tramp loading stalls several seconds on DNS resolution

[Mike Magin]

Xenial's emacs24-common contains a version of tramp.el which attempts to ssh to host.does.not.exist on load which causes loading tramp to stall until this hostname resolution fails (10 seconds for me). This makes my emacs startup (I load tramp via other libraries which use it) take about 12 seconds, instead of a fraction of a second like it should be.

Upstream maintainers seem to have fixed this to attempt ssh to 0.0.0.1 instead, see the git log output attached.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: emacs24-common 24.5+1-6ubuntu1
ProcVersionSignature: Ubuntu 4.4.0-21.37-generic 4.4.6
Uname: Linux 4.4.0-21-generic x86_64
NonfreeKernelModules: zfs zunicode zcommon znvpair zavl
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
Date: Sun Jun 19 13:20:21 2016
InstallationDate: Installed on 2016-06-12 (7 days ago)
InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
PackageArchitecture: all
SourcePackage: emacs24
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[David Sterratt (david-c-sterratt)]

The fix referred to earlier is against emacs 25. There appears to be no backport of the patch in the emacs24 tree, so I have rolled my own patch, based on the fix for emacs 25: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=20015. I've created a deb and checked that it works. If the emacs package maintainers can just incorporate this: great. If not, I suppose I could try to upload the deb to a ppa, though I'll need to work out how to do this.

[Ubuntu Foundations Team Bug Bot (crichton)]

The attachment "change-test-for-controlpath-to-avoid-DNS-timeouts.patch" seems to be a patch. If it isn't, please remove the "patch" flag from the attachment, remove the "patch" tag, and if you are a member of the ~ubuntu-reviewers, unsubscribe the team.

[This is an automated message performed by a Launchpad user owned by ~brian-murray, for any issues please contact him.]

[David Sterratt (david-c-sterratt)]

I've also posted the patch on the relevant Debian emacs24 bug:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=810640