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! greg k-h
