ubus
openwrt提供了一个系统总线ubus,类似linux桌面操作系统的d-bus,目标是提供系统级的进程间通信(IPC)功能。
为了提供各种后台进程和应用程序之间的通信机制,ubus被开发出来,由3部分组成:精灵进程,接口库和实用工具。
工程的核心是ubusd精灵进程,它提供了一个总线层,在系统启动时运行,负责进程间的消息路由和传递。其他进程注册到ubusd进程进行消息的发送和接收。这个接口是用linux文件socket和TLV手法消息实现的。每一个进程在指定命名空间下注册自己的路径。每一个路径都可以提供带有各种参数的多个函数处理过程。函数处理过程程序可以在完成处理后返回消息。
接口库名称为libubus.so,其他进程可以通过该动态链接库来简化对ubus总线的访问。
实用工具ubus是提供命令行的接口调用工具。可以基于该工具来进行脚本编程,也可以使用ubus来诊断问题。
ubus是为进程间发送消息而设计的,不适合传输大量数据(进程间传输大量数据应采用共享内存)。
网址:http://git.openwrt.org/project/ubus.git
$ ls ubus-2015-05-25 cli.c libubus.h libubus-req.c ubus_common.h ubusd_id.c ubusd_proto.c CMakeLists.txt libubus-internal.h libubus-sub.c ubusd.c ubusd_id.h ubusmsg.h examples libubus-io.c lua ubusd_event.c ubusd_obj.c libubus.c libubus-obj.c systemd ubusd.h ubusd_obj.h
ubusd: ubusd.c ubusd_id.c ubusd_obj.c ubusd_proto.c ubusd_event.c libubus: libubus.c libubus-io.c libubus-obj.c libubus-sub.c libubus-req.c cli/ubus: cli.c
1. ubusd
/etc/init.d/ubus中提供ubusd进程的启动,在系统进程启动完成后立即启动。他是在网络进程netifd之前启动的,该进程提供一个文件套接字接口和其他应用程序通信。
ubusd采用SOCK_STREAM的Unix域套接字实现与服务进程间通讯。
提供的功能:
1)提供注册对象和方法供其他实体调用。
2)调用其他应用程序提供的注册对象的控制接口。
3)在特定对象上注册监听事件。
4)向特定对象发送事件消息。
ubus将消息处理抽象为对象object和方法method的概念。一个对象中包含多个方法。对象和方法都有自己的名字,发送请求方在消息中指定要调用的对象和方法名字即可。
ubus的另外一个概念就是订阅(subscriber)。客户端需要向服务器注册收到特定消息时的处理方法。这样当服务器在状态发生改变时会通过ubus总线来通知客户端。
ubus可用于两个进程之间通信,进程之间以TLV格式传递消息。ubus能够以json格式和用户进行数据交换。常见场景(应用详见ubus实现进程间通信举例):
1)客户端/服务器模式。
2)订阅通知模式(struct ubus_subscriber)。
3)事件模式(ubus_event_handler)。
ubusd是一种总线消息服务器,任何消息均通过ubusd进程传递,因此多个进程在相互通信时,均通过ubus收发消息。
编译安装
1)去除lua支持
#ADD_SUBDIRECTORY(lua)
2)编译
mkdir build; cd build; cmake ..; make ;make install
[ 30%] Built target ubus [ 60%] Built target ubusd [ 70%] Built target cli [ 85%] Built target server [100%] Built target client Install the project... -- Install configuration: "" -- Installing: /usr/local/lib/libubus.so -- Installing: /usr/local/bin/ubus -- Set runtime path of "/usr/local/bin/ubus" to "" -- Installing: /usr/local/sbin/ubusd -- Up-to-date: /usr/local/include/ubusmsg.h -- Up-to-date: /usr/local/include/ubus_common.h -- Up-to-date: /usr/local/include/libubus.h -- Installing: /usr/lib/systemd/system/ubus.socket -- Installing: /usr/lib/systemd/system/ubus.service
2. libubus
1) 数据结构
struct ubus_event_handler { struct ubus_object obj; ubus_event_handler_t cb; }; struct ubus_context { struct list_head requests; struct avl_tree objects; /** client端object链表头 */ struct list_head pending; struct uloop_fd sock; /** client端sock对象 */ uint32_t local_id; /** ubusd分配的client id */ uint16_t request_seq; int stack_depth; /** 断开连接回调函数 */ void (*connection_lost)(struct ubus_context *ctx); struct { struct ubus_msghdr hdr; char data[UBUS_MAX_MSGLEN]; } msgbuf; /** 通信报文 */ }; struct ubus_object_data { uint32_t id; uint32_t type_id; const char *path; struct blob_attr *signature; }; struct ubus_request_data { uint32_t object; uint32_t peer; uint16_t seq; /* internal