Setting a static IP hangs until an Ethernet cable is attached to another port

[ssilverman]

NativeEthernet/src/NativeEthernet.cpp

Lines 293 to 294 in 92540fd

	while(!link_status){
	}

This code will hang if I want to set a static IP but don't yet have a cable plugged in. I waited for a while and it looks like the link status is never set to something other than Unknown (0). Is link_callback supposed to be called at all in this case?

[ssilverman]

Related: https://forum.pjrc.com/threads/60857-T4-1-Ethernet-Library?p=266705&viewfull=1#post266705

[ssilverman]

My solution is to just comment out that tight while loop. Then things work as expected.

[ssilverman]

Just pinging on this issue because you answered #13 just now :)

[troy-at-skyfront]

I am also having this issue. I'll try to comment out the while loop as you suggested.

[lorenzofattori]

Having the same issue, currently commented the lines in the library, but it would be nice to have a fix on library level so we don't have to do this manually at every library update.

Cheers!

[ssilverman]

I think that this behaviour shouldn’t be here. I know @vjmuzik you said that the library should block because that’s how you remembered some older Arduino library behaving, however, why would there exist an Ethernet.linkStatus() function at all if it would always return “LinkON”?

If the library blocks until “link”, wouldn’t that contradict the mere existence of that function? For example, the API says there’s also “LinkOFF” and “Unknown” return values. How can code ever even check this if the library blocks until link?

Additionally, this blocking behaviour makes it very easy to “freeze” any Teensy using this library just by unplugging the Ethernet cable at startup. This will prevent any other functions from running, for example data collection.

I’m also going to guess that most users of this library are writing new code and are probably not relying on some “old behaviour”, whatever that was.

My three and a half cents… thank you for reading. :)