基於OpenWrt添加ubus支持的示例分享

http://blog.csdn.net/hbl0307106015/article/details/48249585

寫作說明

• 發佈聲明： 本文發佈於2015年9月6日，內容爲原創，轉載請說明出處，多謝合作，Linux有GPL協議，那麼博客應用也類似，希望大家遵循“GPL”開源精神
• 平臺：OpenWrt 14.07 + 一臺路由器
• 需求：爲一個守護進程添加ubus支持，使之能夠使用ubus call來獲取相關信息
• 參考：netifd，ubus源碼（尤其是examples目錄下的示例）
• 思路：聽聞ubus有封裝好的API，那麼，一定有某些規則讓我們這些開發者去遵循，帶着這個問題去尋找答案，找到如何從零開始給守護進程添加ubus支持的方法。

……經過數日的努力和分析，以下是核心的實現步驟，授人以魚不如授人以漁，我這裏不會貼出完完全全的代碼，希望讀者能夠根據這些啓示，結合netifd和ubus的源碼，自己去領會……

方法介紹

• 第一步：初始化動作

<code class="language-c hljs  has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">    uloop_init(); <span class="hljs-comment" style="margin: 0px; padding: 0px; color: rgb(136, 0, 0); box-sizing: border-box;">// 初始化</span>

    ubus_path = path;
    ubus_ctx = ubus_connect(path);
    <span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!ubus_ctx) {
        <span class="hljs-built_in" style="margin: 0px; padding: 0px; color: rgb(102, 0, 102); box-sizing: border-box;">fprintf</span>(stderr, <span class="hljs-string" style="margin: 0px; padding: 0px; color: rgb(0, 136, 0); box-sizing: border-box;">"failed to connect to ubus\n"</span>);
        <span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">return</span> -EIO;
    }

    <span class="hljs-built_in" style="margin: 0px; padding: 0px; color: rgb(102, 0, 102); box-sizing: border-box;">fprintf</span>(stdout, <span class="hljs-string" style="margin: 0px; padding: 0px; color: rgb(0, 136, 0); box-sizing: border-box;">"connect as %08x\n"</span>, ubus_ctx->local_id);
    ubus_ctx->connection_lost = rp_ubus_connection_lost; <span class="hljs-comment" style="margin: 0px; padding: 0px; color: rgb(136, 0, 0); box-sizing: border-box;">//添加一個重連機制，可以省略的</span>
    rp_ubus_add_fd();

    rp_ubus_add_object(&sample_object);<span class="hljs-comment" style="margin: 0px; padding: 0px; color: rgb(136, 0, 0); box-sizing: border-box;">// 添加對象</span></code><ul class="pre-numbering" style="margin: 0px; padding: 6px 0px 40px; box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">1</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">2</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">3</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">4</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">5</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">6</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">7</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">8</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">9</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">10</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">11</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">12</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">13</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">14</li></ul>

• 第二步：具體業務邏輯相關

<code class="language-c hljs  has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">void</span>
rp_ubus_add_object(<span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">struct</span> ubus_object *obj)
{
    <span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">int</span> ret = ubus_add_object(ubus_ctx, obj);<span class="hljs-comment" style="margin: 0px; padding: 0px; color: rgb(136, 0, 0); box-sizing: border-box;">// 關鍵部分,添加對象</span>

    <span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (ret != <span class="hljs-number" style="margin: 0px; padding: 0px; color: rgb(0, 102, 102); box-sizing: border-box;">0</span>)
        <span class="hljs-built_in" style="margin: 0px; padding: 0px; color: rgb(102, 0, 102); box-sizing: border-box;">fprintf</span>(stderr, <span class="hljs-string" style="margin: 0px; padding: 0px; color: rgb(0, 136, 0); box-sizing: border-box;">"failed to publish object '%s' : %s\n"</span>, obj->name,  ubus_strerror(ret));
}

