On 18.06.2018 22:25, Ben Pfaff wrote: > On Mon, Jun 18, 2018 at 09:31:43AM -0700, Han Zhou wrote: >> On Mon, Jun 18, 2018 at 8:34 AM, Ilya Maximets <[email protected]> >> wrote: >>> >>> On 18.06.2018 18:07, Ben Pfaff wrote: >>>> On Mon, Jun 18, 2018 at 05:18:49PM +0300, Ilya Maximets wrote: >>>>>> On Wed, May 23, 2018 at 09:28:59PM -0700, Ben Pfaff wrote: >>>>>>> On Wed, May 23, 2018 at 06:06:44PM -0700, Han Zhou wrote: >>>>>>>> On Wed, May 23, 2018 at 5:14 PM, Ben Pfaff <blp at ovn.org> wrote: >>>>>>>>> >>>>>>>>> Until now, rconn_get_version() has only reported the OpenFlow >> version in >>>>>>>>> use when the rconn is actually connected. This makes sense, but >> it has a >>>>>>>>> harsh consequence. Consider code like this: >>>>>>>>> >>>>>>>>> if (rconn_is_connected(rconn) && rconn_get_version(rconn) >= >> 0) { >>>>>>>>> for (int i = 0; i < 2; i++) { >>>>>>>>> struct ofpbuf *b = ofputil_encode_echo_request( >>>>>>>>> rconn_get_version(rconn)); >>>>>>>>> rconn_send(rconn, b, NULL); >>>>>>>>> } >>>>>>>>> } >>>>>>>>> >>>>>>>>> Maybe not the smartest code in the world, and probably no one >> would write >>>>>>>>> this exact code in any case, but it doesn't look too risky or >> crazy. >>>>>>>>> >>>>>>>>> But it is. The second trip through the loop can assert-fail inside >>>>>>>>> ofputil_encode_echo_request() because rconn_get_version(rconn) >> returns -1 >>>>>>>>> instead of a valid OpenFlow version. That happens if the first >> call to >>>>>>>>> rconn_send() encounters an error while sending the message and >> therefore >>>>>>>>> destroys the underlying vconn and disconnects so that >> rconn_get_version() >>>>>>>>> doesn't have a vconn to query for its version. >>>>>>>>> >>>>>>>>> In a case like this where all the code to send the messages is >> close by, >>>>>>>> we >>>>>>>>> could just check rconn_get_version() in each loop iteration. We >> could >>>>>>>> even >>>>>>>>> go through the tree and convince ourselves that individual bits of >> code >>>>>>>> are >>>>>>>>> safe, or be conservative and check rconn_get_version() >= 0 in the >> iffy >>>>>>>>> cases. But this seems to me like an ongoing source of risk and a >> way to >>>>>>>>> get things wrong in corner cases. >>>>>>>>> >>>>>>>>> This commit takes a different approach. It introduces a new >> invariant: if >>>>>>>>> an rconn has ever been connected, then it returns a valid OpenFlow >> version >>>>>>>>> from rconn_get_version(). In addition, if an rconn is currently >>>>>>>> connected, >>>>>>>>> then the OpenFlow version it returns is the correct one (that may >> be >>>>>>>>> obvious, but there were corner cases before where it returned -1 >> even >>>>>>>>> though rconn_is_connected() returned true). >>>>>>>>> >>>>>>>>> With this commit, the code above would work OK. If the first call >> to >>>>>>>>> rconn_send() encounters an error sending the message, then >>>>>>>>> rconn_get_version() in the second iteration will return the same >> value as >>>>>>>>> in the first iteration. The message passed to rconn_send() will >> end up >>>>>>>>> being discarded, but that's much better than either an assertion >> failure >>>>>>>> or >>>>>>>>> having to carefully analyze a lot of our code to deal with one >> unusual >>>>>>>>> corner case. >>>>>>>>> >>>>>>>>> Reported-by: Han Zhou <zhouhan at gmail.com> >>>>>>>>> Signed-off-by: Ben Pfaff <blp at ovn.org> >>>>>>>>> --- >>>>>>>>> lib/learning-switch.c | 2 +- >>>>>>>>> lib/rconn.c | 41 >> ++++++++++++++++------------------------- >>>>>>>>> lib/vconn.c | 1 + >>>>>>>>> 3 files changed, 18 insertions(+), 26 deletions(-) >>>>>>>>> >>>>>>>> Acked-by: Han Zhou <hzhou8 at ebay.com> >>>>>>> >>>>>>> Thanks. I applied this to master. I'll backport it to older >> versions >>>>>>> if no one notices trouble soon. >>>>>> >>>>>> I backported as far as branch-2.5. >>>>> >>>>> Sorry for being late, but I just tried to use branch-2.9 on my test >> environment >>>>> and found that this patch produces a lot of "connected" logs that are >> a bit annoying: >>>>> >>>>> 2018-06-18T12:55:06.610Z|03051|rconn|INFO|br-int<->unix#2873: connected >>>>> 2018-06-18T12:55:08.609Z|03052|rconn|INFO|br-int<->unix#2874: connected >>>>> 2018-06-18T12:55:08.610Z|03053|rconn|INFO|br-int<->unix#2875: connected >>>>> 2018-06-18T12:55:10.608Z|03054|rconn|INFO|br-int<->unix#2876: connected >>>>> 2018-06-18T12:55:10.609Z|03055|rconn|INFO|br-int<->unix#2877: connected >>>>> 