Merge pull request #167 from SenseUnit/set-dst

set-dst:// dialer

Author: Snawoot

README.md

@@ -431,6 +431,7 @@ Supported proxy schemes are:
 * `force-resolve` - pseudo-proxy forcing domain name resolve before it will be passed to the next proxy in the chain. Must wrap actual proxy dialer in the chain (i.e. be specified in last `-proxy` argument). Example: `force-resolve://`
 * `chain` - pseudo-proxy assembling a chain from other proxy specifications. Query string parameters are:
   * `next` - specification of the next proxy in chain. This query string parameter can be specified more than once. Example: `chain://?next=http%3A%2F%2F127.0.0.1%3A57800&next=force-resolve%3A%2F%2F`.
+* `set-dst` - pseudo-proxy replacing connection destination address with the one specified in hostname part of URI. It is mostly intended for programmatic usage from within routing JS script. Example: `set-dst://localhost:9999`.
 
 ## Configuration files
 

dialer/dialer.go

@@ -21,6 +21,7 @@ func init() {
 	xproxy.RegisterDialerType("h2", H2ProxyDialerFromURL)
 	xproxy.RegisterDialerType("h2c", H2ProxyDialerFromURL)
 	xproxy.RegisterDialerType("set-src-hints", NewHintsSettingDialerFromURL)
+	xproxy.RegisterDialerType("set-dst", NewFixedDstDialerFromURL)
 	xproxy.RegisterDialerType("cached", GetCachedDialer)
 	xproxy.RegisterDialerType("socks5s", SOCKS5SDialerFromURL)
 	xproxy.RegisterDialerType("socks5hs", SOCKS5SDialerFromURL)

dialer/fixed.go

@@ -0,0 +1,45 @@
+package dialer
+
+import (
+	"context"
+	"errors"
+	"net"
+	"net/url"
+
+	xproxy "golang.org/x/net/proxy"
+)
+
+type FixedDstDialer struct {
+	addr string
+	next Dialer
+}
+
+func NewFixedDstDialerFromURL(u *url.URL, next xproxy.Dialer) (xproxy.Dialer, error) {
+	host, port := u.Hostname(), u.Port()
+	if host == "" {
+		return nil, errors.New("missing hostname")
+	}
+	if port == "" {
+		return nil, errors.New("missing port")
+	}
+	return &FixedDstDialer{
+		addr: net.JoinHostPort(host, port),
+		next: MaybeWrapWithContextDialer(next),
+	}, nil
+}
+
+func (d *FixedDstDialer) Dial(network, address string) (net.Conn, error) {
+	return d.DialContext(context.Background(), network, address)
+}
+
+func (d *FixedDstDialer) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
+	return d.next.DialContext(ctx, network, d.addr)
+}
+
+func (d *FixedDstDialer) WantsHostname(_ context.Context, _, _ string) bool {
+	// there is no point resolving address which we will discard anyway
+	return true
+}
+
+var _ Dialer = new(FixedDstDialer)
+var _ HostnameWanter = new(FixedDstDialer)