|
| 1 | +// Package main is the rdd-guest agent that runs inside the Lima/WSL2 VM. |
| 2 | +// It listens on a vsock port and forwards connections to the Docker socket, |
| 3 | +// enabling the Windows host to reach /var/run/docker.sock via Hyper-V vsock. |
| 4 | +package main |
| 5 | + |
| 6 | +import ( |
| 7 | + "context" |
| 8 | + "errors" |
| 9 | + "io" |
| 10 | + "log" |
| 11 | + "net" |
| 12 | + "os" |
| 13 | + "os/signal" |
| 14 | + "sync" |
| 15 | + "syscall" |
| 16 | + "time" |
| 17 | + |
| 18 | + "github.com/mdlayher/vsock" |
| 19 | +) |
| 20 | + |
| 21 | +const ( |
| 22 | + vsockPort = 6660 |
| 23 | + dockerSockPath = "/var/run/docker.sock" |
| 24 | +) |
| 25 | + |
| 26 | +func main() { |
| 27 | + ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM) |
| 28 | + defer stop() |
| 29 | + |
| 30 | + l, err := vsock.Listen(vsockPort, nil) |
| 31 | + if err != nil { |
| 32 | + log.Fatalf("vsock listen: %v", err) |
| 33 | + } |
| 34 | + |
| 35 | + log.Printf("rdd-guest: listening on vsock port %d", vsockPort) |
| 36 | + |
| 37 | + go func() { |
| 38 | + <-ctx.Done() |
| 39 | + if err := l.Close(); err != nil { |
| 40 | + log.Printf("rdd-guest: close listener: %v", err) |
| 41 | + } |
| 42 | + }() |
| 43 | + |
| 44 | + for { |
| 45 | + conn, err := l.Accept() |
| 46 | + if err != nil { |
| 47 | + if ctx.Err() != nil { |
| 48 | + return |
| 49 | + } |
| 50 | + log.Printf("rdd-guest: accept: %v", err) |
| 51 | + if errors.Is(err, syscall.ECONNABORTED) { |
| 52 | + continue |
| 53 | + } |
| 54 | + select { |
| 55 | + case <-time.After(time.Second): |
| 56 | + case <-ctx.Done(): |
| 57 | + return |
| 58 | + } |
| 59 | + continue |
| 60 | + } |
| 61 | + go handleConn(ctx, conn) |
| 62 | + } |
| 63 | +} |
| 64 | + |
| 65 | +// TODO: once rancher-desktop-daemon is public, replace the inlined halfCloser, |
| 66 | +// pipe(), and handleConn() here with a direct import of pkg/socketbridge, which |
| 67 | +// contains the implementations (HalfCloser interface, Pipe function). |
| 68 | + |
| 69 | +// halfCloser is a net.Conn that can independently close the write side. |
| 70 | +type halfCloser interface { |
| 71 | + net.Conn |
| 72 | + CloseWrite() error |
| 73 | +} |
| 74 | + |
| 75 | +// handleConn forwards bytes between the vsock connection and the Docker socket. |
| 76 | +// It rejects connections that do not originate from the Windows host (CID 2 / |
| 77 | +// vsock.Host): any process in any WSL2 distro shares the same vsock namespace |
| 78 | +// and could otherwise gain root Docker API access. |
| 79 | +func handleConn(ctx context.Context, vsockConn net.Conn) { |
| 80 | + defer func() { |
| 81 | + if err := vsockConn.Close(); err != nil { |
| 82 | + log.Printf("rdd-guest: close vsock conn: %v", err) |
| 83 | + } |
| 84 | + }() |
| 85 | + |
| 86 | + addr, ok := vsockConn.RemoteAddr().(*vsock.Addr) |
| 87 | + if !ok || addr.ContextID != vsock.Host { |
| 88 | + log.Printf("rdd-guest: rejected connection from %v", vsockConn.RemoteAddr()) |
| 89 | + return |
| 90 | + } |
| 91 | + |
| 92 | + dockerConn, err := (&net.Dialer{}).DialContext(ctx, "unix", dockerSockPath) |
| 93 | + if err != nil { |
| 94 | + log.Printf("rdd-guest: dial docker: %v", err) |
| 95 | + return |
| 96 | + } |
| 97 | + defer func() { |
| 98 | + if err := dockerConn.Close(); err != nil { |
| 99 | + log.Printf("rdd-guest: close docker conn: %v", err) |
| 100 | + } |
| 101 | + }() |
| 102 | + |
| 103 | + vsockHC, ok := vsockConn.(halfCloser) |
| 104 | + if !ok { |
| 105 | + log.Printf("rdd-guest: vsock conn from %v does not support CloseWrite", vsockConn.RemoteAddr()) |
| 106 | + return |
| 107 | + } |
| 108 | + dockerHC, ok := dockerConn.(halfCloser) |
| 109 | + if !ok { |
| 110 | + log.Printf("rdd-guest: docker conn for %v does not support CloseWrite", vsockConn.RemoteAddr()) |
| 111 | + return |
| 112 | + } |
| 113 | + pipe(vsockHC, dockerHC) |
| 114 | +} |
| 115 | + |
| 116 | +// pipe bidirectionally proxies between a and b until both directions are done. |
| 117 | +func pipe(a, b halfCloser) { |
| 118 | + var wg sync.WaitGroup |
| 119 | + |
| 120 | + forward := func(dst, src halfCloser) { |
| 121 | + defer wg.Done() |
| 122 | + _, err := io.Copy(dst, src) |
| 123 | + if err != nil && !errors.Is(err, io.EOF) { |
| 124 | + log.Printf("rdd-guest: copy: %v", err) |
| 125 | + } |
| 126 | + _ = dst.CloseWrite() |
| 127 | + } |
| 128 | + |
| 129 | + wg.Add(2) |
| 130 | + go forward(a, b) |
| 131 | + go forward(b, a) |
| 132 | + wg.Wait() |
| 133 | +} |
0 commit comments