selftests: net: Add test cases for link and peer netns

- Add test for creating link in another netns when a link of the same
   name and ifindex exists in current netns.
 - Add test to verify that link is created in target netns directly -
   no link new/del events should be generated in link netns or current
   netns.
 - Add test cases to verify that link-netns is set as expected for
   various drivers and combination of namespace-related parameters.

Signed-off-by: Xiao Liang <shaw.leon@gmail.com>
Link: https://patch.msgid.link/20250219125039.18024-14-shaw.leon@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/Makefile

@@ -36,6 +36,7 @@ TEST_PROGS += cmsg_so_priority.sh
 TEST_PROGS += test_so_rcv.sh
 TEST_PROGS += cmsg_time.sh cmsg_ipv6.sh
 TEST_PROGS += netns-name.sh
+TEST_PROGS += link_netns.py
 TEST_PROGS += nl_netdev.py
 TEST_PROGS += rtnetlink.py
 TEST_PROGS += srv6_end_dt46_l3vpn_test.sh

tools/testing/selftests/net/config

@@ -107,3 +107,8 @@ CONFIG_XFRM_INTERFACE=m
 CONFIG_XFRM_USER=m
 CONFIG_IP_NF_MATCH_RPFILTER=m
 CONFIG_IP6_NF_MATCH_RPFILTER=m
+CONFIG_IPVLAN=m
+CONFIG_CAN=m
+CONFIG_CAN_DEV=m
+CONFIG_CAN_VXCAN=m
+CONFIG_NETKIT=y

