Transparent proxy example add

Author: Artiom N.

src/book01/ch21/python/transparent-proxy.py

@@ -0,0 +1,21 @@
+#!/usr/bin/env python3
+
+import socket
+
+
+IP_TRANSPARENT = 0x13
+
+
+with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
+    sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+    sock.setsockopt(socket.IPPROTO_IP, IP_TRANSPARENT, 1)
+
+    sock.bind(('8.8.8.8', 1234))
+    sock.listen()
+
+    print(f'Listening on {sock.getsockname()}')
+    while True:
+        cln_sock, (remote_ip, remote_port) = sock.accept()
+        local_ip, local_port = cln_sock.getsockname()
+        print(f'Connection from {remote_ip}:{remote_port} to {local_ip}:{local_port}')
+        cln_sock.close()