On Sat, Oct 12, 2019 at 06:38:46PM -0400, Michael S. Tsirkin wrote: > On Fri, Oct 11, 2019 at 04:34:57PM +0200, Stefano Garzarella wrote: > > On Fri, Oct 11, 2019 at 10:19:13AM -0400, Michael S. Tsirkin wrote: > > > On Fri, Oct 11, 2019 at 03:07:56PM +0200, Stefano Garzarella wrote: > > > > We are implementing a test suite for the VSOCK sockets and we discovered > > > > that vmci_transport never allowed half-closed socket on the host side. > > > > > > > > As Jorgen explained [1] this is due to the implementation of VMCI. > > > > > > > > Since we want to have the same behaviour across all transports, this > > > > series adds a section in the "Implementation notes" to exaplain this > > > > behaviour, and changes the vhost_transport to behave the same way. > > > > > > > > [1] https://patchwork.ozlabs.org/cover/847998/#1831400 > > > > > > Half closed sockets are very useful, and lots of > > > applications use tricks to swap a vsock for a tcp socket, > > > which might as a result break. > > > > Got it! > > > > > > > > If VMCI really cares it can implement an ioctl to > > > allow applications to detect that half closed sockets aren't supported. > > > > > > It does not look like VMCI wants to bother (users do not read > > > kernel implementation notes) so it does not really care. > > > So why do we want to cripple other transports intentionally? > > > > The main reason is that we are developing the test suite and we noticed > > the miss match. Since we want to make sure that applications behave in > > the same way on different transports, we thought we would solve it that > > way. > > > > But what you are saying (also in the reply of the patches) is actually > > quite right. Not being publicized, applications do not expect this behavior, > > so please discard this series. > > > > My problem during the tests, was trying to figure out if half-closed > > sockets were supported or not, so as you say adding an IOCTL or maybe > > better a getsockopt() could solve the problem. > > > > What do you think? > > > > Thanks, > > Stefano > > Sure, why not. The aim is for applications using AF_VSOCK sockets to run on any transport. When the semantics differ between transports it creates a compatibility problem. That said, I do think keeping the standard sockets behavior is reasonable. If applications have problems on VMCI a sockopt may be necessary :(. Stefan
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