use */ bool deferred; int fd; }; struct ubus_request { struct list_head list; struct list_head pending; int status_code; bool status_msg; bool blocked; bool cancelled; bool notify; uint32_t peer; uint16_t seq; ubus_data_handler_t raw_data_cb; ubus_data_handler_t data_cb; ubus_fd_handler_t fd_cb; ubus_complete_handler_t complete_cb; struct ubus_context *ctx; void *priv; }; struct ubus_notify_request { struct ubus_request req; ubus_notify_complete_handler_t status_cb; ubus_notify_complete_handler_t complete_cb; uint32_t pending; uint32_t id[UBUS_MAX_NOTIFY_PEERS + 1]; }; struct ubus_auto_conn { struct ubus_context ctx; struct uloop_timeout timer; const char *path; ubus_connect_handler_t cb; };
2)接口函数
* 初始化client端context结构,并连接ubusd struct ubus_context *ubus_connect(const char *path) * 与ubus_connect()函数基本功能相同,但此函数在连接断开后会自动进行重连 void ubus_auto_connect(struct ubus_auto_conn *conn) * 注册新事件 int ubus_register_event_handler(struct ubus_context *ctx, struct ubus_event_handler *ev, const char *pattern) * 发出事件消息 int ubus_send_event(struct ubus_context *ctx, const char *id, struct blob_attr *data) * 向ubusd查询指定UBUS_ATTR_OBJPATH对应对象信息内容 * 内容通过输入回调函数ubus_lookup_handler_t由调用者自行处理 int ubus_lookup(struct ubus_context *ctx, const char *path, ubus_lookup_handler_t cb, void *priv) * 向ubusd查询指定UBUS_ATTR_OBJPATH对应的ID号 int ubus_lookup_id(struct ubus_context *ctx, const char *path, uint32_t *id)
* 向uloop注册fd
static inline void ubus_add_uloop(struct ubus_context *ctx)
{
uloop_fd_add(&ctx->sock, ULOOP_BLOCKING | ULOOP_READ);
}
3. libubus-obj
数据结构
struct ubus_object { struct avl_node avl; /** 关系到struct ubus_context的objects */ const char *name; /** UBUS_ATTR_OBJPATH */ uint32_t id; /** 由ubusd server分配的obj id */ const char *path; struct ubus_object_type *type; /** 第1次被订阅或最后1次补退订时被调用 */ ubus_state_handler_t subscribe_cb; bool has_subscribers; /** 此对象是否被订阅 */ const struct ubus_method *methods; /** 方法数组 */ int n_methods; /** 方法数组个数 */ }; struct ubus_object_type { const char *name; uint32_t id; /** 由ubusd server分配的obj type id */ const struct ubus_method *methods; /** 方法数组 */ int n_methods; /** 方法数组个数 */ }; struct ubus_method { const char *name; /** 方法名称 */ ubus_handler_t handler; /** 方法处理回调函数 */ unsigned long mask; /** 参数过滤掩码 */ const struct blobmsg_policy *policy; /** 参数过滤列表 */ int n_policy; /** 参数过滤列表个数 */ };
#define UBUS_OBJECT_TYPE(_name, _methods) \ { \ .name = _name, \ .id = 0, \ .n_methods = ARRAY_SIZE(_methods), \ .methods = _methods \ } #define __UBUS_METHOD_NOARG(_name, _handler) \ .name = _name, \ .handler = _handler #define __UBUS_METHOD(_name, _handler, _policy) \ __UBUS_METHOD_NOARG(_name, _handler), \ .policy = _policy, \ .n_policy = ARRAY_SIZE(_policy) #define UBUS_METHOD(_name, _handler, _policy) \ { __UBUS_METHOD(_name, _handler, _policy) } #define UBUS_METHOD_MASK(_name, _handler, _policy, _mask) \ { \ __UBUS_METHOD(_name, _handler, _policy),\ .mask = _mask \ } #define UBUS_METHOD_NOARG(_name, _handler) \ { __UBUS_METHOD_NOARG(_name, _handler) }
