From 79f4cbf97df553ae56d3eee1fc0c802c9b9d3960 Mon Sep 17 00:00:00 2001
From: Kioubit <kioubit@localhost.local>
Date: Tue, 21 Dec 2021 06:14:56 -0500
Subject: [PATCH] Filtering on respond implementation

---
 main.go      | 12 +++++++-----
 responder.go | 21 +++++++++++++++++++--
 2 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/main.go b/main.go
index 4b4ab39..7565d3a 100644
--- a/main.go
+++ b/main.go
@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"net"
 	"os"
 	"os/signal"
 	"syscall"
@@ -27,7 +28,8 @@ func main() {
 func simpleRespond(iface string) {
 	requests := make(chan *NDRequest, 100)
 	defer close(requests)
-	go respond(iface, requests, NDP_ADV)
+	_, test, _ := net.ParseCIDR("fd44::/64")
+	go respond(iface, requests, NDP_ADV, []*net.IPNet{test})
 	go listen(iface, requests, NDP_SOL)
 
 	sigCh := make(chan os.Signal)
@@ -43,22 +45,22 @@ func proxy(iface1, iface2 string) {
 	req_iface1_sol_iface2 := make(chan *NDRequest, 100)
 	defer close(req_iface1_sol_iface2)
 	go listen(iface1, req_iface1_sol_iface2, NDP_SOL)
-	go respond(iface2, req_iface1_sol_iface2, NDP_SOL)
+	go respond(iface2, req_iface1_sol_iface2, NDP_SOL, nil)
 
 	req_iface2_sol_iface1 := make(chan *NDRequest, 100)
 	defer close(req_iface2_sol_iface1)
 	go listen(iface2, req_iface2_sol_iface1, NDP_SOL)
-	go respond(iface1, req_iface2_sol_iface1, NDP_SOL)
+	go respond(iface1, req_iface2_sol_iface1, NDP_SOL, nil)
 
 	req_iface1_adv_iface2 := make(chan *NDRequest, 100)
 	defer close(req_iface1_adv_iface2)
 	go listen(iface1, req_iface1_adv_iface2, NDP_ADV)
-	go respond(iface2, req_iface1_adv_iface2, NDP_ADV)
+	go respond(iface2, req_iface1_adv_iface2, NDP_ADV, nil)
 
 	req_iface2_adv_iface1 := make(chan *NDRequest, 100)
 	defer close(req_iface2_adv_iface1)
 	go listen(iface2, req_iface2_adv_iface1, NDP_ADV)
-	go respond(iface1, req_iface2_adv_iface1, NDP_ADV)
+	go respond(iface1, req_iface2_adv_iface1, NDP_ADV, nil)
 
 	sigCh := make(chan os.Signal)
 	signal.Notify(sigCh, os.Interrupt, syscall.SIGTERM)
diff --git a/responder.go b/responder.go
index e462502..2efcb55 100644
--- a/responder.go
+++ b/responder.go
@@ -9,7 +9,7 @@ import (
 
 var globalFd int
 
-func respond(iface string, requests chan *NDRequest, respondType NDPType) {
+func respond(iface string, requests chan *NDRequest, respondType NDPType, filter []*net.IPNet) {
 	fd, err := syscall.Socket(syscall.AF_INET6, syscall.SOCK_RAW, syscall.IPPROTO_RAW)
 	if err != nil {
 		panic(err)
@@ -47,6 +47,20 @@ func respond(iface string, requests chan *NDRequest, respondType NDPType) {
 
 	for {
 		n := <-requests
+		if filter != nil {
+			ok := false
+			for _, i := range filter {
+				if i.Contains(n.answeringForIP) {
+					fmt.Println("filter allowed IP", n.answeringForIP)
+					ok = true
+					break
+				}
+			}
+			if !ok {
+				continue
+			}
+		}
+
 		if n.sourceIface == iface {
 			pkt(result, n.srcIP, n.answeringForIP, niface.HardwareAddr, respondType)
 		} else {
@@ -79,6 +93,9 @@ func pkt(ownIP []byte, dstIP []byte, tgtip []byte, mac []byte, respondType NDPTy
 	fmt.Println("Sending packet of type", respondType, "to")
 	fmt.Printf("% X\n", t)
 
+	fmt.Println(globalFd)
 	err = syscall.Sendto(globalFd, response, 0, &d)
-	fmt.Println(err.Error())
+	if err != nil {
+		fmt.Println(err.Error())
+	}
 }