Implement port testing. Fixes #11

api/api.go

@@ -10,7 +10,9 @@ import (
 	"net/http"
 	"path/filepath"
 	"regexp"
+	"strconv"
 	"strings"
+	"time"
 
 	"github.com/gorilla/mux"
 	geoip2 "github.com/oschwald/geoip2-golang"
@@ -25,6 +27,7 @@ type API struct {
 	Template      string
 	lookupAddr    func(string) ([]string, error)
 	lookupCountry func(net.IP) (string, error)
+	testPort      func(net.IP, uint64) error
 	ipFromRequest func(*http.Request) (net.IP, error)
 }
 
@@ -34,10 +37,17 @@ type Response struct {
 	Hostname string `json:"hostname,omitempty"`
 }
 
+type TestPortResponse struct {
+	IP        net.IP `json:"ip"`
+	Port      uint64 `json:"port"`
+	Reachable bool   `json:"reachable"`
+}
+
 func New() *API {
 	return &API{
 		lookupAddr:    func(addr string) (names []string, err error) { return nil, nil },
 		lookupCountry: func(ip net.IP) (string, error) { return "", nil },
+		testPort:      func(ip net.IP, port uint64) error { return nil },
 		ipFromRequest: ipFromRequest,
 	}
 }
@@ -57,6 +67,10 @@ func (a *API) EnableReverseLookup() {
 	a.lookupAddr = net.LookupAddr
 }
 
+func (a *API) EnablePortTesting() {
+	a.testPort = testPort
+}
+
 func ipFromRequest(r *http.Request) (net.IP, error) {
 	var host string
 	realIP := r.Header.Get("X-Real-IP")
@@ -76,6 +90,14 @@ func ipFromRequest(r *http.Request) (net.IP, error) {
 	return ip, nil
 }
 
+func testPort(ip net.IP, port uint64) error {
+	address := fmt.Sprintf("%s:%d", ip, port)
+	if _, err := net.DialTimeout("tcp", address, 2*time.Second); err != nil {
+		return err
+	}
+	return nil
+}
+
 func lookupCountry(db *geoip2.Reader, ip net.IP) (string, error) {
 	if db == nil {
 		return "", nil
@@ -140,6 +162,34 @@ func (a *API) JSONHandler(w http.ResponseWriter, r *http.Request) *appError {
 	return nil
 }
 
+func (a *API) TestPortHandler(w http.ResponseWriter, r *http.Request) *appError {
+	vars := mux.Vars(r)
+	port, err := strconv.ParseUint(vars["port"], 10, 16)
+	if err != nil {
+		return badRequest(err).WithMessage("Invalid port: " + vars["port"]).AsJSON()
+	}
+	if port < 1 || port > 65355 {
+		return badRequest(nil).WithMessage("Invalid port: " + vars["port"]).AsJSON()
+	}
+	ip, err := a.ipFromRequest(r)
+	if err != nil {
+		return internalServerError(err).AsJSON()
+	}
+	err = testPort(ip, port)
+	response := TestPortResponse{
+		IP:        ip,
+		Port:      port,
+		Reachable: err == nil,
+	}
+	b, err := json.Marshal(response)
+	if err != nil {
+		return internalServerError(err).AsJSON()
+	}
+	w.Header().Set("Content-Type", APPLICATION_JSON)
+	w.Write(b)
+	return nil
+}
+
 func (a *API) DefaultHandler(w http.ResponseWriter, r *http.Request) *appError {
 	response, err := a.newResponse(r)
 	if err != nil {
@@ -218,6 +268,9 @@ func (a *API) Handlers() http.Handler {
 	// Browser
 	r.Handle("/", appHandler(a.DefaultHandler)).Methods("GET")
 
+	// Port testing
+	r.Handle("/port/{port:[0-9]+}", appHandler(a.TestPortHandler)).Methods("GET")
+
 	// Not found handler which returns JSON when appropriate
 	r.NotFoundHandler = appHandler(a.NotFoundHandler)
 

api/api_test.go

@@ -22,6 +22,9 @@ func newTestAPI() *API {
 		ipFromRequest: func(*http.Request) (net.IP, error) {
 			return net.ParseIP("127.0.0.1"), nil
 		},
+		testPort: func(net.IP, uint64) error {
+			return nil
+		},
 	}
 }
 

api/error.go

@@ -21,6 +21,10 @@ func notFound(err error) *appError {
 	return &appError{Error: err, Code: http.StatusNotFound}
 }
 
+func badRequest(err error) *appError {
+	return &appError{Error: err, Code: http.StatusBadRequest}
+}
+
 func (e *appError) AsJSON() *appError {
 	e.ContentType = APPLICATION_JSON
 	return e

index.html

@@ -78,6 +78,20 @@ Date: Fri, 15 Apr 2016 17:26:53 GMT
     "ip": "{{ .IP }}"
 }            
         </pre>
+        <p>Testing port connectivity (only supports JSON output):</p>
+        <pre>
+http --json localhost:8080/port/8080
+HTTP/1.1 200 OK
+Content-Length: 47
+Content-Type: application/json
+Date: Fri, 15 Apr 2016 18:47:20 GMT
+
+{
+    "ip": "127.0.0.1",
+    "port": 8080,
+    "reachable": true
+}
+        </pre>
       </div>
     </div>
     <div class="pure-g">

main.go

@@ -15,6 +15,7 @@ func main() {
 		Listen        string `short:"l" long:"listen" description:"Listening address" value-name:"ADDR" default:":8080"`
 		CORS          bool   `short:"x" long:"cors" description:"Allow requests from other domains"`
 		ReverseLookup bool   `short:"r" long:"reverse-lookup" description:"Perform reverse hostname lookups"`
+		PortTesting   bool   `short:"p" long:"port-testing" description:"Enable port testing"`
 		Template      string `short:"t" long:"template" description:"Path to template" default:"index.html"`
 	}
 	_, err := flags.ParseArgs(&opts, os.Args)
@@ -28,6 +29,10 @@ func main() {
 		log.Println("Enabling reverse lookup")
 		api.EnableReverseLookup()
 	}
+	if opts.PortTesting {
+		log.Println("Enabling port testing")
+		api.EnablePortTesting()
+	}
 	if opts.DBPath != "" {
 		log.Printf("Enabling country lookup (using database: %s)\n", opts.DBPath)
 		if err := api.EnableCountryLookup(opts.DBPath); err != nil {