tests: Remove asserts on the value of local Vsock CID

.github/workflows/pull_request.yml

@@ -41,3 +41,21 @@ jobs:
     with:
       name: "Integration tests"
       matrix_linux_command: "apt-get update -y -q && apt-get install -y -q lsof dnsutils netcat-openbsd net-tools curl jq && ./scripts/integration_tests.sh"
+
+  vsock-tests:
+    name: Vsock tests
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+      - name: Load vsock_loopback kernel module
+        run: sudo modprobe vsock_loopback
+      - name: Build package tests
+        run: swift build --build-tests
+      - name: Run Vsock tests
+        shell: bash  # explicitly choose bash, which ensures -o pipefail
+        run: swift test --filter "(?i)vsock" | tee test.out
+      - name: Check for skipped tests
+        run: test -r test.out && ! grep -i skipped test.out

Sources/NIOPosix/VsockAddress.swift

@@ -217,7 +217,7 @@ extension VsockAddress.ContextID {
     /// - On Darwin, the `ioctl()` request operates on a socket.
     /// - On Linux, the `ioctl()` request operates on the `/dev/vsock` device.
     ///
-    /// - Note: On Linux, ``local`` may be a better choice.
+    /// - Note: The semantics of this `ioctl` vary between vsock transports on Linux; ``local`` may be more suitable.
     static func getLocalContextID(_ socketFD: NIOBSDSocket.Handle) throws -> Self {
         #if canImport(Darwin)
         let request = CNIODarwin_IOCTL_VM_SOCKETS_GET_LOCAL_CID

Tests/NIOPosixTests/AsyncChannelBootstrapTests.swift

@@ -1141,7 +1141,7 @@ final class AsyncChannelBootstrapTests: XCTestCase {
     // MARK: VSock
 
     func testVSock() async throws {
-        try XCTSkipUnless(System.supportsVsock, "No vsock transport available")
+        try XCTSkipUnless(System.supportsVsockLoopback, "No vsock loopback transport available")
         let eventLoopGroup = MultiThreadedEventLoopGroup(numberOfThreads: 3)
         defer {
             try! eventLoopGroup.syncShutdownGracefully()

Tests/NIOPosixTests/EchoServerClientTest.swift

@@ -234,7 +234,7 @@ class EchoServerClientTest: XCTestCase {
     }
 
     func testEchoVsock() throws {
-        try XCTSkipUnless(System.supportsVsock, "No vsock transport available")
+        try XCTSkipUnless(System.supportsVsockLoopback, "No vsock loopback transport available")
         let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
         defer {
             XCTAssertNoThrow(try group.syncShutdownGracefully())

Tests/NIOPosixTests/TestUtils.swift

@@ -30,19 +30,10 @@ extension System {
         }
     }
 
-    static var supportsVsock: Bool {
-        #if canImport(Darwin) || os(Linux) || os(Android)
-        guard let socket = try? Socket(protocolFamily: .vsock, type: .stream) else { return false }
-        XCTAssertNoThrow(try socket.close())
-        #if !canImport(Darwin)
-        do {
-            let fd = try Posix.open(file: "/dev/vsock", oFlag: O_RDONLY | O_CLOEXEC)
-            try Posix.close(descriptor: fd)
-        } catch {
-            return false
-        }
-        #endif
-        return true
+    static var supportsVsockLoopback: Bool {
+        #if os(Linux) || os(Android)
+        guard let modules = try? String(contentsOf: URL(fileURLWithPath: "/proc/modules")) else { return false }
+        return modules.split(separator: "\n").compactMap({ $0.split(separator: " ").first }).contains("vsock_loopback")
         #else
         return false
         #endif

Tests/NIOPosixTests/VsockAddressTest.swift

@@ -58,15 +58,15 @@ class VsockAddressTest: XCTestCase {
     }
 
     func testGetLocalCID() throws {
-        try XCTSkipUnless(System.supportsVsock)
+        try XCTSkipUnless(System.supportsVsockLoopback, "No vsock loopback transport available")
 
         let socket = try ServerSocket(protocolFamily: .vsock, setNonBlocking: true)
         defer { try? socket.close() }
 
-        // Check the local CID is valid: higher than reserved values, but not VMADDR_CID_ANY.
+        // Check we can get the local CID using the static property on ContextID.
         let localCID = try socket.withUnsafeHandle(VsockAddress.ContextID.getLocalContextID)
-        XCTAssertNotEqual(localCID, .any)
-        XCTAssertGreaterThan(localCID.rawValue, VsockAddress.ContextID.host.rawValue)
+
+        // Check the local CID from the socket matches.
         XCTAssertEqual(try socket.getLocalVsockContextID(), localCID)
 
         // Check the local CID from the channel option matches.