Fix #211: Use tcpip_input for IPv6 instead of ethernet_input

src/VirtualTap.cpp

@@ -572,7 +572,20 @@ void zts_lwip_init_interface(void* tapref, const InetAddress& ip)
         LOCK_TCPIP_CORE();
         if (isNewNetif) {
             vtap->netif6 = (void*)n;
-            netif_add(n, NULL, NULL, NULL, (void*)vtap, zts_netif_init6, ethernet_input);
+
+            //
+            // was:
+            // netif_add(n, NULL, NULL, NULL, (void*)vtap, zts_netif_init6, ethernet_input);
+            //
+            // but there is this documentation:
+            // > With NO_SYS=0, this must be set to tcpip_input for all netif types (whether ethernet, PPP, slipif, etc.)
+            // https://lwip.fandom.com/wiki/Writing_a_device_driver
+            //
+            // and also with ethernet_input and lwIP asserts turned on, we get:
+            // Assertion "Function called without core lock" failed at line 236 in /Users/brenton/development/github/libzt/ext/lwip-contrib/ports/unix/port/sys_arch.c
+            //
+            netif_add(n, NULL, NULL, NULL, (void*)vtap, zts_netif_init6, tcpip_input);
+
             n->ip6_autoconfig_enabled = 1;
             vtap->_mac.copyTo(n->hwaddr, n->hwaddr_len);
             netif_create_ip6_linklocal_address(n, 1);