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SMB connections intermittently stall/timeout during Time Machine backup, only recovers via durable reconnect #294

Description

@jamesyc

Samba successfully completes every request it receives but communication then goes silent. macOS closes the connection after its configured SMB response timeout:

  • About 62 seconds with the default timeout
  • About 120 seconds after max_resp_timeout was changed to 120
  • The client immediately creates a replacement SMB connection
  • Ethernet and Wi‑Fi through a separate modern access point are substantially more reliable than the Time Capsule’s own Wi‑Fi
  • Clue: enabling vfs_aio_fork greatly reduces these timeouts

Root cause requires a packet capture and is unclear, could be:

  • A Mac SMB request never reaches Samba
  • Samba’s response never reaches the Mac
  • The Time Capsule Wi‑Fi/NetBSD network stack loses or delays the traffic

This is the main unresolved cause behind #221

The backup failure issue was mitigated by increasing the durable handle retry timeout, which allows recovery after a disconnect, but it does not prevent the underlying unresolved stall.

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