Support classifying packets with netfilter on egress to satisfy user
requirements such as:
* outbound security policies for containers (Laura)
* filtering and mangling intra-node Direct Server Return (DSR) traffic
on a load balancer (Laura)
* filtering locally generated traffic coming in through AF_PACKET,
such as local ARP traffic generated for clustering purposes or DHCP
(Laura; the AF_PACKET plumbing is contained in a follow-up commit)
* L2 filtering from ingress and egress for AVB (Audio Video Bridging)
and gPTP with nftables (Pablo)
* in the future: in-kernel NAT64/NAT46 (Pablo)
The egress hook introduced herein complements the ingress hook added by
commit e687ad60af ("netfilter: add netfilter ingress hook after
handle_ing() under unique static key"). A patch for nftables to hook up
egress rules from user space has been submitted separately, so users may
immediately take advantage of the feature.
Alternatively or in addition to netfilter, packets can be classified
with traffic control (tc). On ingress, packets are classified first by
tc, then by netfilter. On egress, the order is reversed for symmetry.
Conceptually, tc and netfilter can be thought of as layers, with
netfilter layered above tc.
Traffic control is capable of redirecting packets to another interface
(man 8 tc-mirred). E.g., an ingress packet may be redirected from the
host namespace to a container via a veth connection:
tc ingress (host) -> tc egress (veth host) -> tc ingress (veth container)
In this case, netfilter egress classifying is not performed when leaving
the host namespace! That's because the packet is still on the tc layer.
If tc redirects the packet to a physical interface in the host namespace
such that it leaves the system, the packet is never subjected to
netfilter egress classifying. That is only logical since it hasn't
passed through netfilter ingress classifying either.
Packets can alternatively be redirected at the netfilter layer using
nft fwd. Such a packet *is* subjected to netfilter egress classifying
since it has reached the netfilter layer.
Internally, the skb->nf_skip_egress flag controls whether netfilter is
invoked on egress by __dev_queue_xmit(). Because __dev_queue_xmit() may
be called recursively by tunnel drivers such as vxlan, the flag is
reverted to false after sch_handle_egress(). This ensures that
netfilter is applied both on the overlay and underlying network.
Interaction between tc and netfilter is possible by setting and querying
skb->mark.
If netfilter egress classifying is not enabled on any interface, it is
patched out of the data path by way of a static_key and doesn't make a
performance difference that is discernible from noise:
Before: 1537 1538 1538 1537 1538 1537 Mb/sec
After: 1536 1534 1539 1539 1539 1540 Mb/sec
Before + tc accept: 1418 1418 1418 1419 1419 1418 Mb/sec
After + tc accept: 1419 1424 1418 1419 1422 1420 Mb/sec
Before + tc drop: 1620 1619 1619 1619 1620 1620 Mb/sec
After + tc drop: 1616 1624 1625 1624 1622 1619 Mb/sec
When netfilter egress classifying is enabled on at least one interface,
a minimal performance penalty is incurred for every egress packet, even
if the interface it's transmitted over doesn't have any netfilter egress
rules configured. That is caused by checking dev->nf_hooks_egress
against NULL.
Measurements were performed on a Core i7-3615QM. Commands to reproduce:
ip link add dev foo type dummy
ip link set dev foo up
modprobe pktgen
echo "add_device foo" > /proc/net/pktgen/kpktgend_3
samples/pktgen/pktgen_bench_xmit_mode_queue_xmit.sh -i foo -n 400000000 -m "11:11:11:11:11:11" -d 1.1.1.1
Accept all traffic with tc:
tc qdisc add dev foo clsact
tc filter add dev foo egress bpf da bytecode '1,6 0 0 0,'
Drop all traffic with tc:
tc qdisc add dev foo clsact
tc filter add dev foo egress bpf da bytecode '1,6 0 0 2,'
Apply this patch when measuring packet drops to avoid errors in dmesg:
https://lore.kernel.org/netdev/a73dda33-57f4-95d8-ea51-ed483abd6a7a@iogearbox.net/
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: Laura García Liébana <nevola@gmail.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
syzbot reported following (harmless) WARN:
WARNING: CPU: 1 PID: 2648 at net/netfilter/core.c:468
nft_netdev_unregister_hooks net/netfilter/nf_tables_api.c:230 [inline]
nf_tables_unregister_hook include/net/netfilter/nf_tables.h:1090 [inline]
__nft_release_basechain+0x138/0x640 net/netfilter/nf_tables_api.c:9524
nft_netdev_event net/netfilter/nft_chain_filter.c:351 [inline]
nf_tables_netdev_event+0x521/0x8a0 net/netfilter/nft_chain_filter.c:382
reproducer:
unshare -n bash -c 'ip link add br0 type bridge; nft add table netdev t ; \
nft add chain netdev t ingress \{ type filter hook ingress device "br0" \
priority 0\; policy drop\; \}'
Problem is that when netns device exit hooks create the UNREGISTER
event, the .pre_exit hook for nf_tables core has already removed the
base hook. Notifier attempts to do this again.
