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【C】 linux下的简单的ftp实现
作者:匡峰 / 发布于2013/6/4/ 801
支持功能：LIST，RETR，STOR，PORT

	#include "ftp_server.h"
	#include <sys/select.h>
	#include <sys/types.h>
	#include <sys/sem.h>
	#include <sys/ipc.h>
	#include <pthread.h>
	static int servfd;
	static int connlen = 0;
	static struct serv_cntl_conn *cntl_head = NULL;
	static int dataquene_sem;
	in_addr_t localaddr;
	in_port_t localcntlport;
	in_port_t localdataport;
	char homedir[PATH_MAX+1];
	static char cntlsendbuf[LINELEN+1];

	struct serv_cntl_conn *accept_new_client(int servfd);
	int do_server_cmd_port(struct serv_cntl_conn *cntl, char *params);
	void do_server_cmd_transfer(struct serv_data_conn *dconnp);

	static void transfer_over(struct serv_cntl_conn *cntl)
	{
	 struct serv_data_conn *dconnp = cntl->dataconn;

	 printf("close data sock: %d\n", dconnp->sockfd);
	 /* 先shutdown是为了让客户端受到连接关闭的通知 */
	 shutdown(dconnp->sockfd, SHUT_RDWR);
	 close(dconnp->sockfd);
	 cntl->status = CS_WAIT_CMD;
	 dconnp->sockfd = -1;
	 dconnp->pid = -1;
	}

	void sig_child(int sig)
	{
	 pid_t pid = wait(NULL);
	 struct serv_cntl_conn *cntl;
	 for (cntl = cntl_head; cntl; cntl = cntl->next) {
	 struct serv_data_conn *dconnp = cntl->dataconn;
	 if (dconnp && dconnp->pid == pid) {
	 transfer_over(cntl);
	 break;
	 }
	 }
	 if (signal(SIGCHLD, sig_child) == SIG_ERR) {
	 fprintf(stderr, "signal error\n");
	 }
	 printf("sig child handled. pid=%d\n", pid);
	}

	/*
	init socket ,bind, listen
	*/
	static void init_server()
	{
	 struct addrinfo hints;
	 struct addrinfo *result, *rp;
	 int s, val;
	 char hostname[HOST_NAME_MAX+1];
	 gethostname(hostname, HOST_NAME_MAX+1);
	 localdataport = htons(SERVER_DATA_PORT);

	 memset(&hints, 0, sizeof(struct addrinfo));
	 hints.ai_family = AF_INET;
	 hints.ai_socktype = SOCK_STREAM;
	 hints.ai_flags = AI_PASSIVE;

	 s = getaddrinfo(hostname, "ftp", &hints, &result);
	 if(s != 0) {
	 fprintf(stderr, "getaddinfo: %s\n", gai_strerror(s));
	 exit(EXIT_FAILURE);
	 }
	
	 for (rp = result; rp != NULL; rp = rp->ai_next) {
	 servfd = initserver(SOCK_STREAM, rp->ai_addr, rp->ai_addrlen, MAX_CONN);
	 if (servfd >= 0){
	 char addr[INET_ADDRSTRLEN];
	 struct sockaddr_in * sa_in = (struct sockaddr_in*)rp->ai_addr;
	 in_addr_t in_addr = sa_in->sin_addr.s_addr;
	 inet_ntop(AF_INET, &in_addr, addr, INET_ADDRSTRLEN);
	 fprintf(stdout, "bind on address %s:%u\n",
	 addr, ntohs(sa_in->sin_port));
	 localaddr = in_addr;
	 localcntlport = sa_in->sin_port;
	 break;
	 }
	 }
	
	 if (rp == NULL) {
	 fprintf(stderr, "Counld not bind\n");
	 exit(EXIT_FAILURE);
	 }
	 freeaddrinfo(result);
	}

	static void reset_cntl(struct serv_cntl_conn *cntl)
	{
	 if (cntl == NULL)
	 return;
	 cntl->lineused = 0;
	 cntl->status = CS_WAIT_CMD;
	}
	int checkpasswd(char *user, char *passwd)
	{
	 //TODO: check password
	 return 0;
	}
	static int handle_line_request(struct serv_cntl_conn *cntl, char *linerecvd)
	{
	
