Link refactor (#941)

* Link refactoring

* More refactoring

* More tweaking

* Cleaner shutdowns, UNIX socket support, more tweaks

* Actorise links, remove mutex

* SOCKS support

src/core/link_unix.go

@@ -0,0 +1,98 @@
+package core
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/url"
+	"time"
+
+	"github.com/Arceliar/phony"
+)
+
+type linkUNIX struct {
+	phony.Inbox
+	*links
+	dialer     *net.Dialer
+	listener   *net.ListenConfig
+	_listeners map[*Listener]context.CancelFunc
+}
+
+func (l *links) newLinkUNIX() *linkUNIX {
+	lt := &linkUNIX{
+		links: l,
+		dialer: &net.Dialer{
+			Timeout:   time.Second * 5,
+			KeepAlive: -1,
+		},
+		listener: &net.ListenConfig{
+			KeepAlive: -1,
+		},
+		_listeners: map[*Listener]context.CancelFunc{},
+	}
+	return lt
+}
+
+func (l *linkUNIX) dial(url *url.URL, options linkOptions, _ string) error {
+	info := linkInfoFor("unix", "", url.Path)
+	if l.links.isConnectedTo(info) {
+		return fmt.Errorf("duplicate connection attempt")
+	}
+	addr, err := net.ResolveUnixAddr("unix", url.Path)
+	if err != nil {
+		return err
+	}
+	conn, err := l.dialer.DialContext(l.core.ctx, "unix", addr.String())
+	if err != nil {
+		return err
+	}
+	return l.handler(url.String(), info, conn, options, false)
+}
+
+func (l *linkUNIX) listen(url *url.URL, _ string) (*Listener, error) {
+	ctx, cancel := context.WithCancel(l.core.ctx)
+	listener, err := l.listener.Listen(ctx, "unix", url.Path)
+	if err != nil {
+		cancel()
+		return nil, err
+	}
+	entry := &Listener{
+		Listener: listener,
+		closed:   make(chan struct{}),
+	}
+	phony.Block(l, func() {
+		l._listeners[entry] = cancel
+	})
+	l.core.log.Printf("UNIX listener started on %s", listener.Addr())
+	go func() {
+		defer phony.Block(l, func() {
+			delete(l._listeners, entry)
+		})
+		for {
+			conn, err := listener.Accept()
+			if err != nil {
+				cancel()
+				break
+			}
+			info := linkInfoFor("unix", "", url.String())
+			if err = l.handler(url.String(), info, conn, linkOptions{}, true); err != nil {
+				l.core.log.Errorln("Failed to create inbound link:", err)
+			}
+		}
+		listener.Close()
+		close(entry.closed)
+		l.core.log.Printf("UNIX listener stopped on %s", listener.Addr())
+	}()
+	return entry, nil
+}
+
+func (l *linkUNIX) handler(name string, info linkInfo, conn net.Conn, options linkOptions, incoming bool) error {
+	return l.links.create(
+		conn,     // connection
+		name,     // connection name
+		info,     // connection info
+		incoming, // not incoming
+		false,    // not forced
+		options,  // connection options
+	)
+}