On Thursday, November 25, 2021 6:41 PM, Stefano Garzarella wrote:
> On Thu, Nov 25, 2021 at 09:27:40AM +0000, Wang, Wei W wrote:
> >On Thursday, November 25, 2021 3:16 PM, Wang, Wei W wrote:
> >> - /* Update CID in case it has changed after a transport reset event */
> >> - vsk->local_addr.svm_cid = dst.svm_cid;
> >> -
> >> if (space_available)
> >> sk->sk_write_space(sk);
> >>
> >
> >Not sure if anybody knows how this affects the transport reset.
>
> I believe the primary use case is when a guest is migrated.
>
> After the migration, the transport gets a reset event from the hypervisor and
> all connected sockets are closed. The ones in listen remain open though.
>
> Also the guest's CID may have changed after migration. So if an application has
> open listening sockets, bound to the old CID, this should ensure that the socket
> continues to be usable.
OK, thanks for sharing the background.
>
> The patch would then change this behavior.
>
> So maybe to avoid problems, we could update the CID only if it is different
> from VMADDR_CID_ANY:
>
> if (vsk->local_addr.svm_cid != VMADDR_CID_ANY)
> vsk->local_addr.svm_cid = dst.svm_cid;
>
>
> When this code was written, a guest only supported a single transport, so it
> could only have one CID assigned, so that wasn't a problem.
> For that reason I'll add this Fixes tag:
> Fixes: c0cfa2d8a788 ("vsock: add multi-transports support")
Sounds good to me.
Thanks,
Wei
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