From 3d14ea63ba66c1dfe69695bb44814fa53ea6dc24 Mon Sep 17 00:00:00 2001
From: Thomas Wouters <thomaswouters@gmail.com>
Date: Mon, 21 Sep 2015 18:03:52 +0200
Subject: [PATCH] add hostname lookup

---
 api/api.go | 16 +++++++++++++---
 main.go    | 10 ++++++----
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/api/api.go b/api/api.go
index 7801851..ed8f43e 100644
--- a/api/api.go
+++ b/api/api.go
@@ -21,6 +21,7 @@ import (
 const (
 	IP_HEADER        = "x-ifconfig-ip"
 	COUNTRY_HEADER   = "x-ifconfig-country"
+	HOSTNAME_HEADER  = "x-ifconfig-hostname"
 	TEXT_PLAIN       = "text/plain; charset=utf-8"
 	APPLICATION_JSON = "application/json"
 )
@@ -28,9 +29,10 @@ const (
 var cliUserAgentExp = regexp.MustCompile("^(?i)(curl|wget|fetch\\slibfetch)\\/.*$")
 
 type API struct {
-	db       *geoip2.Reader
-	CORS     bool
-	Template string
+	db            *geoip2.Reader
+	CORS          bool
+	ReverseLookup bool
+	Template      string
 }
 
 func New() *API { return &API{} }
@@ -197,6 +199,14 @@ func (a *API) requestFilter(next http.Handler) http.Handler {
 				r.Header.Set(COUNTRY_HEADER, country)
 			}
 		}
+		if a.ReverseLookup {
+			hostname, err := net.LookupAddr(ip.String())
+			if err != nil {
+				r.Header.Set(HOSTNAME_HEADER, err.Error())
+			} else {
+				r.Header.Set(HOSTNAME_HEADER, strings.Join(hostname, ", "))
+			}
+		}
 		if a.CORS {
 			w.Header().Set("Access-Control-Allow-Methods", "GET")
 			w.Header().Set("Access-Control-Allow-Origin", "*")
diff --git a/main.go b/main.go
index 83fef92..218e5d4 100644
--- a/main.go
+++ b/main.go
@@ -11,10 +11,11 @@ import (
 
 func main() {
 	var opts struct {
-		DBPath   string `short:"f" long:"file" description:"Path to GeoIP database" value-name:"FILE" default:""`
-		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" default:"false"`
-		Template string `short:"t" long:"template" description:"Path to template" default:"index.html"`
+		DBPath        string `short:"f" long:"file" description:"Path to GeoIP database" value-name:"FILE" default:""`
+		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" default:"false"`
+		ReverseLookup bool   `short:"r" long:"reverselookup" description:"Perform reverse hostname lookups" default:"false"`
+		Template      string `short:"t" long:"template" description:"Path to template" default:"index.html"`
 	}
 	_, err := flags.ParseArgs(&opts, os.Args)
 	if err != nil {
@@ -32,6 +33,7 @@ func main() {
 	}
 
 	a.CORS = opts.CORS
+	a.ReverseLookup = opts.ReverseLookup
 	a.Template = opts.Template
 
 	log.Printf("Listening on %s", opts.Listen)