接口函数
* client端向ubusd server请求增加一个新object int ubus_add_object(struct ubus_context *ctx, struct ubus_object *obj) * client端向ubusd server请求删除一个object int ubus_remove_object(struct ubus_context *ctx, struct ubus_object *obj) * 处理收到与object相关报文 void __hidden ubus_process_obj_msg(struct ubus_context *ctx, struct ubus_msghdr *hdr) * 处理UBUS_MSG_INVOKE报文 static void ubus_process_invoke(struct ubus_context *ctx, struct ubus_msghdr *hdr, struct ubus_object *obj, struct blob_attr **attrbuf) * 处理UBUS_MSG_UNSUBSCRIBE报文 static void ubus_process_unsubscribe(struct ubus_context *ctx, struct ubus_msghdr *hdr, struct ubus_object *obj, struct blob_attr **attrbuf) * 处理UBUS_MSG_NOTIFY报文 static void ubus_process_notify(struct ubus_context *ctx, struct ubus_msghdr *hdr, struct ubus_object *obj, struct blob_attr **attrbuf)
4. 示例
1) 下面看下logd中ubus操作,ubos的logd注册了一个log对象,两个方法read和write。
static const struct ubus_method log_methods[] = { { .name = "read", .handler = read_log, .policy = &read_policy, .n_policy = 1 }, { .name = "write", .handler = write_log, .policy = &write_policy, .n_policy = 1 }, }; static struct ubus_object_type log_object_type = UBUS_OBJECT_TYPE("log", log_methods); static struct ubus_object log_object = { .name = "log", .type = &log_object_type, .methods = log_methods, .n_methods = ARRAY_SIZE(log_methods), };
static const struct blobmsg_policy read_policy = { .name = "lines", .type = BLOBMSG_TYPE_INT32 }; static const struct blobmsg_policy write_policy = { .name = "event", .type = BLOBMSG_TYPE_STRING };
看下两个方法的处理函数(根据policy解析blobmsg):
static int read_log(struct ubus_context *ctx, struct ubus_object *obj, struct ubus_request_data *req, const char *method, struct blob_attr *msg) { struct client *cl; struct blob_attr *tb; struct log_head *l; int count = 0; int fds[2]; int ret; if (msg) { // 解析blobmsg blobmsg_parse(&read_policy, 1, &tb, blob_data(msg), blob_len(msg)); if (tb) count = blobmsg_get_u32(tb); } // 具体业务处理 if (pipe(fds) == -1) { fprintf(stderr, "logd: failed to create pipe: %s\n", strerror(errno)); return -1; } ubus_request_set_fd(ctx, req, fds[0]); cl = calloc(1, sizeof(*cl)); cl->s.stream.notify_state = client_notify_state; cl->fd = fds[1]; ustream_fd_init(&cl->s, cl->fd); list_add(&cl->list, &clients); l = log_list(count, NULL); while ((!tb || count) && l) { blob_buf_init(&b, 0); blobmsg_add_string(&b, "msg", l->data); blobmsg_add_u32(&b, "id", l->id); blobmsg_add_u32(&b, "priority", l->priority); blobmsg_add_u32(&b, "source", l->source); blobmsg_add_u64(&b, "time", l->ts.tv_sec * 1000LL); l = log_list(count, l); ret = ustream_write(&cl->s.stream, (void *) b.head, blob_len(b.head) + sizeof(struct blob_attr), false); blob_buf_free(&b); if (ret < 0) break; } return 0; }
