[PATCH net-next v8 00/11] net: Improve netns handling in rtnetlink

Xiao Liang
2025-01-13T14:37:39Z

This patch series includes some netns-related improvements and fixes for
rtnetlink, to make link creation more intuitive:

1) Creating link in another net namespace doesn't conflict with link
names in current one.
2) Refector rtnetlink link creation. Create link in target namespace
directly.

So that

# ip link add netns ns1 link-netns ns2 tun0 type gre ...

will create tun0 in ns1, rather than create it in ns2 and move to ns1.
And don't conflict with another interface named "tun0" in current netns.

Patch 01 serves for 1) to avoids link name conflict in different netns.

To achieve 2), there're mainly 3 steps:

- Patch 02 packs newlink() parameters into a struct, including
the original "src_net" along with more netns context. No semantic
changes are introduced.
- Patch 03 ~ 07 converts device drivers to use the explicit netns
extracted from params.
- Patch 08 ~ 09 removes the old netns parameter, and converts
rtnetlink to create device in target netns directly.

Patch 10 ~ 11 adds some tests for link name and link netns.

BTW please note there're some issues found in current code:

- In amt_newlink() drivers/net/amt.c:

amt->net = net;
...
amt->stream_dev = dev_get_by_index(net, ...

Uses net, but amt_lookup_upper_dev() only searches in dev_net.
So the AMT device may not be properly deleted if it's in a different
netns from lower dev.

- In gtp_newlink() in drivers/net/gtp.c:

gtp->net = src_net;
...
gn = net_generic(dev_net(dev), gtp_net_id);
list_add_rcu(&gtp->list, &gn->gtp_dev_list);

Uses src_net, but priv is linked to list in dev_net. So it may not be
properly deleted on removal of link netns.

- In pfcp_newlink() in drivers/net/pfcp.c:

pfcp->net = net;
...
pn = net_generic(dev_net(dev), pfcp_net_id);
list_add_rcu(&pfcp->list, &pn->pfcp_dev_list);

Same as above.

- In lowpan_newlink() in net/ieee802154/6lowpan/core.c:

wdev = dev_get_by_index(dev_net(ldev), nla_get_u32(tb[IFLA_LINK]));

Looks for IFLA_LINK in dev_net, but in theory the ifindex is defined
in link netns.

Kuniyuki has a patchset to address the issues of gtp and pfcp:
https://lore.kernel.org/netdev/20250110014754.33847-1-kuniyu@amazon.com/

---

v8:
- Move dev and ext_ack out from param struct.
- Validate link_net and dev_net are identical for 6lowpan.

v7:
link: https://lore.kernel.org/all/20250104125732.17335-1-shaw.leon@gmail.com/
- Add selftest kconfig.
- Remove a duplicated test of ip6gre.

v6:
link: https://lore.kernel.org/all/20241218130909.2173-1-shaw.leon@gmail.com/
- Split prototype, driver and rtnetlink changes.
- Add more tests for link netns.
- Fix IPv6 tunnel net overwriten in ndo_init().
- Reorder variable declarations.
- Exclude a ip_tunnel-specific patch.

v5:
link: https://lore.kernel.org/all/20241209140151.231257-1-shaw.leon@gmail.com/
- Fix function doc in batman-adv.
- Include peer_net in rtnl newlink parameters.

v4:
link: https://lore.kernel.org/all/20241118143244.1773-1-shaw.leon@gmail.com/
- Pack newlink() parameters to a single struct.
- Use ynl async_msg_queue.empty() in selftest.

v3:
link: https://lore.kernel.org/all/20241113125715.150201-1-shaw.leon@gmail.com/
- Drop "netns_atomic" flag and module parameter. Add netns parameter to
newlink() instead, and convert drivers accordingly.
- Move python NetNSEnter helper to net selftest lib.

