Nginx中发送udp请求

╰半橙微兮° 2022-08-14 04:45 188阅读 0赞

http://blog.aka-cool.net/blog/2014/02/24/udp-in-nginx/

最近简单了解了一下Nginx发送udp请求的过程, 在这里简单记录一下.

主要参考的代码主要有两块, 分别是ngx\_resolver.c以及agentzh的ngx\_lua模块中的udp相关代码(ngx\_http\_lua\_socket\_udp.c). 有兴趣的同学可以看一下.

## 简单分析 ##

首先看一下ngx\_resolver.c这个文件, 主要解决了dns查询的问题, 也就是[resolver][]这个指令. 这个文件长度还是蛮长的, 大概有2000多行, 但是udp部分的代码还是相当简洁的, 主要分为几个步骤: 初始化, 连接, 发送以及回收.

初始化的代码:

ngx\_resolver.c

ngx_resolver_t *
    ngx_resolver_create(ngx_conf_t *cf, ngx_str_t *names, ngx_uint_t n)
    {
        ngx_str_t              s;
        ngx_url_t              u;
        ngx_uint_t             i, j;
        ngx_resolver_t        *r;
        ngx_pool_cleanup_t    *cln;
        ngx_udp_connection_t  *uc;
    
        /* 设置回收函数 */
    
        cln = ngx_pool_cleanup_add(cf->pool, 0);
        if (cln == NULL) {
            return NULL;
        }
    
        cln->handler = ngx_resolver_cleanup;
    
        r = ngx_calloc(sizeof(ngx_resolver_t), cf->log);
        if (r == NULL) {
            return NULL;
        }
    
        cln->data = r;
    
        /*
            省略很多代码, 初始化红黑树以及队列
        */
    
        for (i = 0; i < n; i++) {
            if (ngx_strncmp(names[i].data, "valid=", 6) == 0) {
                /*
                    省略valid参数的设置
                */
            }
    
            /* 进入正题 */
            ngx_memzero(&u, sizeof(ngx_url_t));
    
            u.url = names[i];
            u.default_port = 53;
    
            /* ngx_parse_url用于解析url, 获取ip, port, 地址等信息 */
    
            if (ngx_parse_url(cf->pool, &u) != NGX_OK) {
                if (u.err) {
                    ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                                       "%s in resolver \"%V\"",
                                       u.err, &u.url);
                }
    
                return NULL;
            }
    
            uc = ngx_array_push_n(&r->udp_connections, u.naddrs);
            if (uc == NULL) {
                return NULL;
            }
    
            /* 设置各个ngx_udp_connection_t */
    
            ngx_memzero(uc, u.naddrs * sizeof(ngx_udp_connection_t));
    
            for (j = 0; j < u.naddrs; j++) {
                /* 看上去只需要设置这几个值;) */
                uc[j].sockaddr = u.addrs[j].sockaddr;
                uc[j].socklen = u.addrs[j].socklen;
                uc[j].server = u.addrs[j].name;
            }
        }
    
        return r;
    }

这里主要就是根据配置文件来初始化`ngx_udp_connection_t`类型的变量. 接下来是连接和发送请求:

ngx\_resolver\_send\_query

static ngx_int_t
    ngx_resolver_send_query(ngx_resolver_t *r, ngx_resolver_node_t *rn)
    {
        ssize_t                n;
        ngx_udp_connection_t  *uc;
    
        uc = r->udp_connections.elts;
    
        uc = &uc[r->last_connection++];
        if (r->last_connection == r->udp_connections.nelts) {
            r->last_connection = 0;
        }
    
        if (uc->connection == NULL) {
    
            uc->log = *r->log;
            uc->log.handler = ngx_resolver_log_error;
            uc->log.data = uc;
            uc->log.action = "resolving";
    
            /* 进行连接 */
            if (ngx_udp_connect(uc) != NGX_OK) {
                return NGX_ERROR;
            }
    
            uc->connection->data = r;
            uc->connection->read->handler = ngx_resolver_read_response;
            uc->connection->read->resolver = 1;
        }
    
        /* 发送数据 */
        n = ngx_send(uc->connection, rn->query, rn->qlen);
    
        if (n == -1) {
            return NGX_ERROR;
        }
    
        if ((size_t) n != (size_t) rn->qlen) {
            ngx_log_error(NGX_LOG_CRIT, &uc->log, 0, "send() incomplete");
            return NGX_ERROR;
        }
    
        return NGX_OK;
    }

主要是使用了ngx\_udp\_connect和ngx\_send这两个函数. 用起来还是相当方便的, 里面的实现有兴趣的同学可以看一下. 最后就是关闭连接:

ngx\_resolver\_cleanup

static void
    ngx_resolver_cleanup(void *data)
    {
        ngx_resolver_t  *r = data;
    
        ngx_uint_t             i;
        ngx_udp_connection_t  *uc;
    
        if (r) {
            ngx_log_debug0(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0,
                           "cleanup resolver");
    
            ngx_resolver_cleanup_tree(r, &r->name_rbtree);
    
            ngx_resolver_cleanup_tree(r, &r->addr_rbtree);
    
            if (r->event) {
                ngx_free(r->event);
            }
    
    
            uc = r->udp_connections.elts;
    
