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Diffstat (limited to 'Documentation/networking/tls.rst')
| -rw-r--r-- | Documentation/networking/tls.rst | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/Documentation/networking/tls.rst b/Documentation/networking/tls.rst index 8cb2cd4e2a80..658ed3a71e1b 100644 --- a/Documentation/networking/tls.rst +++ b/Documentation/networking/tls.rst @@ -214,6 +214,44 @@ of calling send directly after a handshake using gnutls. Since it doesn't implement a full record layer, control messages are not supported. +Optional optimizations +---------------------- + +There are certain condition-specific optimizations the TLS ULP can make, +if requested. Those optimizations are either not universally beneficial +or may impact correctness, hence they require an opt-in. +All options are set per-socket using setsockopt(), and their +state can be checked using getsockopt() and via socket diag (``ss``). + +TLS_TX_ZEROCOPY_RO +~~~~~~~~~~~~~~~~~~ + +For device offload only. Allow sendfile() data to be transmitted directly +to the NIC without making an in-kernel copy. This allows true zero-copy +behavior when device offload is enabled. + +The application must make sure that the data is not modified between being +submitted and transmission completing. In other words this is mostly +applicable if the data sent on a socket via sendfile() is read-only. + +Modifying the data may result in different versions of the data being used +for the original TCP transmission and TCP retransmissions. To the receiver +this will look like TLS records had been tampered with and will result +in record authentication failures. + +TLS_RX_EXPECT_NO_PAD +~~~~~~~~~~~~~~~~~~~~ + +TLS 1.3 only. Expect the sender to not pad records. This allows the data +to be decrypted directly into user space buffers with TLS 1.3. + +This optimization is safe to enable only if the remote end is trusted, +otherwise it is an attack vector to doubling the TLS processing cost. + +If the record decrypted turns out to had been padded or is not a data +record it will be decrypted again into a kernel buffer without zero copy. +Such events are counted in the ``TlsDecryptRetry`` statistic. + Statistics ========== @@ -239,3 +277,12 @@ TLS implementation exposes the following per-namespace statistics - ``TlsDeviceRxResync`` - number of RX resyncs sent to NICs handling cryptography + +- ``TlsDecryptRetry`` - + number of RX records which had to be re-decrypted due to + ``TLS_RX_EXPECT_NO_PAD`` mis-prediction. Note that this counter will + also increment for non-data records. + +- ``TlsRxNoPadViolation`` - + number of data RX records which had to be re-decrypted due to + ``TLS_RX_EXPECT_NO_PAD`` mis-prediction. |