Make mip-pcap work on Mac

examples/mip-pcap/README.md

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+#MIP TCP / IP stack over pcap
+
+This example allows to use Mongoose's MIP built-in TCP/IP stack on systems
+that support pcap API, i.e. have libpcap library installed. The application
+opens an interface and uses `pcap_next_ex()` for reading packets from the
+interface, and `pcap_inject()` to write packets to the interface.
+
+NOTE: depending on the libcap implementation, the injected packets may
+or may not be looped back to the interface's TCP/IP stack. If they are
+not looped back, then it is necessary to create a separate interface that
+is bridged to the target interface - see MacOS example below.
+
+## MacOS setup
+
+MacOS has support for `feth` (fake ethernet) interfaces. One can create a pair
+of `feth` interfaces and interlink them. Once a `feth` interface is assigned
+a peer and an IP address, anything that gets injected to it, appears on a
+peer interface and vice versa.
+
+```sh
+$ sudo ifconfig feth0 create
+$ sudo ifconfig feth1 create
+$ sudo ifconfig feth1 peer feth 0     # Link two fake ethernet ifaces together
+$ sudo ifconfig feth1 10.10           # Assign 10.0.0.10 to feth1
+$ sudo ifconfig feth0 up
+$ sudo ifconfig feth1 up
+```
+
+Now we have two Ethernet interfaces, `feth0` and `feth1`, interlinked and active.
+On your Mac, go to "System Preferences" / Sharing, enable "Internet Sharing"
+and choose "Thunderbolt bridge". This enables DHCP on the `bridge0` interface.
+On my system it gets `192.168.2.1` IP address, and serves `192.168.2/24` net.
+which is bridge for all Thunderbolt devices, and adds necessary routes to the
+WiFi interface. We should add one of our fake interfaces to this bridge:
+
+```sh
+$ sudo ifconfig bridge0 addm feth1
+```
+
+We cat start an example using the `feth0`:
+
+```sh
+$ make -C examples/mip-pcap/ clean all ARGS="-i feth0" 
+...
+2386718 3 mip.c:279:arp_cache_add       ARP cache: added 0xc0a80201 @ 36:77:4d:be:e0:80
+2386718 2 mip.c:300:onstatechange       READY, IP: 192.168.2.17
+```