Add channel options for a vsock socket's local and remote addresses - #3689

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VictorDebray wants to merge 5 commits into

VictorDebray:feat/add-remote-vsock-address-channel-option

VictorDebray commented Aug 3, 2026 •

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Add channel options to read a vsock socket's local and remote addresses

Motivation

Channel.remoteAddress and Channel.localAddress are always nil on vsock channels.
NIOCore.SocketAddress has no vsock representation. NIOPosix otherwise supports vsock through VsockAddress, ServerBootstrap.bind(to:) and ClientBootstrap.connect(to:).
So a server accepting a vsock connection can't find out which context (VM) connected. A listener bound to VsockAddress/Port/any can't find out which port the kernel gave it.

The peer's context ID is the only identity a vsock connection carries. The kernel supplies it, not the peer. That makes it the natural thing to key authorization on.
ChannelOptions.localVsockContextID already exists for the same reason on the local side. It reports the context ID without the port. A wildcard bind therefore still leaves servers and tests hard-coding a port and racing for it.

Modifications

Add ChannelOptions.Types.RemoteVsockAddress and LocalVsockAddress. Both are get-only options with Value == VsockAddress.
Add BaseSocket.getRemoteVsockAddress() and getLocalVsockAddress(). On a non-vsock socket these calls fill a different sockaddr. Reinterpreting those bytes would yield a context ID derived from unrelated data, such as an IP address and port. Callers key authorization on the CID, so failing beats returning something meaningless.
Service both in SocketChannel.getOption0. LocalVsockAddress is serviced on ServerSocketChannel too, which is the case which needs it. RemoteVsockAddress isn't: a listener has no peer.
Tests: both options are rejected on a connected non-vsock socket. Over vsock loopback, a client's peer port is the port the listener bound, and the accepted channel reports the same CID the client saw. A listener bound to Port/any reports a concrete port and a context ID matching getLocalVsockContextID(), and the channel option agrees with the socket. The loopback tests are gated on System.supportsVsockLoopback, matching testGetLocalCID and testEchoVsock.

Result

let peer = try await channel.getOption(.remoteVsockAddress).get()
peer.cid    // the connecting context's CID

let local = try await listener.getOption(.localVsockAddress).get()
local.port  // the port a Port/any bind was given

VictorDebray mentioned this pull request

Add vsock peer credentials on Posix.Context grpc/grpc-swift-nio-transport#193

Open

VictorDebray changed the title ~~Aadd remote vsock address channel option~~ Add remote vsock address channel option

VictorDebray changed the title ~~Add remote vsock address channel option~~ Add remote local and remote vsock address channels option

VictorDebray changed the title ~~Add remote local and remote vsock address channels option~~ Add channel options for a vsock socket's local and remote addresses

glbrntt requested changes

View reviewed changes

Sources/NIOPosix/VsockAddress.swift Outdated

+              extension ChannelOptions {
+                  /// - seealso: `LocalVsockAddress`
+                  public static let localVsockAddress = Types.LocalVsockAddress()

glbrntt Aug 21, 2026

Contributor

this can also be a static computed var

VictorDebray Aug 28, 2026

Author

Address comment cleanup review and localVsockAddress is a var

Sources/NIOPosix/VsockAddress.swift Outdated

Comment on lines +194 to +200

+                  ///
+                  /// `Channel/localAddress` cannot report a vsock address, because `SocketAddress` has no vsock
+                  /// representation. This option exposes the address that `getsockname` reports for the socket
+                  /// instead.
+                  ///
+                  /// ``LocalVsockContextID`` reports only the context ID, so it can't tell you which port a
+                  /// listener bound to when it was bound to `VsockAddress/Port/any`. This option reports both.

