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Tue, 10 Nov 2026 08:55:04 -0800 (PST) Received: from [10.0.0.48] ([71.69.222.122]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-67c589a2354sm2255948d50.6.2026.11.10.08.55.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 10 Nov 2026 08:55:03 -0800 (PST) Message-ID: Date: Tue, 10 Nov 2026 11:55:03 -0500 X-Mailing-List: kernel-tls-handshake@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next v6 5/6] tls: send a KeyUpdate at the record limit and on request To: netdev-bot+sashiko@kernel.org Cc: john.fastabend@gmail.com, kuba@kernel.org, sd@queasysnail.net, davem@davemloft.net, edumazet@kernel.org, pabeni@redhat.com, horms@kernel.org, corbet@lwn.net, skhan@linuxfoundation.org, rdunlap@infradead.org, shuah@kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, hare@kernel.org, cel@kernel.org, kernel-tls-handshake@lists.linux.dev, alistair.francis@wdc.com, martin.belanger@dell.com References: <20261105-keyupdate-rfc-v6-5-99b695f9eb4f@gmail.com> <179424471332.994134.12793914111732564453@kernel.org> Content-Language: en-US From: Martin Belanger In-Reply-To: <179424471332.994134.12793914111732564453@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/9/26 12:18, netdev-bot+sashiko@kernel.org wrote: > Is 2^24 the right limit for AES-128-CCM? No. RFC 9147 section 4.5.3 and Appendix B.1 give 2^23 records for AES-128-CCM, for the same 2^-60 target as TLS 1.3. v7 will use a limit below 2^23 for CCM. > Should TLS_TX and TLS_TX_TRAFFIC_SECRET take tx_lock, as > TLS_TX_KEY_UPDATE and TLS_TX_MAX_PAYLOAD_LEN do? This is the lock drop listed under "Not changed" since v4. A TLS_TX setsockopt() during a sendmsg() in another thread is an application error. Mainline has the same window: the existing rekey takes only the socket lock, and the records of that sendmsg() can go out under two keys. Taking tx_lock in TLS_TX would make the setsockopt() wait behind a blocked sendmsg(), which changes mainline behavior. The design of this path is under discussion in the thread on 0/6, so I keep it unchanged until that is settled. > Can setsockopt(SOL_TLS, TLS_TX_KEY_UPDATE) block indefinitely on a > non-blocking socket? Yes. v7 will remove TLS_TX_KEY_UPDATE (see my reply on 0/6). The kernel will then send a KeyUpdate only from sendmsg(), with the caller's flags. > This isn't a bug, but two parts of this text don't seem to match the code. In v7, the text will say "before the next Application Data record". The TLS_TX_KEY_UPDATE text will go away with the option.