As per mbedtls documentation. This is different to lwip_getaddrinfo() which uses loopback for a NULL address. Fixes bug mentioned here https://groups.google.com/forum/#!topic/esp-open-rtos/3KH5TZSTMUw
mbedTLS version 2.1.0 (current stable) Has some known issues/hacks: * Entropy source not hooked in at all * Linker script has a messy hack in it to store some (not all) data in irom