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Thu, 28 Nov 2024 10:38:04 -0800 (PST) Received: from localhost ([2601:647:6881:9060:c1c1:c76b:dac2:9d68]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-2ee2aff1f28sm1803743a91.7.2024.11.28.10.38.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 Nov 2024 10:38:04 -0800 (PST) Date: Thu, 28 Nov 2024 10:38:03 -0800 From: Cong Wang To: John Fastabend Cc: Zijian Zhang , netdev@vger.kernel.org, bpf@vger.kernel.org, Cong Wang , Daniel Borkmann Subject: Re: [External] [Patch bpf 2/2] selftests/bpf: Add a BPF selftest for bpf_skb_change_tail() Message-ID: References: <20241107034141.250815-1-xiyou.wangcong@gmail.com> <20241107034141.250815-2-xiyou.wangcong@gmail.com> <67a0fb14-f791-4499-8751-01bbbd1cafcb@bytedance.com> <6746cb81870d7_f422208e@john.notmuch> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6746cb81870d7_f422208e@john.notmuch> On Tue, Nov 26, 2024 at 11:34:25PM -0800, John Fastabend wrote: > Zijian Zhang wrote: > > > > LGTM! > > > > I think it will be better if the test could also cover the case you > > indicated in the first patch, where skb_transport_offset is a negative > > value. > > > > Thanks, > > Zijian > > > > Hi Cong, > > I agree it would be great to see the skb_transport_offset is > negative pattern. Could we add it? Hmm? It is already negative for sockmap, as I already mentioned in patch 1/1: "skb_transport_offset() and skb_transport_offset() can be negative when they are called after we pull the transport header, for example, when we use eBPF sockmap (aka at the point of ->sk_data_ready())." My test case uses skb verdict, which is one of the sockmap hooks. Or I guess you mean positive? In that case, we would need hook different locations, like TC. I can certainly add it, but once again, it would make backporting this patchset even harder. Thanks!