mongoose httpserver浅析

文章目录

前言
一、结构体及其功能
二、函数
- - MG_LOG
  - mg_http_listen
  - mg_mgr_poll
question
参考链接

前言

mongoose是一款基于C/C++的网络库，可以实现TCP, UDP, HTTP, WebSocket, MQTT通讯。mongoose是的嵌入式网络程序更快、健壮，易于实现。

mongoose只有mongoose.c和mongoose.h两个文件，其它的例子基本是基于这两个文件加上对应的xxx.c文件。mongoose.ws/documentation/介绍了mongoose.h文件中的API。

它通过单向链表维护所有连接的client对象，其数据结构不是线程安全的。在httserver中，该程序是单线成的通过epoll模式处理连接，因此比较适合嵌入式等硬件资源有限的条件，在不修改源码的情况下并发性能受限。

一、结构体及其功能

struct mg_mgr
struct mg_mgr为时间管理结构体，保存一系列的链接
conns指向单向链表的头部，每有新的链接都LIST_ADD_HEAD

struct mg_mgr {struct mg_connection *conns;  // 每个连接都是一个struct mg_connection，指向连接组成的单向链表的头部struct mg_dns dns4;           // DNS for IPv4struct mg_dns dns6;           // DNS for IPv6int dnstimeout;               // DNS resolve timeout in millisecondsbool use_dns6;                // Use DNS6 server by default, see #1532unsigned long nextid;         // Next connection ID，该数字逐渐增大，不会减小 ？unsigned long timerid;        // Next timer IDvoid *userdata;               // Arbitrary user data pointervoid *tls_ctx;                // TLS context shared by all TLS sessionsuint16_t mqtt_id;             // MQTT IDs for pub/subvoid *active_dns_requests;    // DNS requests in progressstruct mg_timer *timers;      // Active timersint epoll_fd;                 // Used when MG_EPOLL_ENABLE=1void *priv;                   // Used by the MIP stacksize_t extraconnsize;         // Used by the MIP stackMG_SOCKET_TYPE pipe;          // Socketpair end for mg_wakeup()
#if MG_ENABLE_FREERTOS_TCPSocketSet_t ss;  // NOTE(lsm): referenced from socket struct
#endif
};

struct mg_connection
每次调用accept函数获得一个有效的fd时都新建一个该对象并将其加入单向链表中，保存了连接的client的相关信息

struct mg_connection {struct mg_connection *next;  // 指向下一个clientstruct mg_mgr *mgr;          // Our containerstruct mg_addr loc;          // host地址信息struct mg_addr rem;          // client地址信息void *fd;                    // Connected socket, or LWIP dataunsigned long id;            // Auto-incrementing unique connection ID，给client的唯一id，但不一定连续不知道有什么含义struct mg_iobuf recv;        // Incoming datastruct mg_iobuf send;        // Outgoing datastruct mg_iobuf prof;        // Profile data enabled by MG_ENABLE_PROFILEstruct mg_iobuf rtls;        // TLS only. Incoming encrypted datamg_event_handler_t fn;       // User-specified event handler function,在main中，cbvoid *fn_data;               // User-specified function parametermg_event_handler_t pfn;      // Protocol-specific handler function，处理协议的函数，如http_cbvoid *pfn_data;              // Protocol-specific function parameterchar data[MG_DATA_SIZE];     // Arbitrary connection datavoid *tls;                   // TLS specific data// 位域，下面这么多总共占4个字节unsigned is_listening : 1;   // Listening connection, 是否为监听fdunsigned is_client : 1;      // Outbound (client) connection  mongoose作为client程序时会用到unsigned is_accepted : 1;    // Accepted (server) connection  接受来自client的链接时设为1（在accept_conn处）// 在http server中并 监听描述符以及client描述符都是非阻塞的unsigned is_resolving : 1;   // Non-blocking DNS resolution is in progressunsigned is_arplooking : 1;  // Non-blocking ARP resolution is in progressunsigned is_connecting : 1;  // Non-blocking connect is in progressunsigned is_tls : 1;         // TLS-enabled connectionunsigned is_tls_hs : 1;      // TLS handshake is in progressunsigned is_udp : 1;         // UDP connectionunsigned is_websocket : 1;   // WebSocket connectionunsigned is_mqtt5 : 1;       // For MQTT connection, v5 indicatorunsigned is_hexdumping : 1;  // Hexdump in/out trafficunsigned is_draining : 1;    // Send remaining data, then close and freeunsigned is_closing : 1;     // Close and free the connection immediatelyunsigned is_full : 1;        // Stop reads, until clearedunsigned is_resp : 1;        // Response is still being generated，生在生成c->sendunsigned is_readable : 1;    // Connection is ready to readunsigned is_writable : 1;    // Connection is ready to write
};

struct mg_http_message
存储解析后的http信息

struct mg_str {const char *ptr;  // Pointer to string datasize_t len;       // String len
};struct mg_http_header {struct mg_str name;   // Header namestruct mg_str value;  // Header value
};struct mg_http_message {struct mg_str method, uri, query, proto;             // Request/response linestruct mg_http_header headers[MG_MAX_HTTP_HEADERS];  // Headers  MG_MAX_HTTP_HEADERS=30struct mg_str body;                                  // Bodystruct mg_str head;                                  // Request + headersstruct mg_str message;  // Request + headers + body
};

