added error handling to server

pkg/cmd/flags/server/server.go

@@ -1,7 +1,10 @@
 package server
 
 import (
+	"errors"
 	"fmt"
+	"net"
+	"net/url"
 	"os"
 	"strings"
 
@@ -44,15 +47,19 @@ func PrepareServer(serverSlice []string) (*Server, error) {
 		// split flag http.address or grpc.address for example
 		serverParts := strings.SplitN(endpoint, ".", 2)
 		if len(serverParts) < 2 {
-			return nil, fmt.Errorf("cannot process http or grpc alone")
+			return nil, fmt.Errorf("cannot process the flag: try grpc.Xxx or http.Xxx instead")
 		}
 		switch serverParts[0] {
 		//flag http.Xxx
 		case HTTPServer:
 			httpParts := strings.SplitN(serverParts[1], "=", 2)
 			switch httpParts[0] {
 			case ListenEndpointFlag:
-				server.HTTPServer = http.New(httpParts[1])
+				if isValidAddr(httpParts[1]) {
+					server.HTTPServer = http.New(httpParts[1])
+				} else {
+					return nil, errors.New("invalid http address")
+				}
 			case MetricsEndpointFlag:
 				if strings.Compare(httpParts[1], "true") == 0 {
 					enableMetrics = true
@@ -69,10 +76,12 @@ func PrepareServer(serverSlice []string) (*Server, error) {
 				if strings.Compare(httpParts[1], "true") == 0 {
 					enablePyroscope = true
 				}
+			default:
+				return nil, errors.New("invalid http flag, consider using one of the following commands: address, metrics, healthz, pprof, pyroscope")
 			}
 		//flag grpc.Xxx
 		case GRPCServer:
-			grpcParts := strings.SplitN(serverParts[1], "=", 1)
+			grpcParts := strings.SplitN(serverParts[1], "=", 2)
 			switch grpcParts[0] {
 			case ListenEndpointFlag:
 				addressParts := strings.SplitN(grpcParts[1], ":", 2)
@@ -92,19 +101,15 @@ func PrepareServer(serverSlice []string) (*Server, error) {
 						addressParts = append(addressParts, "4466")
 					}
 				default:
-					return nil, errfmt.Errorf("grpc supported protocols are tcp or unix. eg: tcp:4466, unix:/tmp/tracee.sock")
+					return nil, errfmt.Errorf("grpc supported protocols are tcp or unix. eg: tcp:4466, unix:/var/run/tracee.sock")
 				}
 				server.GRPCServer = grpc.New(addressParts[0], addressParts[1])
 
 			default:
-				if _, err = os.Stat("/var/run/tracee.sock"); err == nil {
-					err = os.Remove("/var/run/tracee.sock")
-					if err != nil {
-						return nil, errfmt.Errorf("failed to cleanup gRPC listening address (%s): %v", "/var/run/tracee.sock", err)
-					}
-				}
-				server.GRPCServer = grpc.New("unix", "/var/run/tracee.sock")
+				return nil, errors.New("invalid grpc flag, consider using address")
 			}
+		default:
+			return nil, fmt.Errorf("cannot process the flag: try grpc.Xxx or http.Xxx instead")
 		}
 	}
 
@@ -131,3 +136,27 @@ func PrepareServer(serverSlice []string) (*Server, error) {
 
 	return &server, nil
 }
+
+func isValidAddr(addr string) bool {
+	_, err := url.ParseRequestURI("http://" + addr)
+	if err != nil {
+		return false
+	}
+
+	host, port, err := net.SplitHostPort(addr)
+	if err != nil {
+		return false
+	}
+
+	ip := net.ParseIP(host)
+	if ip == nil && host != "localhost" && host != "0.0.0.0" {
+		return false
+	}
+
+	_, err = net.LookupPort("tcp", port)
+	if err != nil {
+		return false
+	}
+
+	return true
+}