            /* 关闭每一个建立的连接 */
            for (i = 0; i < r->udp_connections.nelts; i++) {
                if (uc[i].connection) {
                    ngx_close_connection(uc[i].connection);
                }
            }
    
            ngx_free(r);
        }
    }

主要是调用了ngx\_close\_connection这个函数. 通过以上操作就完成了一次udp数据的发送. ngx\_lua当中也基本是这个步骤.

总结下就是:

1.  初始化ngx\_udp\_connection\_t类型的变量(通常会用到ngx\_parse\_url)
2.  使用ngx\_udp\_connect进行连接
3.  使用ngx\_send进行数据发送
4.  关闭连接, 可以在数据回收的回调中进行关闭

## 自己写一个试试 ##

看明白了基本步骤, 自己验证一下, 写一个的对应的简单handler模块. 在配置文件中设置udp\_address来设置要发送的地址, nginx接受到请求之后即向这个地址发送信息.

ngx\_resolver\_cleanup

#include <ngx_config.h>
    #include <ngx_core.h>
    #include <ngx_http.h>
    
    #include "ddebug.h"
    
    typedef struct {
        ngx_flag_t  enable;
    
        ngx_udp_connection_t *play_udp_uc;
    } ngx_http_play_loc_conf_t;
    
    ngx_int_t ngx_udp_connect(ngx_udp_connection_t *uc);
    
    static void *ngx_http_play_create_loc_conf(ngx_conf_t *cf);
    
    static char *ngx_conf_play(ngx_conf_t *cf, ngx_command_t *cmd, void *conf);
    
    static void ngx_http_upstream_play_cleanup(void *data);
    
    static char *ngx_conf_set_udp_addr(ngx_conf_t *cf, ngx_command_t *cmd, void *conf);
    
    static ngx_int_t ngx_http_play_handler(ngx_http_request_t *r);
    
    
    static ngx_command_t ngx_http_play_commands[] = {
        {
            ngx_string("play"),
            NGX_HTTP_LOC_CONF | NGX_CONF_TAKE1,
            ngx_conf_play,
            NGX_HTTP_LOC_CONF_OFFSET,
            0,
            NULL
        },
        {
            ngx_string("udp_address"),
            NGX_HTTP_LOC_CONF | NGX_CONF_TAKE1,
            ngx_conf_set_udp_addr,
            NGX_HTTP_LOC_CONF_OFFSET,
            0,
            NULL
        },
        ngx_null_command
    };
    
    static ngx_http_module_t ngx_http_play_module_ctx = {
        NULL,                              /* preconfiguration */
        //ngx_http_play_init,              /* postconfiguration */
        NULL,                              /* postconfiguration */
    
        NULL,                              /* create main configuration */
        NULL,                              /* init main configuration */
    
        NULL,                              /* create server configuration */
        NULL,                              /* merge server configuration */
    
        ngx_http_play_create_loc_conf,     /* create location configuration */
        NULL                               /* merge location configuration */
    };
    
    ngx_module_t  ngx_http_play_module = {
        NGX_MODULE_V1,
        &ngx_http_play_module_ctx,                      /* module context */
        ngx_http_play_commands,                         /* module directives */
        NGX_HTTP_MODULE,                                /* module type */
        NULL,                                           /* init master */
        NULL,                                           /* init module */
        NULL,                                           /* init process */
        NULL,                                           /* init thread */
        NULL,                                           /* exit thread */
        NULL,                                           /* exit process */
        NULL,                                           /* exit master */
        NGX_MODULE_V1_PADDING
    };
    
    static char *
    ngx_conf_play(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
    {
        ngx_http_play_loc_conf_t *plcf;
        ngx_http_core_loc_conf_t *clcf;
        ngx_str_t                *value;
    
        clcf = ngx_http_conf_get_module_loc_conf(cf, ngx_http_core_module);
        plcf = conf;
    
        value = cf->args->elts;
    
        ngx_conf_log_error(NGX_LOG_INFO, cf, 0, "play: %s", value[1].data);
    
        plcf->enable = 0;
        if (ngx_strncmp(value[1].data, "on", 2) == 0) {
            clcf->handler = ngx_http_play_handler;
            plcf->enable  = 1;
        }
    
        return NGX_CONF_OK;
    }
    
    static char *
    ngx_conf_set_udp_addr(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
    {
        ngx_http_play_loc_conf_t   *plcf;
        ngx_str_t                  *value;
        ngx_url_t                   u;
        ngx_pool_cleanup_t         *cln;
        ngx_udp_connection_t       *uc;
    
        plcf = conf;
    
        ngx_memzero(&u, sizeof(ngx_url_t));
    
        value = cf->args->elts;
    
