runtime: add debug console service

Add `kata-runtime exec` to enter guest OS
through shell started by agent

Fixes: #245

Signed-off-by: bin liu <bin@hyper.sh>

src/runtime/pkg/kata-monitor/shim_client.go

@@ -0,0 +1,81 @@
+// Copyright (c) 2020 Ant Financial
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+package katamonitor
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net"
+	"net/http"
+	"time"
+)
+
+const (
+	defaultTimeout = 3 * time.Second
+)
+
+func commonServeError(w http.ResponseWriter, status int, err error) {
+	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+	w.WriteHeader(status)
+	if err != nil {
+		fmt.Fprintln(w, err.Error())
+	}
+}
+
+func getSandboxIdFromReq(r *http.Request) (string, error) {
+	sandbox := r.URL.Query().Get("sandbox")
+	if sandbox != "" {
+		return sandbox, nil
+	}
+	return "", fmt.Errorf("sandbox not found in %+v", r.URL.Query())
+}
+
+func (km *KataMonitor) buildShimClient(sandboxID, namespace string, timeout time.Duration) (*http.Client, error) {
+	socket, err := km.getMonitorAddress(sandboxID, namespace)
+	if err != nil {
+		return nil, err
+	}
+
+	transport := &http.Transport{
+		DisableKeepAlives: true,
+		Dial: func(proto, addr string) (conn net.Conn, err error) {
+			return net.Dial("unix", "\x00"+socket)
+		},
+	}
+
+	client := &http.Client{
+		Transport: transport,
+	}
+
+	if timeout > 0 {
+		client.Timeout = timeout
+	}
+
+	return client, nil
+}
+
+func (km *KataMonitor) doGet(sandboxID, namespace string, timeoutInSeconds time.Duration, urlPath string) ([]byte, error) {
+	client, err := km.buildShimClient(sandboxID, namespace, timeoutInSeconds)
+	if err != nil {
+		return nil, err
+	}
+
+	resp, err := client.Get(fmt.Sprintf("http://shim/%s", urlPath))
+	if err != nil {
+		return nil, err
+	}
+
+	defer func() {
+		resp.Body.Close()
+	}()
+
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	return body, nil
+}