'sysctl' claims invalid input for valid inputs
The sysctl utility claims malformed inputs for valid inputs.
# sysctl -w net.ipv4.ip_local_reserved_ports=''
sysctl: malformed setting "net.ipv4.ip_local_reserved_ports="
# echo -n '' > /proc/sys/net/ipv4/ip_local_reserved_ports
#
Of course you can work around this with a newline:
# sysctl -w net.ipv4.ip_local_reserved_ports='
'
#
But an empty string is a valid input here, afaict.