On 25/05/2022 14:45, Greg KH wrote: > On Wed, May 25, 2022 at 02:36:10PM +0200, Matthieu Baerts wrote: >> On 25/05/2022 14:25, Greg KH wrote: >>> On Wed, May 25, 2022 at 12:32:04PM +0200, Matthieu Baerts wrote: >>>> Hi Greg, Mat, >>>> >>>> On 25/05/2022 09:51, Greg KH wrote: >>>>> On Tue, May 24, 2022 at 11:10:41AM -0700, Mat Martineau wrote: >>>>>> [ Upstream commit ae66fb2ba6c3dcaf8b9612b65aa949a1a4bed150 ] >>>>>> >>>>>> RFC 8684 section 3.7 describes several opportunities for a MPTCP >>>>>> connection to "fall back" to regular TCP early in the connection >>>>>> process, before it has been confirmed that MPTCP options can be >>>>>> successfully propagated on all SYN, SYN/ACK, and data packets. If a peer >>>>>> acknowledges the first received data packet with a regular TCP header >>>>>> (no MPTCP options), fallback is allowed. >>>>>> >>>>>> If the recipient of that first data packet finds a MPTCP DSS checksum >>>>>> error, this provides an opportunity to fail gracefully with a TCP >>>>>> fallback rather than resetting the connection (as might happen if a >>>>>> checksum failure were detected later). >>>>>> >>>>>> This commit modifies the checksum failure code to attempt fallback on >>>>>> the initial subflow of a MPTCP connection, only if it's a failure in the >>>>>> first data mapping. In cases where the peer initiates the connection, >>>>>> requests checksums, is the first to send data, and the peer is sending >>>>>> incorrect checksums (see >>>>>> https://github.com/multipath-tcp/mptcp_net-next/issues/275), this allows >>>>>> the connection to proceed as TCP rather than reset. >>>>>> >>>>>> Cc: <stable@xxxxxxxxxxxxxxx> # 5.17.x >>>>>> Cc: <stable@xxxxxxxxxxxxxxx> # 5.15.x >>>>>> Fixes: dd8bcd1768ff ("mptcp: validate the data checksum") >>>>>> Acked-by: Paolo Abeni <pabeni@xxxxxxxxxx> >>>>>> Signed-off-by: Mat Martineau <mathew.j.martineau@xxxxxxxxxxxxxxx> >>>>>> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> >>>>>> [mathew.j.martineau: backport: Resolved bitfield conflict in protocol.h] >>>>>> Signed-off-by: Mat Martineau <mathew.j.martineau@xxxxxxxxxxxxxxx> >>>>>> --- >>>>>> >>>>>> This patch is already in 5.17.10-rc1 and 5.15.42-rc1, but involves a >>>>>> context dependency on upstream commit 4cf86ae84c71 which I have >>>>>> requested to be dropped from the stable queues. >>>>>> >>>>>> I'm posting this backport without the protocol.h conflict to >>>>>> (hopefully?) make it easier for the stable maintainers to drop >>>>>> 4cf86ae84c71. >>>>>> >>>>>> For context see https://lore.kernel.org/stable/fa953ec-288f-7715-c6fb-47a222e85270@xxxxxxxxxxxxxxx/ >>>>> >>>>> THanks, will take this after this round of releases. >>>> >>>> It might already be too late but is it possible to have this patch >>>> ("mptcp: Do TCP fallback on early DSS checksum failure") and "mptcp: fix >>>> checksum byte order" in the same stable release? >>>> >>>> Note that "mptcp: fix checksum byte order" patch has been recently >>>> queued by Sasha at the same time as "mptcp: Do TCP fallback on early DSS >>>> checksum failure". >>>> >>>> A bit of context: "mptcp: fix checksum byte order" fixes an important >>>> encoding issue but it also breaks the interoperability with previous >>>> Linux versions not having this patch. >>>> >>>> The patch from Mat ("mptcp: Do TCP fallback on early DSS checksum >>>> failure") improves the situation when there is this interoperability >>>> issue with a previous Linux versions not implementing the RFC properly. >>>> The improvement is there to make the MPTCP connections falling back to >>>> TCP instead of resetting them: at least there is a connection. >>>> >>>> In other words, that would be really nice to have these two commits >>>> backported together. If it is easier, it looks best to me to delay the >>>> main fix ("mptcp: fix checksum byte order") than having the two patches >>>> in different stable versions. But I understand it was not clear and >>>> maybe too late to do these modifications. >>>> >>>> Anyway, thank you for your work maintaining these stable versions! :) >>> >>> I have already done a release with the first change in it, sorry, but >>> have queued this up now. Given that this is fixing a problem with that >>> commit, I'll go do a release right now for 5.17 and 5.15. >> >> I'm sorry for the troubles this is causing you but thank you for doing that! >> >> Please note that on the bright side, the DSS Checksum feature is >> disabled by default so hopefully, this interoperability issue should not >> affect too many people. It is hard to quantify but I guess there is no >> need to rush if you prefer to wait before doing this release. > > No worries, it was easy to do a new release, now done! Wow, our first MPTCP-only stable release! :-) Again thank you! Cheers, Matt -- Tessares | Belgium | Hybrid Access Solutions www.tessares.net
