When tunelp is invoked with the '-i' option, and the option
value is not a number, the somewhat confusing error "sscanf
error: Success" is reported.
tunelp /dev/lp0 -i x
sscanf error: Success
You are right, that's clearly a mistake, and I've forwarded it on to
the util-linux maintainers list, as tunelp is now part of util-linux.
In the meantime, I guess the workaround is "don't do that then..." :-)
Andries fixed it in the upstream sources, so we'll get the fix in the next
util-linux release. Thanks!