In a lot of places, we use this kind of comparison to detect if a
device has a lower link:
dev->ifindex != dev_get_iflink(dev)
This seems to be a leftover of the pre-netns days, when the ifindex
was unique over the whole system. Nowadays, with network namespaces,
it's very easy to create a device with the same ifindex as its lower
link:
ip netns add main
ip netns add peer
ip -net main link add dummy0 type dummy
ip -net main link add link dummy0 macvlan0 netns peer type macvlan
ip -net main link show type dummy
9: dummy0: <BROADCAST,NOARP> mtu 1500 qdisc noop ...
ip -net peer link show type macvlan
9: macvlan0@if9: <BROADCAST,MULTICAST> mtu 1500 qdisc noop ...
To detect if a device has a lower link, we can simply check the
existence of the dev->netdev_ops->ndo_get_iflink operation, instead of
checking its return value. In particular, I attempted to fix one of
these checks in commit feadc4b6cf42 ("rtnetlink: always put IFLA_LINK
for links with a link-netnsid"), but this patch isn't correct, since
tunnel devices can export IFLA_LINK_NETNSID without IFLA_LINK. That
patch needs to be reverted.
This series will fix all those bogus comparisons, and export missing
IFLA_LINK_NETNSID attributes in bridge and ipv6 dumps.
ipvlan and geneve are also missing the get_link_net operation, so
userspace can't know when those device are cross-netns. There are a
couple of other device types that have an ndo_get_iflink op but no
get_link_net (virt_wifi, ipoib), and should probably also have a
get_link_net.
Sabrina Dubroca (12):
ipvlan: add get_link_net
geneve: add get_link_net
Revert "rtnetlink: always put IFLA_LINK for links with a link-netnsid"
rtnetlink: always put IFLA_LINK for links with ndo_get_iflink
bridge: always put IFLA_LINK for ports with ndo_get_iflink
bridge: advertise IFLA_LINK_NETNSID when dumping bridge ports
ipv6: always put IFLA_LINK for devices with ndo_get_iflink
ipv6: advertise IFLA_LINK_NETNSID when dumping ipv6 addresses
net: link_watch: fix operstate when the link has the same index as the
device
net: link_watch: fix detection of urgent events
batman-adv: fix iflink detection in batadv_is_on_batman_iface
batman-adv: fix detection of lower link in batadv_get_real_netdevice
drivers/net/can/vxcan.c | 2 +-
drivers/net/geneve.c | 8 ++++++++
drivers/net/ipvlan/ipvlan_main.c | 9 +++++++++
drivers/net/veth.c | 2 +-
include/net/rtnetlink.h | 4 ++++
net/batman-adv/hard-interface.c | 4 ++--
net/bridge/br_netlink.c | 4 +++-
net/core/link_watch.c | 4 ++--
net/core/rtnetlink.c | 25 ++++++++++++-------------
net/ipv6/addrconf.c | 11 ++++++++++-
10 files changed, 52 insertions(+), 21 deletions(-)
--
2.28.0
