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Having two ring buffers per-peer means that every peer results in two
massive ring allocations. On an 8-core x86_64 machine, this commit
reduces the per-peer allocation from 18,688 bytes to 1,856 bytes, which
is an 90% reduction. Ninety percent! With some single-machine
deployments approaching 500,000 peers, we're talking about a reduction
from 7 gigs of memory down to 700 megs of memory.
In order to get rid of these per-peer allocations, this commit switches
to using a list-based queueing approach. Currently GSO fragments are
chained together using the skb->next pointer (the skb_list_* singly
linked list approach), so we form the per-peer queue around the unused
skb->prev pointer (which sort of makes sense because the links are
pointing backwards). Use of skb_queue_* is not possible here, because
that is based on doubly linked lists and spinlocks. Multiple cores can
write into the queue at any given time, because its writes occur in the
start_xmit path or in the udp_recv path. But reads happen in a single
workqueue item per-peer, amounting to a multi-producer, single-consumer
paradigm.
The MPSC queue is implemented locklessly and never blocks. However, it
is not linearizable (though it is serializable), with a very tight and
unlikely race on writes, which, when hit (some tiny fraction of the
0.15% of partial adds on a fully loaded 16-core x86_64 system), causes
the queue reader to terminate early. However, because every packet sent
queues up the same workqueue item after it is fully added, the worker
resumes again, and stopping early isn't actually a problem, since at
that point the packet wouldn't have yet been added to the encryption
queue. These properties allow us to avoid disabling interrupts or
spinning. The design is based on Dmitry Vyukov's algorithm [1].
Performance-wise, ordinarily list-based queues aren't preferable to
ringbuffers, because of cache misses when following pointers around.
However, we *already* have to follow the adjacent pointers when working
through fragments, so there shouldn't actually be any change there. A
potential downside is that dequeueing is a bit more complicated, but the
ptr_ring structure used prior had a spinlock when dequeueing, so all and
all the difference appears to be a wash.
Actually, from profiling, the biggest performance hit, by far, of this
commit winds up being atomic_add_unless(count, 1, max) and atomic_
dec(count), which account for the majority of CPU time, according to
perf. In that sense, the previous ring buffer was superior in that it
could check if it was full by head==tail, which the list-based approach
cannot do.
But all and all, this enables us to get massive memory savings, allowing
WireGuard to scale for real world deployments, without taking much of a
performance hit.
[1] http://www.1024cores.net/home/lock-free-algorithms/queues/intrusive-mpsc-node-based-queue
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Now that wg_examine_packet_protocol has been added for general
consumption as ip_tunnel_parse_protocol, it's possible to remove
wg_examine_packet_protocol and simply use the new
ip_tunnel_parse_protocol function directly.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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It's important that we clear most header fields during encapsulation and
decapsulation, because the packet is substantially changed, and we don't
want any info leak or logic bug due to an accidental correlation. But,
for encapsulation, it's wrong to clear skb->hash, since it's used by
fq_codel and flow dissection in general. Without it, classification does
not proceed as usual. This change might make it easier to estimate the
number of innerflows by examining clustering of out of order packets,
but this shouldn't open up anything that can't already be inferred
otherwise (e.g. syn packet size inference), and fq_codel can be disabled
anyway.
Furthermore, it might be the case that the hash isn't used or queried at
all until after wireguard transmits the encrypted UDP packet, which
means skb->hash might still be zero at this point, and thus no hash
taken over the inner packet data. In order to address this situation, we
force a calculation of skb->hash before encrypting packet data.
Of course this means that fq_codel might transmit packets slightly more
out of order than usual. Toke did some testing on beefy machines with
high quantities of parallel flows and found that increasing the
reply-attack counter to 8192 takes care of the most pathological cases
pretty well.
Reported-by: Dave Taht <dave.taht@gmail.com>
Reviewed-and-tested-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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This backports upstream commit 2c64605b590edadb3fb46d1ec6badb49e940b479.
