feat: Allow specifying vmnet network UUID to disable DHCP (on vmnet.host network only)

This commit introduces a new `--vmnet-network-uuid` command-line option to allow
setting the `vmnet_network_identifier_key` for vmnet.

This property is only applicable to a vmnet_interface in
VMNET_HOST_MODE.

If this property is set, the vmnet_interface is added to an isolated
network with the specified identifier.

No DHCP service is provided on this network.

This is useful for certain applications where the users need an isolated
network and are running their own dhcp to assign IPs in such network.

See issue [#139](#139)

Signed-off-by: Angelo (pallotron) Failla <[email protected]>

Author: pallotron

README.md

@@ -351,6 +351,12 @@ sudo launchctl bootout system /Library/LaunchDaemons/io.github.lima-vm.socket_vm
 sudo rm /Library/LaunchDaemons/io.github.lima-vm.socket_vmnet.bridged.${BRIDGED}.plist
 ```
 
+### No DHCP mode
+
+By passing `--vmnet-mode=host` without `--vmnet-gateway` to `socket_vmnet`, the internal DHCP will be disabled.
+This is useful for situations where the users want to create a network with statically assigned IP addresses or where another VMs is running its own DHCP server.
+This mode does not come with a launchd service.
+
 ## FAQs
 
 ### Why does `socket_vmnet` require root?
@@ -430,6 +436,15 @@ sudo /usr/libexec/ApplicationFirewall/socketfilterfw --add /usr/libexec/bootpd
 /usr/libexec/ApplicationFirewall/socketfilterfw --unblock /usr/libexec/bootpd
 ```
 
+### How to setup a vmnet host network without DHCP
+
+You may need to disable the vmnet framework's DHCP to:
+- Create a host network where all VMs have static IPs.
+- Run a custom DHCP server on one VM to assign IPs to others on the same network.
+
+To disable the internal DHCP, use `--vmnet-mode=host` without `--vmnet-gateway`. This allows you to use static IP addresses for your VMs.
+You can optionally provide a `--vmnet-network-uuid`.
+
 ## Links
 
 - https://developer.apple.com/documentation/vmnet

cli.c

@@ -48,6 +48,12 @@ static void print_usage(const char *argv0) {
          "specified\n");
   printf("--vmnet-interface-id=UUID           vmnet interface ID (default: "
          "random)\n");
+  printf("--vmnet-network-identifier=UUID     vmnet network identifier (UUID string, \"random\", "
+         "or \"\")\n"
+         "                                    When vmnet mode is \"host\" and --vmnet-gateway is "
+         "not set, the internal DHCP will be disabled.\n"
+         "                                    (default: \"random\")\n");
+
   printf("--vmnet-nat66-prefix=PREFIX::       The IPv6 prefix to use with "
          "shared mode.\n");
   printf("                                    The prefix must be a ULA i.e. "
@@ -72,6 +78,7 @@ enum {
   CLI_OPT_VMNET_MASK,
   CLI_OPT_VMNET_INTERFACE_ID,
   CLI_OPT_VMNET_NAT66_PREFIX,
+  CLI_OPT_VMNET_NETWORK_IDENTIFIER,
 };
 
 struct cli_options *cli_options_parse(int argc, char *argv[]) {
@@ -82,18 +89,19 @@ struct cli_options *cli_options_parse(int argc, char *argv[]) {
   }
 
