From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 26A161A3165 for ; Fri, 8 May 2026 21:46:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778276795; cv=none; b=WWPnOCjN5wGb/7Wnn97RYODRav4BDnYTc3cEu3si7PwWVn/W71OBMshVy83IGCwIoHlnzgUEP3X9wtnhno8/qxaQfuD0O103kbRoMbhCNUpEsEx/plab1G6C2LgWXLLbvHXYZEb/7r9S08JXL0YxuIMtkpGOcQzOB1MTtC7TIE0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778276795; c=relaxed/simple; bh=xlvaJKipbHmqqS3BiYENQFy3ug5B0xP9nkZFBmddAag=; h=From:Subject:To:Cc:In-Reply-To:References:Content-Type:Date: Message-Id; b=FL2P71rQp/0R+FOS6Bak8WyMRL4kSGU9sxe/jN5KDOQhg2KNsL5EiSmMoLJHshy2jW1QBz5IcJXiXRn7ByQtIUMNJNI+/21kfuMP7Vwte/mrcQ92DJlE8C4h1fsfR+tX3b4EX08c4NiW8kaEeqXSsPIPWVmktpJHgTgv6EySEeA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=TQWS/Csi; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="TQWS/Csi" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A0ABBC2BCB0; Fri, 8 May 2026 21:46:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778276794; bh=xlvaJKipbHmqqS3BiYENQFy3ug5B0xP9nkZFBmddAag=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date:From; b=TQWS/CsiUsjMSDeU1MxJ0vkW3faHtlhRPOHf+pfrhzdCyYDffZHWyDBDYaTn3w8M4 yObgVc59ALM97LKbEptiN94/bXe5MYgTyG/UHaq8b5CqA09rCb+TqtYoRzTCz0EgxN FhCriGoVyOef59o5rl8bOXKHdWM8GviZce+rJTJZtetCM/77Z9vP5/3zATGUohU2hf QrpPT+ilE++E2YnWVHQvH1iKYW7NlN8ljnqgbZe84XtDfg+9KzZGbbwvWNwEcpaa5u QqaYlRulSVrkGpdsuqkA1LwyNbkCZMQIYh5q2SyPu3jlLMG0jBkJ/ATXHOPmZdWmUG B5NGo6WvM+OXQ== From: sashiko-bot@kernel.org Subject: Re: [PATCH v1 bpf-next 7/8] bpf: tcp: Add SOCK_OPS rcvlowat hook. Reply-To: sashiko@lists.linux.dev To: "Kuniyuki Iwashima" Cc: bpf@vger.kernel.org In-Reply-To: <20260508073355.3916746-8-kuniyu@google.com> References: <20260508073355.3916746-8-kuniyu@google.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Fri, 08 May 2026 21:46:34 +0000 Message-Id: <20260508214634.A0ABBC2BCB0@smtp.kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Thank you for your contribution! Sashiko AI review found 1 potential issue(= s) to consider: - [High] The new BPF_SOCK_OPS_RCVLOWAT_CB hook is incorrectly rejected by i= s_locked_tcp_sock_ops(), preventing the BPF program from modifying callback= flags. -- commit ef96e613bd920ae4e567781955c5e3d4f11f7f57 Author: Kuniyuki Iwashima bpf: tcp: Add SOCK_OPS rcvlowat hook. This commit introduces a new BPF_SOCK_OPS_RCVLOWAT_CB hook that is invoked when TCP enqueues an skb or completes recvmsg(). The hook allows BPF programs to dynamically adjust sk->sk_rcvlowat to suppress unnecessary wakeups. [ ... ] > diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c > index 7e26503fd96d4..a70a8f5830258 100644 > --- a/net/ipv4/tcp_input.c > +++ b/net/ipv4/tcp_input.c > @@ -204,6 +204,12 @@ static void bpf_skops_established(struct sock *sk, i= nt bpf_op, > /* sk with TCP_REPAIR_ON does not have skb in tcp_finish_connect */ > bpf_skops_common_locked(sk, bpf_op, skb, skb ? tcp_hdrlen(skb) : 0); > } > + > +void bpf_skops_rcvlowat(struct sock *sk, struct sk_buff *skb) > +{ > + /* skb is NULL when called from __tcp_cleanup_rbuf(). */ > + bpf_skops_common_locked(sk, BPF_SOCK_OPS_RCVLOWAT_CB, skb, 0); > +} Does this regression prevent the BPF program from dynamically disabling the hook once the RPC boundaries are known? Since BPF_SOCK_OPS_RCVLOWAT_CB is greater than BPF_SOCK_OPS_WRITE_HDR_OPT_C= B, is_locked_tcp_sock_ops() will return false for this hook: net/core/filter.c:is_locked_tcp_sock_ops() { return bpf_sock->op <=3D BPF_SOCK_OPS_WRITE_HDR_OPT_CB; } While this intentionally prevents bpf_setsockopt() from being used unnecessarily, bpf_sock_ops_cb_flags_set() also relies on this check: net/core/filter.c:bpf_sock_ops_cb_flags_set() { if (!is_locked_tcp_sock_ops(bpf_sock)) return -EOPNOTSUPP; ... } This means any attempt to clear the callback flag using bpf_sock_ops_cb_flags_set() within the hook will fail with -EOPNOTSUPP. This could force the callback to run on every single SKB enqueue for the lifetime of the connection. Should is_locked_tcp_sock_ops() or bpf_sock_ops_cb_flags_set() be updated to allow disabling the callback flag for this new hook? --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20260508073355.3916= 746-1-kuniyu@google.com?part=3D7