服务器架设笔记——使用Apache插件解析简单请求

一般来说，对于一个请求，服务器都会对其进行解析，以确定请求的合法性以及行进的路径。于是本节将讲解如何获取请求的数据。（转载请指明出于breaksoftware的csdn博客）

我们使用《服务器架设笔记——编译Apache及其插件》一文中的方法创建一个Handler工程——get_request。该工程中，我们可以操作的入口函数是

static int get_request_handler(request_rec *r)
{r->content_type = "text/html";  

通过该入口函数，我们可以直接得到的数据就是request_rec结构体对象指针r。通过查阅源码，我们得到其定义

/*** @brief A structure that represents the current request*/
struct request_rec {/** The pool associated with the request */apr_pool_t *pool;/** The connection to the client */conn_rec *connection;/** The virtual host for this request */server_rec *server;/** Pointer to the redirected request if this is an external redirect */request_rec *next;/** Pointer to the previous request if this is an internal redirect */request_rec *prev;/** Pointer to the main request if this is a sub-request* (see http_request.h) */request_rec *main;/* Info about the request itself... we begin with stuff that only* protocol.c should ever touch...*//** First line of request */char *the_request;/** HTTP/0.9, "simple" request (e.g. GET /foo\n w/no headers) */int assbackwards;/** A proxy request (calculated during post_read_request/translate_name)*  possible values PROXYREQ_NONE, PROXYREQ_PROXY, PROXYREQ_REVERSE,*                  PROXYREQ_RESPONSE*/int proxyreq;/** HEAD request, as opposed to GET */int header_only;/** Protocol version number of protocol; 1.1 = 1001 */int proto_num;/** Protocol string, as given to us, or HTTP/0.9 */char *protocol;/** Host, as set by full URI or Host: */const char *hostname;/** Time when the request started */apr_time_t request_time;/** Status line, if set by script */const char *status_line;/** Status line */int status;/* Request method, two ways; also, protocol, etc..  Outside of protocol.c,* look, but don't touch.*//** M_GET, M_POST, etc. */int method_number;/** Request method (eg. GET, HEAD, POST, etc.) */const char *method;/***  'allowed' is a bitvector of the allowed methods.**  A handler must ensure that the request method is one that*  it is capable of handling.  Generally modules should DECLINE*  any request methods they do not handle.  Prior to aborting the*  handler like this the handler should set r->allowed to the list*  of methods that it is willing to handle.  This bitvector is used*  to construct the "Allow:" header required for OPTIONS requests,*  and HTTP_METHOD_NOT_ALLOWED and HTTP_NOT_IMPLEMENTED status codes.**  Since the default_handler deals with OPTIONS, all modules can*  usually decline to deal with OPTIONS.  TRACE is always allowed,*  modules don't need to set it explicitly.**  Since the default_handler will always handle a GET, a*  module which does *not* implement GET should probably return*  HTTP_METHOD_NOT_ALLOWED.  Unfortunately this means that a Script GET*  handler can't be installed by mod_actions.*/apr_int64_t allowed;/** Array of extension methods */apr_array_header_t *allowed_xmethods;/** List of allowed methods */ap_method_list_t *allowed_methods;/** byte count in stream is for body */apr_off_t sent_bodyct;/** body byte count, for easy access */apr_off_t bytes_sent;/** Last modified time of the requested resource */apr_time_t mtime;/* HTTP/1.1 connection-level features *//** The Range: header */const char *range;/** The "real" content length */apr_off_t clength;/** sending chunked transfer-coding */int chunked;/** Method for reading the request body* (eg. REQUEST_CHUNKED_ERROR, REQUEST_NO_BODY,*  REQUEST_CHUNKED_DECHUNK, etc...) */int read_body;/** reading chunked transfer-coding */int read_chunked;/** is client waiting for a 100 response? */unsigned expecting_100;/** The optional kept body of the request. */apr_bucket_brigade *kept_body;/** For ap_body_to_table(): parsed body *//* XXX: ap_body_to_table has been removed. Remove body_table too or* XXX: keep it to reintroduce ap_body_to_table without major bump? */apr_table_t *body_table;/** Remaining bytes left to read from the request body */apr_off_t remaining;/** Number of bytes that have been read  from the request body */apr_off_t read_length;/* MIME header environments, in and out.  Also, an array containing* environment variables to be passed to subprocesses, so people can* write modules to add to that environment.** The difference between headers_out and err_headers_out is that the* latter are printed even on error, and persist across internal redirects* (so the headers printed for ErrorDocument handlers will have them).