On 8/24/22 11:29 AM, Xin Long wrote:
On Wed, Aug 17, 2022 at 4:11 PM Adel Abouchaev <adel.abushaev@xxxxxxxxx> wrote:
QUIC requires end to end encryption of the data. The application usually
prepares the data in clear text, encrypts and calls send() which implies
multiple copies of the data before the packets hit the networking stack.
Similar to kTLS, QUIC kernel offload of cryptography reduces the memory
pressure by reducing the number of copies.
The scope of kernel support is limited to the symmetric cryptography,
leaving the handshake to the user space library. For QUIC in particular,
the application packets that require symmetric cryptography are the 1RTT
packets with short headers. Kernel will encrypt the application packets
on transmission and decrypt on receive. This series implements Tx only,
because in QUIC server applications Tx outweighs Rx by orders of
magnitude.
Supporting the combination of QUIC and GSO requires the application to
correctly place the data and the kernel to correctly slice it. The
encryption process appends an arbitrary number of bytes (tag) to the end
of the message to authenticate it. The GSO value should include this
overhead, the offload would then subtract the tag size to parse the
input on Tx before chunking and encrypting it.
With the kernel cryptography, the buffer copy operation is conjoined
with the encryption operation. The memory bandwidth is reduced by 5-8%.
When devices supporting QUIC encryption in hardware come to the market,
we will be able to free further 7% of CPU utilization which is used
today for crypto operations.
Adel Abouchaev (6):
Documentation on QUIC kernel Tx crypto.
Define QUIC specific constants, control and data plane structures
Add UDP ULP operations, initialization and handling prototype
functions.
Implement QUIC offload functions
Add flow counters and Tx processing error counter
Add self tests for ULP operations, flow setup and crypto tests
Documentation/networking/index.rst | 1 +
Documentation/networking/quic.rst | 185 ++++
include/net/inet_sock.h | 2 +
include/net/netns/mib.h | 3 +
include/net/quic.h | 63 ++
include/net/snmp.h | 6 +
include/net/udp.h | 33 +
include/uapi/linux/quic.h | 60 +
include/uapi/linux/snmp.h | 9 +
include/uapi/linux/udp.h | 4 +
net/Kconfig | 1 +
net/Makefile | 1 +
net/ipv4/Makefile | 3 +-
net/ipv4/udp.c | 15 +
net/ipv4/udp_ulp.c | 192 ++++
net/quic/Kconfig | 16 +
net/quic/Makefile | 8 +
net/quic/quic_main.c | 1417 ++++++++++++++++++++++++
net/quic/quic_proc.c | 45 +
tools/testing/selftests/net/.gitignore | 4 +-
tools/testing/selftests/net/Makefile | 3 +-
tools/testing/selftests/net/quic.c | 1153 +++++++++++++++++++
tools/testing/selftests/net/quic.sh | 46 +
23 files changed, 3267 insertions(+), 3 deletions(-)
create mode 100644 Documentation/networking/quic.rst
create mode 100644 include/net/quic.h
create mode 100644 include/uapi/linux/quic.h
create mode 100644 net/ipv4/udp_ulp.c
create mode 100644 net/quic/Kconfig
create mode 100644 net/quic/Makefile
create mode 100644 net/quic/quic_main.c
create mode 100644 net/quic/quic_proc.c
create mode 100644 tools/testing/selftests/net/quic.c
create mode 100755 tools/testing/selftests/net/quic.sh
base-commit: fd78d07c7c35de260eb89f1be4a1e7487b8092ad
--
2.30.2
Hi, Adel,
I don't see how the key update(rfc9001#section-6) is handled on the TX
path, which is not using TLS Key update, and "Key Phase" indicates
which key will be used after rekeying. Also, I think it is almost
impossible to handle the peer rekeying on the RX path either based on
your current model in the future.
The update is not present in these patches, but it is an important part
of the QUIC functionality. As this patch is only storing a single key,
you are correct that this approach does not handle the key rotation. To
implement re-keying on Tx and on Rx a rolling secret will need to be
stored in kernel. In that case, the subsequent 1RTT (Application space)
keys will be refreshed by the kernel. After all, when the hardware is
mature enough to support QUIC encryption and decryption - the secret
will need to be kept in the hardware to react on time on Rx, especially.
Tx path could solicit the re-key at any point or by the exhaustion of
the counter of GCM (packet number in this case). The RFC expects the
implementation to retain 2 keys, at least, while keeping 3 (old, current
and next) is not prohibited either. Keeping more is not necessary.
The patch seems to get the crypto_ctx by doing a connection hash table
lookup in the sendmsg(), which is not good from the performance side.
One QUIC connection can go over multiple UDP sockets, but I don't
think one socket can be used by multiple QUIC connections. So why not
save the ctx in the socket instead?
A single socket could have multiple connections originated from it,
having different destinations, if the socket is not connected. An
optimization could be made for connected sockets to cache the context
and save time on a lookup. The measurement of kernel operations timing
did not reveal a significant amount of time spent in this lookup due to
a relatively small number of connections per socket in general. A shared
table across multiple sockets might experience a different performance
grading.
The patch is to reduce the copying operations between user space and
the kernel. I might miss something in your user space code, but the
msg to send is *already packed* into the Stream Frame in user space,
what's the difference if you encrypt it in userspace and then
sendmsg(udp_sk) with zero-copy to the kernel.
It is possible to do it this way. Zero-copy works best with packet sizes
starting at 32K and larger. Anything less than that would consume the
improvements of zero-copy by zero-copy pre/post operations and needs to
align memory. The other possible obstacle would be that eventual support
of QUIC encryption and decryption in hardware would integrate well with
this current approach.
Didn't really understand the "GSO" you mentioned, as I don't see any
code about kernel GSO, I guess it's just "Fragment size", right?
BTW, it‘s not common to use "//" for the kernel annotation.
Once the payload arrives into the kernel, the GSO on the interface would
instruct L3/L4 stack on fragmentation. In this case, the plaintext QUIC
packets should be aligned on the GSO marks less the tag size that would
be added by encryption. For GSO size 1000, the QUIC packets in the batch
for transmission should all be 984 bytes long, except maybe the last
one. Once the tag is attached, the new size of 1000 will correctly split
the QUIC packets further down the stack for transmission in individual
IP/UDP packets. The code is also saving processing time by sending all
packets at once to UDP in a single call, when GSO is enabled.
I'm not sure if it's worth adding a ULP layer over UDP for this QUIC
TX only. Honestly, I'm more supporting doing a full QUIC stack in the
kernel independently with socket APIs to use it:
https://github.com/lxin/tls_hs.
Thanks.
