disabling ipv6 at the kernel level in stemcells

Dmitriy Kalinin

hey all,

we've disabled ipv6 via ipv6.disable=1 in grub in 3363.19+ linux stemcells
some time ago. in previous stemcells it was disabled via sysctl at bootup.

we are now aware that small number of releases may be affected (one release
for example was disabling portion of ipv6 functionality themselves but no
longer can succeed since /proc/... entry is gone and that code was not
checking for its existence). we also had a report that some java processes
may be affected if they were using particular libraries that for some
reason try to obtain local ipv6 address (even though ipv6 was disabled
before their startup).

we try very hard to avoid making any breaking changes in minor stemcell
versions; however, this changed turned out to be more disruptive than we
expected. given that it affects only small number of releases we have
decided to keep it in (hoping that it should be easy for release authors to
issue a patch if necessary).

(for folks thinking about the future ipv6 support, bosh-agent will
automatically turn it on at runtime if necessary.)

as usual feel free to reach out to us on #bosh slack if you need any help.