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 4B7582253E4 for ; Mon, 17 Mar 2025 09:41:51 +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=1742204511; cv=none; b=ky8nw1nlfSoLJjdjCPT0oobiDyY31ti2mEAugZ0BLdD2aM3wRksvV67smTi36rIWj1wjIVTc6mG1pBbwSEYjmSPZrRMVjy+RmZfy+NRTBOM6W22pgUVqkEQxQlAVGURkkk6dGEjeeadvCyBjxs9BuecBlqcXMQDoKUBszNFt5EU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742204511; c=relaxed/simple; bh=Tu8f9vB/3B5gn7OzTLzNIf9q+7X6ha1bePaFQE3qOQo=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=pZg9ulUdIlnqMYgeN0eZh3qHFsIJktNDnAMEvogsuXUkVeM451fKeaUwgvsMaSaQFQDI6wpTXYvityTWeiOZ+HIFMUeMdiMhnZf9Uuot8Y42BhSpl55trPV83jf7gaSLOZCQfYHnIFkTrPshqUsut6WyzI4SpaiDdLB5mLoWCa4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Rl2cx/P9; 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="Rl2cx/P9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E2F4CC4CEE3; Mon, 17 Mar 2025 09:41:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1742204511; bh=Tu8f9vB/3B5gn7OzTLzNIf9q+7X6ha1bePaFQE3qOQo=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=Rl2cx/P9A9KztvG8FZZoACBcmRJF5knI1UnpoH44A6y/qVZB8JSehik0WO72N/yCI fkItQrA4lGHZ4HvfwK8a+Q+hb7KKN1odimT0RGJE73Qd5Lip+GEMPEB2lm0QhUPZdr r61YX7Z+8MxM0dyy0UoQ4NqD5mTFOgB+cMuxP27v4QRxqSnsd85vvvUQPeNFULbtO1 pIUSDDEmEWjWkY3icyT904mE9pbypSgkAd8l4kENVCoz6HvRFhapZJFfl9KpeyM3IV XgcpMKdoxXIsBQxYv2c9wVkjBBtr+vT2oZ2vAMfiQuLOGpwXEIvIY7+jkPu5Bl9A8I UD1smOglhAZtA== Message-ID: Subject: Re: [PATCH mptcp-next v3 1/2] mptcp: add bpf_iter_task for mptcp_sock From: Geliang Tang To: mptcp@lists.linux.dev Cc: Geliang Tang , Mat Martineau Date: Mon, 17 Mar 2025 17:41:46 +0800 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.52.3-0ubuntu1 Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Mon, 2025-03-10 at 11:30 +0800, Geliang Tang wrote: > From: Geliang Tang > > To make sure the mptcp_subflow bpf_iter is running in the > MPTCP context. This patch adds a simplified version of tracking > for it: > > 1. Add a 'struct task_struct *bpf_iter_task' field to struct > mptcp_sock. > > 2. Do a WRITE_ONCE(msk->bpf_iter_task, current) before calling > a MPTCP BPF hook, and WRITE_ONCE(msk->bpf_iter_task, NULL) after > the hook returns. > > 3. In bpf_iter_mptcp_subflow_new(), check > > "READ_ONCE(msk->bpf_scheduler_task) == current" > > to confirm the correct task, return -EINVAL if it doesn't match. > > Also creates helpers for setting, clearing and checking that value. > > Suggested-by: Mat Martineau > Signed-off-by: Geliang Tang > --- >  net/mptcp/bpf.c      |  2 ++ >  net/mptcp/protocol.c |  1 + >  net/mptcp/protocol.h | 20 ++++++++++++++++++++ >  net/mptcp/sched.c    | 15 +++++++++++---- >  4 files changed, 34 insertions(+), 4 deletions(-) > > diff --git a/net/mptcp/bpf.c b/net/mptcp/bpf.c > index c0da9ac077e4..0a78604742c7 100644 > --- a/net/mptcp/bpf.c > +++ b/net/mptcp/bpf.c > @@ -261,6 +261,8 @@ bpf_iter_mptcp_subflow_new(struct > bpf_iter_mptcp_subflow *it, >   return -EINVAL; >   >   msk = mptcp_sk(sk); > + if (!mptcp_check_bpf_iter_task(msk)) > + return -EINVAL; >   >   msk_owned_by_me(msk); >   > diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c > index 01157ad2e2dc..d98e48ce8cd8 100644 > --- a/net/mptcp/protocol.c > +++ b/net/mptcp/protocol.c > @@ -2729,6 +2729,7 @@ static void __mptcp_init_sock(struct sock *sk) >   inet_csk(sk)->icsk_sync_mss = mptcp_sync_mss; >   WRITE_ONCE(msk->csum_enabled, > mptcp_is_checksum_enabled(sock_net(sk))); >   WRITE_ONCE(msk->allow_infinite_fallback, true); > + mptcp_clear_bpf_iter_task(msk); >   msk->recovery = false; >   msk->subflow_id = 1; >   msk->last_data_sent = tcp_jiffies32; > diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h > index 3492b256ecba..1c6958d64291 100644 > --- a/net/mptcp/protocol.h > +++ b/net/mptcp/protocol.h > @@ -334,6 +334,7 @@ struct mptcp_sock { >   */ >   struct mptcp_pm_data pm; >   struct mptcp_sched_ops *sched; > + struct task_struct *bpf_iter_task; >   struct { >   u32 space; /* bytes copied in last measurement > window */ >   u32 copied; /* bytes copied in this measurement > window */ > @@ -1291,4 +1292,23 @@ mptcp_token_join_cookie_init_state(struct > mptcp_subflow_request_sock *subflow_re >  static inline void mptcp_join_cookie_init(void) {} >  #endif >   > +static inline void mptcp_set_bpf_iter_task(struct mptcp_sock *msk) > +{ > + WRITE_ONCE(msk->bpf_iter_task, current); > +} > + > +static inline void mptcp_clear_bpf_iter_task(struct mptcp_sock *msk) > +{ > + WRITE_ONCE(msk->bpf_iter_task, NULL); > +} > + > +static inline bool mptcp_check_bpf_iter_task(struct mptcp_sock *msk) > +{ > + struct task_struct *task = READ_ONCE(msk->bpf_iter_task); > + > + if (task && task == current) > + return true; > + return false; > +} This v3 has a bug. When I was testing MPTCP BPF selftests in a loop, I found that the test would break in some cases. After debugging, I found that "task" and "current" were not equal: [ 520.209749][T11984] MPTCP: bpf_iter_mptcp_subflow_new msk=00000000fc8f7370 in_interrupt=0 task=00000000ef28139f current=0000000024db2987 I will try to fix it, but haven't found a solution yet. Thanks, -Geliang > + >  #endif /* __MPTCP_PROTOCOL_H */ > diff --git a/net/mptcp/sched.c b/net/mptcp/sched.c > index f09f7eb1d63f..161398f8960c 100644 > --- a/net/mptcp/sched.c > +++ b/net/mptcp/sched.c > @@ -155,6 +155,7 @@ void mptcp_subflow_set_scheduled(struct > mptcp_subflow_context *subflow, >  int mptcp_sched_get_send(struct mptcp_sock *msk) >  { >   struct mptcp_subflow_context *subflow; > + int ret; >   >   msk_owned_by_me(msk); >   > @@ -176,12 +177,16 @@ int mptcp_sched_get_send(struct mptcp_sock > *msk) >   >   if (msk->sched == &mptcp_sched_default || !msk->sched) >   return mptcp_sched_default_get_send(msk); > - return msk->sched->get_send(msk); > + mptcp_set_bpf_iter_task(msk); > + ret = msk->sched->get_send(msk); > + mptcp_clear_bpf_iter_task(msk); > + return ret; >  } >   >  int mptcp_sched_get_retrans(struct mptcp_sock *msk) >  { >   struct mptcp_subflow_context *subflow; > + int ret; >   >   msk_owned_by_me(msk); >   > @@ -196,7 +201,9 @@ int mptcp_sched_get_retrans(struct mptcp_sock > *msk) >   >   if (msk->sched == &mptcp_sched_default || !msk->sched) >   return mptcp_sched_default_get_retrans(msk); > - if (msk->sched->get_retrans) > - return msk->sched->get_retrans(msk); > - return msk->sched->get_send(msk); > + mptcp_set_bpf_iter_task(msk); > + ret = msk->sched->get_retrans ? msk->sched->get_retrans(msk) > : > + msk->sched->get_send(msk); > + mptcp_clear_bpf_iter_task(msk); > + return ret; >  }