net: use Go DNS resolver when nsswitch.conf permits #10485
Comments
|
Here is the default one on the solaris builder |
|
This is the default one for the netbsd/386 builder: |
|
FreeBSD 10: |
|
Ubuntu 14.04: |
|
Arch with Avahi. |
|
Ubuntu 14.04.02 |
|
On OpenBSD there's no nsswitch.conf file. Instead, host resolution database ordering is controlled by the "lookup" option in /etc/resolv.conf. E.g., "lookup bind file" (the default) means to check DNS, then fall back to /etc/hosts. There are also no "criterion" like in nsswitch.conf files, just a list of databases. See http://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man5/resolv.conf.5 |
|
|
|
Linux ncegcolnx329 3.0.13-0.27-default #1 SMP Wed Feb 15 13:33:49 UTC 2012 (d73692b) x86_64 x86_64 x86_64 GNU/Linux A SLES11 SP2 box, running in a corporate environment using centrify: |
|
openSUSE 13.2 |
|
Xen.org XCP Host 1.6.10-61809c Debian squeeze (6.0) LTS |
|
Gentoo with net-dns/avahi-0.6.31-r6 |
|
A customized file I've used on Ubuntu 10.04/12.04/14.04 with sssd: |
|
Ubuntu 14.10 |
|
Debian Jessie |
|
CoreOS
|
|
Please note, that So a way to switch this assumption off in Go is needed. |
|
@nightlyone, I know that local doesn't mean Avahi. But I also know that it's not a valid DNS TLD and Go doesn't do mDNS or Active Directory etc. So if it is seen, we use C like before. Why do you need a switch for that assumption? |
Amazon Linux AMI 2014.09 # # /etc/nsswitch.conf # # An example Name Service Switch config file. This file should be # sorted with the most-used services at the beginning. # # The entry '[NOTFOUND=return]' means that the search for an # entry should stop if the search in the previous entry turned # up nothing. Note that if the search failed due to some other reason # (like no NIS server responding) then the search continues with the # next entry. # # Valid entries include: # # nisplus Use NIS+ (NIS version 3) # nis Use NIS (NIS version 2), also called YP # dns Use DNS (Domain Name Service) # files Use the local files # db Use the local database (.db) files # compat Use NIS on compat mode # hesiod Use Hesiod for user lookups # [NOTFOUND=return] Stop searching if not found so far # # To use db, put the "db" in front of "files" for entries you want to be # looked up first in the databases # # Example: #passwd: db files nisplus nis #shadow: db files nisplus nis #group: db files nisplus nis passwd: files shadow: files group: files #hosts: db files nisplus nis dns hosts: files dns # Example - obey only what nisplus tells us... #services: nisplus [NOTFOUND=return] files #networks: nisplus [NOTFOUND=return] files #protocols: nisplus [NOTFOUND=return] files #rpc: nisplus [NOTFOUND=return] files #ethers: nisplus [NOTFOUND=return] files #netmasks: nisplus [NOTFOUND=return] files bootparams: nisplus [NOTFOUND=return] files ethers: files netmasks: files networks: files protocols: files rpc: files services: files netgroup: files publickey: nisplus automount: files aliases: files nisplus |
|
As an extra kink for [server]
#host-name=foo
#domain-name=localBeyond avahi unless there is an explicit and well documented switch to force the use of the libc resolver this feels like a can of worms. There are a variety of options that can be set in /etc/host.conf (influences /etc/hosts) /etc/gai.conf (influences getaddrinfo in general) as well as the usual /etc/resolv.conf and /etc/nsswitch.conf. In the mind of a sysadmin or a distro maintainer I really need a way to tell Go to use libc because it isn't practical for Go to reliably know when its behavior differs from libc. |
|
@bradfitz i would argue that local is a valid dns top-level domain but it has special treatment as you say "Any DNS query for a name ending with ".local." MUST be sent to the mDNS IPv4 link-local multicast address 224.0.0.251" http://tools.ietf.org/html/rfc6762 |
|
openSUSE 13.2 |
|
FreeBSD 10.1, almost stock, but I've added |
|
Fedora 21. I seem to recall that I modified it from stock in order to favor IPv6 for mDNS since more of my devices are IPv6 than IPv4. Initial comment paragraphs stripped. |
|
Debian 7.8 Same comments apply. |
|
Looks like this issue was fixed by https://go.googlesource.com/go/+/4a0ba7aa171a80fe798811a3fdc7c42b83dcda01. |
and others
We should prefer the Go DNS resolver (over libc's) if the /etc/nsswitch.conf file permits, to avoid the cgo & thread overhead.
Initial CL is https://go-review.googlesource.com/8945
But before I submit that, I want to gather a bunch of
/etc/nsswitch.conffiles from different systems for more test data.Please post yours here if it's unique.
Please include the OS/distro/version information, and which interesting OS packages you might have installed (e.g. Avahi) or not. Whatever's interesting info.
Thanks.
The text was updated successfully, but these errors were encountered: