feat(ext/net): add reuseAddress option for UDP (#13849)

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.

Co-authored-by: Luca Casonato <hello@lcas.dev>

1 files changed, 51 insertions, 0 deletions

diff --git a/cli/tests/unit/tls_test.ts b/cli/tests/unit/tls_test.ts
index 860965e49..df82f6ef6 100644
--- a/cli/tests/unit/tls_test.ts
+++ b/cli/tests/unit/tls_test.ts
@@ -1376,3 +1376,54 @@ Deno.test(
     await Promise.all([server(), startTlsClient()]);
   },
 );
+
+Deno.test(
+  { permissions: { read: false, net: true } },
+  async function listenTlsWithReuseAddr() {
+    const resolvable1 = deferred();
+    const hostname = "localhost";
+    const port = 3500;
+
+    const listener1 = Deno.listenTls({ hostname, port, cert, key });
+
+    const response1 = encoder.encode(
+      "HTTP/1.1 200 OK\r\nContent-Length: 12\r\n\r\nHello World\n",
+    );
+
+    listener1.accept().then(
+      async (conn) => {
+        await conn.write(response1);
+        setTimeout(() => {
+          conn.close();
+          resolvable1.resolve();
+        }, 0);
+      },
+    );
+
+    const conn1 = await Deno.connectTls({ hostname, port, caCerts });
+    conn1.close();
+    listener1.close();
+    await resolvable1;
+
+    const resolvable2 = deferred();
+    const listener2 = Deno.listenTls({ hostname, port, cert, key });
+    const response2 = encoder.encode(
+      "HTTP/1.1 200 OK\r\nContent-Length: 12\r\n\r\nHello World\n",
+    );
+
+    listener2.accept().then(
+      async (conn) => {
+        await conn.write(response2);
+        setTimeout(() => {
+          conn.close();
+          resolvable2.resolve();
+        }, 0);
+      },
+    );
+
+    const conn2 = await Deno.connectTls({ hostname, port, caCerts });
+    conn2.close();
+    listener2.close();
+    await resolvable2;
+  },
+);