linux.git/include/net/l3mdev.h, branch v6.18.21

net: fib_rules: Fix iif / oif matching on L3 master device

2025-04-16T00:54:56+00:00

Before commit 40867d74c374 ("net: Add l3mdev index to flow struct and
avoid oif reset for port devices") it was possible to use FIB rules to
match on a L3 domain. This was done by having a FIB rule match on iif /
oif being a L3 master device. It worked because prior to the FIB rule
lookup the iif / oif fields in the flow structure were reset to the
index of the L3 master device to which the input / output device was
enslaved to.

The above scheme made it impossible to match on the original input /
output device. Therefore, cited commit stopped overwriting the iif / oif
fields in the flow structure and instead stored the index of the
enslaving L3 master device in a new field ('flowi_l3mdev') in the flow
structure.

While the change enabled new use cases, it broke the original use case
of matching on a L3 domain. Fix this by interpreting the iif / oif
matching on a L3 master device as a match against the L3 domain. In
other words, if the iif / oif in the FIB rule points to a L3 master
device, compare the provided index against 'flowi_l3mdev' rather than
'flowi_{i,o}if'.

Before cited commit, a FIB rule that matched on 'iif vrf1' would only
match incoming traffic from devices enslaved to 'vrf1'. With the
proposed change (i.e., comparing against 'flowi_l3mdev'), the rule would
also match traffic originating from a socket bound to 'vrf1'. Avoid that
by adding a new flow flag ('FLOWI_FLAG_L3MDEV_OIF') that indicates if
the L3 domain was derived from the output interface or the input
interface (when not set) and take this flag into account when evaluating
the FIB rule against the flow structure.

Avoid unnecessary checks in the data path by detecting that a rule
matches on a L3 master device when the rule is installed and marking it
as such.

Tested using the following script [1].

Output before 40867d74c374 (v5.4.291):

default dev dummy1 table 100 scope link
default dev dummy1 table 200 scope link

Output after 40867d74c374:

default dev dummy1 table 300 scope link
default dev dummy1 table 300 scope link

Output with this patch:

default dev dummy1 table 100 scope link
default dev dummy1 table 200 scope link

[1]
 #!/bin/bash

 ip link add name vrf1 up type vrf table 10
 ip link add name dummy1 up master vrf1 type dummy

 sysctl -wq net.ipv4.conf.all.forwarding=1
 sysctl -wq net.ipv4.conf.all.rp_filter=0

 ip route add table 100 default dev dummy1
 ip route add table 200 default dev dummy1
 ip route add table 300 default dev dummy1

 ip rule add prio 0 oif vrf1 table 100
 ip rule add prio 1 iif vrf1 table 200
 ip rule add prio 2 table 300

 ip route get 192.0.2.1 oif dummy1 fibmatch
 ip route get 192.0.2.1 iif dummy1 from 198.51.100.1 fibmatch

Fixes: 40867d74c374 ("net: Add l3mdev index to flow struct and avoid oif reset for port devices")
Reported-by: hanhuihui 
Closes: https://lore.kernel.org/netdev/ec671c4f821a4d63904d0da15d604b75@huawei.com/
Signed-off-by: Ido Schimmel 
Acked-by: David Ahern 
Link: https://patch.msgid.link/20250414172022.242991-2-idosch@nvidia.com
Signed-off-by: Jakub Kicinski

vrf: use RCU protection in l3mdev_l3_out()

2025-02-11T02:09:09+00:00

l3mdev_l3_out() can be called without RCU being held:

raw_sendmsg()
 ip_push_pending_frames()
  ip_send_skb()
   ip_local_out()
    __ip_local_out()
     l3mdev_ip_out()

Add rcu_read_lock() / rcu_read_unlock() pair to avoid
a potential UAF.

Fixes: a8e3e1a9f020 ("net: l3mdev: Add hook to output path")
Signed-off-by: Eric Dumazet 
Reviewed-by: David Ahern 
Reviewed-by: Kuniyuki Iwashima 
Link: https://patch.msgid.link/20250207135841.1948589-7-edumazet@google.com
Signed-off-by: Jakub Kicinski

net: Remove likely from l3mdev_master_ifindex_by_index

2024-10-10T09:57:34+00:00

The likely() annotation in l3mdev_master_ifindex_by_index() has been
found to be incorrect 100% of the time in real-world workloads (e.g.,
web servers).

Annotated branches shows the following in these servers:

	correct incorrect  %        Function                  File              Line
	      0 169053813 100 l3mdev_master_ifindex_by_index l3mdev.h             81

This is happening because l3mdev_master_ifindex_by_index() is called
from __inet_check_established(), which calls
l3mdev_master_ifindex_by_index() passing the socked bounded interface.

	l3mdev_master_ifindex_by_index(net, sk->sk_bound_dev_if);

Since most sockets are not going to be bound to a network device,
the likely() is giving the wrong assumption.

Remove the likely() annotation to ensure more accurate branch
prediction.

Signed-off-by: Breno Leitao 
Reviewed-by: David Ahern 
Reviewed-by: Eric Dumazet 
Link: https://patch.msgid.link/20241008163205.3939629-1-leitao@debian.org
Signed-off-by: Paolo Abeni

l3mdev: add infrastructure for table to VRF mapping

2020-06-21T00:22:22+00:00

Add infrastructure to l3mdev (the core code for Layer 3 master devices) in
order to find out the corresponding VRF device for a given table id.
Therefore, the l3mdev implementations:
 - can register a callback that returns the device index of the l3mdev
   associated with a given table id;
 - can offer the lookup function (table to VRF device).

