disable unwanted forwarding

README.md

@@ -120,8 +120,6 @@ sudo lnxrouter -i eth1 -o isp5  --no-dns  --dhcp-dns 1.1.1.1  -6 --dhcp-dns6 [26
 > 1. Stop serving local DNS
 > 2. Tell clients which DNS to use (ISP5's DNS. Or, a safe public DNS, like above example)
 
-> Also, read *Notice 1*
-
 </details>
 
 ### Create LAN without providing Internet
@@ -136,8 +134,6 @@ sudo lnxrouter -n -i eth1
 sudo lnxrouter -n --ap wlan0 MyAccessPoint -p MyPassPhrase
 ```
 
-> Read _Notice 1_
-
 </details>
 
 ### Internet for LXC
@@ -312,17 +308,16 @@ Options:
                             and to provide Internet to
                             (To create WiFi hotspot use '--ap' instead)
     -o <interface>          Specify an inteface to provide Internet from.
-                            (See Notice 1)
                             (Note using this with default DNS option may leak
                             queries to other interfaces)
-    -n                      Do not provide Internet (See Notice 1)
+    -n                      Do not provide Internet
     --ban-priv              Disallow clients to access my private network
     
     -g <ip>                 This host's IPv4 address in subnet (mask is /24)
                             (example: '192.168.5.1' or '5' shortly)
     -6                      Enable IPv6 (NAT)
-    --no4                   Disable IPv4 Internet (not forwarding IPv4)
+    --no4                   Disable IPv4 Internet (not forwarding IPv4).
-                            (See Notice 1). Usually used with '-6'
+                            Usually used with '-6'
                             
     --p6 <prefix>           Set IPv6 LAN address prefix (length 64) 
                             (example: 'fd00:0:0:5::' or '5' shortly) 
@@ -419,11 +414,10 @@ Options:
         For <id> you can use PID or subnet interface name.
         You can get them with '--list-running'
                 
-    Notice 1:   This script assume your host's default policy won't forward
+Examples:
-                packets, so the script won't explictly ban forwarding in any
+    lnxrouter -i eth1
-                mode. In some unexpected case (eg. mistaken configurations) may
+    lnxrouter --ap wlan0 MyAccessPoint -p MyPassPhrase
-                cause unwanted packets leakage between 2 networks, which you
+    lnxrouter -i eth1 --tp <transparent-proxy> --dns <dns-proxy>
-                should be aware of if you want isolated network
 ```
 
 </details>
@@ -455,20 +449,6 @@ Visit [**my homepage** 🏡](https://garywill.github.io) to see **more tools and
 - 🍃 Also some [unfulfilled enhancements in the Issues](https://github.com/garywill/linux-router/issues?q=is%3Aissue+is%3Aopen+label%3Aenhancement)
 - 🙋‍♂️ Contributions are not limited to coding. There're [some posts and questions](https://github.com/garywill/linux-router/issues) that need more people to answer
 
-## Notice
-
-<details>
-
-```
-    Notice 1:   This script assume your host's default policy won't forward
-                packets, so the script won't explictly ban forwarding in any
-                mode. In some unexpected case (eg. mistaken configurations) may
-                cause unwanted packets leakage between 2 networks, which you
-                should be aware of if you want isolated network
-```
-
-</details>
-
 ## TODO
 
 Sooner is better:
@@ -478,7 +458,6 @@ Future:
 - WPA3
 - Global IPv6
 - Explictly ban forwarding if not needed
-- Bring bridging method back
 
 ## License
 

lnxrouter

@@ -29,17 +29,16 @@ Options:
                             and to provide Internet to
                             (To create WiFi hotspot use '--ap' instead)
     -o <interface>          Specify an inteface to provide Internet from.
-                            (See Notice 1)
                             (Note using this with default DNS option may leak
                             queries to other interfaces)
-    -n                      Do not provide Internet (See Notice 1)
+    -n                      Do not provide Internet
     --ban-priv              Disallow clients to access my private network
     
     -g <ip>                 This host's IPv4 address in subnet (mask is /24)
                             (example: '192.168.5.1' or '5' shortly)
     -6                      Enable IPv6 (NAT)
-    --no4                   Disable IPv4 Internet (not forwarding IPv4)
+    --no4                   Disable IPv4 Internet (not forwarding IPv4).
-                            (See Notice 1). Usually used with '-6'
+                            Usually used with '-6'
                             
