feat(agent): add agent support (#1828)

api/http/client/client.go

@@ -0,0 +1,77 @@
+package client
+
+import (
+	"crypto/tls"
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/portainer/portainer"
+	"github.com/portainer/portainer/crypto"
+)
+
+// ExecutePingOperationFromEndpoint will send a SystemPing operation HTTP request to a Docker environment
+// using the specified endpoint configuration. It is used exclusively when
+// specifying an endpoint from the CLI via the -H flag.
+func ExecutePingOperationFromEndpoint(endpoint *portainer.Endpoint) (bool, error) {
+	if strings.HasPrefix(endpoint.URL, "unix://") {
+		return false, nil
+	}
+
+	transport := &http.Transport{}
+
+	scheme := "http"
+
+	if endpoint.TLSConfig.TLS || endpoint.TLSConfig.TLSSkipVerify {
+		tlsConfig, err := crypto.CreateTLSConfiguration(&endpoint.TLSConfig)
+		if err != nil {
+			return false, err
+		}
+		scheme = "https"
+		transport.TLSClientConfig = tlsConfig
+	}
+
+	client := &http.Client{
+		Timeout:   time.Second * 3,
+		Transport: transport,
+	}
+
+	target := strings.Replace(endpoint.URL, "tcp://", scheme+"://", 1)
+	return pingOperation(client, target)
+}
+
+// ExecutePingOperation will send a SystemPing operation HTTP request to a Docker environment
+// using the specified host and optional TLS configuration.
+func ExecutePingOperation(host string, tlsConfig *tls.Config) (bool, error) {
+	transport := &http.Transport{}
+
+	scheme := "http"
+	if tlsConfig != nil {
+		transport.TLSClientConfig = tlsConfig
+		scheme = "https"
+	}
+
+	client := &http.Client{
+		Timeout:   time.Second * 3,
+		Transport: transport,
+	}
+
+	target := strings.Replace(host, "tcp://", scheme+"://", 1)
+	return pingOperation(client, target)
+}
+
+func pingOperation(client *http.Client, target string) (bool, error) {
+	pingOperationURL := target + "/_ping"
+
+	response, err := client.Get(pingOperationURL)
+	if err != nil {
+		return false, err
+	}
+
+	agentOnDockerEnvironment := false
+	if response.Header.Get(portainer.PortainerAgentHeader) != "" {
+		agentOnDockerEnvironment = true
+	}
+
+	return agentOnDockerEnvironment, nil
+}