	 struct serv_data_conn *dconnp;
	 int sockfd, n, bufsize, retval;
	 char *params;
	 enum FTP_CMD cmd;
	 struct sembuf sems[] = {{0,1,0}};
	 if (!cntl || !linerecvd)
	 goto errout;
	 puts("handle_line_request");
	 retval = pharsecmdline(linerecvd, &cmd, &params);
	 if (retval < 0) {
	 fprintf(stderr, "wrong command: %s\n", linerecvd);
	 goto errout;
	 }

	 fprintf(stdout, "line left --> [%d] %s\n", cntl->lineused, cntl->line);

	 cntl->lastcmd = cmd;
	 if (cntl->lastparams)
	 free(cntl->lastparams);
	 cntl->lastparams = params;
	 switch(cmd) {
	 case CMD_ABOR: break;
	 case CMD_LIST: goto trans;
	 case CMD_PASS:
	 if (cntl->user) {
	 if (checkpasswd(cntl->user, params) == 0) {
	snprintf(cntlsendbuf, LINELEN, "230 User logged in, proceed.\n");
	cntl->logon = 1;
	 }
	 else
	snprintf(cntlsendbuf, LINELEN, "530 Not logged in.\n");
	 } else {
	 snprintf(cntlsendbuf, LINELEN, "332 Need account for login.\n");
	 }
	 write(cntl->sockfd,cntlsendbuf,strlen(cntlsendbuf));
	 puts(cntlsendbuf);
	 break;
	 case CMD_PORT:
	 if (cntl->status == CS_WAIT_CMD) {
	 if (do_server_cmd_port(cntl, params) == 0) {
	/* ready for transfer, send response for PORT command */
	snprintf(cntlsendbuf, LINELEN,
	 "225 Data connection open; no transfer in progress.\n");
	write(cntl->sockfd,cntlsendbuf,strlen(cntlsendbuf));
	puts(cntlsendbuf);
	return 0;
	 } else {
	goto errout;
	 }
	 } else {
	 printf("receive PORT while status not CS_WAIT_CMD.\n");
	 goto errout;
	 }
	 break;
	 case CMD_QUIT: break;
	 case CMD_RETR: goto trans;
	 case CMD_STOR: goto trans;
	 case CMD_SYST: break;
	 case CMD_TYPE: break;
	 case CMD_USER:
	 if (!params)
	 break;
	 if (cntl->user)
	 free(cntl->user);
	 cntl->user = strdup(params);
	 cntl->logon = 0;
	 snprintf(cntlsendbuf, LINELEN, "331 User name okay, need password.\n");
	 write(cntl->sockfd,cntlsendbuf,strlen(cntlsendbuf));
	 puts(cntlsendbuf);
	 break;
	 default: goto errout;
	 }
	 /* 忽略的命令直接进入 */
	defaultout:
	 cntl->lastcmd = cmd;
	 cntl->status = CS_WAIT_CMD;
	 return 0;
	trans:
	 if (cntl->status == CS_PORT_RECVD && cntl->dataconn &&
	 cntl->dataconn->status == DS_READY) {
	 pid_t pid;
	 struct serv_data_conn *dconnp = cntl->dataconn;
	 dconnp->cmd = cmd;
	 dconnp->filename = params ? strdup(params):NULL;
	 snprintf(cntlsendbuf, LINELEN,
	 "125 Data connection already open; transfer starting.\n");
	 write(cntl->sockfd, cntlsendbuf, strlen(cntlsendbuf));
	 printf("%s", cntlsendbuf);
	 do_server_cmd_transfer(dconnp);
	 //transfer_over(cntl);

	 //cntl->status = CS_WAIT_CMD;
	 cntl->status = CS_WAIT_TRANS;
	 dconnp->status = DS_TRANSING;
	 // puts("data conn closed.");
	 return 0;
	 } else {
	 goto errout;
	 }
	errout:
	 cntl->status = CS_WAIT_CMD;
	 return -1;
	}
	static int handle_request(struct serv_cntl_conn *cntl)
	{
	 int n;
	 char *linerecvd = NULL;
	 if (!cntl)
	 return -1;
	 puts("handle_request");
	 do {
	 if (!linerecvd)
	 free(linerecvd);
	 n = readline(cntl->sockfd, cntl->line, LINELEN,
	 &cntl->lineused, &linerecvd);