static int write_log(struct ubus_context *ctx, struct ubus_object *obj, struct ubus_request_data *req, const char *method, struct blob_attr *msg) { struct blob_attr *tb; char *event; if (msg) { //解析blobmsg blobmsg_parse(&write_policy, 1, &tb, blob_data(msg), blob_len(msg)); if (tb) { event = blobmsg_get_string(tb); log_add(event, strlen(event) + 1, SOURCE_SYSLOG); } } return 0; }
上层调度
static struct ubus_auto_conn conn;
uloop_init(); conn.cb = ubus_connect_handler; ubus_auto_connect(&conn);
uloop_run(); static void ubus_connect_handler(struct ubus_context *ctx) { int ret; ret = ubus_add_object(ctx, &log_object); if (ret) { fprintf(stderr, "Failed to add object: %s\n", ubus_strerror(ret)); exit(1); } fprintf(stderr, "log: connected to ubus\n"); }
logd是守护进程,永不退出,所以没必要remove object。
2) 客户端/服务器模式
/* ubus_invoke()的声明如下: int ubus_invoke(struct ubus_context *ctx, uint32_t obj, const char *method, struct blob_attr *msg, ubus_data_handler_t cb, void *priv, int timeout); 其中cb参数是消息回调函数,其函数类型定义为: typedef void (*ubus_data_handler_t)(struct ubus_request *req, int type, struct blob_attr *msg); 参数type是请求消息的类型,如UBUS_MSG_INVOKE,UBUS_MSG_DATA等。 参数msg存放从服务端得到的回复消息,struct blob_attr类型,同样用blobmsg_parse()来解析。 参数req保存了请求方的消息属性,其中req->priv即ubus_invoke()中的priv参数, 用这个参数可以零活的传递一些额外的数据。 */
// ser.c #include <stdio.h> #include <unistd.h> #include <libubox/uloop.h> #include <libubox/ustream.h> #include <libubox/utils.h> #include <libubox/blobmsg_json.h> #include <libubus.h> static int stu_no = 0; static char *ubus_socket = NULL; struct ubus_context *ctx = NULL; static struct blob_buf b; enum { STU_NO, __STU_MAX }; static const struct blobmsg_policy stu_policy[__STU_MAX] ={ [STU_NO] = {.name = "no", .type = BLOBMSG_TYPE_INT32 } }; static int stu_add(struct ubus_context *ctx, struct ubus_object *obj, struct ubus_request_data *req, const char *method, struct blob_attr *msg) { struct blob_attr *tb[__STU_MAX]; blobmsg_parse(stu_policy, ARRAY_SIZE(stu_policy), tb, blob_data(msg), blob_len(msg)); if(tb[STU_NO]) stu_no += blobmsg_get_u32(tb[STU_NO]); blob_buf_init(&b, 0); blobmsg_add_u32(&b, "no", stu_no); ubus_send_reply(ctx, req, b.head); return 0; } static int stu_sub(struct ubus_context *ctx, struct ubus_object *obj, struct ubus_request_data *req, const char *method, struct blob_attr *msg) { struct blob_attr *tb[__STU_MAX]; blobmsg_parse(stu_policy, ARRAY_SIZE(stu_policy), tb, blob_data(msg), blob_len(msg)); if(tb[STU_NO]) stu_no -= blobmsg_get_u32(tb[STU_NO]); blob_buf_init(&b, 0); blobmsg_add_u32(&b, "no", stu_no); ubus_send_reply(ctx, req, b.head); return 0; } static const struct ubus_method stu_methods[] = { /* { .name = "add", .handler = stu_add, .policy = stu_policy, .n_policy = 1 }, { .name = "sub", .handler = stu_sub, .policy = stu_policy, .n_policy = 1 } */ UBUS_METHOD("add", stu_add, stu_policy), UBUS_METHOD("sub", stu_sub, stu_policy), }; static struct ubus_object_type stu_object_type = UBUS_OBJECT_TYPE("stu", stu_methods); static