[FS#604] no recognition for plug out ethernet cable on WAN Port

[LEDE Bugs]

The following task has a new comment added:

FS#604 - no recognition for plug out ethernet cable on WAN Port 
User who did this - Vittorio Gambaletta (VittGam) (VittGam)

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@jow: the switch hardware (AR8327) normally sends IRQs to notify the kernel of port link change switches, and the kernel used to pick them up in CC 15.05.1.

I opened FS#631 last day describing the same problem happening on a TL-WR1043ND v3, which has a AR8327 rev. 4.

Instead, my WDR4300 has a AR8327 rev. 2 like the WDR3600 of @cs, and the problem does not happen there (if I tested it correctly... but I'm going to recheck soon).

As I said on the other issue, this problem has implications such as the kernel not cleaning the ARL table of the switch when a cable is disconnected from a port.
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=604#comment2177