在这里插入图片描述

二、函数

MG_LOG

默认log级别为MG_LL_INFO=2

#define MG_ERROR(args) MG_LOG(MG_LL_ERROR, args)
#define MG_INFO(args) MG_LOG(MG_LL_INFO, args)
#define MG_DEBUG(args) MG_LOG(MG_LL_DEBUG, args)
#define MG_VERBOSE(args) MG_LOG(MG_LL_VERBOSE, args)#define MG_LOG(level, args)                                 \do {                                                      \if ((level) <= mg_log_level) {                          \mg_log_prefix((level), __FILE__, __LINE__, __func__); \mg_log args;                                          \}                                                       \} while (0)
// log的前缀
void mg_log_prefix(int level, const char *file, int line, const char *fname) {const char *p = strrchr(file, '/');char buf[41];size_t n;if (p == NULL) p = strrchr(file, '\\');n = mg_snprintf(buf, sizeof(buf), "%-6llx %d %s:%d:%s", mg_millis(), level,p == NULL ? file : p + 1, line, fname);if (n > sizeof(buf) - 2) n = sizeof(buf) - 2;while (n < sizeof(buf)) buf[n++] = ' ';logs(buf, n - 1);
}
// 打印内容
void mg_log(const char *fmt, ...) {va_list ap;va_start(ap, fmt);mg_vxprintf(s_log_func, s_log_func_param, fmt, &ap);va_end(ap);logs("\r\n", 2);
}

mg_http_listen

struct mg_connection *mg_http_listen(struct mg_mgr *mgr, const char *url,mg_event_handler_t fn, void *fn_data)

该函数精简后类似于：

if ( (fd = socket(af, type, proto)) == -1 ) {MG_ERROR(("socket: %d", MG_SOCK_ERR(-1)));
} else if ((rc = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (char *) &on, sizeof(on))) != 0) {MG_ERROR(("setsockopt(SO_REUSEADDR): %d", MG_SOCK_ERR(rc)));
} else if ((rc = bind(fd, &usa.sa, slen)) != 0) {MG_ERROR(("bind: %d", MG_SOCK_ERR(rc)));
} else if ( (rc = listen(fd, 128)) != 0 ) {MG_ERROR(("listen: %d", MG_SOCK_ERR(rc)));
} else {// 这里考虑到了是否有ipv6所以掉了个函数处理setlocaddr(fd, &c->loc);  // 将host地址写入监听描述符对应的struct mg_connection中mg_set_non_blocking_mode(fd);  // 设置描述符的O_NONBLOCK以及FD_CLOEXECc->fd = S2PTR(fd);MG_EPOLL_ADD(c);  // 加入epollsuccess = true;
}
设置监听描述符对应的结构体并将其加入mgr的conns链表

MG_EPOLL_X宏
水平触发模式

#define MG_EPOLL_ADD(c)                                                    \do {                                                                     \struct epoll_event ev = {EPOLLIN | EPOLLERR | EPOLLHUP, {c}};          \epoll_ctl(c->mgr->epoll_fd, EPOLL_CTL_ADD, (int) (size_t) c->fd, &ev); \} while (0)
#define MG_EPOLL_MOD(c, wr)                                                \do {                                                                     \struct epoll_event ev = {EPOLLIN | EPOLLERR | EPOLLHUP, {c}};          \if (wr) ev.events |= EPOLLOUT;                                         \epoll_ctl(c->mgr->epoll_fd, EPOLL_CTL_MOD, (int) (size_t) c->fd, &ev); \} while (0)

mg_mgr_poll

man函数最终会进入while (s_signo == 0) mg_mgr_poll(&mgr, 1000); 死循环中

在1000并发量时测试点：

max有多大
n = epoll_wait有多大
链表的大小是多少，其中有效的有多少个，无效的有多少个
最大文件描述符的值是多少

void mg_mgr_poll(struct mg_mgr *mgr, int ms) {struct mg_connection *c, *tmp;
// 获取epoll通知(epoll_wait)，设置对应mg_connection的标志位mg_iotest(mgr, ms);// 遍历单向链表for (c = mgr->conns; c != NULL; c = tmp) {tmp = c->next;if (c->is_resolving || c->is_closing) {// Do nothing} else if (c->is_listening && c->is_udp == 0) {if (c->is_readable) accept_conn(mgr, c);} else if (c->is_connecting) {  // http server中这里几乎一直处于0if (c->is_readable || c->is_writable) connect_conn(c);} else {if (c->is_readable) read_conn(c);if (c->is_writable) write_conn(c);}if (c->is_draining && c->send.len == 0) c->is_closing = 1;if (c->is_closing) close_conn(c);}
}static void mg_iotest(struct mg_mgr *mgr, int ms) {size_t max = 1;for (struct mg_connection *c = mgr->conns; c != NULL; c = c->next) {c->is_readable = c->is_writable = 0;if (c->rtls.len > 0) ms = 1, c->is_readable = 1;if (can_write(c)) MG_EPOLL_MOD(c, 1);  // 只要c->send.len > 0就触发EPOLLOUTif (c->is_closing) ms = 1;max++;}struct epoll_event *evs = (struct epoll_event *) alloca(max * sizeof(evs[0]));int n = epoll_wait(mgr->epoll_fd, evs, (int) max, ms);for (int i = 0; i < n; i++) {struct mg_connection *c = (struct mg_connection *) evs[i].data.ptr;if (evs[i].events & EPOLLERR) {mg_error(c, "socket error");  // 当c->send.len的大小和http报文的Content-Length大小不对应时会导致EPOLLERR，原因未知} else if (c->is_readable == 0) {bool rd = evs[i].events & (EPOLLIN | EPOLLHUP);bool wr = evs[i].events & EPOLLOUT;c->is_readable = can_read(c) && rd ? 1U : 0;c->is_writable = can_write(c) && wr ? 1U : 0;if (c->rtls.len > 0) c->is_readable = 1;}}
}

