simh debug integration is only done during simh builds, the original QEMU debug functionality is preserved. The slirp debug flags can be set by the environment variable SLIRP_DEBUG. Mask values 1 - CALL, 2 - MISC, 3 - ERROR.
This version of slirp is a fork from QEMU Version 2.4.0.1 slirp implementation
Taken from commit id of 474590efc51f262fb5d81ca417d510cb7fb7a914
in the qemu repository git://repo.or.cz/qemu/ar7.git
Thanks to Fabrice Bellard.