   const struct option longopts[] = {
-      {"socket-group",       required_argument, NULL, CLI_OPT_SOCKET_GROUP      },
-      {"vmnet-mode",         required_argument, NULL, CLI_OPT_VMNET_MODE        },
-      {"vmnet-interface",    required_argument, NULL, CLI_OPT_VMNET_INTERFACE   },
-      {"vmnet-gateway",      required_argument, NULL, CLI_OPT_VMNET_GATEWAY     },
-      {"vmnet-dhcp-end",     required_argument, NULL, CLI_OPT_VMNET_DHCP_END    },
-      {"vmnet-mask",         required_argument, NULL, CLI_OPT_VMNET_MASK        },
-      {"vmnet-interface-id", required_argument, NULL, CLI_OPT_VMNET_INTERFACE_ID},
-      {"vmnet-nat66-prefix", required_argument, NULL, CLI_OPT_VMNET_NAT66_PREFIX},
-      {"pidfile",            required_argument, NULL, 'p'                       },
-      {"help",               no_argument,       NULL, 'h'                       },
-      {"version",            no_argument,       NULL, 'v'                       },
-      {0,                    0,                 0,    0                         },
+      {"socket-group",             required_argument, NULL, CLI_OPT_SOCKET_GROUP            },
+      {"vmnet-mode",               required_argument, NULL, CLI_OPT_VMNET_MODE              },
+      {"vmnet-interface",          required_argument, NULL, CLI_OPT_VMNET_INTERFACE         },
+      {"vmnet-gateway",            required_argument, NULL, CLI_OPT_VMNET_GATEWAY           },
+      {"vmnet-dhcp-end",           required_argument, NULL, CLI_OPT_VMNET_DHCP_END          },
+      {"vmnet-mask",               required_argument, NULL, CLI_OPT_VMNET_MASK              },
+      {"vmnet-interface-id",       required_argument, NULL, CLI_OPT_VMNET_INTERFACE_ID      },
+      {"vmnet-nat66-prefix",       required_argument, NULL, CLI_OPT_VMNET_NAT66_PREFIX      },
+      {"vmnet-network-identifier", required_argument, NULL, CLI_OPT_VMNET_NETWORK_IDENTIFIER},
+      {"pidfile",                  required_argument, NULL, 'p'                             },
+      {"help",                     no_argument,       NULL, 'h'                             },
+      {"version",                  no_argument,       NULL, 'v'                             },
+      {0,                          0,                 0,    0                               },
   };
   int opt = 0;
   while ((opt = getopt_long(argc, argv, "hvp:", longopts, NULL)) != -1) {
@@ -134,6 +142,16 @@ struct cli_options *cli_options_parse(int argc, char *argv[]) {
     case CLI_OPT_VMNET_NAT66_PREFIX:
       res->vmnet_nat66_prefix = strdup(optarg);
       break;
+    case CLI_OPT_VMNET_NETWORK_IDENTIFIER:
+      if (strcmp(optarg, "random") == 0) {
+        uuid_generate_random(res->vmnet_network_identifier);
+      } else if (strcmp(optarg, "") == 0) {
+        uuid_clear(res->vmnet_network_identifier);
+      } else if (uuid_parse(optarg, res->vmnet_network_identifier) < 0) {
+        ERRORF("Failed to parse UUID \"%s\"", optarg);
+        goto error;
+      }
+      break;
     case 'p':
       res->pidfile = strdup(optarg);
       break;
@@ -191,7 +209,7 @@ struct cli_options *cli_options_parse(int argc, char *argv[]) {
     goto error;
   }
   if (res->vmnet_gateway == NULL) {
-    if (res->vmnet_mode != VMNET_BRIDGED_MODE) {
+    if (res->vmnet_mode != VMNET_BRIDGED_MODE && res->vmnet_mode != VMNET_HOST_MODE) {
       WARN("--vmnet-gateway=IP should be explicitly specified to "
            "avoid conflicting with other applications");
     }

cli.h

@@ -20,6 +20,8 @@ struct cli_options {
   char *vmnet_mask;
   // --vmnet-interface-id, corresponds to vmnet_interface_id_key
   uuid_t vmnet_interface_id;
+  // --vmnet-network-identifier, corresponds to vmnet_network_identifier_key
+  uuid_t vmnet_network_identifier;
   // --vmnet-nat66-prefix, corresponds to vmnet_nat66_prefix_key
   char *vmnet_nat66_prefix;
   // -p, --pidfile; writes pidfile using permissions of socket_vmnet

main.c

@@ -230,10 +230,21 @@ static interface_ref start(struct state *state, struct cli_options *cliopt) {
     INFOF("Using network interface \"%s\"", cliopt->vmnet_interface);
     xpc_dictionary_set_string(dict, vmnet_shared_interface_name_key, cliopt->vmnet_interface);
   }
-  if (cliopt->vmnet_gateway != NULL) {
-    xpc_dictionary_set_string(dict, vmnet_start_address_key, cliopt->vmnet_gateway);
-    xpc_dictionary_set_string(dict, vmnet_end_address_key, cliopt->vmnet_dhcp_end);
-    xpc_dictionary_set_string(dict, vmnet_subnet_mask_key, cliopt->vmnet_mask);
+
+  // no dhcp
+  if (cliopt->vmnet_mode == VMNET_HOST_MODE && cliopt->vmnet_gateway == NULL) {
+    if (!uuid_is_null(cliopt->vmnet_network_identifier)) {
+      xpc_dictionary_set_uuid(dict, vmnet_network_identifier_key, cliopt->vmnet_network_identifier);
+      uuid_string_t uuid_str;
+      uuid_unparse(cliopt->vmnet_network_identifier, uuid_str);
+      INFOF("Using network identifier \"%s\" and no vmnet gateway -> NO DHCP will be enabled on this vmnet", uuid_str);
+    }
+  } else  {
+    if (cliopt->vmnet_gateway != NULL) {
+      xpc_dictionary_set_string(dict, vmnet_start_address_key, cliopt->vmnet_gateway);
+      xpc_dictionary_set_string(dict, vmnet_end_address_key, cliopt->vmnet_dhcp_end);
+      xpc_dictionary_set_string(dict, vmnet_subnet_mask_key, cliopt->vmnet_mask);
+    }
   }
 
   xpc_dictionary_set_uuid(dict, vmnet_interface_id_key, cliopt->vmnet_interface_id);