tools/testing/selftests/net/link_netns.py

@@ -0,0 +1,141 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import time
+
+from lib.py import ksft_run, ksft_exit, ksft_true
+from lib.py import ip
+from lib.py import NetNS, NetNSEnter
+from lib.py import RtnlFamily
+
+
+LINK_NETNSID = 100
+
+
+def test_event() -> None:
+    with NetNS() as ns1, NetNS() as ns2:
+        with NetNSEnter(str(ns2)):
+            rtnl = RtnlFamily()
+
+        rtnl.ntf_subscribe("rtnlgrp-link")
+
+        ip(f"netns set {ns2} {LINK_NETNSID}", ns=str(ns1))
+        ip(f"link add netns {ns1} link-netnsid {LINK_NETNSID} dummy1 type dummy")
+        ip(f"link add netns {ns1} dummy2 type dummy", ns=str(ns2))
+
+        ip("link del dummy1", ns=str(ns1))
+        ip("link del dummy2", ns=str(ns1))
+
+        time.sleep(1)
+        rtnl.check_ntf()
+        ksft_true(rtnl.async_msg_queue.empty(),
+                  "Received unexpected link notification")
+
+
+def validate_link_netns(netns, ifname, link_netnsid) -> bool:
+    link_info = ip(f"-d link show dev {ifname}", ns=netns, json=True)
+    if not link_info:
+        return False
+    return link_info[0].get("link_netnsid") == link_netnsid
+
+
+def test_link_net() -> None:
+    configs = [
+        # type, common args, type args, fallback to dev_net
+        ("ipvlan", "link dummy1", "", False),
+        ("macsec", "link dummy1", "", False),
+        ("macvlan", "link dummy1", "", False),
+        ("macvtap", "link dummy1", "", False),
+        ("vlan", "link dummy1", "id 100", False),
+        ("gre", "", "local 192.0.2.1", True),
+        ("vti", "", "local 192.0.2.1", True),
+        ("ipip", "", "local 192.0.2.1", True),
+        ("ip6gre", "", "local 2001:db8::1", True),
+        ("ip6tnl", "", "local 2001:db8::1", True),
+        ("vti6", "", "local 2001:db8::1", True),
+        ("sit", "", "local 192.0.2.1", True),
+        ("xfrm", "", "if_id 1", True),
+    ]
+
+    with NetNS() as ns1, NetNS() as ns2, NetNS() as ns3:
+        net1, net2, net3 = str(ns1), str(ns2), str(ns3)
+
+        # prepare link netnsid  and a dummy link needed by certain drivers
+        ip(f"netns set {net3} {LINK_NETNSID}", ns=str(net2))
+        ip("link add dummy1 type dummy", ns=net3)
+
+        cases = [
+            # source, "netns", "link-netns", expected link-netns
+            (net3, None, None, None, None),
+            (net3, net2, None, None, LINK_NETNSID),
+            (net2, None, net3, LINK_NETNSID, LINK_NETNSID),
+            (net1, net2, net3, LINK_NETNSID, LINK_NETNSID),
+        ]
+
+        for src_net, netns, link_netns, exp1, exp2 in cases:
+            tgt_net = netns or src_net
+            for typ, cargs, targs, fb_dev_net in configs:
+                cmd = "link add"
+                if netns:
+                    cmd += f" netns {netns}"
+                if link_netns:
+                    cmd += f" link-netns {link_netns}"
+                cmd += f" {cargs} foo type {typ} {targs}"
+                ip(cmd, ns=src_net)
+                if fb_dev_net:
+                    ksft_true(validate_link_netns(tgt_net, "foo", exp1),
+                              f"{typ} link_netns validation failed")
+                else:
+                    ksft_true(validate_link_netns(tgt_net, "foo", exp2),
+                              f"{typ} link_netns validation failed")
+                ip(f"link del foo", ns=tgt_net)
+
+
+def test_peer_net() -> None:
+    types = [
+        "vxcan",
+        "netkit",
+        "veth",
+    ]
+
+    with NetNS() as ns1, NetNS() as ns2, NetNS() as ns3, NetNS() as ns4:
+        net1, net2, net3, net4 = str(ns1), str(ns2), str(ns3), str(ns4)
+
+        ip(f"netns set {net3} {LINK_NETNSID}", ns=str(net2))
+
+        cases = [
+            # source, "netns", "link-netns", "peer netns", expected
+            (net1, None, None, None, None),
+            (net1, net2, None, None, None),
+            (net2, None, net3, None, LINK_NETNSID),
+            (net1, net2, net3, None, None),
+            (net2, None, None, net3, LINK_NETNSID),
+            (net1, net2, None, net3, LINK_NETNSID),
+            (net2, None, net2, net3, LINK_NETNSID),
+            (net1, net2, net4, net3, LINK_NETNSID),
+        ]
+
+        for src_net, netns, link_netns, peer_netns, exp in cases:
+            tgt_net = netns or src_net
+            for typ in types:
+                cmd = "link add"
+                if netns:
+                    cmd += f" netns {netns}"
+                if link_netns:
+                    cmd += f" link-netns {link_netns}"
+                cmd += f" foo type {typ}"
+                if peer_netns:
+                    cmd += f" peer netns {peer_netns}"
+                ip(cmd, ns=src_net)
+                ksft_true(validate_link_netns(tgt_net, "foo", exp),
+                          f"{typ} peer_netns validation failed")
+                ip(f"link del foo", ns=tgt_net)
+
+
+def main() -> None:
+    ksft_run([test_event, test_link_net, test_peer_net])
+    ksft_exit()
+
+
+if __name__ == "__main__":
+    main()

tools/testing/selftests/net/netns-name.sh

@@ -78,6 +78,16 @@ ip -netns $NS link show dev $ALT_NAME 2> /dev/null &&
     fail "Can still find alt-name after move"
 ip -netns $test_ns link del $DEV || fail
 
+#
+# Test no conflict of the same name/ifindex in different netns
+#
+ip -netns $NS link add name $DEV index 100 type dummy || fail
+ip -netns $NS link add netns $test_ns name $DEV index 100 type dummy ||
+    fail "Can create in netns without moving"
+ip -netns $test_ns link show dev $DEV >> /dev/null || fail "Device not found"
+ip -netns $NS link del $DEV || fail
+ip -netns $test_ns link del $DEV || fail
+
 echo -ne "$(basename $0) \t\t\t\t"
 if [ $RET_CODE -eq 0 ]; then
     echo "[  OK  ]"