** The 'notes' apr_table_t is for notes from one module to another, with no* other set purpose in mind...*//** MIME header environment from the request */apr_table_t *headers_in;/** MIME header environment for the response */apr_table_t *headers_out;/** MIME header environment for the response, printed even on errors and* persist across internal redirects */apr_table_t *err_headers_out;/** Array of environment variables to be used for sub processes */apr_table_t *subprocess_env;/** Notes from one module to another */apr_table_t *notes;/* content_type, handler, content_encoding, and all content_languages* MUST be lowercased strings.  They may be pointers to static strings;* they should not be modified in place.*//** The content-type for the current request */const char *content_type;   /* Break these out --- we dispatch on 'em *//** The handler string that we use to call a handler function */const char *handler;        /* What we *really* dispatch on *//** How to encode the data */const char *content_encoding;/** Array of strings representing the content languages */apr_array_header_t *content_languages;/** variant list validator (if negotiated) */char *vlist_validator;/** If an authentication check was made, this gets set to the user name. */char *user;/** If an authentication check was made, this gets set to the auth type. */char *ap_auth_type;/* What object is being requested (either directly, or via include* or content-negotiation mapping).*//** The URI without any parsing performed */char *unparsed_uri;/** The path portion of the URI, or "/" if no path provided */char *uri;/** The filename on disk corresponding to this response */char *filename;/* XXX: What does this mean? Please define "canonicalize" -aaron *//** The true filename, we canonicalize r->filename if these don't match */char *canonical_filename;/** The PATH_INFO extracted from this request */char *path_info;/** The QUERY_ARGS extracted from this request */char *args;/*** Flag for the handler to accept or reject path_info on* the current request.  All modules should respect the* AP_REQ_ACCEPT_PATH_INFO and AP_REQ_REJECT_PATH_INFO* values, while AP_REQ_DEFAULT_PATH_INFO indicates they* may follow existing conventions.  This is set to the* user's preference upon HOOK_VERY_FIRST of the fixups.*/int used_path_info;/** A flag to determine if the eos bucket has been sent yet */int eos_sent;/* Various other config info which may change with .htaccess files* These are config vectors, with one void* pointer for each module* (the thing pointed to being the module's business).*//** Options set in config files, etc. */struct ap_conf_vector_t *per_dir_config;/** Notes on *this* request */struct ap_conf_vector_t *request_config;/** Optional request log level configuration. Will usually point*  to a server or per_dir config, i.e. must be copied before*  modifying */const struct ap_logconf *log;/** Id to identify request in access and error log. Set when the first*  error log entry for this request is generated.*/const char *log_id;/*** A linked list of the .htaccess configuration directives* accessed by this request.* N.B. always add to the head of the list, _never_ to the end.* that way, a sub request's list can (temporarily) point to a parent's list*/const struct htaccess_result *htaccess;/** A list of output filters to be used for this request */struct ap_filter_t *output_filters;/** A list of input filters to be used for this request */struct ap_filter_t *input_filters;/** A list of protocol level output filters to be used for this*  request */struct ap_filter_t *proto_output_filters;/** A list of protocol level input filters to be used for this*  request */struct ap_filter_t *proto_input_filters;/** This response can not be cached */int no_cache;/** There is no local copy of this response */int no_local_copy;/** Mutex protect callbacks registered with ap_mpm_register_timed_callback* from being run before the original handler finishes running*/apr_thread_mutex_t *invoke_mtx;/** A struct containing the components of URI */apr_uri_t parsed_uri;/**  finfo.protection (st_mode) set to zero if no such file */apr_finfo_t finfo;/** remote address information from conn_rec, can be overridden if* necessary by a module.* This is the address that originated the request.*/apr_sockaddr_t *useragent_addr;char *useragent_ip;/** MIME trailer environment from the request */apr_table_t *trailers_in;/** MIME trailer environment from the response */apr_table_t *trailers_out;
};

