feat: Allow specifying vmnet network UUID to disable DHCP

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 +48,9 @@ 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 +75,7 @@ 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[]) {
@@ -90,6 +94,7 @@ struct cli_options *cli_options_parse(int argc, char *argv[]) {
       {"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'                       },
@@ -134,6 +139,16 @@ 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 +206,7 @@ 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);