add example for a network namespace with slirp4netns

1 files changed, 45 insertions, 0 deletions

diff --git a/examples/netnsslirp.py b/examples/netnsslirp.py
new file mode 100755
index 0000000..0818fba
--- /dev/null
+++ b/examples/netnsslirp.py
@@ -0,0 +1,45 @@
+#!/usr/bin/python3
+# Copyright 2024 Helmut Grohne <helmut@subdivi.de>
+# SPDX-License-Identifier: GPL-3
+
+"""Construct a network namespace with a host0 interface backed by slirp4netns.
+"""
+
+import os
+import sys
+
+if __file__.split("/")[-2:-1] == ["examples"]:
+    sys.path.insert(0, "/".join(__file__.split("/")[:-2]))
+
+import linuxnamespaces
+
+
+def main() -> None:
+    mainpid = os.getpid()
+    rfd, wfd = os.pipe()
+    if os.fork() == 0:
+        os.set_inheritable(rfd, True)
+        os.execlp(
+            "slirp4netns",
+            "slirp4netns",
+            "--exit-fd",
+            "%d" % rfd,
+            "--configure",
+            "--disable-host-loopback",
+            "%d" % mainpid,
+            "host0",
+        )
+
+    linuxnamespaces.unshare_user_idmap_nohelper(
+        0,
+        0,
+        linuxnamespaces.CloneFlags.NEWUSER | linuxnamespaces.CloneFlags.NEWNET,
+    )
+    # Leave write end of --exit-fd behind as fd 252.
+    os.dup2(wfd, 252)
+    os.close(wfd)
+    os.execlp(os.environ["SHELL"], os.environ["SHELL"])
+
+
+if __name__ == "__main__":
+    main()