这是个非常大的结构体，可谓是包罗万象。对于初学者来说，想完全弄明白各项是什么还是比较困难的。而我们的需求很简单，我们就列出我们可能需要关心的数据

    /** First line of request */char *the_request;

请求的第一行数据

    /** Protocol version number of protocol; 1.1 = 1001 */int proto_num;/** Protocol string, as given to us, or HTTP/0.9 */char *protocol;/** Host, as set by full URI or Host: */const char *hostname;

协议的版本和请求的类型

    /** Time when the request started */apr_time_t request_time;

请求的时间

    /** The URI without any parsing performed */char *unparsed_uri;/** The path portion of the URI, or "/" if no path provided */char *uri;/** The filename on disk corresponding to this response */char *filename;

未进行urldecode的URI、经过urldecode的URI和处理该请求的文件路径

    /** The PATH_INFO extracted from this request */char *path_info;/** The QUERY_ARGS extracted from this request */char *args;

请求中的路径和参数

    /** A struct containing the components of URI */apr_uri_t parsed_uri;

请求解析的详细结果

    char *useragent_ip;

请求来源的IP

/** MIME header environment from the request */apr_table_t *headers_in;

以table形式保存的http头信息

对于基础数据类型我们很容易编写出例程

	if (r->the_request) {ap_rprintf(r, "the request : %s\n", r->the_request);}else {ap_rprintf(r, "the request is NULL\n");}if (r->protocol) {ap_rprintf(r, "protocol : %s\n", r->protocol);}else {ap_rprintf(r, "protocol is NULL\n");}ap_rprintf(r, "proto_num is %d\n", r->proto_num);

而对于请求时间apr_time_t类型，我们可以参考《服务器架设笔记——Apache模块开发基础知识》中对模块的介绍。我们查看源码，可以编写出如下例程

static void print_time(request_rec* r) {if (!r) {ap_rprintf(r, "request_rec pointer is NULL\n");return;}char data_str[128] = {0};apr_status_t status = apr_ctime(data_str, r->request_time);if (APR_SUCCESS != status) {ap_rprintf(r, "apr_ctime error\n");	}else {ap_rprintf(r, "ctime\t:\t%s\n", data_str);}apr_time_exp_t exp_t;memset(&exp_t, 0, sizeof(exp_t));status = apr_time_exp_gmt(&exp_t, r->request_time);if (APR_SUCCESS != status) {ap_rprintf(r, "apr_time_exp_gmt error\n");}else {ap_rprintf(r, "exp time\t:\n");ap_rprintf(r, "\ttm_usec\t:\t%d\n", exp_t.tm_usec);ap_rprintf(r, "\ttm_sec\t:\t%d\n", exp_t.tm_sec);ap_rprintf(r, "\ttm_min\t:\t%d\n", exp_t.tm_min);ap_rprintf(r, "\ttm_hour\t:\t%d\n", exp_t.tm_hour);ap_rprintf(r, "\ttm_mday\t:\t%d\n", exp_t.tm_mday);ap_rprintf(r, "\ttm_mon\t:\t%d\n", exp_t.tm_mon);ap_rprintf(r, "\ttm_year\t:\t%d\n", exp_t.tm_year);ap_rprintf(r, "\ttm_wday\t:\t%d\n", exp_t.tm_wday);ap_rprintf(r, "\ttm_yday\t:\t%d\n", exp_t.tm_yday);ap_rprintf(r, "\ttm_isdst\t:\t%d\n", exp_t.tm_isdst);ap_rprintf(r, "\ttm_gmtoff\t:\t%d\n", exp_t.tm_gmtoff);}
}

