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Tue, 20 Oct 2026 10:58:21 -0700 (PDT) Received: from localhost ([2a03:2880:2ff:6::]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3ad82f0c0b1sm133581a91.0.2026.10.20.10.58.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Oct 2026 10:58:21 -0700 (PDT) Date: Tue, 20 Oct 2026 10:58:13 -0700 From: Stanislav Fomichev To: Jakub Sitnicki Cc: Willem Ferguson , netdev@vger.kernel.org, davem@davemloft.net, edumazet@kernel.org, kuba@kernel.org, pabeni@redhat.com, ncardwell@google.com, bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com, linux-doc@vger.kernel.org, corbet@lwn.net, linux-kselftest@vger.kernel.org, shuah@kernel.org, linux-kernel@vger.kernel.org, kernel-team@cloudflare.com Subject: Re: [RFC PATCH net-next 0/4] tcp: carry a BPF-chosen identifier in TSval low bits Message-ID: References: <20261013103906.2660384-1-wferguson@cloudflare.com> <87a4oaf3mv.fsf@cloudflare.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <87a4oaf3mv.fsf@cloudflare.com> On 10/19, Jakub Sitnicki wrote: > Hey Stan, > > On Thu, Oct 15, 2026 at 02:45 PM -07, Stanislav Fomichev wrote: > > On 10/13, Willem Ferguson wrote: > > [...] > > >> Questions for reviewers: > >> > >> 1. Is encoding an identifier in the low bits of TSval acceptable in > >> principle, given the trade-offs above? > >> 2. If so, what feedback do you have on the implementation? > > > > Don't see any feedback yet, so from the top of my head: looks like you > > control two sides of the communication, so why not a custom (bpf) tcp option? > > Would you need that on every packet and it makes it expensive? > > > > Or any other field you can abuse maybe? IPv6 Flow label? > > Nah, we don't control the client unfortunately. > > Client here is any device that connects to our edge PoP. I see, so you rely on the fact that it gets mirrored back.. Btw, looks like there is already some similar tsoffset/ts_off infra? Have you considered plugging into that?