The need to do base hook unregister unconditionally was needed in the past,
because notifier was last stage where reg->dev dereference was safe.
Now that nf_tables does the hook removal in .pre_exit, this isn't
needed anymore.
Reported-and-tested-by: syzbot+154bd5be532a63aa778b@syzkaller.appspotmail.com
Fixes: 767d1216bf ("netfilter: nftables: fix possible UAF over chains from packet path in netns")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
The functions pass extra skb arg, but either its not used or the helpers
can already access it via pkt->skb.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This moves all nf_tables pernet data from struct net to a net_generic
extension, with the exception of the gencursor.
The latter is used in the data path and also outside of the nf_tables
core. All others are only used from the configuration plane.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This patch adds a new ingress hook for the inet family. The inet ingress
hook emulates the IP receive path code, therefore, unclean packets are
drop before walking over the ruleset in this basechain.
This patch also introduces the nft_base_chain_netdev() helper function
to check if this hook is bound to one or more devices (through the hook
list infrastructure). This check allows to perform the same handling for
the inet ingress as it would be a netdev ingress chain from the control
plane.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This patch allows you to register one netdev basechain to multiple
devices. This adds a new NFTA_HOOK_DEVS netlink attribute to specify
the list of netdevices. Basechains store a list of hooks.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
The new nft_meta_bridge code fails to link as built-in when NF_TABLES
is a loadable module.
net/bridge/netfilter/nft_meta_bridge.o: In function `nft_meta_bridge_get_eval':
nft_meta_bridge.c:(.text+0x1e8): undefined reference to `nft_meta_get_eval'
net/bridge/netfilter/nft_meta_bridge.o: In function `nft_meta_bridge_get_init':
nft_meta_bridge.c:(.text+0x468): undefined reference to `nft_meta_get_init'
nft_meta_bridge.c:(.text+0x49c): undefined reference to `nft_parse_register'
nft_meta_bridge.c:(.text+0x4cc): undefined reference to `nft_validate_register_store'
net/bridge/netfilter/nft_meta_bridge.o: In function `nft_meta_bridge_module_exit':
nft_meta_bridge.c:(.exit.text+0x14): undefined reference to `nft_unregister_expr'
net/bridge/netfilter/nft_meta_bridge.o: In function `nft_meta_bridge_module_init':
nft_meta_bridge.c:(.init.text+0x14): undefined reference to `nft_register_expr'
net/bridge/netfilter/nft_meta_bridge.o:(.rodata+0x60): undefined reference to `nft_meta_get_dump'
net/bridge/netfilter/nft_meta_bridge.o:(.rodata+0x88): undefined reference to `nft_meta_set_eval'
This can happen because the NF_TABLES_BRIDGE dependency itself is just a
'bool'. Make the symbol a 'tristate' instead so Kconfig can propagate the
dependencies correctly.
Fixes: 30e103fe24 ("netfilter: nft_meta: move bridge meta keys into nft_meta_bridge")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
When a netnsamespace exits, the nf_tables pernet_ops will remove all rules.
However, there is one caveat:
Base chains that register ingress hooks will cause use-after-free:
device is already gone at that point.
The device event handlers prevent this from happening:
netns exit synthesizes unregister events for all devices.
However, an improper fix for a race condition made the notifiers a no-op
in case they get called from netns exit path, so revert that part.
This is safe now as the previous patch fixed nf_tables pernet ops
and device notifier initialisation ordering.
Fixes: 0a2cf5ee43 ("netfilter: nf_tables: close race between netns exit and rmmod")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
We must register nfnetlink ops last, as that exposes nf_tables to
userspace. Without this, we could theoretically get nfnetlink request
before net->nft state has been initialized.
Fixes: 99633ab29b ("netfilter: nf_tables: complete net namespace support")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Continue to use nftnl subsys mutex to protect (un)registration of hook types,
expressions and so on, but force batch operations to do their own
locking.
This allows distinct net namespaces to perform transactions in parallel.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
If net namespace is exiting while nf_tables module is being removed
we can oops:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000040
IP: nf_tables_flowtable_event+0x43/0xf0 [nf_tables]
PGD 0 P4D 0
Oops: 0000 [#1] SMP PTI
Modules linked in: nf_tables(-) nfnetlink [..]
unregister_netdevice_notifier+0xdd/0x130
nf_tables_module_exit+0x24/0x3a [nf_tables]
SyS_delete_module+0x1c5/0x240
do_syscall_64+0x74/0x190
Avoid this by attempting to take reference on the net namespace from
the notifiers. If it fails the namespace is exiting already, and nft
core is taking care of cleanup work.
We also need to make sure the netdev hook type gets removed
before netns ops removal, else notifier might be invoked with device
event for a netns where net->nft was never initialised (because
pernet ops was removed beforehand).
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
One module per supported filter chain family type takes too much memory
for very little code - too much modularization - place all chain filter
definitions in one single file.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
