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Thu, 25 Jun 2026 10:53:51 -0700 (PDT) From: Jakub Sitnicki To: "Alexei Starovoitov" Cc: "Jiayuan Chen" , "Amery Hung" , "Kuniyuki Iwashima" , "bpf" , "Alexei Starovoitov" , "Daniel Borkmann" , "Jakub Kicinski" , "John Fastabend" , "Network Development" , "kernel-team" Subject: Re: [PATCH bpf-next v2] bpf, unix: Guard sk_msg-dependent code behind CONFIG_NET_SOCK_MSG In-Reply-To: (Alexei Starovoitov's message of "Wed, 24 Jun 2026 13:57:07 -0700") References: <20260623-bpf-sk_msg-split-unix-v2-1-ca7a626a94a5@cloudflare.com> <87v7b9ysep.fsf@cloudflare.com> <87mrwlyqg4.fsf@cloudflare.com> <878q85yoy5.fsf@cloudflare.com> User-Agent: mu4e 1.14.1; emacs 30.2 Date: Thu, 25 Jun 2026 19:53:50 +0200 Message-ID: <87cxxey09d.fsf@cloudflare.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Wed, Jun 24, 2026 at 01:57 PM -07, Alexei Starovoitov wrote: > On Tue Jun 23, 2026 at 6:32 PM PDT, Jiayuan Chen wrote: >> >> Hi Alexei and Jakub, >> >> skmsg is actually still pretty useful for gateways. >> I started with bpf by integrating skmsg into nginx as a module and envoy >> has something similar. >> The usual setup is cgroup/sk for L4 bypass (reject SYN), and skmsg for >> L7, redirecting >> between local apps by looking at the payload. So there are real users. > > ... > >> Agree, just like we remove skmsg from KTLS which is rarely used. > > ... > >> Hope not have skmsg disabled by default. > > I wasn't suggesting to delete the whole skmsg, > but to disable combinations that are causing issues. > Like what was done for skmsg and ktls. > I'd allow plain tcp and udp sockets only. > Allowing unix sockets was fishy. I think we should reject it too. For unix & vsock we know Bytedance built a proxy using it. We've been showcasing it as one of sockmap use cases [1]. That said, I don't know if it's still being used or not. If we don't want to go through the config-knob-then-deprecate process, then I guess the only option is to kill it and see if anyone complains. [1] Slide 117, https://github.com/sockmap-project/sockmap-project/blob/810d259af6e7a5793922af3991c9dc7ff502fe19/talks/2024-09%20-%20NDC%20TechTown%20-%20Splicing%20Sockets%20with%20SOCKMAP.pdf