rpc rewrite: control RPCs using gRPC + separate RPC for data transfer

transport/ssh: update go-netssh to new version
    => supports CloseWrite and Deadlines
    => build: require Go 1.11 (netssh requires it)

transport/tcp/connect_tcp.go

@@ -0,0 +1,30 @@
+package tcp
+
+import (
+	"context"
+	"net"
+
+	"github.com/zrepl/zrepl/config"
+	"github.com/zrepl/zrepl/transport"
+)
+
+type TCPConnecter struct {
+	Address string
+	dialer  net.Dialer
+}
+
+func TCPConnecterFromConfig(in *config.TCPConnect) (*TCPConnecter, error) {
+	dialer := net.Dialer{
+		Timeout: in.DialTimeout,
+	}
+
+	return &TCPConnecter{in.Address, dialer}, nil
+}
+
+func (c *TCPConnecter) Connect(dialCtx context.Context) (transport.Wire, error) {
+	conn, err := c.dialer.DialContext(dialCtx, "tcp", c.Address)
+	if err != nil {
+		return nil, err
+	}
+	return conn.(*net.TCPConn), nil
+}

transport/tcp/serve_tcp.go

@@ -0,0 +1,82 @@
+package tcp
+
+import (
+	"github.com/zrepl/zrepl/config"
+	"net"
+	"github.com/pkg/errors"
+	"context"
+	"github.com/zrepl/zrepl/transport"
+)
+
+type ipMapEntry struct {
+	ip net.IP
+	ident string
+}
+
+type ipMap struct {
+	entries []ipMapEntry
+}
+
+func ipMapFromConfig(clients map[string]string) (*ipMap, error) {
+	entries := make([]ipMapEntry, 0, len(clients))
+	for clientIPString, clientIdent := range clients {
+		clientIP := net.ParseIP(clientIPString)
+		if clientIP == nil {
+			return nil, errors.Errorf("cannot parse client IP %q", clientIPString)
+		}
+		if err := transport.ValidateClientIdentity(clientIdent); err != nil {
+			return nil, errors.Wrapf(err,"invalid client identity for IP %q", clientIPString)
+		}
+		entries = append(entries, ipMapEntry{clientIP, clientIdent})
+	}
+	return &ipMap{entries: entries}, nil
+}
+
+func (m *ipMap) Get(ip net.IP) (string, error) {
+	for _, e := range m.entries {
+		if e.ip.Equal(ip) {
+			return e.ident, nil
+		}
+	}
+	return "", errors.Errorf("no identity mapping for client IP %s", ip)
+}
+
+func TCPListenerFactoryFromConfig(c *config.Global, in *config.TCPServe) (transport.AuthenticatedListenerFactory, error) {
+	addr, err := net.ResolveTCPAddr("tcp", in.Listen)
+	if err != nil {
+		return nil, errors.Wrap(err, "cannot parse listen address")
+	}
+	clientMap, err := ipMapFromConfig(in.Clients)
+	if err != nil {
+		return nil, errors.Wrap(err, "cannot parse client IP map")
+	}
+	lf := func() (transport.AuthenticatedListener, error) {
+		l, err := net.ListenTCP("tcp", addr)
+		if err != nil {
+			return nil, err
+		}
+		return &TCPAuthListener{l, clientMap}, nil
+	}
+	return lf, nil
+}
+
+type TCPAuthListener struct {
+	*net.TCPListener
+	clientMap *ipMap
+}
+
+func (f *TCPAuthListener) Accept(ctx context.Context) (*transport.AuthConn, error) {
+	nc, err := f.TCPListener.AcceptTCP()
+	if err != nil {
+		return nil, err
+	}
+	clientIP := nc.RemoteAddr().(*net.TCPAddr).IP
+	clientIdent, err := f.clientMap.Get(clientIP)
+	if err != nil {
+		transport.GetLogger(ctx).WithField("ip", clientIP).Error("client IP not in client map")
+		nc.Close()
+		return nil, err
+	}
+	return transport.NewAuthConn(nc, clientIdent), nil
+}
+