From f30d7fc2ed9228d23372a6c96a367c82c9ff951a Mon Sep 17 00:00:00 2001
From: Calvin Buckley <calvin@cmpct.info>
Date: Sun, 26 Jan 2025 15:11:54 -0400
Subject: [PATCH] Check for macOS 10.15 to used bridge mode, make usage clear

Bridged devices require macOS 10.15 to work correctly. Check if we're on
macOS 10.15 at runtime (so a newer SDK can be used to make simh binaries
that target older macOS), and at compile time (so an older SDK can be
used to build simh).

Also make it so vmnet: for host only is deprecated; you must explicitly
provide either host, shared, or a bridged device name.
---
 sim_ether.c | 37 +++++++++++++++++++++++++++----------
 1 file changed, 27 insertions(+), 10 deletions(-)

diff --git a/sim_ether.c b/sim_ether.c
index eb4104ee..5ff5db5a 100644
--- a/sim_ether.c
+++ b/sim_ether.c
@@ -1219,8 +1219,10 @@ if (used < max) {
 }
 // vmnet.framework has an allowed list of devices for bridging
 // handy for user if we list them since ifconfig is noisy
-__block int used_block;
-{
+#if (TARGET_OS_OSX && __MAC_OS_X_VERSION_MAX_ALLOWED >= 101500)
+if (__builtin_available(macOS 10.15, *)) {
+  // avoid putting a __block marker on used on other platforms
+  __block int used_block;
   xpc_object_t bridge_list = vmnet_copy_shared_interface_list();
 
   xpc_array_apply(bridge_list, ^bool(size_t index, xpc_object_t value) {
@@ -1237,6 +1239,7 @@ __block int used_block;
   xpc_release(bridge_list);
 }
 #endif
+#endif
 
 if (used < max) {
   sprintf(list[used].name, "%s", "udp:sourceport:remotehost:remoteport");
@@ -2317,8 +2320,8 @@ if (bufsz < ETH_MAX_JUMBO_FRAME)
 /* attempt to connect device */
 memset(errbuf, 0, PCAP_ERRBUF_SIZE);
 
-#if defined(HAVE_VMNET_NETWORK)
   if (0 == strncmp("vmnet:", savname, 6)) {
+#if defined(HAVE_VMNET_NETWORK)
     xpc_object_t if_desc;
     dispatch_queue_t vmn_queue;
     interface_ref vmn_interface;
@@ -2330,16 +2333,28 @@ memset(errbuf, 0, PCAP_ERRBUF_SIZE);
     const char *devname = savname + sizeof("vmnet:") - 1;
 
     if_desc = xpc_dictionary_create(NULL, NULL, 0);
-    // VMNET_HOST_MODE:    Host and other guests
-    // VMNET_SHARED_MODE:  NAT
-    // VMNET_BRIDGED_MODE: Requires macOS 10.15
     if (0 == strcmp(devname, "shared")) {
       xpc_dictionary_set_uint64(if_desc, vmnet_operation_mode_key, VMNET_SHARED_MODE);
-    } else if (strlen(devname) == 0 || 0 == strcmp(devname, "host")) {
+    } else if (0 == strcmp(devname, "host")) {
       xpc_dictionary_set_uint64(if_desc, vmnet_operation_mode_key, VMNET_HOST_MODE);
+#if (TARGET_OS_OSX && __MAC_OS_X_VERSION_MAX_ALLOWED >= 101500)
     } else if (strlen(devname) > 0) { // Bridged, this is the device name
-      xpc_dictionary_set_uint64(if_desc, vmnet_operation_mode_key, VMNET_BRIDGED_MODE);
-      xpc_dictionary_set_string(if_desc, vmnet_shared_interface_name_key, devname);
+      if (__builtin_available(macOS 10.15, *)) {
+        xpc_dictionary_set_uint64(if_desc, vmnet_operation_mode_key, VMNET_BRIDGED_MODE);
+        xpc_dictionary_set_string(if_desc, vmnet_shared_interface_name_key, devname);
+      } else {
+        xpc_release(if_desc);
+        return sim_messagef (SCPE_OPENERR, "Eth: You must be using macOS 10.15 or newer for bridged devices\n");
+      }
+#endif
+    } else {
+      if (__builtin_available(macOS 10.15, *)) {
+        xpc_release(if_desc);
+        return sim_messagef (SCPE_OPENERR, "Eth: You must pick either shared, host, or an allowed bridge device\n");
+      } else {
+        xpc_release(if_desc);
+        return sim_messagef (SCPE_OPENERR, "Eth: You must pick either shared or host\n");
+      }
     }
 
     vmn_queue = dispatch_get_global_queue(QOS_CLASS_UTILITY, 0);
@@ -2362,8 +2377,10 @@ memset(errbuf, 0, PCAP_ERRBUF_SIZE);
     *eth_api = ETH_API_VMN;
     *handle = (void *)vmn_interface;  /* Flag used to indicated open */
     return SCPE_OK;
-  }
+#else
+    return sim_messagef (SCPE_OPENERR, "Eth: No support for vmnet devices\n");
 #endif
+  }
 
 if (0 == strncmp("tap:", savname, 4)) {
   int  tun = -1;    /* TUN/TAP Socket */