windows and Linux setting SO_REUSEADDR actually uses that option under the hood. For the other *nix systems SO_REUSEPORT is actually used.

@bartlomieju sorry for the ping. Should I change the title after these changes (since now also UDP should be covered). In addition, is this still a requested feature? Should I provide any additional documentation?

[bartlomieju]

@littledivy @lucacasonato could you take a look at this PR?

[lucacasonato]

I have rebased this PR.

I have removed the reuseAddress option for TCP sockets. For TCP, this option is unconfigurably true on all platforms but Windows. This behaviour matches Node.js and Go. Neither of these systems support disabling SO_REUSEADDR on socket listeners.

For UDP, reuseAddress is supported. It has the same port stealing behaviour on all systems we support, but to achieve this it uses different syscalls on different platforms. macOS and other BSDs use SO_REUSEADDR, while Linux and Windows use SO_REUSEPORT. This behaviour matches libuv.

As a follow up PR we can add a reusePort option to enable the kernel connection load balancing behaviour found in Linux, for TCP sockets.

I think this PR is now good to go.

[Trolloldem]

I have rebased this PR.

I have removed the reuseAddress option for TCP sockets. For TCP, this option is unconfigurably true on all platforms but Windows. This behaviour matches Node.js and Go. Neither of these systems support disabling SO_REUSEADDR on socket listeners.

For UDP, reuseAddress is supported. It has the same port stealing behaviour on all systems we support, but to achieve this it uses different syscalls on different platforms. macOS and other BSDs use SO_REUSEADDR, while Linux and Windows use SO_REUSEPORT. This behaviour matches libuv.

As a follow up PR we can add a reusePort option to enable the kernel connection load balancing behaviour found in Linux, for TCP sockets.

I think this PR is now good to go.

Thank you for reviewing my PR @lucacasonato! Just as a little remark, in your summary: macOS and other BSDs use SO_REUSEADDR, while Linux and Windows use SO_REUSEPORT. This behaviour matches libuv, it is actually the opposite (as pointed out in the comment referring libuv in ops.rs

[lucacasonato]

LGTM

[littledivy]

LGTM!