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<a href="https://gitlab.com/juaristi">Ander Juaristi</a> created an issue <a href="https://gitlab.com/gnutls/gnutls/-/issues/1113">#1113</a>:
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<p dir="auto">The Linux kernel has been supporting KTLS for some time now.</p>
<p dir="auto">This is basically a kernel-side TLS record encryption offloading. The kernel receives plaintext data on the socket descriptor via <code>write()</code> and it builds a valid TLS record around it. The same happens when data is read with <code>read()</code>: a TLS record is expected, then decrypted and the plaintext it contains returned.</p>
<p dir="auto">After a successful TLS handshake (this happens normally on userland), you need to obtain the TLS secrets. You do this with <code>gnutls_record_get_state()</code>.</p>
<p dir="auto">Then you enable KTLS on a connected TCP socket with <code>setsockopt</code>:</p>
<pre class="code highlight js-syntax-highlight plaintext" lang="plaintext" v-pre="true"><code><span id="LC1" class="line" lang="plaintext">setsockopt(sockfd, SOL_TCP, TCP_ULP, "tls", sizeof("tls");</span></code></pre>
<p dir="auto">And finally you copy the TLS master secret to the kernel so that it can build the read and write keys.</p>
<p dir="auto">I think GnuTLS should transparently use KTLS if it's available, when either <code>gnutls_record_recv()</code> or <code>gnutls_record_write()</code> are called.</p>
<p dir="auto">If it's not available, fall back to userland encryption using Nettle, just like now.</p>
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