From b079e6988f8b58b0eb12c322dd5b23aeecbeb011 Mon Sep 17 00:00:00 2001
From: Niklas <niklas@kapelle.org>
Date: Wed, 23 Dec 2020 21:44:33 +0100
Subject: [PATCH] implemented forwarding

---
 config.yml |  7 ++-----
 coolDns.go | 47 ++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 48 insertions(+), 6 deletions(-)

diff --git a/config.yml b/config.yml
index bfdc939..f490914 100644
--- a/config.yml
+++ b/config.yml
@@ -1,15 +1,12 @@
 zones:
 - zone: example.com.
   file: zonefile.txt
-  acl:
-    - vpn
 
 acl:
 - name: vpn
   cidr: 10.0.0.0/24
 
 forward:
-  alc:
+  acl:
     - vpn
-
-
+  server: "8.8.8.8:53"
diff --git a/coolDns.go b/coolDns.go
index 86178b4..c4024fa 100644
--- a/coolDns.go
+++ b/coolDns.go
@@ -29,7 +29,8 @@ type config struct {
 }
 
 type configForward struct {
-	ACL []string `yaml:"acl"`
+	ACL    []string `yaml:"acl"`
+	Server string   `yaml:"server"`
 }
 
 type configACL struct {
@@ -145,6 +146,7 @@ func createACLList(config []configACL) (map[string]*net.IPNet, error) {
 
 func createServer(zones []zone, config config, aclList map[string]*net.IPNet) *dns.ServeMux {
 	srv := dns.NewServeMux()
+	c := new(dns.Client)
 
 	for _, z := range zones {
 		srv.HandleFunc(z.zone, func(w dns.ResponseWriter, r *dns.Msg) {
@@ -248,6 +250,49 @@ func createServer(zones []zone, config config, aclList map[string]*net.IPNet) *d
 		})
 	}
 
+	// Handle any other request
+	srv.HandleFunc(".", func(w dns.ResponseWriter, r *dns.Msg) {
+		remoteIP, _, err := net.SplitHostPort(w.RemoteAddr().String())
+		ip := net.ParseIP(remoteIP)
+
+		if err != nil && ip != nil {
+			log.Printf("Faild to parse remote IP WTF? :%s", err.Error())
+			return
+		}
+
+		// Check ACL rules
+		if len(config.Forward.ACL) != 0 {
+			passed := false
+			for _, rule := range config.Forward.ACL {
+
+				if aclList[rule].Contains(ip) {
+					passed = true
+				}
+			}
+
+			if !passed {
+				m := new(dns.Msg)
+				m.SetReply(r)
+				m.SetRcode(r, dns.RcodeRefused)
+				w.WriteMsg(m)
+				return
+			}
+		}
+
+		// Forward request
+		in, _, err := c.Exchange(r, config.Forward.Server)
+
+		if err != nil {
+			m := new(dns.Msg)
+			m.SetReply(r)
+			m.SetRcode(r, dns.RcodeServerFailure)
+			w.WriteMsg(m)
+			return
+		}
+
+		w.WriteMsg(in)
+	})
+
 	return srv
 }