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(-)
BATMAN compares ifindex with dev_get_iflink to detect devices that don't have a parent, but that's wrong, since a device can have the same index as its parent if it's created in a different network namespace:
ip netns add main ip netns add peer ip -net main link add dummy0 type dummy # keep ifindex in sync between the namespaces ip -net peer link add eatidx type dummy
ip netns exec main batctl if add dummy0 # macsec0 and bat0 have the same ifindex ip -net main link add link bat0 netns peer type macsec ip netns exec peer batctl if add macsec0
That last command would fail if we didn't keep the ifindex in sync between the two namespaces, and should also fail when the macsec0 device has the same ifindex as its link. Let's use the presence of a ndo_get_iflink operation, rather than the value it returns, to detect a device without a link.
Fixes: b7eddd0b3950 ("batman-adv: prevent using any virtual device created on batman-adv as hard-interface") Signed-off-by: Sabrina Dubroca sd@queasysnail.net --- net/batman-adv/hard-interface.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c index fa06b51c0144..0d87c5d56844 100644 --- a/net/batman-adv/hard-interface.c +++ b/net/batman-adv/hard-interface.c @@ -159,7 +159,7 @@ static bool batadv_is_on_batman_iface(const struct net_device *net_dev)
/* no more parents..stop recursion */ if (dev_get_iflink(net_dev) == 0 || - dev_get_iflink(net_dev) == net_dev->ifindex) + !(net_dev->netdev_ops && net_dev->netdev_ops->ndo_get_iflink)) return false;
parent_net = batadv_getlink_net(net_dev, net);
On Thursday, 1 October 2020 09:59:35 CEST Sabrina Dubroca wrote:
device has the same ifindex as its link. Let's use the presence of a ndo_get_iflink operation, rather than the value it returns, to detect a device without a link.
There wasn't any activity in this patchset since a while, it doesn't apply anymore and the assumptions made here doesn't seem to be reflect the current situation in the kernel. See commit 6c1f41afc1db ("batman-adv: Don't expect inter-netns unique iflink indices"):
But only checking for dev->netdev_ops->ndo_get_iflink is also not an option because ipoib_get_iflink implements it even when it sometimes returns an iflink != ifindex and sometimes iflink == ifindex. The caller must therefore make sure itself to check both netns and iflink + ifindex for equality. Only when they are equal, a "physical" interface was detected which should stop the traversal. On the other hand, vxcan_get_iflink can also return 0 in case there was currently no valid peer. In this case, it is still necessary to stop.
It would would be nice when the situation would be better but the proposed patches don't solve it. So I will mark the two patches as "Rejected" (from "Changes requested") in batadv's patchwork. It is not meant as sign of disapproval of someone working in this area to improve the situation - I just don't want to wait for the v2 [1] anymore.
Kind regards, Sven
[1] https://lore.kernel.org/all/20201002090703.GD3565727@bistromath.localdomain/
Currently, batadv_get_real_netdevice can return different results in this situation:
ip netns add main ip netns add peer ip -net main link add dummy1 type dummy ip -net main link add link dummy1 netns peer type macsec # same ifindex as dummy1 ip -net main link add link dummy1 netns peer type macsec port 2
Let's use the presence of a ndo_get_iflink operation, rather than the value it returns, to detect a device without a link.
Fixes: 5ed4a460a1d3 ("batman-adv: additional checks for virtual interfaces on top of WiFi") Signed-off-by: Sabrina Dubroca sd@queasysnail.net --- net/batman-adv/hard-interface.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c index 0d87c5d56844..8f7d2dd37321 100644 --- a/net/batman-adv/hard-interface.c +++ b/net/batman-adv/hard-interface.c @@ -223,7 +223,7 @@ static struct net_device *batadv_get_real_netdevice(struct net_device *netdev) if (!netdev) return NULL;
- if (netdev->ifindex == dev_get_iflink(netdev)) { + if (!(netdev->netdev_ops && netdev->netdev_ops->ndo_get_iflink)) { dev_hold(netdev); return netdev; }
On Thu, 1 Oct 2020 09:59:24 +0200 Sabrina Dubroca sd@queasysnail.net wrote:
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)
Since this is a common operation, it would be good to add a new helper function in netdevice.h
In your patch set, you are copying the same code snippet which seems to indicate that it should be a helper.
Something like:
static inline bool netdev_has_link(const struct net_device *dev) { const struct net_device_ops *ops = dev->netdev_ops;
return ops && ops->ndo_get_iflink; }
2020-10-01, 14:25:38 -0700, Stephen Hemminger wrote:
On Thu, 1 Oct 2020 09:59:24 +0200 Sabrina Dubroca sd@queasysnail.net wrote:
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)
Since this is a common operation, it would be good to add a new helper function in netdevice.h
In your patch set, you are copying the same code snippet which seems to indicate that it should be a helper.
Something like:
static inline bool netdev_has_link(const struct net_device *dev) { const struct net_device_ops *ops = dev->netdev_ops;
return ops && ops->ndo_get_iflink; }
Good idea, I'll add that in v2.
b.a.t.m.a.n@lists.open-mesh.org
-
Sabrina Dubroca -
Stephen Hemminger -
Sven Eckelmann