From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-177.mta1.migadu.com (out-177.mta1.migadu.com [95.215.58.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A355A1EBA1E for ; Fri, 13 Dec 2024 23:55:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.177 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734134148; cv=none; b=eU9NkGdxxO1kcW1gzdo8VLOn1Q23QLUcR8KnY4c4qabsqa9BGd4pigqEvOc8sCTZBr3x1YdFMJutiTue+ssC+iPF6/JK9EuZIjunyCdPgqziTMhw3vI8a0jQU953Rp6MDcQ7PzhRaCMAFePE7ypkd+yGuwBk5TS5J4B4BQTYq48= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734134148; c=relaxed/simple; bh=XqG2JijYRpxL2/j3DukylYuY6FOBReLBkzB2NTjm1OM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=IM4I9N/WkbU9xGG/w2y4h+h8m4xaYK2rEoca7l+YdYujFzF2zzRcbXMT3CH7oc84SvWspnVgckXvPVPKJU/O6hK3t0njcWNxcett4Uhro/oS27+ggIJGjHWS0PpwNScuC8akyV4ju49iTw2Vlk+UuJSQOxnpgDABmEzG0183m9U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=c/Op9mKR; arc=none smtp.client-ip=95.215.58.177 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="c/Op9mKR" Message-ID: <55384b37-005d-48e9-894b-8bbe4f7a6b24@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1734134143; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=7Wx0ubisvuXuYNQ0Vjor9tnJWsgXG5tKeIY4c7YfW0I=; b=c/Op9mKR5nKAnru1LNVAA0LkoQNk8blbd8PtEgJ22dGt1HlBaR/S774tkeh8sCkpXkgqXZ XV4bAC5TNVMC5VoaX1toJx9ndFTAC/GxGD0Df0zapA/MCwGtYixfB7FZu09C2n043gvMQ6 LhVzK6dYN06cIUVrOLkcrzyxvXXOwzU= Date: Fri, 13 Dec 2024 15:55:33 -0800 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH net-next v4 10/11] net-timestamp: export the tskey for TCP bpf extension To: Jason Xing Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, dsahern@kernel.org, willemdebruijn.kernel@gmail.com, willemb@google.com, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, bpf@vger.kernel.org, netdev@vger.kernel.org, Jason Xing References: <20241207173803.90744-1-kerneljasonxing@gmail.com> <20241207173803.90744-11-kerneljasonxing@gmail.com> <9f5081bb-ed66-4171-acef-786ae02cf69c@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Martin KaFai Lau Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 12/13/24 7:44 AM, Jason Xing wrote: >>> @@ -5569,7 +5569,10 @@ static void __skb_tstamp_tx_bpf(struct sock *sk, struct sk_buff *skb, >>> return; >>> } >>> >>> - bpf_skops_tx_timestamping(sk, skb, op, 2, args); >>> + if (sk_is_tcp(sk)) >>> + args[2] = skb_shinfo(skb)->tskey; >> Instead of only passing one info "skb_shinfo(skb)->tskey" of a skb, pass the >> whole skb ptr to the bpf prog. Take a look at bpf_skops_init_skb. Lets start >> with end_offset = 0 for now so that the bpf prog won't use it to read the >> skb->data. It can be revisited later. >> >> bpf_skops_init_skb(&sock_ops, skb, 0); >> >> The bpf prog can use bpf_cast_to_kern_ctx() and bpf_core_cast() to get to the >> skb_shinfo(skb). Take a look at the md_skb example in type_cast.c. > Sorry, I didn't give it much thought on getting to the shinfo. That's > why I quickly gave up using bpf_skops_init_skb() after I noticed the > seq of skb is always zero 🙁 > > I will test it tomorrow. Thanks. > >> Then it needs to add a bpf_sock->op check to the existing >> bpf_sock_ops_{load,store}_hdr_opt() helpers to ensure these helpers can only be >> used by the BPF_SOCK_OPS_PARSE_HDR_OPT_CB, BPF_SOCK_OPS_HDR_OPT_LEN_CB, and >> BPF_SOCK_OPS_WRITE_HDR_OPT_CB callback. > Forgive me. I cannot see how the bpf_sock_ops_load_hdr_opt helper has > something to do with the current thread? Could you enlighten me? Sure. This is the same discussion as in patch 2, so may be worth to highlight something that I guess may be missing: a bpf prog does not need to use a helper does not mean: a bpf prog is not allowed to call a helper because it is not safe. The sockops prog running at the new timestamp hook does not need to call bpf_setsockopt() but it does not mean the bpf prog is not allowed to call bpf_setsockopt() without holding the sk_lock which is then broken. The sockops timestamp prog does not need to use the bpf_sock_ops_{load,store}_hdr_opt but it does not mean the bpf prog is not allowed to call bpf_sock_ops_{load,store}_hdr_opt to change the skb which is then also broken. Now, skops->skb is not NULL only when the sockops prog is allowed to read/write the skb. With bpf_skops_init_skb(), skops->skb will not be NULL in the new timestamp callback hook. bpf_sock_ops_{load,store}_hdr_opt() will be able to use the skops->skb and it will be broken. > >> btw, how is the ack_skb used for the SCM_TSTAMP_ACK by the user space now? > To be honest, I hardly use the ack_skb[1] under this circumstance... I > think if someone offers a suggestion to use it, then we can support > it? Thanks for the pointer. Yep, supporting it later is fine. I am curious because the ack_skb is used in the user space time stamping now but not in your patch. I was asking to ensure that we should be able to support it in the future if there is a need. We should be able to reuse the skops->syn_skb to support that in the future. > > [1] > commit e7ed11ee945438b737e2ae2370e35591e16ec371 > Author: Yousuk Seung > Date: Wed Jan 20 12:41:55 2021 -0800 > > tcp: add TTL to SCM_TIMESTAMPING_OPT_STATS > > This patch adds TCP_NLA_TTL to SCM_TIMESTAMPING_OPT_STATS that exports > the time-to-live or hop limit of the latest incoming packet with > SCM_TSTAMP_ACK. The value exported may not be from the packet that acks > the sequence when incoming packets are aggregated. Exporting the > time-to-live or hop limit value of incoming packets helps to estimate > the hop count of the path of the flow that may change over time.