	 if (n == 0) { // connection closed
	 close(cntl->sockfd);
	 fprintf(stdout, "LOG: close socket %d\n", cntl->sockfd);
	 cntl->sockfd = -1;
	 cntl->status = CS_FINISHED;
	 return 0;
	 } else if (n < 0) { /* error receive */
	 if (errno == EAGAIN || errno == EWOULDBLOCK) /* no data */
	break;
	 else {
	fprintf(stderr, "error receive data : %s\n", strerror(errno));
	reset_cntl(cntl);
	// exit(EXIT_FAILURE);
	return -1;
	 }
	 }
	 if (linerecvd) {
	 fprintf(stdout, "LOG: received line --> %s\n", linerecvd);
	 handle_line_request(cntl, linerecvd);
	 }
	 } while (n > 0 && linerecvd != NULL);
	 return 0;
	}
	/*
	 1) select one fd
	 2) accept to get connection, add the connection to pool
	 3) read request, dispatch
	*/
	static void server()
	{
	 fd_set rfds;
	 int retval, flags, maxfd = 0;
	 struct serv_cntl_conn *curcntl, *lastcntl;

	
	 /* set NONBLOCK */
	 // fcntl(servfd, F_SETOWN, getpid());
	 flags = fcntl(servfd, F_GETFL);
	 fcntl(servfd, F_SETFL, flags|O_NONBLOCK);

	 fprintf(stdout,"server for loop\n");
	 connlen = 0;
	 cntl_head = NULL;
	 for (;;) {
	 FD_ZERO(&rfds);
	 FD_SET(servfd, &rfds);
	 maxfd = servfd;
	 lastcntl = NULL;
	 for (curcntl = cntl_head; curcntl; ) {
	 /* 删除已经关闭的客户端 */
	 if (curcntl->status == CS_FINISHED) {
	struct serv_cntl_conn *next = curcntl->next;
	if (lastcntl) {
	 lastcntl->next = next;
	} else {
	 cntl_head = next;
	}
	if (curcntl->lastparams)
	 free(curcntl->lastparams);
	if (curcntl->cwd)
	 free(curcntl->cwd);
	free(curcntl);
	curcntl = next;
	connlen --;
	continue;
	 }
	 int fd = curcntl->sockfd;
	 FD_SET(fd, &rfds);
	 maxfd = maxfd < fd ? fd : maxfd;
	 lastcntl = curcntl;
	 curcntl = curcntl->next;
	 }

	 while (select(maxfd+1, &rfds, NULL, NULL, NULL) == -1) {
	 if (errno == EINTR) {
	continue;
	 } else {
	fprintf(stderr,"select(): %s\n", strerror(errno));
	exit(EXIT_FAILURE);
	 }
	 }
	 for (curcntl = cntl_head; curcntl; curcntl = curcntl->next) {
	 int fd = curcntl->sockfd;
	 if (FD_ISSET(fd, &rfds)) {
	fprintf(stdout,"fd %d is set\n", fd);
	handle_request(curcntl);
	printf("hand fd %d ok\n",fd);
	 }
	 }

	 if (FD_ISSET(servfd, &rfds)) { /*new connect*/
	 struct serv_cntl_conn *servconn;
	 servconn = accept_new_client(servfd);
	 if (servconn != NULL) {
	if (connlen < MAX_CONN) {
	 servconn->next = cntl_head;
	 cntl_head = servconn;
	 connlen ++;
	 fprintf(stdout, "accepted, fd = %d, connlen = %d\n",
	 servconn->sockfd,connlen);
	} else {
	 fprintf(stderr, "reach max connection size\n");
	 shutdown(servconn->sockfd, SHUT_RDWR);
	 close(servconn->sockfd);
	 free(servconn);
	}
	 }
	 }
	 }
	}

	int main(int argc, const char* argv[])
	{
	 int err;
	 pthread_t tid;
	 strcpy(homedir, "/home/kuangf/ftptmp/");
	 init_server();
	
	#if 1
	 if (signal(SIGCHLD, sig_child) == SIG_ERR) {
	 fprintf(stderr, "signal error\n");
	 }
	#endif
	 server();
	 fprintf(stdout, "server out\n");
	 return 0;
	}
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