v2:
link: https://lore.kernel.org/all/20241107133004.7469-1-shaw.leon@gmail.com/
- Check NLM_F_EXCL to ensure only link creation is affected.
- Add self tests for link name/ifindex conflict and notifications
in different netns.
- Changes in dummy driver and ynl in order to add the test case.

v1:
link: https://lore.kernel.org/all/20241023023146.372653-1-shaw.leon@gmail.com/

Xiao Liang (11):
rtnetlink: Lookup device in target netns when creating link
rtnetlink: Pack newlink() params into struct
net: Use link netns in newlink() of rtnl_link_ops
ieee802154: 6lowpan: Validate link netns in newlink() of rtnl_link_ops
net: ip_tunnel: Use link netns in newlink() of rtnl_link_ops
net: ipv6: Use link netns in newlink() of rtnl_link_ops
net: xfrm: Use link netns in newlink() of rtnl_link_ops
rtnetlink: Remove "net" from newlink params
rtnetlink: Create link directly in target net namespace
selftests: net: Add python context manager for netns entering
selftests: net: Add test cases for link and peer netns

drivers/infiniband/ulp/ipoib/ipoib_netlink.c | 9 +-
drivers/net/amt.c | 11 +-
drivers/net/bareudp.c | 9 +-
drivers/net/bonding/bond_netlink.c | 6 +-
drivers/net/can/dev/netlink.c | 4 +-
drivers/net/can/vxcan.c | 7 +-
.../ethernet/qualcomm/rmnet/rmnet_config.c | 9 +-
drivers/net/geneve.c | 9 +-
drivers/net/gtp.c | 8 +-
drivers/net/ipvlan/ipvlan.h | 3 +-
drivers/net/ipvlan/ipvlan_main.c | 8 +-
drivers/net/ipvlan/ipvtap.c | 6 +-
drivers/net/macsec.c | 9 +-
drivers/net/macvlan.c | 7 +-
drivers/net/macvtap.c | 7 +-
drivers/net/netkit.c | 7 +-
drivers/net/pfcp.c | 7 +-
drivers/net/ppp/ppp_generic.c | 9 +-
drivers/net/team/team_core.c | 6 +-
drivers/net/veth.c | 7 +-
drivers/net/vrf.c | 5 +-
drivers/net/vxlan/vxlan_core.c | 9 +-
drivers/net/wireguard/device.c | 7 +-
drivers/net/wireless/virtual/virt_wifi.c | 8 +-
drivers/net/wwan/wwan_core.c | 16 +-
include/net/ip_tunnels.h | 5 +-
include/net/rtnetlink.h | 40 ++++-
net/8021q/vlan_netlink.c | 9 +-
net/batman-adv/soft-interface.c | 9 +-
net/bridge/br_netlink.c | 6 +-
net/caif/chnl_net.c | 5 +-
net/core/rtnetlink.c | 33 ++--
net/hsr/hsr_netlink.c | 12 +-
net/ieee802154/6lowpan/core.c | 7 +-
net/ipv4/ip_gre.c | 24 ++-
net/ipv4/ip_tunnel.c | 10 +-
net/ipv4/ip_vti.c | 9 +-
net/ipv4/ipip.c | 9 +-
net/ipv6/ip6_gre.c | 30 ++--
net/ipv6/ip6_tunnel.c | 19 ++-
net/ipv6/ip6_vti.c | 15 +-
net/ipv6/sit.c | 17 ++-
net/xfrm/xfrm_interface_core.c | 15 +-
tools/testing/selftests/net/Makefile | 1 +
tools/testing/selftests/net/config | 5 +
.../testing/selftests/net/lib/py/__init__.py | 2 +-
tools/testing/selftests/net/lib/py/netns.py | 18 +++
tools/testing/selftests/net/link_netns.py | 141 ++++++++++++++++++
tools/testing/selftests/net/netns-name.sh | 10 ++
49 files changed, 479 insertions(+), 165 deletions(-)
create mode 100755 tools/testing/selftests/net/link_netns.py

--
2.47.1