add new files for compat layer

overlay/wireguard_tun_linux.go

@@ -0,0 +1,102 @@
+//go:build linux && !android && !e2e_testing
+
+package overlay
+
+import (
+	"fmt"
+	"sync"
+
+	wgtun "github.com/slackhq/nebula/wgstack/tun"
+)
+
+type wireguardTunIO struct {
+	dev       wgtun.Device
+	mtu       int
+	batchSize int
+
+	readMu   sync.Mutex
+	readBufs [][]byte
+	readLens []int
+	pending  [][]byte
+	pendIdx  int
+
+	writeMu   sync.Mutex
+	writeBuf  []byte
+	writeWrap [][]byte
+}
+
+func newWireguardTunIO(dev wgtun.Device, mtu int) *wireguardTunIO {
+	batch := dev.BatchSize()
+	if batch <= 0 {
+		batch = 1
+	}
+	if mtu <= 0 {
+		mtu = DefaultMTU
+	}
+	bufs := make([][]byte, batch)
+	for i := range bufs {
+		bufs[i] = make([]byte, wgtun.VirtioNetHdrLen+mtu)
+	}
+	return &wireguardTunIO{
+		dev:       dev,
+		mtu:       mtu,
+		batchSize: batch,
+		readBufs:  bufs,
+		readLens:  make([]int, batch),
+		pending:   make([][]byte, 0, batch),
+		writeBuf:  make([]byte, wgtun.VirtioNetHdrLen+mtu),
+		writeWrap: make([][]byte, 1),
+	}
+}
+
+func (w *wireguardTunIO) Read(p []byte) (int, error) {
+	w.readMu.Lock()
+	defer w.readMu.Unlock()
+
+	for {
+		if w.pendIdx < len(w.pending) {
+			segment := w.pending[w.pendIdx]
+			w.pendIdx++
+			n := copy(p, segment)
+			return n, nil
+		}
+
+		n, err := w.dev.Read(w.readBufs, w.readLens, wgtun.VirtioNetHdrLen)
+		if err != nil {
+			return 0, err
+		}
+		w.pending = w.pending[:0]
+		w.pendIdx = 0
+		for i := 0; i < n; i++ {
+			length := w.readLens[i]
+			if length == 0 {
+				continue
+			}
+			segment := w.readBufs[i][wgtun.VirtioNetHdrLen : wgtun.VirtioNetHdrLen+length]
+			w.pending = append(w.pending, segment)
+		}
+	}
+}
+
+func (w *wireguardTunIO) Write(p []byte) (int, error) {
+	if len(p) > w.mtu {
+		return 0, fmt.Errorf("wireguard tun: payload exceeds MTU (%d > %d)", len(p), w.mtu)
+	}
+	w.writeMu.Lock()
+	defer w.writeMu.Unlock()
+	buf := w.writeBuf[:wgtun.VirtioNetHdrLen+len(p)]
+	for i := 0; i < wgtun.VirtioNetHdrLen; i++ {
+		buf[i] = 0
+	}
+	copy(buf[wgtun.VirtioNetHdrLen:], p)
+	w.writeWrap[0] = buf
+	n, err := w.dev.Write(w.writeWrap, wgtun.VirtioNetHdrLen)
+	if err != nil {
+		return n, err
+	}
+	return len(p), nil
+}
+
+func (w *wireguardTunIO) Close() error {
+	return nil
+}