On Thu, Dec 10, 2015 at 05:59:33PM +0530, Soumya Koduri wrote: > > > On 12/10/2015 04:02 PM, Omar Walid Llorente wrote: > > > >Hi, Jeff, Bruce, finally I got some time to get the capture of the nfs > >packets (you can find them in attached file nfs-problem-nks.pcap.zip). > >Sorry for being so late. > > > >What I did was the following: > > > >1st) Create the RO file: > >cdc@l056:~/prueba-git$ rm -f kk.txt 444.txt; echo "prueba" > 444.txt; > >chmod 444 444.txt; > > > >2nd) Init the capture: > >root@l056:~# tcpdump -i eth2 -w /tmp/nfs.pcap -s 512 port 2049 > >tcpdump: listening on eth2, link-type EN10MB (Ethernet), capture size > >512 bytes > > > GlusterFS protocol is added to wireshark from version 1.8.0 [1]. It > may be helpful to see what GlusterFS operations are being processed > as part of NFS WRITE call (which has failed in this case). > > Could you please try taking the packet trace on the machine where > NFS server is running (without filtering out based on the port > number). > > Also I tried out the same test on Fedora22 machine, but haven't run > into any issue. What are the fuse mount options you have used to > mount gluster volume? Oh, I think this is a simple problem (but maybe hard to fix). The capture shows NFSv3 traffic like: CREATE -> OK SETATTR (mode set to 0400) -> OK WRITE -> NFS3ERR_ACCES That write would succeed locally (because the mode doesn't matter to a local application that already holds the file open). It would fail over NFSv3, which doesn't know about the open--except that there's a hack for this case: NFSv3 servers allow IO operations to ignore the mode, if the operation comes from the owner of the file. NFSv3 clients are then careful to perform necessary access checks on open to ensure that this owner-override rule doesn't grant too many permissions. That allows NFSv3 applications to see behavior that's mostly like a local filesystem, without opening much of a security hole (since the owner could always chmod anyway). So, knfsd is making this special exception--but gluster (which I believe it's exporting in this case, via fuse?)--probably doesn't.... I'm not sure what you can do about that. --b. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
