Mattermost's own embedded-coturn fallback hardcoded the same relay range
(49153-49352) for every instance, with no per-instance offset -- running
two Mattermost instances without the shared coturn service (or one
alongside Asterisk's own dedicated coturn, now possible via the prior
commit) would silently reproduce the exact pre-merge collision bug this
repo's coturn history warns about, just among Mattermost instances
instead of Asterisk/Mattermost.
Adds find_free_coturn_range() (lib/common.sh, standalone-mode-stubbed in
both services matching the existing port_in_use/find_free_port
convention): a coturn relay range can't be collision-checked with live
socket scanning the way a single port can -- coturn only opens ports
inside its configured range on demand, so an idle range looks the same
as an unclaimed one to ss/netstat. The only reliable check is reading
what every other coturn-owning service's .env on the box actually
claims (COTURN_MAX_PORT for the shared instance, TURN_MAX_PORT for each
dedicated one) and picking a range starting safely past the highest.
Also adds Mattermost's own opt-out prompt for the shared coturn
preference, matching the one just added to Asterisk (fresh-install-only,
never re-asked on update, same as every other coturn-shape decision in
that file). An update now explicitly preserves its existing dedicated
range from .env rather than silently recomputing a new one.
Verified end-to-end: a shared instance + Asterisk's dedicated coturn +
two independent Mattermost instances, each discovering and avoiding
every range already claimed by the others, land on entirely
non-overlapping port blocks.
Claude
d835e0d734