A bizarre macOS bug is obstructing new community connections after 49 days of uptime

Facepalm: Apple’s macOS seems to be affected by a kernel-level bug that blocks new community connections if a tool stays constantly operational for 49 days. Apple has not but launched an official repair, however restarting the affected machine briefly resolves the difficulty, permitting customers to reconnect to any community. Nonetheless, the workaround solely lasts one other 49 days earlier than the bug reoccurs.

The difficulty is reportedly attributable to a 32-bit integer overflow within the macOS XNU kernel and is linked to how the system makes use of a TCP/IP variable to trace TCP timestamps in milliseconds for the reason that system booted.

Researchers at Photon defined {that a} 32-bit integer can maintain a most worth of 4,294,967,295. As a result of macOS measures timestamps in milliseconds, this restrict is reached after 49 days, 17 hours, 2 minutes, and 47.296 seconds of steady operation.

As soon as the TCP/IP integer reaches its most worth, the counter rolls over to zero as anticipated. Nonetheless, the monotonicity guard – designed to forestall overflow – additionally blocks the inner clock from restarting at zero, successfully freezing the TCP timestamp clock. This prevents the system from cleansing up previous TIME_WAIT connections, permitting lifeless connections to stay open indefinitely, consuming all out there ephemeral ports and inflicting the TCP/IP stack to dam all new connections.

With all new TCP connections blocked, customers are unable to open new web sites or begin video calls. Current connections proceed to work usually as a result of they have already got assigned ports. ICMP (ping) additionally features, because it doesn’t use TCP ports or the TCP timer subsystem. Apparently, the truth that ping requests and present TCP connections continued working confused researchers and made diagnosing the issue harder.

As with many points in fashionable working programs, this TCP/IP bug briefly disappears after a reboot, however returns if the machine stays powered on for an additional 49 days. No official repair is at the moment out there, although Apple is predicted to launch a patch to deal with the issue. Within the meantime, the Photon analysis staff says they’re creating a workaround that mitigates the difficulty with out requiring a restart.