struct ubus_object stu_object = { .name = "stu", .type = &stu_object_type, .methods = stu_methods, .n_methods = ARRAY_SIZE(stu_methods) }; static void ubus_add_fd(void) { ubus_add_uloop(ctx); #ifdef FD_CLOEXEC fcntl(ctx->sock.fd, F_SETFD, fcntl(ctx->sock.fd, F_GETFD) | FD_CLOEXEC); #endif } static void ubus_reconn_timer(struct uloop_timeout *timeout) { static struct uloop_timeout retry = { .cb = ubus_reconn_timer,}; int t = 2; if (ubus_reconnect(ctx, ubus_socket) != 0) { uloop_timeout_set(&retry, t * 1000); return; } ubus_add_fd(); } static void ubus_connection_lost(struct ubus_context *ctx) { ubus_reconn_timer(NULL); } int main(int argc, char **argv) { char ch; int ret = 0; while((ch = getopt(argc, argv, "s:"))!= -1){ switch(ch){ case 's': ubus_socket = optarg; break; default: /* ? */ break; } } uloop_init(); ctx = ubus_connect(ubus_socket); if(!ctx){ printf("ubus connect error.\n"); return -1; } ctx->connection_lost = ubus_connection_lost; ret = ubus_add_object(ctx, &stu_object); if(ret){ printf("Failed to add object to ubus:%s\n", ubus_strerror(ret)); return 0; } //ubus_add_uloop(ctx); ubus_add_fd(); uloop_run(); if(ctx) ubus_free(ctx); uloop_done(); return 0; }
#include <stdio.h> #include <unistd.h> #include <libubox/uloop.h> #include <libubox/ustream.h> #include <libubox/utils.h> #include <libubox/blobmsg_json.h> #include <libubus.h> static struct blob_buf b; static void receive_call_result_data(struct ubus_request *req, int type, struct blob_attr *msg) { char *str; if(!msg) return; str = blobmsg_format_json_indent(msg, true, 0); printf("%s\n", str); free(str); } static int client_main(struct ubus_context *ctx, int argc, char**argv) { uint32_t id; int ret; printf("argc =%d, argv[0] =%s\n", argc, argv[0]); if(argc != 3) return -2; blob_buf_init(&b, 0); if(!blobmsg_add_json_from_string(&b, argv[2])){ printf("Failed to parse message data\n"); return -1; } ret = ubus_lookup_id(ctx, argv[0], &id); if(ret) return ret; return ubus_invoke(ctx, id, argv[1], b.head, receive_call_result_data, NULL, 30*1000); } int main(int argc, char **argv) { struct ubus_context *ctx = NULL; char ch; char *ubus_socket = NULL; int ret = 0; while((ch = getopt(argc, argv, "s:"))!= -1){ switch(ch){ case 's': ubus_socket = optarg; break; default: /* ? */ break; } } argc -= optind; argv += optind; ctx = ubus_connect(ubus_socket); if(!ctx){ printf("ubus connect error.\n"); return -1; } ret = client_main(ctx, argc, argv); if(ret < 0) return ret; if(ctx) ubus_free(ctx); return 0; }
编译:
gcc cli.c -Wall -lubox -lubus -lblobmsg_json -o cli
gcc ser.c -Wall -lubox -lubus -lblobmsg_json -o ser
执行:
ubuntu:~/test/ubus/test$ sudo ./cli stu add '{"no":20}' argc =3, argv[0] =stu { "no": 20 } ubuntu:~/test/ubus/test$ sudo ./cli stu add '{"no":20}' argc =3, argv[0] =stu { "no": 40 } ubuntu:~/test/ubus/test$ sudo ./cli stu add '{"no":20}' argc =3, argv[0] =stu { "no": 60 }
参考文档: