> On Apr 14, 2017, at 1:52 PM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote: > > On Fri, Apr 14, 2017 at 12:10:03PM -0400, Chuck Lever wrote: >> >>> On Apr 14, 2017, at 11:56 AM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote: >>> >>> On Sun, Apr 09, 2017 at 01:06:41PM -0400, Chuck Lever wrote: >>>> Observed at Connectathon 2017. >>>> >>>> If a client has underestimated the size of a Write or Reply chunk, >>>> the Linux server writes as much payload data as it can, then it >>>> recognizes there was a problem and closes the connection without >>>> sending the transport header. >>> >>> Why would the client underestimate? Is this a client-side bug? >> >> It can be a bug, and the behavior in this case is that the >> client retransmits indefinitely and deadlocks the transport, >> because the client's upper layer never sees a reply. >> >> But as you know there are some NFS operations where the client >> cannot predict in advance how large the reply will be. In >> particular the upper bound size of an NFSACL GETACL reply or >> certain NFSv4 GETATTR attributes are not predictable. > > Oh, I'd forgotten about those cases. > >> These >> I might categorize as protocol bugs. >> >> A client can do its best by posting a very large reply buffer >> for such operations, but since these situations typically >> are in practice rare, but NFSv4 GETATTR can be a relatively >> common operation, clients post a few dozen KB for the reply >> buffer and call it a day. >> >> In these cases (if they should ever fail IRL), returning an >> error is polite and allows operation of other RPCs on that >> transport to continue. > > Got it, thanks. (I assume this is documented somewhere in the specs?) I've written about it in rfc5667bis-09. It's a short document, review comments welcome. -- Chuck Lever -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