<span class="hljs-comment" style="margin: 0px; padding: 0px; color: rgb(136, 0, 0); box-sizing: border-box;">// 處理函數</span>
<span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">int</span>
rp_handle_hook_status(<span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">struct</span> ubus_context *ctx, <span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">struct</span> ubus_object *obj,
                     <span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">struct</span> ubus_request_data *req, <span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">const</span> <span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">char</span> *method,
                     <span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">struct</span> blob_attr *msg)
{
    <span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">int</span> ret = -<span class="hljs-number" style="margin: 0px; padding: 0px; color: rgb(0, 102, 102); box-sizing: border-box;">1</span>;

    blob_buf_init(&b, <span class="hljs-number" style="margin: 0px; padding: 0px; color: rgb(0, 102, 102); box-sizing: border-box;">0</span>);

    blobmsg_add_u32(&b, <span class="hljs-string" style="margin: 0px; padding: 0px; color: rgb(0, 136, 0); box-sizing: border-box;">"status"</span>, hs); <span class="hljs-comment" style="margin: 0px; padding: 0px; color: rgb(136, 0, 0); box-sizing: border-box;">/* hook status */</span>
    blobmsg_add_string(&b, <span class="hljs-string" style="margin: 0px; padding: 0px; color: rgb(0, 136, 0); box-sizing: border-box;">"account"</span>, usrname);

    ubus_send_reply(ctx, req, b.head);
    <span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-number" style="margin: 0px; padding: 0px; color: rgb(0, 102, 102); box-sizing: border-box;">0</span>;
}

<span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">struct</span> ubus_method hook_methods[] = {
    { .name = <span class="hljs-string" style="margin: 0px; padding: 0px; color: rgb(0, 136, 0); box-sizing: border-box;">"sample"</span>, .handler = rp_handle_hook_status },<span class="hljs-comment" style="margin: 0px; padding: 0px; color: rgb(136, 0, 0); box-sizing: border-box;">// 這是其中一種成員添加的模板,名字叫什麼，處理函數是誰，說清楚來，</span>
};

<span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">struct</span> ubus_object_type hook_object_type =
    UBUS_OBJECT_TYPE(<span class="hljs-string" style="margin: 0px; padding: 0px; color: rgb(0, 136, 0); box-sizing: border-box;">"package.sample"</span>, hook_methods);

<span class="hljs-comment" style="margin: 0px; padding: 0px; color: rgb(136, 0, 0); box-sizing: border-box;">// 這個結構體就是整個框架的縮影</span>
<span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="margin: 0px; padding: 0px; color: rgb(0, 0, 136); box-sizing: border-box;">struct</span> ubus_object hook_object = {
    .name = <span class="hljs-string" style="margin: 0px; padding: 0px; color: rgb(0, 136, 0); box-sizing: border-box;">"package.sample"</span>,
    .type = &hook_object_type,
    .methods = hook_methods,
    .n_methods = ARRAY_SIZE(hook_methods),
};</code><ul class="pre-numbering" style="margin: 0px; padding: 6px 0px 40px; box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">1</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">2</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">3</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">4</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">5</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">6</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">7</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">8</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">9</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">10</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">11</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">12</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">13</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">14</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">15</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">16</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">17</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">18</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">19</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">20</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">21</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">22</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">23</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">24</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">25</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">26</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">27</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">28</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">29</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">30</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">31</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">32</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">33</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">34</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">35</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">36</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">37</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">38</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">39</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">40</li></ul>

• 第三步：釋放對象動作

<code class="language-c hljs  has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">    ubus_free(ubus_ctx);
    uloop_done();</code><ul class="pre-numbering" style="margin: 0px; padding: 6px 0px 40px; box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">1</li><li style="margin: 0px; padding: 0px 5px; box-sizing: border-box;">2</li></ul>

依賴的庫

• libubus
• libubox
• libblobmsg_json

作者

[email protected]