glbrntt Aug 21, 2026

Contributor

This is unnecessary context

VictorDebray Aug 28, 2026

Author

Address comment cleanup review and localVsockAddress is a var

Sources/NIOPosix/VsockAddress.swift Outdated

+              extension ChannelOptions {
+                  /// - seealso: `RemoteVsockAddress`
+                  public static let remoteVsockAddress = Types.RemoteVsockAddress()

glbrntt Aug 21, 2026

Contributor

This can be a static computed var

VictorDebray Aug 28, 2026

Author

Address comment cleanup review and localVsockAddress is a var

Sources/NIOPosix/VsockAddress.swift Outdated

Comment on lines +218 to +223

+                  ///
+                  /// `Channel/remoteAddress` cannot report a vsock peer, because `SocketAddress` has no vsock
+                  /// representation. This option exposes the peer address that `getpeername` reports for the
+                  /// connection instead, which is where the peer's context ID (CID) comes from.
+                  ///
+                  /// Only meaningful on a connected vsock channel; getting it on a listening channel fails.

glbrntt Aug 21, 2026

Contributor

This is unnecessary context

VictorDebray Aug 28, 2026

Author

Address comment cleanup review and localVsockAddress is a var

Sources/NIOPosix/VsockAddress.swift Outdated

Comment on lines +343 to +345

+                  ///
+                  /// ``getLocalVsockContextID()`` reports only the context ID, so it can't say which port a
+                  /// listener bound to when it was bound to `VsockAddress/Port/any`. This reports both.

glbrntt Aug 21, 2026

Contributor

This is unnecessary context

VictorDebray Aug 28, 2026

Author

Address comment cleanup review and localVsockAddress is a var

Tests/NIOPosixTests/VsockAddressTest.swift Outdated

+                      let address = try socket.getLocalVsockAddress()
+                      XCTAssertNotEqual(address.port, .any, "The kernel should have assigned a concrete port")
+                      XCTAssertEqual(address.cid, try socket.getLocalVsockContextID())

glbrntt Aug 24, 2026

Contributor

Can you remove this? We're not testing getLocalVsockContextID here.

VictorDebray Aug 28, 2026

Author

Address comment cleanup review and localVsockAddress is a var

Tests/NIOPosixTests/VsockAddressTest.swift Outdated

Comment on lines +117 to +118

		/// A non-vsock socket must not report a vsock local address, for the same reason
		/// ``testGetRemoteVsockAddressRejectsNonVsockSocket()`` covers on the peer side.

glbrntt Aug 24, 2026

Contributor

Unnecessary context.

VictorDebray Aug 28, 2026

Author

Address comment cleanup review and localVsockAddress is a var

Tests/NIOPosixTests/VsockAddressTest.swift Outdated

Comment on lines +131 to +135

+                  /// A non-vsock socket must not report a vsock peer address.
+                  ///
+                  /// `getpeername` on a UDS socket fills a `sockaddr_un`; if those bytes were reinterpreted as a
+                  /// `sockaddr_vm` the option would return a context ID derived from unrelated memory. Callers use
+                  /// the CID to make trust decisions, so this must fail instead.

glbrntt Aug 24, 2026

Contributor

More noise.

VictorDebray Aug 28, 2026

Author

Address comment cleanup review and localVsockAddress is a var

Tests/NIOPosixTests/VsockAddressTest.swift Outdated

Comment on lines +158 to +162

+                  /// Both ends of a real vsock connection report the peer's address.
+                  ///
+                  /// This is the path the option exists for, so it needs a live connection: it exercises
+                  /// `getpeername` on an `AF_VSOCK` socket and the reinterpretation of the resulting
+                  /// `sockaddr_vm`.

glbrntt Aug 24, 2026

Contributor

More unnecessary context.

VictorDebray Aug 28, 2026

Author

Address comment cleanup review and localVsockAddress is a var

Tests/NIOPosixTests/VsockAddressTest.swift Outdated

Comment on lines +171 to +172

		// Read the peer address on the accepted channel. Sending the address rather than the
		// channel through the promise keeps this Sendable-clean.

glbrntt Aug 24, 2026

Contributor

I think this comment is wrong. Channel is Sendable so there's nothing about sending a channel through a promise that would make this sendable-unclean.