其中apr_time_exp_t的定义在《apr_time.h》中。

/*** a structure similar to ANSI struct tm with the following differences:*  - tm_usec isn't an ANSI field*  - tm_gmtoff isn't an ANSI field (it's a BSDism)*/
struct apr_time_exp_t {/** microseconds past tm_sec */apr_int32_t tm_usec;/** (0-61) seconds past tm_min */apr_int32_t tm_sec;/** (0-59) minutes past tm_hour */apr_int32_t tm_min;/** (0-23) hours past midnight */apr_int32_t tm_hour;/** (1-31) day of the month */apr_int32_t tm_mday;/** (0-11) month of the year */apr_int32_t tm_mon;/** year since 1900 */apr_int32_t tm_year;/** (0-6) days since Sunday */apr_int32_t tm_wday;/** (0-365) days since January 1 */apr_int32_t tm_yday;/** daylight saving time */apr_int32_t tm_isdst;/** seconds east of UTC */apr_int32_t tm_gmtoff;
};

对于已分析过了的请求结构体apr_uri_t的例程也非常简单，我就不再列出来，只是把其结构体定义贴一下。大家一看就明白

/*** A structure to encompass all of the fields in a uri*/
struct apr_uri_t {/** scheme ("http"/"ftp"/...) */char *scheme;/** combined [user[:password]\@]host[:port] */char *hostinfo;/** user name, as in http://user:passwd\@host:port/ */char *user;/** password, as in http://user:passwd\@host:port/ */char *password;/** hostname from URI (or from Host: header) */char *hostname;/** port string (integer representation is in "port") */char *port_str;/** the request path (or NULL if only scheme://host was given) */char *path;/** Everything after a '?' in the path, if present */char *query;/** Trailing "#fragment" string, if present */char *fragment;/** structure returned from gethostbyname() */struct hostent *hostent;/** The port number, numeric, valid only if port_str != NULL */apr_port_t port;/** has the structure been initialized */unsigned is_initialized:1;/** has the DNS been looked up yet */unsigned dns_looked_up:1;/** has the dns been resolved yet */unsigned dns_resolved:1;
};

这些例程中麻烦的是对apr_table_t的解析。因为网上很难找到对该table的遍历代码，于是我只能参考apr_table_clone中代码得出如下

static void print_table(request_rec *r, const apr_table_t* t) {const apr_array_header_t* array = apr_table_elts(t);apr_table_entry_t* elts = (apr_table_entry_t*)array->elts;for (int i = 0; i < array->nelts; i++) {ap_rprintf(r, "\t%s : %s\n", elts[i].key, elts[i].val);}
}

我们请求一个URL：http://192.168.191.129/AP%26AC%3aHE?a=b#c

其返回如下

headers_in startHost : 192.168.191.129Connection : keep-aliveCache-Control : max-age=0Accept : text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8User-Agent : Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/28.0.1500.72 Safari/537.36Accept-Encoding : gzip,deflate,sdchAccept-Language : zh-CN,zh;q=0.8
headers_in endheaders_out start
headers_out endthe request : GET /AP%26AC%3aHE?a=b HTTP/1.1
protocol : HTTP/1.1
proto_num is 1001
method : GET
host name : 192.168.191.129
unparsed uri : /AP%26AC%3aHE?a=b
uri : /AP&AC:HE
filename : /usr/local/apache2/htdocs/AP&AC:HE
path info : 
args : a=b
user is NULL
log id is NULL
useragent ip : 192.168.191.1
ctime	:	Mon Feb 16 18:20:39 2015
exp time	:tm_usec	:	200039tm_sec	:	39tm_min	:	20tm_hour	:	10tm_mday	:	16tm_mon	:	1tm_year	:	115tm_wday	:	1tm_yday	:	46tm_isdst	:	0tm_gmtoff	:	0
scheme is NULL
hostinfo is NULL
user is NULL
password is NULL
hostname is NULL
port_str is NULL
path : /AP&AC:HE
query : a=b
fragment is NULL
The sample page from mod_get_request.c