On Wed, Aug 17, 2022 at 4:11 PM Adel Abouchaev [off-list ref] 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 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?

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.

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.

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.