From dbd915351316ec2cc899db1757b3ae13c809ea0b Mon Sep 17 00:00:00 2001
From: yo <johan@nosd.in>
Date: Mon, 18 Apr 2022 13:53:18 +0200
Subject: [PATCH] Get default router and gateways, IPv4 & IPv6

---
 cmd/jailhost.go | 109 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 109 insertions(+)
 create mode 100644 cmd/jailhost.go

diff --git a/cmd/jailhost.go b/cmd/jailhost.go
new file mode 100644
index 0000000..dbef5ac
--- /dev/null
+++ b/cmd/jailhost.go
@@ -0,0 +1,109 @@
+package cmd
+
+import (
+	"fmt"
+	"net"
+	"golang.org/x/net/route"
+)
+
+var defaultRoute4 = [4]byte{0, 0, 0, 0}
+var defaultRoute6 = [16]byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
+var local6 = [16]byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1}
+
+func Inet4AddrToString(ip4 route.Inet4Addr) string {
+	return fmt.Sprintf("%v.%v.%v.%v", ip4.IP[0], ip4.IP[1], ip4.IP[2], ip4.IP[3])
+}
+
+func Inet6AddrToString(ip6 route.Inet6Addr) string {
+	return fmt.Sprintf("%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x", 
+					   ip6.IP[0], ip6.IP[1], ip6.IP[2], ip6.IP[3], ip6.IP[4], ip6.IP[5], ip6.IP[6], ip6.IP[7],
+					ip6.IP[8], ip6.IP[9], ip6.IP[10], ip6.IP[11], ip6.IP[12], ip6.IP[13], ip6.IP[14], ip6.IP[15])
+}
+
+/*****************************************************************************
+* Initialize default_interface, default_gatway4, default_gateway6
+*****************************************************************************/
+func (jh *JailHost) InitNetworkProperties() {
+	rib, _ := route.FetchRIB(0, route.RIBTypeRoute, 0)
+	messages, err := route.ParseRIB(route.RIBTypeRoute, rib)
+	if err != nil {
+		panic(err)
+	}
+	
+	for _, message := range messages {
+		route_message := message.(*route.RouteMessage)
+		addresses := route_message.Addrs
+		card_index := route_message.Index
+		
+		if addresses[0].Family() == 2 {
+			var destination4, gateway4 *route.Inet4Addr
+			ok := false
+			
+			if destination4, ok = addresses[0].(*route.Inet4Addr); !ok {
+				continue
+			}
+			
+			if gateway4, ok = addresses[1].(*route.Inet4Addr); !ok {
+				continue
+			}
+			
+			if destination4 == nil || gateway4 == nil {
+				continue
+			}
+			
+			if destination4.IP == defaultRoute4 {
+				card, _ := net.InterfaceByIndex(card_index)
+				//fmt.Printf("Default IPv4 gateway is %v on card %s\n", Inet4AddrToString(*gateway4), card.Name)
+				jh.default_interface = card.Name
+				jh.default_gateway4 = Inet4AddrToString(*gateway4)
+			}
+		} else if addresses[0].Family() == 28 {
+			var destination6, gateway6 *route.Inet6Addr
+			ok := false
+			
+			if destination6, ok = addresses[0].(*route.Inet6Addr); !ok {
+				continue
+			}
+			
+			if gateway6, ok = addresses[1].(*route.Inet6Addr); !ok {
+				continue
+			}
+			
+			if destination6 == nil || gateway6 == nil {
+				continue
+			}
+			
+			if destination6.IP == defaultRoute6 && gateway6.IP != local6 {
+				card, _ := net.InterfaceByIndex(card_index)
+				//fmt.Printf("Default IPv6 gateway is %v on card %s\n", Inet6AddrToString(*gateway6), card.Name)
+				jh.default_interface = card.Name
+				jh.default_gateway6 = Inet6AddrToString(*gateway6)
+			}
+		}
+	}
+}
+
+
+func (jh *JailHost) GetDefaultInterface() string {
+	if len(jh.default_interface) == 0 {
+		jh.InitNetworkProperties()
+	}
+	return jh.default_interface
+}
+
+
+func (jh *JailHost) GetDefaultGateway4() string {
+	if len(jh.default_gateway4) == 0 {
+		jh.InitNetworkProperties()
+	}
+	return jh.default_gateway4
+}
+
+
+func(jh *JailHost) GetDefaultGateway6() string {
+	if len(jh.default_gateway6) == 0 {
+		jh.InitNetworkProperties()
+	}
+	return jh.default_gateway6
+}
+