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From: Eric Dumazet <eric.dumazet@gmail.com>
To: Paolo Abeni <pabeni@redhat.com>,
	Eric Dumazet <eric.dumazet@gmail.com>,
	Mat Martineau <mathew.j.martineau@linux.intel.com>,
	netdev@vger.kernel.org, mptcp@lists.01.org
Subject: Re: [MPTCP] Re: [PATCH net-next 09/11] tcp: Check for filled TCP option space before SACK
Date: Mon, 16 Dec 2019 08:55:34 -0800	[thread overview]
Message-ID: <d5b3a6ed-fb57-e74d-ef63-ebc4ce49e4b7@gmail.com> (raw)
In-Reply-To: <b9833b748f61c043a2827daee060d4ad4171996e.camel@redhat.com>



On 12/16/19 4:52 AM, Paolo Abeni wrote:

> Thank you for the feedback!
> 
> Unfortunatelly, the above commit is not enough when MPTCP is enabled,
> as, without this patch, we can reach the following code:
> 
> 		const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
> 		opts->num_sack_blocks =
> 			min_t(unsigned int, eff_sacks,
> 			      (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
> 			      TCPOLEN_SACK_PERBLOCK);
> 
> with 'size == MAX_TCP_OPTION_SPACE' and num_sack_blocks will be
> miscalculated. So we need 'fix' but only for MPTCP/when MPTCP is
> enabled. Still ok for a -net commit?
> 

Does it means MPTCP flows can not use SACK at all ? That would be very bad.

What is the size of MPTCP options ?


  reply	other threads:[~2019-12-16 16:55 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-13 23:00 [PATCH net-next 00/11] Multipath TCP: Prerequisites Mat Martineau
2019-12-13 23:00 ` [PATCH net-next 01/11] net: Make sock protocol value checks more specific Mat Martineau
2019-12-13 23:00 ` [PATCH net-next 02/11] sock: Make sk_protocol a 16-bit value Mat Martineau
2019-12-13 23:16   ` Eric Dumazet
2019-12-14  0:06     ` Mat Martineau
2019-12-13 23:00 ` [PATCH net-next 03/11] tcp: Define IPPROTO_MPTCP Mat Martineau
2019-12-13 23:00 ` [PATCH net-next 04/11] tcp: Add MPTCP option number Mat Martineau
2019-12-13 23:00 ` [PATCH net-next 05/11] tcp, ulp: Add clone operation to tcp_ulp_ops Mat Martineau
2019-12-13 23:00 ` [PATCH net-next 06/11] mptcp: Add MPTCP to skb extensions Mat Martineau
2019-12-13 23:00 ` [PATCH net-next 07/11] tcp: Prevent coalesce/collapse when skb has MPTCP extensions Mat Martineau
2019-12-13 23:00 ` [PATCH net-next 08/11] tcp: Export TCP functions and ops struct Mat Martineau
2019-12-13 23:00 ` [PATCH net-next 09/11] tcp: Check for filled TCP option space before SACK Mat Martineau
2019-12-13 23:22   ` Eric Dumazet
2019-12-14  0:28     ` Mat Martineau
2019-12-16 12:52     ` [MPTCP] " Paolo Abeni
2019-12-16 16:55       ` Eric Dumazet [this message]
2019-12-16 17:28         ` Paolo Abeni
2019-12-13 23:00 ` [PATCH net-next 10/11] tcp: clean ext on tx recycle Mat Martineau
2019-12-13 23:00 ` [PATCH net-next 11/11] skb: add helpers to allocate ext independently from sk_buff Mat Martineau

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