I recently updated a couple servers that were running OpenBSD 6.3 with bind 9.11.3 to OpenBSD 6.4 and bind 9.11.4pl2. Since then, I'm been getting a large number of "error sending response: would block" log messages:
Nov 15 11:03:58 lisa named[79587]: client @0x6f2f02bc440 10.128.30.77#65198 (p64-keyvalueservice.icloud.com): view internal: error sending response: would block Nov 15 11:07:42 lisa named[79587]: client @0x6f325b7a440 10.128.0.19#1851 (alt1.gmail-smtp-in.l.google.com): view internal: error sending response: would block I reviewed the article at https://kb.isc.org/docs/aa-00717 ; but it's not clear if this just a warning message, and it tries again and successfully responds to the client, or is it's a hard error and the client never gets a response? I wasn't getting any errors before the upgrade, and I don't think the load on these servers is anywhere near high enough to cause them to be overloaded. Any thoughts on what might be going on? New bug in bind? Change in OpenBSD? So far I haven't gotten a response on the bind mailing list. Thanks...