2018-06-18T12:55:12.609Z|03056|rconn|INFO|br-int<->unix#2878: connected >>>>> 2018-06-18T12:55:12.609Z|03057|rconn|INFO|br-int<->unix#2879: connected >>>>> 2018-06-18T12:55:14.612Z|03058|rconn|INFO|br-int<->unix#2880: connected >>>>> 2018-06-18T12:55:14.613Z|03059|rconn|INFO|br-int<->unix#2881: connected >>>>> 2018-06-18T12:55:16.613Z|03060|rconn|INFO|br-int<->unix#2882: connected >>>>> 2018-06-18T12:55:16.614Z|03061|rconn|INFO|br-int<->unix#2883: connected >>>>> 2018-06-18T12:55:18.609Z|03062|rconn|INFO|br-int<->unix#2884: connected >>>>> 2018-06-18T12:55:18.610Z|03063|rconn|INFO|br-int<->unix#2885: connected >>>>> 2018-06-18T12:55:20.610Z|03064|rconn|INFO|br-int<->unix#2886: connected >>>>> 2018-06-18T12:55:20.611Z|03065|rconn|INFO|br-int<->unix#2887: connected >>>>> >>>>> On my system it's about 2 log messages on each 2 seconds. It has only >>>>> ovsdb-server, ovs-vswitchd and ovsdb-client monitor running. >>>>> >>>>> Could you please check? >>>> >>>> Are you sure that it's this patch that makes a difference? It doesn't >>>> change anything in the logging. >>> >>> I don't know much about this part of OVS. That is wat I have with >> reverted patch >>> and debug enabled: >>> >>> 2018-06-18T15:31:09.162Z|00423|rconn|DBG|br-int<->unix#150: entering >> ACTIVE >>> 2018-06-18T15:31:09.163Z|00424|rconn|DBG|br-int<->unix#150: connection >> closed by peer >>> 2018-06-18T15:31:09.163Z|00425|rconn|DBG|br-int<->unix#150: entering >> DISCONNECTED >>> 2018-06-18T15:31:11.162Z|00426|rconn|DBG|br-int<->unix#151: entering >> ACTIVE >>> 2018-06-18T15:31:11.162Z|00427|rconn|DBG|br-int<->unix#151: connection >> closed by peer >>> 2018-06-18T15:31:11.162Z|00428|rconn|DBG|br-int<->unix#151: entering >> DISCONNECTED >>> 2018-06-18T15:31:11.162Z|00429|rconn|DBG|br-int<->unix#152: entering >> ACTIVE >>> 2018-06-18T15:31:11.163Z|00430|rconn|DBG|br-int<->unix#152: connection >> closed by peer >>> 2018-06-18T15:31:11.163Z|00431|rconn|DBG|br-int<->unix#152: entering >> DISCONNECTED >>> >>> Without revert (just branch-2.9 with patch applied): >>> >>> 2018-06-18T15:26:32.366Z|00658|rconn|DBG|br-int<->unix#198: entering >> ACTIVE >>> 2018-06-18T15:26:32.366Z|00659|rconn|DBG|br-int<->unix#198: connection >> closed by peer >>> 2018-06-18T15:26:32.366Z|00660|rconn|DBG|br-int<->unix#198: entering >> DISCONNECTED >>> 2018-06-18T15:26:34.365Z|00661|rconn|DBG|br-int<->unix#199: entering >> CONNECTING >>> 2018-06-18T15:26:34.365Z|00662|rconn|INFO|br-int<->unix#199: connected >>> 2018-06-18T15:26:34.365Z|00663|rconn|DBG|br-int<->unix#199: entering >> ACTIVE >>> 2018-06-18T15:26:34.365Z|00664|rconn|DBG|br-int<->unix#199: connection >> closed by peer >>> 2018-06-18T15:26:34.365Z|00665|rconn|DBG|br-int<->unix#199: entering >> DISCONNECTED >>> 2018-06-18T15:26:34.365Z|00666|rconn|DBG|br-int<->unix#200: entering >> CONNECTING >>> 2018-06-18T15:26:34.365Z|00667|rconn|INFO|br-int<->unix#200: connected >>> 2018-06-18T15:26:34.365Z|00668|rconn|DBG|br-int<->unix#200: entering >> ACTIVE >>> 2018-06-18T15:26:34.366Z|00669|rconn|DBG|br-int<->unix#200: connection >> closed by peer >>> 2018-06-18T15:26:34.366Z|00670|rconn|DBG|br-int<->unix#200: entering >> DISCONNECTED >>> 2018-06-18T15:26:36.365Z|00671|rconn|DBG|br-int<->unix#201: entering >> CONNECTING >>> 2018-06-18T15:26:36.365Z|00672|rconn|INFO|br-int<->unix#201: connected >>> 2018-06-18T15:26:36.365Z|00673|rconn|DBG|br-int<->unix#201: entering >> ACTIVE >>> 2018-06-18T15:26:36.365Z|00674|rconn|DBG|br-int<->unix#201: connection >> closed by peer >>> 2018-06-18T15:26:36.365Z|00675|rconn|DBG|br-int<->unix#201: entering >> DISCONNECTED >>> 2018-06-18T15:26:36.365Z|00676|rconn|DBG|br-int<->unix#202: entering >> CONNECTING >>> 2018-06-18T15:26:36.366Z|00677|rconn|INFO|br-int<->unix#202: connected >>> >>> Looks like that patch just changed a workflow a bit introducing >> "CONNECTING" >>> state in case where was just direct transition to "ACTIVE". >>> >> Hi Ilya, >> >> From the debug log it looks like the connection is flapping, even without >> the patch. The patch just revealed the problem by an info level log. > > Probably these are just connections from "ovs-ofctl" or similar. We try > to suppress logging for them because it isn't too useful.
Yes, you're right. There was some monitoring tool running that uses ovs-ofctl. I just didn't recognize it at the first glance. Best regards, Ilya Maximets. _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
