Re: [s6-dns] is there a particular reason skadns_packet would return NULL errno ENETUNREACH?
Neither of those conditions actually apply - my network is up and my resolver is responding (albeit slowly - it takes about a second). I get the expected response on the first batch of queries I fire off, but then the second batch gets ENETUNREACH. This happens every time I run my program (albeit on special snowflake illumos; I have not tried on other OSes). If you think s6-dns is behaving incorrectly, please pastebin a strace (or local equivalent) of skadnsd somewhere, so we can check what it is doing. -- Laurent
Re: [s6-dns] is there a particular reason skadns_packet would return NULL errno ENETUNREACH?
Neither of those conditions actually apply - my network is up and my resolver is responding (albeit slowly - it takes about a second). I get the expected response on the first batch of queries I fire off, but then the second batch gets ENETUNREACH. This happens every time I run my program (albeit on special snowflake illumos; I have not tried on other OSes). On 6 October 2022 11:23:20 UTC, Laurent Bercot wrote: > >> i source spelunked and the story is that, if the error is coming from >> s6dns_engine_prepare, dt->protostate exceeds or equals 4. I chased that >> struct member around a few times and I couldn't figure out what it means to >> s6dns. > > dt->protostate is used for two things: > > - in UDP mode, to track how many times the query has been sent to the >whole list of caches and all of them have failed to answer within a >given timeout. The timeout increases for each round. > > - in TCP mode, to track how many bytes of the query have been written >and how many bytes of the answer have been received (a congested >network may result in short writes or reads). > > The error you got indeed happens when you're in UDP mode (the starting >default for every query), dt->protostate has reached 4 and >s6dns_engine_prepare() returns 0 ENETUNREACH, which >s6dns_engine_timeout() stores into dt->status and skadnsd then sends >back to your client. > > What it means is that your query was sent in succession to every >cache listed in dt->servers (most likely, the list of "nameserver" >entries in your /etc/resolv.conf, unless you overrode it with the >DNSCACHEIP environment variable), and every one of them failed to >answer within 1 second, then within 3 seconds, then within 11 >seconds, then within 45 seconds. That sounds like either your >nameserver list is bad, or your own network is down; and s6-dns reports >this as ENETUNREACH. > >-- > Laurent > -- Ellenor Bjornsdottir (she) sysadmin umbrellix.net
Re: [s6-dns] is there a particular reason skadns_packet would return NULL errno ENETUNREACH?
i source spelunked and the story is that, if the error is coming from s6dns_engine_prepare, dt->protostate exceeds or equals 4. I chased that struct member around a few times and I couldn't figure out what it means to s6dns. dt->protostate is used for two things: - in UDP mode, to track how many times the query has been sent to the whole list of caches and all of them have failed to answer within a given timeout. The timeout increases for each round. - in TCP mode, to track how many bytes of the query have been written and how many bytes of the answer have been received (a congested network may result in short writes or reads). The error you got indeed happens when you're in UDP mode (the starting default for every query), dt->protostate has reached 4 and s6dns_engine_prepare() returns 0 ENETUNREACH, which s6dns_engine_timeout() stores into dt->status and skadnsd then sends back to your client. What it means is that your query was sent in succession to every cache listed in dt->servers (most likely, the list of "nameserver" entries in your /etc/resolv.conf, unless you overrode it with the DNSCACHEIP environment variable), and every one of them failed to answer within 1 second, then within 3 seconds, then within 11 seconds, then within 45 seconds. That sounds like either your nameserver list is bad, or your own network is down; and s6-dns reports this as ENETUNREACH. -- Laurent