It makes no difference for us, but it's nice to keep this code in sync
with upstream as much as possible.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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We carry out checks to the effect of:
if (skb->protocol != wg_examine_packet_protocol(skb))
goto err;
By having wg_skb_examine_untrusted_ip_hdr return 0 on failure, this
means that the check above still passes in the case where skb->protocol
is zero, which is possible to hit with AF_PACKET:
struct sockaddr_pkt saddr = { .spkt_device = "wg0" };
unsigned char buffer[5] = { 0 };
sendto(socket(AF_PACKET, SOCK_PACKET, /* skb->protocol = */ 0),
buffer, sizeof(buffer), 0, (const struct sockaddr *)&saddr, sizeof(saddr));
Additional checks mean that this isn't actually a problem in the code
base, but I could imagine it becoming a problem later if the function is
used more liberally.
I would prefer to fix this by having wg_examine_packet_protocol return a
32-bit ~0 value on failure, which will never match any value of
skb->protocol, which would simply change the generated code from a mov
to a movzx. However, sparse complains, and adding __force casts doesn't
seem like a good idea, so instead we just add a simple helper function
to check for the zero return value. Since wg_examine_packet_protocol
itself gets inlined, this winds up not adding an additional branch to
the generated code, since the 0 return value already happens in a
mergable branch.
Reported-by: Fabian Freyer <fabianfreyer@radicallyopensecurity.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Suggested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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This required a bit of pruning of our christmas trees.
Suggested-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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I understand why this must be done, though I'm not so happy about having
to do it. In some places, it puts us over 80 chars and we have to break
lines up in further ugly ways. And in general, I think this makes things
harder to read. Yet another thing we must do to please upstream.
Maybe this can be replaced in the future by some kind of automatic
module namespacing logic in the linker, or even combined with LTO and
aggressive symbol stripping.
Suggested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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The kernel has very specific rules correlating file type with comment
type, and also SPDX identifiers can't be merged with other comments.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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This is the worst commit in the whole repo, making the code much less
readable, but so it goes with upstream maintainers.
We are now woefully wrapped at 80 columns.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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We don't want a consumer to read plaintext when it's supposed to be
reading ciphertext, which means we need to synchronize across cores.
Suggested-by: Jann Horn <jann@thejh.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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After we atomic_set, the peer is allowed to be freed, which means if we
want to continue to reference it, we need to bump the reference count.
This was introduced a few commits ago by b713ab0e when implementing some
simplification suggestions.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Use RCU reference counts only when we must, and otherwise use a more
reasonably named function.
Reported-by: Jann Horn <jann@thejh.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Suggested-by: Jason A. Donenfeld <Jason@zx2c4.com>
[Jason: fixed up the flushing of the rx_queue in peer_remove]
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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It might be that a particular route has a different MTU than the
interface, via `ip route add ... dev wg0 mtu 1281`, for example. In this
case, it's important that we don't accidently pad beyond the end of the
MTU. We accomplish that in this patch by carrying forward the MTU from
the dst if it exists. We also add a unit test for this issue.
Reported-by: Roman Mamedov <rm.wg@romanrm.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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This was avoided for a long time, because I wanted the packet to be
charged to the original socket for as long as possible. However, this
broke net_cls, which looks at skb->sk for additional late-stage routing
decisions. So we had no choice but to ensure that skb->sk is NULL by the
time of xmit, and this means calling the skb destructor.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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It's good to have SPDX identifiers in all files as the Linux kernel
developers are working to add these identifiers to all files.
Update all files with the correct SPDX license identifier based on the license
text of the project or based on the license in the file itself. The SPDX
identifier is a legally binding shorthand, which can be used instead of the
full boiler plate text.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Modified-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Suggested-by: Sultan Alsawaf <sultanxda@gmail.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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This removes our dependency on padata and moves to a different mode of
multiprocessing that is more efficient.
This began as Samuel Holland's GSoC project and was gradually
reworked/redesigned/rebased into this present commit, which is a
combination of his initial contribution and my subsequent rewriting and
redesigning.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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