[Bug network/18279] New: Long running programs don't detect resolv.conf being updated when roaming

["philipp at redfish-solutions dot com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=18279

            Bug ID: 18279
           Summary: Long running programs don't detect resolv.conf being
                    updated when roaming
           Product: glibc
           Version: 2.20
            Status: NEW
          Severity: normal
          Priority: P2
         Component: network
          Assignee: unassigned at sourceware dot org
          Reporter: philipp@redfish-solutions.com

Thanks to the stability of Linux, I run it on my laptop and leaving it running
for weeks at a time. During that time, I might (a) have Thunderbird running and
(b) roam from my home wired network on my docking station to a Wifi hotspot at
an airport or Starbucks or hotel to the office wired network and back again.

Unfortunately, during this time, /etc/resolv.conf will get rewritten by
dhclient multiple times, but the contents that were in it when Thunderbird (for
example) originally started will long have become irrelevant.

A simple fix would be to either stat() /etc/resolv.conf or to have inotify()
detect when /etc/resolv.conf has been written, deleted, or created and to
re-run res_init() at that time.

It might be possible to configure /etc/resolv.conf to point to a local proxy
which then is a little smarter about detecting network configuration changes,
but most distros aren't going to do that: it's complexity that they don't want
to deal with, and it complicates troubleshooting for the end-user.

Or you could tell users to shutdown and restart all of their applications
because libresolv doesn't handle roaming, but I don't think that advice will be
well received either.

We're living in the age of pervasive internet, and we roam constantly because
we can.

Time for libresolv to get caught up to a 21st century paradigm. This isn't 1985
anymore.

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