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 1881032ABCA for ; Thu, 26 Mar 2026 16:42:49 +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=1774543370; cv=none; b=oMIkEdn8R1OpQ+bwEpizwLozMzSwpCWQUwcytefF8x3PV6ri8o8oFtbX3XntW3jJRo/oQkMr1n6FVrK60f6ySKXC3DiHg5Z2i7JMFwjYHutJ3kUYVkzlnYZ+m+je6FYczV4yVB2nCES/7vGHhostOhwUrElFfosX2MuOe6XfQzA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774543370; c=relaxed/simple; bh=SeEZekrLBy8o17HgV465Yez2LzpT6n8JCStYRvR7ZVU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=KaDnx7cErwda9bjOGYDByTsvhJRQOkKz0zAZNLZOhc7x1baT6vkpXcR71r9WNPoG6hZSqgPxACn5u1iUICZnoDzOKDrC/R/Ybs9mJ0T+KJImh1HLLiKzokaQSbejhjLTqsZEyJxbC9SvVcIEgKYFlvbC0TWFE57Z7jKAe7+Pgrc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lLU80fQz; 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="lLU80fQz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 791C6C116C6; Thu, 26 Mar 2026 16:42:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774543369; bh=SeEZekrLBy8o17HgV465Yez2LzpT6n8JCStYRvR7ZVU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=lLU80fQzYCZFaCu+exfsh77A37mGabzZCK2Suczum6Jl/OGKSdOJIqILkW+UMcQMw JzoqeL8KZlBauIJwmQUaeLTFrPeryVJEg0L1fYRyfCjHWUg2aAqTnJQ86N84k387hS RSr/oIqOft2zuavkvoD755uZOsIXXUECHtHpAVRDJsNXEEjw3hlRDfwd7BWav0dJm7 h8pQ4t9WEBSHNiVQr0pfBR9EFKsuz9LYd/ZHBaIPySGnFJHjrsu62CfmwBXv9L6oUU B+PIlmVpbmNRMhb9mGHNQ7Ru27jxjhl9QehvgJ3hOsysfsO1bvZrWNzyTqpChRcoZH Y2qeOMySL+1xg== Message-ID: Date: Thu, 26 Mar 2026 17:42:46 +0100 Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH mptcp-next] mptcp: preserve MSG_EOR semantics in sendmsg path Content-Language: fr To: Gang Yan , mptcp@lists.linux.dev Cc: pabeni@redhat.com, geliang@kernel.org, Gang Yan References: <20260309025431.125943-1-gang.yan@linux.dev> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Gang, Thank you for the new version. On 09/03/2026 03:54, Gang Yan wrote: > From: Gang Yan > > Extend MPTCP's sendmsg handling to recognize and honor the MSG_EOR flag, > which marks the end of a record for application-level message boundaries. > > Data fragments tagged with MSG_EOR are explicitly marked in the > mptcp_data_frag structure and skb context to prevent unintended > coalescing with subsequent data chunks. This ensures the intent of > applications using MSG_EOR is preserved across MPTCP subflows, > maintaining consistent message segmentation behavior. > > Signed-off-by: Gang Yan > --- > > Notes: > - This patch incorporates feedback and suggestions from Paolo Abeni > and Geliang Tang, including memory alignment optimizations for the > mptcp_data_frag struct (shrinking overhead to u8 and using bitfield > for eor to avoid size increase) and compile-time checks with BUILD_BUG_ON. Please mention why you shrank "overhead" to a u8 (not to increase the struct size), and why it is OK to do so (u16 not needed because ...) + explaining the BUILD_BUG_ON(). > - Packetdrill test cases validating this feature are available at: > https://github.com/multipath-tcp/packetdrill/pull/189/changes/d6ce92a4786704fe749bbd848ced0c047632282e Thank you, I just reviewed it. Do you mind checking the AI review there please: https://netdev-ai.bots.linux.dev/ai-review.html?id=22434689-7326-48c8-af75-273d99fbef55 I think it is valid, but better to double-check. > diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c > index 17e43aff4459..3e574c87301b 100644 > --- a/net/mptcp/protocol.c > +++ b/net/mptcp/protocol.c (...) > @@ -4621,6 +4638,9 @@ void __init mptcp_proto_init(void) > inet_register_protosw(&mptcp_protosw); > > BUILD_BUG_ON(sizeof(struct mptcp_skb_cb) > sizeof_field(struct sk_buff, cb)); > + /* Compile-time check: ensure 'overhead' (alignment + struct size) fits in u8 */ > + BUILD_BUG_ON(ALIGN(1, sizeof(long)) + sizeof(struct mptcp_data_frag) > U8_MAX); Sorry, I'm not sure what you are checking here. Do you mind explaining it please? Cheers, Matt -- Sponsored by the NGI0 Core fund.