Move TCPProxy to pkg

pkg/tcpproxy/tcp.go

@@ -0,0 +1,133 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package tcpproxy
+
+import (
+	"fmt"
+	"io"
+	"net"
+
+	"k8s.io/klog/v2"
+
+	"pault.ag/go/sniff/parser"
+)
+
+// TCPServer describes a server that works in passthrough mode.
+type TCPServer struct {
+	Hostname      string
+	IP            string
+	Port          int
+	ProxyProtocol bool
+}
+
+// TCPProxy describes the passthrough servers and a default as catch all.
+type TCPProxy struct {
+	ServerList []*TCPServer
+	Default    *TCPServer
+}
+
+// Get returns the TCPServer to use for a given host.
+func (p *TCPProxy) Get(host string) *TCPServer {
+	if p.ServerList == nil {
+		return p.Default
+	}
+
+	for _, s := range p.ServerList {
+		if s.Hostname == host {
+			return s
+		}
+	}
+
+	return p.Default
+}
+
+// Handle reads enough information from the connection to extract the hostname
+// and open a connection to the passthrough server.
+func (p *TCPProxy) Handle(conn net.Conn) {
+	defer conn.Close()
+	data := make([]byte, 4096)
+
+	length, err := conn.Read(data)
+	if err != nil {
+		klog.V(4).ErrorS(err, "Error reading the first 4k of the connection")
+		return
+	}
+
+	proxy := p.Default
+	hostname, err := parser.GetHostname(data[:])
+	if err == nil {
+		klog.V(4).InfoS("TLS Client Hello", "host", hostname)
+		proxy = p.Get(hostname)
+	}
+
+	if proxy == nil {
+		klog.V(4).InfoS("There is no configured proxy for SSL connections.")
+		return
+	}
+
+	hostPort := net.JoinHostPort(proxy.IP, fmt.Sprintf("%v", proxy.Port))
+	clientConn, err := net.Dial("tcp", hostPort)
+	if err != nil {
+		klog.V(4).ErrorS(err, "error dialing proxy", "ip", proxy.IP, "port", proxy.Port, "hostname", proxy.Hostname)
+		return
+	}
+	defer clientConn.Close()
+
+	if proxy.ProxyProtocol {
+		// write out the Proxy Protocol header
+		localAddr := conn.LocalAddr().(*net.TCPAddr)
+		remoteAddr := conn.RemoteAddr().(*net.TCPAddr)
+		protocol := "UNKNOWN"
+		if remoteAddr.IP.To4() != nil {
+			protocol = "TCP4"
+		} else if remoteAddr.IP.To16() != nil {
+			protocol = "TCP6"
+		}
+		proxyProtocolHeader := fmt.Sprintf("PROXY %s %s %s %d %d\r\n", protocol, remoteAddr.IP.String(), localAddr.IP.String(), remoteAddr.Port, localAddr.Port)
+		klog.V(4).InfoS("Writing Proxy Protocol", "header", proxyProtocolHeader)
+		_, err = fmt.Fprintf(clientConn, proxyProtocolHeader)
+	}
+	if err != nil {
+		klog.ErrorS(err, "Error writing Proxy Protocol header")
+		clientConn.Close()
+	} else {
+		_, err = clientConn.Write(data[:length])
+		if err != nil {
+			klog.Errorf("Error writing the first 4k of proxy data: %v", err)
+			clientConn.Close()
+		}
+	}
+
+	pipe(clientConn, conn)
+}
+
+func pipe(client, server net.Conn) {
+	doCopy := func(s, c net.Conn, cancel chan<- bool) {
+		io.Copy(s, c)
+		cancel <- true
+	}
+
+	cancel := make(chan bool, 2)
+
+	go doCopy(server, client, cancel)
+	go doCopy(client, server, cancel)
+
+	select {
+	case <-cancel:
+		return
+	}
+}