From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f51.google.com (mail-pj1-f51.google.com [209.85.216.51]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 66AE83E4C8A for ; Mon, 18 May 2026 08:24:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.51 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779092655; cv=none; b=LoEvXwS5dq3r+wxi4xFW03U5zKtj/1ezHcGlefh2NDAng51ROMSMdq/sf0V2lqCU2TjGFZRQvoRNy8s4Zuclayh7p8tJkyMTIAYaEUW+bK+sYLJtQYYcFtQaeb3wNBg/wZfwLPn3NDq7i2RlZyeVKjmGrDF6iHPOYDoS2NChlpY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779092655; c=relaxed/simple; bh=DOfWH6hLKc3o9vRvYL5MSuCO1dG989HvIXld9/XiNFU=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=epQBlkp12j0LClbJ6ocFE8zBoszylYxI8NRRNwF8FDCEpzyqSZqNofgudbwUeUYCmri9sr+p8oynkWCc8PX4KjCi5NAoX/Z7yB95NYxzFr3K5yNKoRhXfqL5B4tY5YlcKsRznhejbdy65DRqX1sWGujhzIaM4q+vMryj9raC6wk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=mO0o0eTP; arc=none smtp.client-ip=209.85.216.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="mO0o0eTP" Received: by mail-pj1-f51.google.com with SMTP id 98e67ed59e1d1-365cae89bf5so689475a91.3 for ; Mon, 18 May 2026 01:24:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1779092654; x=1779697454; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=A4/cZz+D5VB55BisYY3cQwNyjxNuoDjRYz6rglyNSPk=; b=mO0o0eTPa3N8fHbdHmiWgjWP3+npe4MPM60zDiziD7kqb1Iw0JK2DnZwzQ41UW2tSY I8G6Lvhcp2ACn0kHXI117LybXaOUHzlJtJz58Wfltd8OIE2r3pH8SLng9GAZ7gA2gf1W auRyO8HsEcqKJkGrGvBXOzWYs0ojDJQd4q3HdmwrWcJN3ovcgGgBh7v99CPwGYbs8vMo uflE+EVN5RAY5C90op/ZcQx5f2VbA7N42PD4XagUzWf9pSvtdfCiaQ9hyT/cs0XzcT5C 1LzRqowhikY4FH5EUfc9s2iIDbOVygGU5mhji47vslZvH+chXhkvLAdb3V0xYD9bbSMZ Eh9w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1779092654; x=1779697454; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=A4/cZz+D5VB55BisYY3cQwNyjxNuoDjRYz6rglyNSPk=; b=csNpdjVKApX9E+JBDiSG0eyw1x7j2z60guQevQGMRj6JDh+8D0yWyExzfqsNU2B2Ub ZGvfFvLXJ0lMr7SMKtNhPoDGRy2HWx9i/EsUL1YZ1UQh+EUqwsDuDMVDCmmfj4aS/F+h UuyuVM+hrxYhiXIqy2azjyZG7oo8rLJrCCa3prr8t04qN5BA0itBWm+1YqXBqZ3gS45m ubG3THTLUdCcRzDAsU6i7sejeRM+sL3eSw0q/CcXIUJ43AGxXDvaARgAp0WXfwfbz9cM Li1DIIwGHaNjffh7It/sEpJyhC9zQLq0HQtZbvdXv/3DjbHej4LBTk0opX1BRmkel4lz Z7Yg== X-Forwarded-Encrypted: i=1; AFNElJ+Mn03xholAZdGvcARXMopylK4Y8HpxmNsCogDETsHs5EYP9U9SdJFmxxGPaiEPTG/ujLs=@vger.kernel.org X-Gm-Message-State: AOJu0YzB4j+VfeCZ6grzKXN4UI1v1CoqoH7efItDkd1u2z8oIl3upYw2 ZwFaxqH0mxyg/i0z0A36t3+Y457zroRalX3siXlTW8m4xBL1pAWWo6V/ X-Gm-Gg: Acq92OHkJbPwkSFbWUYWGlcQ9lKFtv7rl5meLvH4D1Xt00zP+T/Y7Fl0SicR+5NuZ+D 43yQUY2cT6yGafnFT8gQ6/bOe1TbFXK8ZdaC3CvUq7rcGkr+SLaZcwdrh0ozUdUmXQQaJUl32X8 f00sclRWON7Nvm9IKUXgA9TQGKBqUf1PPb8VyUbIacYAyjdvtV4AloiLKbcKO1v96nMHBDSI5+3 MVQuOkOo/k3dbLuEoea2avF5Q9FTLqU3L6NLCM0exbLh5OhCFpgpFIW+cuGjOX9liDHfcMUN4/1 8xfAhgvT+KSz1ILsG4e7lzVR6xGc+omskPe6p0rjF+xHFa8P1BTHg82LbkluMGldWTtj1A7BPdQ g2jPkxTWtxlOj8YLk61wBB9C+VnHWLfbr41nc0C5uN6y3AN0GswXX2Qt7V2VmniWpuV0HUpoDt+ xYaUE6WV32GBQxav5nLrQyEniFwwoR7GHhWEdPIDBaW834CqJq8HAYpBDmv0NjKRqZdvHYJxiNx bi2u2blRb1WG+eDfzwq0SJmcDO2hw== X-Received: by 2002:a17:90b:3505:b0:365:3154:7b1 with SMTP id 98e67ed59e1d1-36951dd55famr13420003a91.26.1779092653628; Mon, 18 May 2026 01:24:13 -0700 (PDT) Received: from KERNELXING-MB0.tencent.com ([43.132.141.25]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-369517ed182sm10382060a91.15.2026.05.18.01.24.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 May 2026 01:24:12 -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, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, memxor@gmail.com, song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org, john.fastabend@gmail.com, sdf@fomichev.me Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, Jason Xing Subject: [PATCH net-next 1/6] bpf: Add bpf_ktime_get_real_ns() kfunc Date: Mon, 18 May 2026 16:23:39 +0800 Message-Id: <20260518082344.96647-2-kerneljasonxing@gmail.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20260518082344.96647-1-kerneljasonxing@gmail.com> References: <20260518082344.96647-1-kerneljasonxing@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Jason Xing Currently BPF programs can obtain timestamps via bpf_ktime_get_ns(), which returns CLOCK_MONOTONIC time. However, the skb->tstamp field populated by the network stack uses ktime_get_real() which is in the CLOCK_REALTIME domain. In the series, kernel reports the software/hardware timestamps through sockopt and then userspace bpf application gets them and calculate the delta only through an unified time unit. However, prior to this, when a BPF program tries to measure RX packet delay by comparing skb->tstamp with bpf_ktime_get_ns(), the result is incorrect because the two clocks have different epochs. Introduce a new BPF kfunc bpf_ktime_get_real_ns() that returns the current CLOCK_REALTIME time. This allows BPF programs to perform accurate delay calculations without clock domain mismatch issue. Signed-off-by: Jason Xing --- kernel/bpf/helpers.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 2bb60200c266..863645d096ef 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2317,6 +2317,11 @@ void bpf_rb_root_free(const struct btf_field *field, void *rb_root, __bpf_kfunc_start_defs(); +__bpf_kfunc u64 bpf_ktime_get_real_ns(void) +{ + return ktime_get_real_fast_ns(); +} + /** * bpf_obj_new() - allocate an object described by program BTF * @local_type_id__k: type ID in program BTF @@ -4859,6 +4864,7 @@ BTF_ID_FLAGS(func, bpf_task_work_schedule_resume, KF_IMPLICIT_ARGS) BTF_ID_FLAGS(func, bpf_dynptr_from_file) BTF_ID_FLAGS(func, bpf_dynptr_file_discard) BTF_ID_FLAGS(func, bpf_timer_cancel_async) +BTF_ID_FLAGS(func, bpf_ktime_get_real_ns) BTF_KFUNCS_END(common_btf_ids) static const struct btf_kfunc_id_set common_kfunc_set = { -- 2.43.7