feat: expand device networking and management

internal/exportproxy/proxy_shared.go

@@ -0,0 +1,55 @@
+package exportproxy
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"time"
+)
+
+const proxyTimeout = 30 * time.Second
+
+func dialTarget(ctx context.Context, address string, dialer *net.Dialer, resolver *net.Resolver) (net.Conn, error) {
+	host, port, err := net.SplitHostPort(address)
+	if err != nil {
+		return nil, err
+	}
+	if ip := net.ParseIP(host); ip != nil {
+		return dialer.DialContext(ctx, "tcp", net.JoinHostPort(ip.String(), port))
+	}
+	ips, err := resolver.LookupIPAddr(ctx, host)
+	if err != nil {
+		return nil, err
+	}
+	var lastErr error
+	for _, ip := range ips {
+		connection, err := dialer.DialContext(ctx, "tcp", net.JoinHostPort(ip.IP.String(), port))
+		if err == nil {
+			return connection, nil
+		}
+		lastErr = err
+	}
+	if lastErr == nil {
+		lastErr = fmt.Errorf("%w: no addresses for %s", errors.ErrUnsupported, host)
+	}
+	return nil, lastErr
+}
+
+func pipe(left, right net.Conn) {
+	done := make(chan struct{}, 2)
+	go func() { _, _ = copyConnection(right, left); done <- struct{}{} }()
+	go func() { _, _ = copyConnection(left, right); done <- struct{}{} }()
+	<-done
+}
+
+func copyConnection(destination net.Conn, source net.Conn) (int64, error) {
+	written, err := io.CopyBuffer(destination, source, make([]byte, 32*1024))
+	if err == nil && written > 0 {
+		if connection, ok := destination.(interface{ CloseWrite() error }); ok {
+			_ = connection.CloseWrite()
+		}
+	}
+	return written, err
+}