        /* resolve url */
        u.url          = value[1];
        u.default_port = 12345;
        u.no_resolve   = 0;
    
        if (ngx_parse_url(cf->pool, &u) != NGX_OK) {
            ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "parse udp addr failed, %s", value[1].data);
            return NGX_CONF_ERROR;
        }
    
        /* init udp connection */
        plcf->play_udp_uc = ngx_pcalloc(cf->pool, sizeof(ngx_udp_connection_t));
        uc                = plcf->play_udp_uc;
    
        if (uc == NULL) {
            return NGX_CONF_ERROR;
        }
    
        /* implement udp connection */
        uc->sockaddr = u.addrs[0].sockaddr;
        uc->socklen  = u.addrs[0].socklen;
        uc->server   = u.addrs[0].name;
        uc->log      = cf->cycle->new_log;
    
        /* implement clean handler */
        cln = ngx_pool_cleanup_add(cf->pool, 0);
        if (cln == NULL) {
            return NGX_CONF_ERROR;
        }
    
        cln->data    = uc;
        cln->handler = ngx_http_upstream_play_cleanup;   // set the cleanup handler
    
        return NGX_OK;
    }
    
    static void
    ngx_http_upstream_play_cleanup(void *data)
    {
        ngx_udp_connection_t  *uc = data;
    
        ngx_log_debug0(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0,
                       "cleanup http_upstream_keepalive_fluentd");
    
        if (uc->connection) {
            ngx_close_connection(uc->connection);
        }
    }
    
    static void ngx_http_play_dummy_handler(ngx_event_t *ev)
    {
        /* just empty */
    }
    
    
    static void
    ngx_http_play_send_udp(ngx_http_request_t *r, ngx_udp_connection_t *uc)
    {
        if (uc->connection == NULL) {
            if (ngx_udp_connect(uc) != NGX_OK) {
                return;
            }
    
            uc->connection->data = NULL;
            uc->connection->read->handler = ngx_http_play_dummy_handler;
            uc->connection->read->resolver = 1;
        }
    
        ngx_send(uc->connection, (u_char*)"hello", 5);
    
        return;
    }
    
    /* the main function */
    static ngx_int_t
    ngx_http_play_handler(ngx_http_request_t *r)
    {
        ngx_int_t    rc;
        ngx_buf_t   *b;
        ngx_chain_t  out;
        ngx_variable_value_t *var;
    
        ngx_http_play_loc_conf_t *plcf;
    
        plcf = ngx_http_get_module_loc_conf(r, ngx_http_play_module);
    
        /* here we go ;) */
        rc = ngx_http_discard_request_body(r);
        if (rc != NGX_OK) {
            return rc;
        }
    
        ngx_str_set(&r->headers_out.content_type, "text/html");
    
        b = ngx_pcalloc(r->pool, sizeof(ngx_buf_t));
        if (b == NULL) {
            return NGX_HTTP_INTERNAL_SERVER_ERROR;
        }
    
        out.buf  = b;
        out.next = NULL;
    
        /*
         *
         * I want to change here ;)
         *
         * */
    
        ngx_http_play_send_udp(r, plcf->play_udp_uc);
    
        b->pos  = (u_char *)"send";
        b->last = b->pos + 4;
    
    
        ///
    
        b->memory   = 1;
        b->last_buf = 1;
    
        r->headers_out.status = NGX_HTTP_OK;
        //r->headers_out.content_length_n = var.len;
    
        rc = ngx_http_send_header(r);
        return ngx_http_output_filter(r, &out);
    }
    
    
    static void *
    ngx_http_play_create_loc_conf(ngx_conf_t *cf)
    {
        ngx_http_play_loc_conf_t *plcf =  NULL;
    
        plcf = ngx_pcalloc(cf->pool, sizeof(ngx_http_play_loc_conf_t));
    
        if (plcf == NULL) {
            return NULL;
        }
    
        return plcf;
    }

使用nc监听一下发现可以成功~

[resolver]: http://nginx.org/en/docs/http/ngx_http_core_module.html#resolver