2023-09-05 04:00:26 -04:00
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ICMP 回显
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===========
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:link_to_translation:`en:[English]`
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概述
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----
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网际控制报文协议 (ICMP) 通常用于诊断或控制目的，或响应 IP 操作中的错误。常用的网络工具 ``ping`` 的应答，即 ``Echo Reply``，就是基于类型字段值为 0 的 ICMP 数据包实现的。
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在 ping 会话中，首先由源主机发出请求包 (ICMP echo request)，然后等待应答包 (ICMP echo reply)，等待具有超时限制。通过这一过程，还能测量出信息的往返用时。收到有效的应答包后，源主机会生成 IP 链路层的统计数据（如失包率、运行时间等）。
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IoT 设备通常需要检查远程服务器是否可用。如果服务器离线，设备应向用户发出警告。通过创建 ping 会话，定期发送或解析 ICMP echo 数据包，就能实现这一功能。
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为简化这一过程方便用户操作，ESP-IDF 提供了一些好用的 API。
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创建 ping 会话
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^^^^^^^^^^^^^^^^^^^^^^^^^^^
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要创建 ping 会话，首先需填写 ``esp_ping_config_t``，指定目标芯片 IP 地址、间隔时间等配置。此外，还可以通过 ``esp_ping_callbacks_t`` 注册回调函数。
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创建 ping 会话并注册回调函数示例：
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.. code-block:: c
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static void test_on_ping_success(esp_ping_handle_t hdl, void *args)
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{
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// optionally, get callback arguments
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// const char* str = (const char*) args;
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// printf("%s\r\n", str); // "foo"
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uint8_t ttl;
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uint16_t seqno;
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uint32_t elapsed_time, recv_len;
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ip_addr_t target_addr;
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esp_ping_get_profile(hdl, ESP_PING_PROF_SEQNO, &seqno, sizeof(seqno));
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esp_ping_get_profile(hdl, ESP_PING_PROF_TTL, &ttl, sizeof(ttl));
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esp_ping_get_profile(hdl, ESP_PING_PROF_IPADDR, &target_addr, sizeof(target_addr));
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esp_ping_get_profile(hdl, ESP_PING_PROF_SIZE, &recv_len, sizeof(recv_len));
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esp_ping_get_profile(hdl, ESP_PING_PROF_TIMEGAP, &elapsed_time, sizeof(elapsed_time));
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printf("%d bytes from %s icmp_seq=%d ttl=%d time=%d ms\n",
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recv_len, inet_ntoa(target_addr.u_addr.ip4), seqno, ttl, elapsed_time);
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}
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static void test_on_ping_timeout(esp_ping_handle_t hdl, void *args)
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{
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uint16_t seqno;
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ip_addr_t target_addr;
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esp_ping_get_profile(hdl, ESP_PING_PROF_SEQNO, &seqno, sizeof(seqno));
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esp_ping_get_profile(hdl, ESP_PING_PROF_IPADDR, &target_addr, sizeof(target_addr));
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printf("From %s icmp_seq=%d timeout\n", inet_ntoa(target_addr.u_addr.ip4), seqno);
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}
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static void test_on_ping_end(esp_ping_handle_t hdl, void *args)
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{
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uint32_t transmitted;
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uint32_t received;
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uint32_t total_time_ms;
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esp_ping_get_profile(hdl, ESP_PING_PROF_REQUEST, &transmitted, sizeof(transmitted));
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esp_ping_get_profile(hdl, ESP_PING_PROF_REPLY, &received, sizeof(received));
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esp_ping_get_profile(hdl, ESP_PING_PROF_DURATION, &total_time_ms, sizeof(total_time_ms));
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printf("%d packets transmitted, %d received, time %dms\n", transmitted, received, total_time_ms);
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}
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void initialize_ping()
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{
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/* convert URL to IP address */
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ip_addr_t target_addr;
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struct addrinfo hint;
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struct addrinfo *res = NULL;
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memset(&hint, 0, sizeof(hint));
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memset(&target_addr, 0, sizeof(target_addr));
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getaddrinfo("www.espressif.com", NULL, &hint, &res);
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struct in_addr addr4 = ((struct sockaddr_in *) (res->ai_addr))->sin_addr;
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inet_addr_to_ip4addr(ip_2_ip4(&target_addr), &addr4);
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freeaddrinfo(res);
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esp_ping_config_t ping_config = ESP_PING_DEFAULT_CONFIG();
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ping_config.target_addr = target_addr; // target IP address
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ping_config.count = ESP_PING_COUNT_INFINITE; // ping in infinite mode, esp_ping_stop can stop it
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/* set callback functions */
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esp_ping_callbacks_t cbs;
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cbs.on_ping_success = test_on_ping_success;
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cbs.on_ping_timeout = test_on_ping_timeout;
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cbs.on_ping_end = test_on_ping_end;
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cbs.cb_args = "foo"; // arguments that will feed to all callback functions, can be NULL
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cbs.cb_args = eth_event_group;
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esp_ping_handle_t ping;
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esp_ping_new_session(&ping_config, &cbs, &ping);
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}
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启动和停止 ping 会话
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^^^^^^^^^^^^^^^^^^^^^^^^^^
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使用 ``esp_ping_new_session`` 返回的句柄可以启动或停止 ping 会话。注意，ping 会话在创建后不会自动启动。如果 ping 会话停止后重启，ICMP 数据包的序列号会归零重新计数。
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删除 ping 会话
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^^^^^^^^^^^^^^^^^^^
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如果不再使用 ping 会话，可用 ``esp_ping_delete_session`` 将其删除。在删除 ping 会话时，确保该会话已处于停止状态（即已调用了 ``esp_ping_stop`` ，或该会话已完成所有步骤）。
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获取运行时间数据
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^^^^^^^^^^^^^^^^^^
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在回调函数中调用 ``esp_ping_get_profile``，可获取 ping 会话的不同运行时间数据，如上文代码示例所示。
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应用示例
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----------
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ICMP echo 示例： :example:`protocols/icmp_echo`
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API 参考
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--------------
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2024-01-19 01:40:33 -05:00
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.. include-build-file:: inc/ping_sock.inc
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