Merge pull request torvalds#519 from thehajime/feature-nameserver

lkl: add nameserver config for json

Author: thehajime

Documentation/lkl.txt

@@ -449,6 +449,17 @@ The following are the list of keys to describe a JSON file.
      "delay_main":"500000"
 ```
 
+* nameserver
+
+  key: "nameserver"
+  value type: string
+
+  a name server address, which will be written in /etc/resolv.conf into a
+  filesystem used by a LKL instance.
+```
+     "nameserver":"8.8.8.8"
+```
+
 FAQ
 ===
 

tools/lkl/include/lkl_config.h

@@ -50,6 +50,7 @@ struct lkl_config {
 	char *boot_cmdline;
 	char *dump;
 	char *delay_main;
+	char *nameserver;
 };
 
 #ifdef LKL_HOST_CONFIG_JSMN

tools/lkl/lib/config.c

@@ -178,6 +178,8 @@ int lkl_load_config_json(struct lkl_config *cfg, const char *jstr)
 			cfgptr = &cfg->dump;
 		} else if (jsoneq(jstr, &toks[pos], "delay_main") == 0) {
 			cfgptr = &cfg->delay_main;
+		} else if (jsoneq(jstr, &toks[pos], "nameserver") == 0) {
+			cfgptr = &cfg->nameserver;
 		} else {
 			lkl_printf("unexpected key in json %.*s\n",
 					toks[pos].end-toks[pos].start,
@@ -218,6 +220,7 @@ void lkl_show_config(struct lkl_config *cfg)
 		return;
 	lkl_printf("gateway: %s\n", cfg->gateway);
 	lkl_printf("gateway6: %s\n", cfg->gateway6);
+	lkl_printf("nameserver: %s\n", cfg->nameserver);
 	lkl_printf("debug: %s\n", cfg->debug);
 	lkl_printf("mount: %s\n", cfg->mount);
 	lkl_printf("singlecpu: %s\n", cfg->single_cpu);
@@ -689,6 +692,7 @@ static int lkl_clean_config(struct lkl_config *cfg)
 	free_cfgparam(cfg->boot_cmdline);
 	free_cfgparam(cfg->dump);
 	free_cfgparam(cfg->delay_main);
+	free_cfgparam(cfg->nameserver);
 	return 0;
 }
 
@@ -777,6 +781,20 @@ int lkl_load_config_post(struct lkl_config *cfg)
 		}
 	}
 
+	if (cfg->nameserver) {
+		int fd;
+		char ns[32] = "nameserver ";
+
+		/* ignore error */
+		lkl_sys_mkdir("/etc", 0xff);
+		lkl_sys_chdir("/etc");
+		fd = lkl_sys_open("/etc/resolv.conf", LKL_O_CREAT | LKL_O_RDWR, 0);
+
+		strcat(ns, cfg->nameserver);
+		lkl_sys_write(fd, ns, sizeof(ns));
+		lkl_sys_close(fd);
+	}
+
 	return 0;
 }
 

tools/lkl/tests/config.c

@@ -11,6 +11,7 @@ static const char *config_json =
 "{\n"
 "	\"gateway\":\"192.168.113.1\",\n"
 "	\"gateway6\":\"fc03::1\",\n"
+"	\"nameserver\":\"2001:4860:4860::8888\",\n"
 "	\"debug\":\"1\",\n"
 "	\"interfaces\": [\n"
 "		{\n"
@@ -56,6 +57,11 @@ int lkl_test_config_load_json(void)
 		return TEST_FAILURE;
 	}
 
+	if (strcmp(cfg->nameserver, "2001:4860:4860::8888") != 0) {
+		lkl_test_logf("bad nameserver\n");
+		return TEST_FAILURE;
+	}
+
 	if (strcmp(cfg->debug, "1") != 0) {
 		lkl_test_logf("bad debug\n");
 		return TEST_FAILURE;