Well, it'd be nice not to loop forever, but my question remains, is this due to a server bug (the DS not knowing about new stateid from MDS)? -dros On Oct 10, 2013, at 10:14 AM, Weston Andros Adamson <dros@xxxxxxxxxx> wrote: > So is this a server bug? It seems like the client is behaving correctly... > > -dros > > On Oct 10, 2013, at 5:56 AM, "Mkrtchyan, Tigran" <tigran.mkrtchyan@xxxxxxx> wrote: > >> >> >> Today we was 'luck' to have such situation at day time. >> Here is what happens: >> >> The client sends an OPEN and gets an open state id. >> This is followed by LAYOUTGET ... and READ to DS. >> At some point, server returns back BAD_STATEID. >> This triggers client to issue a new OPEN and use >> new open stateid with READ request to DS. As new >> stateid is not known to DS, it keeps returning >> BAD_STATEID and becomes an infinite loop. >> >> Regards, >> Tigran. >> >> >> >> ----- Original Message ----- >>> From: "Tigran Mkrtchyan" <tigran.mkrtchyan@xxxxxxx> >>> To: linux-nfs@xxxxxxxxxxxxxxx >>> Cc: "Andy Adamson" <william.adamson@xxxxxxxxxx>, "Steve Dickson" <steved@xxxxxxxxxx> >>> Sent: Wednesday, October 9, 2013 10:48:32 PM >>> Subject: DoS with NFSv4.1 client >>> >>> >>> Hi, >>> >>> last night we got a DoS attack with one of the NFS clients. >>> The farm node, which was accessing data with pNFS, >>> went mad and have tried to kill dCache NFS server. As usually >>> this have happened over night and we was not able to >>> get a network traffic or bump the debug level. >>> >>> The symptoms are: >>> >>> client starts to bombard the MDS with OPEN requests. As we see >>> state created on the server side, the requests was processed by >>> server. Nevertheless, for some reason, client did not like it. Here >>> is the result of mountstats: >>> >>> OPEN: >>> 17087065 ops (99%) 1 retrans (0%) 0 major timeouts >>> avg bytes sent per op: 356 avg bytes received per op: 455 >>> backlog wait: 0.014707 RTT: 4.535704 total execute time: 4.574094 >>> (milliseconds) >>> CLOSE: >>> 290 ops (0%) 0 retrans (0%) 0 major timeouts >>> avg bytes sent per op: 247 avg bytes received per op: 173 >>> backlog wait: 308.827586 RTT: 1748.479310 total execute time: 2057.365517 >>> (milliseconds) >>> >>> >>> As you can see there is a quite a big difference between number of open and >>> close requests. >>> The same picture we can see on the server side as well: >>> >>> NFSServerV41 Stats: average±stderr(ns) min(ns) >>> max(ns) Sampes >>> DESTROY_SESSION 26056±4511.89 13000 >>> 97000 17 >>> OPEN 1197297± 0.00 816000 >>> 31924558000 54398533 >>> RESTOREFH 0± 0.00 0 >>> 25018778000 54398533 >>> SEQUENCE 1000± 0.00 1000 >>> 26066722000 55601046 >>> LOOKUP 4607959± 0.00 375000 >>> 26977455000 32118 >>> GETDEVICEINFO 13158±100.88 4000 >>> 655000 11378 >>> CLOSE 16236211± 0.00 5000 >>> 21021819000 20420 >>> LAYOUTGET 271736361± 0.00 10003000 >>> 68414723000 21095 >>> >>> The last column is the number of requests. >>> >>> This is with RHEL6.4 as the client. By looking at the code, >>> I can see a loop at nfs4proc.c#nfs4_do_open() which can be >>> the cause of the problem. Nevertheless, I can't >>> fine any reason why this look turned into an 'infinite' one. >>> >>> At the and our server ran out of memory and we have returned >>> NFSERR_SERVERFAULT to the client. This triggered client to >>> reestablish the session and all open state ids was >>> invalidated and cleaned up. >>> >>> I am still trying to reproduce this behavior (on client >>> and server) and any hint is welcome. >>> >>> Tigran. >>> -- >>> 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 >>> >> -- >> 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 > > -- > 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 -- 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
