From 345106c989356c27189f0053438fa145aa7897a0 Mon Sep 17 00:00:00 2001
From: sanyo <sanyo0714@163.com>
Date: Wed, 29 Jul 2020 11:54:51 +0800
Subject: [PATCH] use golang net lib to parse google json param [ecs]

---
 doh-server/google.go | 62 ++++++++++++++------------------------------
 1 file changed, 20 insertions(+), 42 deletions(-)

diff --git a/doh-server/google.go b/doh-server/google.go
index 8504784..3d3f069 100644
--- a/doh-server/google.go
+++ b/doh-server/google.go
@@ -83,52 +83,30 @@ func (s *Server) parseRequestGoogle(ctx context.Context, w http.ResponseWriter,
 	}
 
 	ednsClientSubnet := r.FormValue("edns_client_subnet")
-	ednsClientFamily := uint16(0)
-	ednsClientAddress := net.IP(nil)
-	ednsClientNetmask := uint8(255)
+
+	var (
+		ednsClientFamily  = uint16(1)
+		ednsClientAddress = net.IP(nil)
+		ednsClientNetmask = 24
+		ipLen             int
+		ipNet             *net.IPNet
+		err               error
+	)
+
 	if ednsClientSubnet != "" {
 		if ednsClientSubnet == "0/0" {
 			ednsClientSubnet = "0.0.0.0/0"
 		}
-		slash := strings.IndexByte(ednsClientSubnet, '/')
-		if slash < 0 {
-			ednsClientAddress = net.ParseIP(ednsClientSubnet)
-			if ednsClientAddress == nil {
-				return &DNSRequest{
-					errcode: 400,
-					errtext: fmt.Sprintf("Invalid argument value: \"edns_client_subnet\" = %q", ednsClientSubnet),
-				}
-			}
-			if ipv4 := ednsClientAddress.To4(); ipv4 != nil {
-				ednsClientFamily = 1
-				ednsClientAddress = ipv4
-				ednsClientNetmask = 24
-			} else {
-				ednsClientFamily = 2
-				ednsClientNetmask = 56
-			}
-		} else {
-			ednsClientAddress = net.ParseIP(ednsClientSubnet[:slash])
-			if ednsClientAddress == nil {
-				return &DNSRequest{
-					errcode: 400,
-					errtext: fmt.Sprintf("Invalid argument value: \"edns_client_subnet\" = %q", ednsClientSubnet),
-				}
-			}
-			if ipv4 := ednsClientAddress.To4(); ipv4 != nil {
-				ednsClientFamily = 1
-				ednsClientAddress = ipv4
-			} else {
-				ednsClientFamily = 2
+		ednsClientAddress, ipNet, err = net.ParseCIDR(ednsClientSubnet)
+		if err != nil {
+			return &DNSRequest{
+				errcode: 400,
+				errtext: fmt.Sprintf("Invalid argument value: \"edns_client_subnet\" = %q", ednsClientSubnet),
 			}
-			netmask, err := strconv.ParseUint(ednsClientSubnet[slash+1:], 10, 8)
-			if err != nil {
-				return &DNSRequest{
-					errcode: 400,
-					errtext: fmt.Sprintf("Invalid argument value: \"edns_client_subnet\" = %q", ednsClientSubnet),
-				}
-			}
-			ednsClientNetmask = uint8(netmask)
+		}
+		ednsClientNetmask, ipLen = ipNet.Mask.Size()
+		if ipLen == 128 {
+			ednsClientFamily = uint16(2)
 		}
 	} else {
 		ednsClientAddress = s.findClientIP(r)
@@ -156,7 +134,7 @@ func (s *Server) parseRequestGoogle(ctx context.Context, w http.ResponseWriter,
 		edns0Subnet := new(dns.EDNS0_SUBNET)
 		edns0Subnet.Code = dns.EDNS0SUBNET
 		edns0Subnet.Family = ednsClientFamily
-		edns0Subnet.SourceNetmask = ednsClientNetmask
+		edns0Subnet.SourceNetmask = uint8(ednsClientNetmask)
 		edns0Subnet.SourceScope = 0
 		edns0Subnet.Address = ednsClientAddress
 		opt.Option = append(opt.Option, edns0Subnet)