Signed-off-by: Andrea Mayer 
Signed-off-by: David S. Miller

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152

2019-05-30T18:26:32+00:00

Based on 1 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license as published by
  the free software foundation either version 2 of the license or at
  your option any later version

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 3029 file(s).

Signed-off-by: Thomas Gleixner 
Reviewed-by: Allison Randal 
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de
Signed-off-by: Greg Kroah-Hartman

ipvlan, l3mdev: fix broken l3s mode wrt local routes

2019-01-31T06:13:34+00:00

While implementing ipvlan l3 and l3s mode for kubernetes CNI plugin,
I ran into the issue that while l3 mode is working fine, l3s mode
does not have any connectivity to kube-apiserver and hence all pods
end up in Error state as well. The ipvlan master device sits on
top of a bond device and hostns traffic to kube-apiserver (also running
in hostns) is DNATed from 10.152.183.1:443 to 139.178.29.207:37573
where the latter is the address of the bond0. While in l3 mode, a
curl to https://10.152.183.1:443 or to https://139.178.29.207:37573
works fine from hostns, neither of them do in case of l3s. In the
latter only a curl to https://127.0.0.1:37573 appeared to work where
for local addresses of bond0 I saw kernel suddenly starting to emit
ARP requests to query HW address of bond0 which remained unanswered
and neighbor entries in INCOMPLETE state. These ARP requests only
happen while in l3s.

Debugging this further, I found the issue is that l3s mode is piggy-
backing on l3 master device, and in this case local routes are using
l3mdev_master_dev_rcu(dev) instead of net->loopback_dev as per commit
f5a0aab84b74 ("net: ipv4: dst for local input routes should use l3mdev
if relevant") and 5f02ce24c269 ("net: l3mdev: Allow the l3mdev to be
a loopback"). I found that reverting them back into using the
net->loopback_dev fixed ipvlan l3s connectivity and got everything
working for the CNI.

Now judging from 4fbae7d83c98 ("ipvlan: Introduce l3s mode") and the
l3mdev paper in [0] the only sole reason why ipvlan l3s is relying
on l3 master device is to get the l3mdev_ip_rcv() receive hook for
setting the dst entry of the input route without adding its own
ipvlan specific hacks into the receive path, however, any l3 domain
semantics beyond just that are breaking l3s operation. Note that
ipvlan also has the ability to dynamically switch its internal
operation from l3 to l3s for all ports via ipvlan_set_port_mode()
at runtime. In any case, l3 vs l3s soley distinguishes itself by
'de-confusing' netfilter through switching skb->dev to ipvlan slave
device late in NF_INET_LOCAL_IN before handing the skb to L4.

Minimal fix taken here is to add a IFF_L3MDEV_RX_HANDLER flag which,
if set from ipvlan setup, gets us only the wanted l3mdev_l3_rcv() hook
without any additional l3mdev semantics on top. This should also have
minimal impact since dev->priv_flags is already hot in cache. With
this set, l3s mode is working fine and I also get things like
masquerading pod traffic on the ipvlan master properly working.

  [0] https://netdevconf.org/1.2/papers/ahern-what-is-l3mdev-paper.pdf

Fixes: f5a0aab84b74 ("net: ipv4: dst for local input routes should use l3mdev if relevant")
Fixes: 5f02ce24c269 ("net: l3mdev: Allow the l3mdev to be a loopback")
Fixes: 4fbae7d83c98 ("ipvlan: Introduce l3s mode")
Signed-off-by: Daniel Borkmann 
Cc: Mahesh Bandewar 
Cc: David Ahern 
Cc: Florian Westphal 
Cc: Martynas Pumputis 
Acked-by: David Ahern 
Signed-off-by: David S. Miller

l3mdev: add function to retreive upper master

2018-12-03T22:15:26+00:00

Existing functions to retreive the l3mdev of a device did not walk the
master chain to find the upper master. This patch adds a function to
find the l3mdev, even indirect through e.g. a bridge:

+----------+
|          |
| vrf-blue |
|          |
+----+-----+
     |
     |
+----+-----+
|          |
| br-blue  |
|          |
+----+-----+
     |
     |
+----+-----+
|          |
|   eth0   |
|          |
+----------+

This will properly resolve the l3mdev of eth0 to vrf-blue.

Signed-off-by: Alexis Bauvin 
Reviewed-by: Amine Kherbouche 
Reviewed-by: David Ahern 
Tested-by: Amine Kherbouche 
Signed-off-by: David S. Miller

net: ipv4: Do not drop to make_route if oif is l3mdev

2016-10-13T16:05:26+00:00

Commit e0d56fdd7342 was a bit aggressive removing l3mdev calls in
the IPv4 stack. If the fib_lookup fails we do not want to drop to
make_route if the oif is an l3mdev device.

Also reverts 19664c6a0009 ("net: l3mdev: Remove netif_index_is_l3_master")
which removed netif_index_is_l3_master.

Fixes: e0d56fdd7342 ("net: l3mdev: remove redundant calls")
Signed-off-by: David Ahern 
Signed-off-by: David S. Miller

net: l3mdev: Remove netif_index_is_l3_master

2016-09-17T14:05:05+00:00

No longer used after e0d56fdd73422 ("net: l3mdev: remove redundant calls")

Signed-off-by: David Ahern 
Signed-off-by: David S. Miller

net: l3mdev: remove get_rtable method

2016-09-11T06:12:53+00:00

No longer used

Signed-off-by: David Ahern 
Signed-off-by: David S. Miller