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Sat, 19 Sep 2026 07:39:17 -0700 (PDT) Received: from KERNELXING-MC1.tencent.com ([43.132.141.21]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2ddc179ed79sm10711715ad.43.2026.09.19.07.39.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Sep 2026 07:39:15 -0700 (PDT) From: Jason Xing To: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, willemb@google.com, kuniyu@google.com Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, Jason Xing Subject: [PATCH RFC net-next 8/9] net: generate the start time for every skb in the rx path Date: Sat, 19 Sep 2026 22:37:31 +0800 Message-Id: <20260919143732.11772-9-kerneljasonxing@gmail.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20260919143732.11772-1-kerneljasonxing@gmail.com> References: <20260919143732.11772-1-kerneljasonxing@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Extend net_timestamp_check(), so that it also records an in-kernel start time in the skb's shared hwtstamps. This gives received skbs the same start_time semantics that TCP already gives to transmitted skbs, letting a BPF program compute how long an skb has spent in the stack. In the receiving path, net_timestamp_check() will 1) reuse the hardware timestamp because the hardware time always takes precedence, or 2) uses skb->tstamp if any, or 3) generate a current timestamp. Signed-off-by: Jason Xing --- net/core/dev.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/net/core/dev.c b/net/core/dev.c index 4479fc87b789..8a9d2205a884 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -2501,11 +2501,17 @@ static inline void net_timestamp_set(struct sk_buff *skb) skb->tstamp = ktime_get_real(); } -#define net_timestamp_check(COND, SKB) \ - if (static_branch_unlikely(&netstamp_needed_key)) { \ - if ((COND) && !(SKB)->tstamp) \ - (SKB)->tstamp = ktime_get_real(); \ - } \ +#define net_timestamp_check(COND, SKB) \ + if (static_branch_unlikely(&netstamp_needed_key) || \ + static_branch_unlikely(&bpfts_v2_needed_key)) { \ + if (static_branch_unlikely(&netstamp_needed_key) && \ + (COND) && !(SKB)->tstamp) \ + (SKB)->tstamp = ktime_get_real(); \ + if (static_branch_unlikely(&bpfts_v2_needed_key) && \ + !skb_hwtstamps(SKB)->hwtstamp) \ + skb_hwtstamps(SKB)->start_time = \ + (SKB)->tstamp ?: ktime_get_real(); \ + } \ bool is_skb_forwardable(const struct net_device *dev, const struct sk_buff *skb) { -- 2.43.7