On Mon, 20 Mar 2017 13:26:35 -0000 Launchpad Bug Tracker <1674...@bugs.launchpad.net> wrote: > You have been subscribed to a public bug by Martin Pitt (pitti): > > The /etc/network/if-up.d/openssh-server hack was introduced ten > years ago [1] as a response to bug 103436. At least from today's > perspective this isn't justified: > > I can't seem to be able to actually reproduce that issue: I can > start a VM with no network interfaces, remove the above hack, then > start sshd, then bring up an ethernet interface, and I can connect > to ssh via ethernet just fine.
sshd has no internal support to open and close listening addresses on its own, so I suspect you're wrong. Why don't you try the actual use case, which is changing addresses rather than an initial open. However, I haven't used ubuntu in at least eight years and have no way to help you. > Also, e. g. Fedora has no > counterpart of this hack, and these days a lot of people would > complain if that would cause problems, How many people regularly ssh into their laptops on multiple networks? I would guess very few. > The hack introduces a race: you run into connection errors after > bringing up a new interface as sshd stops listening briefly while > being reloaded. Well, yah, but when you change networks you're also not listening to the network. This isn't a race, this is just expected behavior. Even if sshd did this on its own this would happen. And it isn't a "hack", this is exactly what ifup/down scripts are for. Perry -- Perry E. Metzger pe...@piermont.com -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to openssh in Ubuntu. https://bugs.launchpad.net/bugs/1674330 Title: Please consider dropping /etc/network/if-up.d/openssh-server Status in openssh package in Ubuntu: New Bug description: The /etc/network/if-up.d/openssh-server hack was introduced ten years ago [1] as a response to bug 103436. At least from today's perspective this isn't justified: I can't seem to be able to actually reproduce that issue: I can start a VM with no network interfaces, remove the above hack, then start sshd, then bring up an ethernet interface, and I can connect to ssh via ethernet just fine. Also, e. g. Fedora has no counterpart of this hack, and these days a lot of people would complain if that would cause problems, as hotpluggable/roaming network devices are everywhere. The hack introduces a race: you run into connection errors after bringing up a new interface as sshd stops listening briefly while being reloaded. That's the reason why I looked at it, as this regularly happens in upstream's cockpit integration tests. Also, /etc/network/if-up.d/ isn't being run when using networkd/netplan, i. e. in more recent Ubuntnu cloud instances. So far this doesn't seem to have caused any issues. I asked the original reporter of bug 103436 for some details, and to check whether that hack is still necessary. There is actually a proposed patch upstream [2] to use IP_FREEBIND, which is the modern solution to listening to all "future" interfaces as well. But at least for the majority of cases it seems to work fine without that even. So I wonder if it's time to bury that hack? [1] https://anonscm.debian.org/cgit/pkg-ssh/openssh.git/commit/?id=ba6b55ed6 [2] https://bugzilla.mindrot.org/show_bug.cgi?id=2512 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/1674330/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
