nc requires open stdin to not terminate early

[haarp]

Hey,

I found a bug in Toybox 0.8.11 on a CalyxOS device. nc appears to require something on its stdin, or it will terminate after a random amount of time/data. This can be problematic inside scripts or SSH sessions where stdin is not available or redirected from /dev/null.

Reproducer:

# provider
dd if=/dev/random bs=1M count=10 | /system/bin/nc -s 127.0.0.1 -l -p 8000 -w 10 &
sleep 1
# consumer
/system/bin/nc 127.0.0.1 8000 | wc -c

reads all of the 10M bytes (if run in an interactive shell!)

# provider
dd if=/dev/random bs=4M count=10 | /system/bin/nc -s 127.0.0.1 -l -p 8000 -w 10 &
sleep 1
# consumer
</dev/null /system/bin/nc 127.0.0.1 8000 | wc -c

nc terminates after reading 0 to a few thousand bytes

Thanks!

[haarp]

A hacky workaround when provider and consumer are in the same shell:

while [ -e /proc/$! ]; do sleep 1; done | /system/bin/nc 127.0.0.1 8000