在一个mg_mgr_poll循环中受限通过mg_iotest将对应事件的标志位进行设置is_readable，is_writable，再通过循环即标志位处理对应事件

accept_conn函数通过accept获取client fd然后对其结构体和fd进行设置

static void accept_conn(struct mg_mgr *mgr, struct mg_connection *lsn) {struct mg_connection *c = NULL;union usa usa; socklen_t sa_len = sizeof(usa);int fd = accept(FD(lsn), &usa->sa, &sa_len);if (fd < 0) {MG_ERROR(("%lu accept failed, errno %d", lsn->id, MG_SOCK_ERR(-1)));} else if ((c = mg_alloc_conn(mgr)) == NULL) {MG_ERROR(("%lu OOM", lsn->id));close(fd);} else {tomgaddr(&usa, &c->rem, sa_len != sizeof(usa.sin));  // 将remote地址写入c->remLIST_ADD_HEAD(struct mg_connection, &mgr->conns, c);c->fd = S2PTR(fd);MG_EPOLL_ADD(c);mg_set_non_blocking_mode(FD(c));  // 设置描述符的O_NONBLOCK以及FD_CLOEXECsetsockopts(c);                   // setsockoptc->is_accepted = 1;c->is_hexdumping = lsn->is_hexdumping;c->loc = lsn->loc;c->pfn = lsn->pfn;c->pfn_data = lsn->pfn_data;c->fn = lsn->fn;c->fn_data = lsn->fn_data;MG_DEBUG(("%lu %ld accepted %M -> %M", c->id, c->fd, mg_print_ip_port,&c->rem, mg_print_ip_port, &c->loc));// http server 下无事发生mg_call(c, MG_EV_OPEN, NULL);mg_call(c, MG_EV_ACCEPT, NULL);}
}

read_conn函数非阻塞读到c->recv.buf中，然后交由iolog处理。iolog会判断n的返回值。if EINPROGRESS || EWOULDBLOCK则什么也不做；elif<=0则设is_closing = 1，随后会TODO:；elif n>0 则调用mg_call(c, MG_EV_READ, &n)，它通过函数指针调用http_cb函数解析http协议。
static void http_cb(struct mg_connection *c, int ev=待处理事件(该函数只处理MG_EV_READ，MG_EV_CLOSE), void *ev_data=未使用)函数会解析c->recv.buf中的http协议(解析字符)，之后f (c->is_accepted) c->is_resp = 1;调用mg_call(c, MG_EV_HTTP_MSG, &hm);将http解析结果交由cb函数进行处理该函数会写c->send.buf, return; 然后清除c->recv，http_cb return。
iolog(c, buf, n, true);返回后read_conn结束。

n = recv(FD(c), (char *) buf, len, MSG_NONBLOCKING);static void read_conn(struct mg_connection *c) {if (ioalloc(c, &c->recv)) {char *buf = (char *) &c->recv.buf[c->recv.len];size_t len = c->recv.size - c->recv.len;long n = -1；n = recv(FD(c), (char *) buf, len, MSG_NONBLOCKING);  // 文件描述符是非阻塞的，非阻塞接收// n 经过处理后可为 -1 -2 -3iolog(c, buf, n, true);}
}

write_conn函数通过send函数将c->send.buf发送，然后调用iolog
对n处理。然后清理c->send，然后if (c->send.len == 0)MG_EPOLL_MOD(c, 0);再掉mg_call(c, MG_EV_WRITE, &n);iolog return后write_conn也结束

static void write_conn(struct mg_connection *c) {long n = send(FD(c), c->send.buf, c->send.len, MSG_NONBLOCKING);// 文件描述符是非阻塞的，非阻塞接收// n 经过处理后可为 -1 -2 -3iolog(c, buf, n, false);
}

question

mg_http_reply函数，当继续调用mg_printf(c, fmt, …)而不修改Content-Length时浏览器不能接收全部的数据？
is_closing何时被设置为1的？如果client发一次，server发一次不会触发is_closing=1，莫非是等待conn_fd断开的时候触发EPOLLHUP然后间接关闭？若是如此如何触发的问题1？