'In-depth understanding of Nginx' notes: ngx_mail related structures

Nginx mail related module structure

ngx_mail_module_t

This is the abstract interface of the mail module, that is, the mail module-specific interface pointed to by the ctx member in ngx_module_t. Each mail module implements its own ngx_mail_module_t structure.

<code><span>typedef</span><span>struct</span> {
     <span>// POP3 STMP IMAP邮件模块提取出的通用接口</span>
    ngx_mail_protocol_t        *protocol;

     <span>// 用于创建main级别配置项的结构体</span><span>void</span>                       *(*create_main_conf)(ngx_conf_t *cf);

    <span>// 解析完main级别配置项后被回调的函数</span><span>char</span>                       *(*init_main_conf)(ngx_conf_t *cf, <span>void</span> *conf);

     <span>// 用于创建srv级别配置项的结构体</span><span>void</span>                       *(*create_srv_conf)(ngx_conf_t *cf);

    <span>// 根据具体模块处理srv下和main下同名的配置项</span><span>char</span>                       *(*merge_srv_conf)(ngx_conf_t *cf, <span>void</span> *prev,
                                      <span>void</span> *conf);
} ngx_mail_module_t;</code>

ngx_protocol_s

<code><span>typedef</span><span>struct</span> ngx_mail_protocol_s ngx_mail_protocol_t;

<span>// 四个POP3 SMTP IMAP等应用级别的邮件模块所需要实现的接口方法</span><span>typedef</span><span>void</span> (*ngx_mail_init_session_pt)(ngx_mail_session_t *s,
    ngx_connection_t *c);
<span>typedef</span><span>void</span> (*ngx_mail_init_protocol_pt)(ngx_event_t *rev);
<span>typedef</span><span>void</span> (*ngx_mail_auth_state_pt)(ngx_event_t *rev);
<span>typedef</span> ngx_int_t (*ngx_mail_parse_command_pt)(ngx_mail_session_t *s);


<span>struct</span> ngx_mail_protocol_s {
     <span>// 邮件模块名称</span>
    ngx_str_t                   name;

    <span>// 当前邮件模块中所要监听的最常用4个端口</span>
    in_port_t                   port[<span>4</span>];

    <span>// 邮件模块类型</span>
    ngx_uint_t                  type;

     <span>// 与客户端建立起TCP连接后的初始化方法</span>
    ngx_mail_init_session_pt    init_session;

    <span>// 接收、解析客户端请求的方法</span>
    ngx_mail_init_protocol_pt   init_protocol;

    <span>// 解析客户端邮件协议的接口方法</span>
    ngx_mail_parse_command_pt   parse_command;
    ngx_mail_auth_state_pt      auth_state;

     <span>// 当处理中没有遇到错误时，返回internal_server_error指定的响应给客户端</span>
    ngx_str_t                   internal_server_error;
    ngx_str_t                   cert_error;
    ngx_str_t                   no_cert;
};</code>

ngx_mail_session_t

After Nginx establishes a TCP connection with the client, it will call back the ngx_mail_init_connection function to initialize the email protocol. At this time, a core structure similar to ngx_http_request_t in HTTP requests will be created: ngx_mail_session_s.

<code><span>typedef</span><span>struct</span> {
    uint32_t                signature;         <span>/* "MAIL" */</span><span>// 下游客户端和Nginx之间的连接</span>
    ngx_connection_t       *connection;

     <span>// 可存需要向下游客户端发送的内容</span>
    ngx_str_t               out;

    <span>// 用于接收来自客户端的请求</span>
    ngx_buf_t              *buffer;

     <span>// 指向一个指针数组，保存着这个请求中各个邮件模块的上下文建构体指针</span><span>void</span>                  **ctx;

    <span>// main级别配置结构体组成的指针数组</span><span>void</span>                  **main_conf;

    <span>// srv级别配置结构体组成的指针数组</span><span>void</span>                  **srv_conf;

     <span>// 解析主机域名</span>
    ngx_resolver_ctx_t     *resolver_ctx;

     <span>// proxy上下文，用于Nginx双向透传客户端与邮件服务器间的通信</span>
    ngx_mail_proxy_ctx_t   *proxy;

     <span>// 表示与邮件服务器交互时，当前处于哪种状态</span>
    ngx_uint_t              mail_state;

     <span>// 邮件协议类型</span><span>unsigned</span>                protocol:<span>3</span>;

    <span>// 1：表示当前读或写操作需要被阻塞</span><span>unsigned</span>                blocked:<span>1</span>;

    <span>// 1：请求需要结束</span><span>unsigned</span>                quit:<span>1</span>;

    <span>// 一下三个标志位仅在解析具体邮件协议时由邮件框架使用</span><span>unsigned</span>                quoted:<span>1</span>;
    <span>unsigned</span>                backslash:<span>1</span>;
    <span>unsigned</span>                no_sync_literal:<span>1</span>;

    <span>// 当使用SSL协议时才有意义</span><span>unsigned</span>                starttls:<span>1</span>;
    <span>unsigned</span>                esmtp:<span>1</span>;

    <span>// 表示与认证服务器交互时的记录认证方式</span><span>unsigned</span>                auth_method:<span>3</span>;

    <span>// 1：表示认证服务器要求暂缓接收响应，Nginx会继续等待认证服务器的后续响应</span><span>unsigned</span>                auth_wait:<span>1</span>;

     <span>// 验证时的用户名</span>
    ngx_str_t               login;

    <span>// 验证时的密码</span>
    ngx_str_t               passwd;

     <span>// 作为Auth-Salt验证的信息</span>
    ngx_str_t               salt;

    <span>// 一下三个成员仅用于IMAP通信</span>
    ngx_str_t               tag;
    ngx_str_t               tagged_line;
    ngx_str_t               text;

     <span>// 当前连接上对应的Nginx服务器地址</span>
    ngx_str_t              *addr_text;

    <span>// 主机地址</span>
    ngx_str_t               host;

    <span>//一下四个成员仅用于SMTP通信</span>
    ngx_str_t               smtp_helo;
    ngx_str_t               smtp_from;
    ngx_str_t               smtp_to;

    ngx_str_t               cmd;

     <span>// 在于邮件服务器交互时，表示解析自邮件服务器的消息类型</span>
    ngx_uint_t              command;

    <span>// 存放来自下游客户端的邮件协议中的参数</span>
    ngx_array_t             args;

     <span>// 当前请求尝试访问服务器验证的次数</span>
    ngx_uint_t              login_attempt;

    <span>/* used to parse POP3/IMAP/SMTP command */</span>    ngx_uint_t              state;
    u_char                 *cmd_start;
    u_char                 *arg_start;
    u_char                 *arg_end;
    ngx_uint_t              literal_len;
} ngx_mail_session_t;</code>

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