     --p6 <prefix>           Set IPv6 LAN address prefix (length 64) 
                             (example: 'fd00:0:0:5::' or '5' shortly) 
@@ -136,12 +135,6 @@ Options:
         For <id> you can use PID or subnet interface name.
         You can get them with '--list-running'
                 
-    Notice 1:   This script assume your host's default policy won't forward
-                packets, so the script won't explictly ban forwarding in any
-                mode. In some unexpected case (eg. mistaken configurations) may
-                cause unwanted packets leakage between 2 networks, which you
-                should be aware of if you want isolated network
-                
 Examples:
     $PROGNAME -i eth1
     $PROGNAME --ap wlan0 MyAccessPoint -p MyPassPhrase
@@ -1001,7 +994,25 @@ iptb()
     return $?
 }
 
+disable_unwanted_forwarding() {
+    for iv in "${IP_VERs[@]}"; do
+        if [[ "$INTERNET_IFACE" ]]; then
+            iptb "$iv" n filter I FORWARD  \
+                -i "$SUBNET_IFACE"      ! -o "$INTERNET_IFACE" \
+                -j REJECT || die
+            iptb "$iv" n filter I FORWARD  \
+                ! -i "$INTERNET_IFACE"    -o "$SUBNET_IFACE" \
+                -j REJECT || die
+        fi
         
+        if [[ "$SHARE_METHOD" == 'redsocks' || "$SHARE_METHOD" == 'none' \
+            || ( "$iv" -eq "4" && "$NO4" -eq 1  ) ]];then
+            iptb "$iv" n filter I FORWARD  -i "$SUBNET_IFACE"  -j REJECT || die
+            iptb "$iv" n filter I FORWARD  -o "$SUBNET_IFACE"  -j REJECT || die
+        fi
+    done
+        
+}
 start_nat() {
     local SUBNET_NET
     
@@ -1026,18 +1037,11 @@ start_nat() {
             iptb "$iv" v filter I FORWARD  -i "$SUBNET_IFACE"  -s "$SUBNET_NET" \
                 -o $INTERNET_IFACE \
                 -j ACCEPT || die
-            iptb "$iv" v filter I FORWARD  -i "$SUBNET_IFACE" \
-                ! -o $INTERNET_IFACE \
-                -j REJECT || die
             
             # forward any -> subnet
             iptb "$iv" v filter I FORWARD  -o "$SUBNET_IFACE"  -d "$SUBNET_NET"  \
                 -i "$INTERNET_IFACE" \
                 -j ACCEPT || die
-            iptb "$iv" v filter I FORWARD  -o "$SUBNET_IFACE"    \
-                ! -i "$INTERNET_IFACE" \
-                -j REJECT || die
-
         else # any interface can be Internet
             # masquerade subnet -> any(!subnet)
             iptb "$iv" v nat I POSTROUTING -s "$SUBNET_NET"  ! -d "$SUBNET_NET" \
@@ -2215,27 +2219,22 @@ check_iptables
 
 echo "NOTICE: Not showing all operations done to iptables rules"
 
-[[ "$NO4" -eq 1 ]] && echo -e "\nWARN: Since you're using in this mode (no IPv4 Internet), make sure you've read Notice 1\n" >&2
-
 if [[ "$IPV6" -eq 0 ]]; then
     IP_VERs=("4")
 else
     IP_VERs=("4" "6")
 fi
 
+disable_unwanted_forwarding
+
 # enable Internet sharing
 if [[ "$SHARE_METHOD" == "none" ]]; then
 
     echo "No Internet sharing"
     
-    echo -e "\nWARN: Since you're using in this mode (no Internet share), make sure you've read Notice 1\n" >&2
-    
     [[ "$BANLAN" -eq 1 ]] && start_ban_lan
     
 elif [[ "$SHARE_METHOD" == "nat" ]]; then
-
-    [[ "$INTERNET_IFACE" ]] && echo -e "\nWARN: Since you're using in this mode (specify Internet interface), make sure you've read Notice 1\n" >&2
-
     [[ "$INTERNET_IFACE" && "$dnsmasq_NO_DNS" -eq 0 ]] && echo -e "\nWARN: You specified Internet interface but this host is providing local DNS. In some unexpected case (eg. mistaken configurations), queries may leak to other interfaces, which you should be aware of.\n" >&2
     
     start_nat