VictorDebray Aug 28, 2026

Author

Address comment cleanup review and localVsockAddress is a var

VictorDebray added 5 commits

August 28, 2026 07:44


          Add a remoteVsockAddress channel option

62682b5

Exposes an accepted vsock connection's peer address -- and therefore the peer
context ID (CID) -- without changing `NIOCore.SocketAddress`.

`Channel/remoteAddress` returns `SocketAddress?`, which has no vsock representation, so it is always nil for vsock channels. Rather than add a `.vsock` case to that public enum (a source-breaking change for every exhaustive switch over it, in NIO and downstream), this mirrors the pattern NIO already uses for the same problem on the local side: `localVsockContextID` is a get-only `ChannelOption` precisely because `localAddress` cannot report a vsock address either.

The helper validates the address family before trusting the result.
On a non-vsock socket `getpeername` fills a different `sockaddr`, and reinterpreting those bytes would yield a context ID derived from unrelated data such as a peer's IP address and port.
Callers use the CID for trust decisions, so a mismatch throws `SocketAddressError.unsupported` instead.
A socketpair-based test covers this and fails if the guard is removed.

All additive: a new option type, a new static accessor, and a new arm in an internal switch. No existing declaration changes, so no exhaustive switch anywhere needs updating.


          Add an end-to-end vsock test for remoteVsockAddress

13501cb

Covers the path the option exists for: a live vsock connection over loopback, where `getpeername` really does fill a `sockaddr_vm`.

The client asserts its peer's port is the one the listener bound, which is what would catch a misread `sockaddr_vm.
Wrong field offsets could not happen to reproduce the chosen port. The accepted channel then asserts reading its peer succeeds and reports the same CID the client saw, since both ends of a loopback connection live in the same context.

Gated on `System.supportsVsockLoopback` in the same way as `testGetLocalCID` and `testEchoVsock`, so it skips on hosts without the transport and runs in the `vsock-tests` CI job, which loads `vsock_loopback` and fails on skipped tests.


          Add a localVsockAddress channel option

84f222f

Mirrors remoteVsockAddress: exposes a vsock socket's local
address (including bound port) since Channel/localAddress
can't represent vsock addresses and LocalVsockContextID
alone can't report the port chosen for Port/any binds.


          fix: vsock test assertion

97a19e9


          Address comment cleanup review and localVsockAddress is a var

770febe

VictorDebray force-pushed the feat/add-remote-vsock-address-channel-option branch from cd798aa to 770febe Compare

August 28, 2026 15:07

VictorDebray commented Aug 28, 2026

Author

Addressed all reviews!

VictorDebray commented Aug 28, 2026

Author

Address all comment reviews and make remote and localvsock a var.

glbrntt requested changes

View reviewed changes

Sources/NIOPosix/VsockAddress.swift

Comment on lines +347 to +353

+                          var addr = sockaddr_vm()
+                          var len = socklen_t(MemoryLayout<sockaddr_vm>.size)
+                          try withUnsafeMutablePointer(to: &addr) { addrPtr in
+                              try addrPtr.withMemoryRebound(to: sockaddr.self, capacity: 1) { sockaddrPtr in
+                                  try getName(fd, sockaddrPtr, &len)
+                              }
+                          }

glbrntt Sep 1, 2026

Contributor

sockaddr_vm and sockaddr are different sizes on Darwin (12 vs. 16; they're both 16 on Linux), so this rebinds out of bounds. This should use sockaddr_storage:

var addr = sockaddr_storage()
try addr.withMutableSockAddr { addrPtr, size in
    var size = socklen_t(size)
    try self.withUnsafeHandle {
        try getName($0, addrPtr, &size)
    }
}

You can then call convert() to get the sockaddr_vm.

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