3 ms·

The inotify script likely has a race condition; if the directory is modified while an update is running, it won't pick up the second modification, and will wait

by ambrop7 14y ago

The inotify script likely has a race condition; if the directory is modified while an update is running, it won't pick up the second modification, and will wait in a dirty state until it is modified again. If anyone wants a race-free solution, you should check out my NCD scripting language [1] which has an integrated command to receive directory change notifications (last example in Blockers section is a race-free solution to this problem). [1] http://code.google.com/p/badvpn/wiki/NCD http://code.google.com/p/badvpn/wiki/NCD

nitrogen 14y ago
After a very brief look, NCD looks very cool. I'm curious about the first complete example. Is it possible to implement a delay of a few seconds before the IP address is reset when the link is lost?
- ambrop7 14y ago
  I've never seen why that would be useful. Switches and Ethernet cards aren't that unreliable in my experience, and I've plugged cables into a different switch in less than a few seconds :) I think if you really needed that, the nicest way would be to add it as a feature to net.backend.waitlink(). See source [1] of this command, and source of sleep() [2] to see how to use a timer. It may also be possible to hack it up without C-coding using blocker(), spawn(), sleep() and maybe other control commands. [1] http://code.google.com/p/badvpn/source/browse/trunk/ncd/modules/net_backend_waitlink.c http://code.google.com/p/badvpn/source/browse/trunk/ncd/modu... [2] http://code.google.com/p/badvpn/source/browse/trunk/ncd/modules/sleep.c http://code.google.com/p/badvpn/source/browse/trunk/ncd/modu...
  - nitrogen 14y ago
    I've had a situation where an Ethernet connection would occasionally drop link for a very small fraction of a second, which unnecessarily shut down the interface and reset all TCP connections. Maybe a few second delay is too long, but 500ms seems reasonable. Also, maybe I wouldn't want to keep the old address blindly, but trigger a DCHP request if the link is dropped and restored before the timeout. Also, thanks for the pointers into the source code. It looks like I would want to make the change around line 67 of net_backend_waitlink.c. I highly doubt I'll actually get around to doing it though :).
    - ambrop7 14y ago
      So you really need this, would that mean you may be able to use my language for something? If so, just say, and I can add this little feature, but I wouldn't like spending time for nothing :)
      - nitrogen 14y ago
        I haven't seen this problem recently, so don't worry about it. I appreciate the offer, though. Maybe some day I'll look into adding the feature for my embedded Linux systems, if I ever add Ethernet disconnection detection.
    - deleted 14y ago
      [deleted]

by ambrop7 14y ago

nitrogen 14y ago

After a very brief look, NCD looks very cool. I'm curious about the first complete example. Is it possible to implement a delay of a few seconds before the IP address is reset when the link is lost?

ambrop7 14y ago
I've never seen why that would be useful. Switches and Ethernet cards aren't that unreliable in my experience, and I've plugged cables into a different switch in less than a few seconds :) I think if you really needed that, the nicest way would be to add it as a feature to net.backend.waitlink(). See source [1] of this command, and source of sleep() [2] to see how to use a timer. It may also be possible to hack it up without C-coding using blocker(), spawn(), sleep() and maybe other control commands. [1] http://code.google.com/p/badvpn/source/browse/trunk/ncd/modules/net_backend_waitlink.c http://code.google.com/p/badvpn/source/browse/trunk/ncd/modu... [2] http://code.google.com/p/badvpn/source/browse/trunk/ncd/modules/sleep.c http://code.google.com/p/badvpn/source/browse/trunk/ncd/modu...
- nitrogen 14y ago
  I've had a situation where an Ethernet connection would occasionally drop link for a very small fraction of a second, which unnecessarily shut down the interface and reset all TCP connections. Maybe a few second delay is too long, but 500ms seems reasonable. Also, maybe I wouldn't want to keep the old address blindly, but trigger a DCHP request if the link is dropped and restored before the timeout. Also, thanks for the pointers into the source code. It looks like I would want to make the change around line 67 of net_backend_waitlink.c. I highly doubt I'll actually get around to doing it though :).
  - ambrop7 14y ago
    So you really need this, would that mean you may be able to use my language for something? If so, just say, and I can add this little feature, but I wouldn't like spending time for nothing :)
    - nitrogen 14y ago
      I haven't seen this problem recently, so don't worry about it. I appreciate the offer, though. Maybe some day I'll look into adding the feature for my embedded Linux systems, if I ever add Ethernet disconnection detection.
  - deleted 14y ago
    [deleted]