ftp_assist.c

#include "ftp_assist.h"
#include "common.h"
#include "sysutil.h"
#include "session.h"
#include "configure.h"
#include "parse_conf.h"
#include "ftp_codes.h"
#include "command_map.h"
#include "hash.h"

unsigned int num_of_clients = 0; //表示连接数目

Hash_t *ip_to_clients;
Hash_t *pid_to_ip;

static void handle_sigchld(int sig);
static unsigned int hash_func(unsigned int buckets, void *key);
//获取当前ip的数目，并且+1
static unsigned int add_ip_to_hash(uint32_t ip);


void check_permission()
{
    //root 的uid为0
    if(getuid())
    {
        fprintf(stderr, "FtpServer must be started by root\n");
        exit(EXIT_FAILURE);
    }
}

void setup_signal_chld()
{
    //signal第二个参数是handler，则signal阻塞，执行handler函数
    if(signal(SIGCHLD, handle_sigchld) == SIG_ERR)
        ERR_EXIT("signal");
}

void print_conf()
{
    printf("tunable_pasv_enable=%d\n", tunable_pasv_enable);
    printf("tunable_port_enable=%d\n", tunable_port_enable);

    printf("tunable_listen_port=%u\n", tunable_listen_port);
    printf("tunable_max_clients=%u\n", tunable_max_clients);
    printf("tunable_max_per_ip=%u\n", tunable_max_per_ip);
    printf("tunable_accept_timeout=%u\n", tunable_accept_timeout);
    printf("tunable_connect_timeout=%u\n", tunable_connect_timeout);
    printf("tunable_idle_session_timeout=%u\n", tunable_idle_session_timeout);
    printf("tunable_data_connection_timeout=%u\n", tunable_data_connection_timeout);
    printf("tunable_local_umask=0%o\n", tunable_local_umask);
    printf("tunable_upload_max_rate=%u\n", tunable_upload_max_rate);
    printf("tunable_download_max_rate=%u\n", tunable_download_max_rate);

    if (tunable_listen_address == NULL)
        printf("tunable_listen_address=NULL\n");
    else
        printf("tunable_listen_address=%s\n", tunable_listen_address);
}

void limit_num_clients(Session_t *sess)
{
    if(tunable_max_clients > 0 && sess->curr_clients > tunable_max_clients)
    {
        //421 There are too many connected users, please try later.
        ftp_reply(sess, FTP_TOO_MANY_USERS, "There are too many connected users, please try later.");
        exit(EXIT_FAILURE);
    }

    if(tunable_max_per_ip > 0 && sess->curr_ip_clients > tunable_max_per_ip)
    {
        //421 There are too many connections from your internet address.
        ftp_reply(sess, FTP_IP_LIMIT, "There are too many connections from your internet address.");
        exit(EXIT_FAILURE);
    }
}

static void handle_sigchld(int sig)
{
    pid_t pid;
    //waitpid挂起当前进程的执行，直到孩子状态发生改变
    //孩子状态发生变化，伴随着孩子进程相关资源的释放，这可以解决僵尸进程
    while((pid = waitpid(-1, NULL, WNOHANG)) > 0)
    {
        --num_of_clients;
        //pid -> ip
        uint32_t *p_ip = hash_lookup_value_by_key(pid_to_ip, &pid, sizeof(pid));
        assert(p_ip != NULL); //ip必须能找到
        uint32_t ip = *p_ip;
        //ip -> clients
        unsigned int *p_value = (unsigned int *)hash_lookup_value_by_key(ip_to_clients, &ip, sizeof(ip));
        assert(p_value != NULL && *p_value > 0);
        --*p_value;

        //释放hash表的结点
        hash_free_entry(pid_to_ip, &pid, sizeof(pid));
    }
}

//hash函数
static unsigned int hash_func(unsigned int buckets, void *key)
{
    unsigned int *number = (unsigned int*)key;

    return (*number) % buckets;
}


//在对应的ip记录中+1,返回当前ip的客户数量
static unsigned int add_ip_to_hash(uint32_t ip)
{
    unsigned int *p_value = (unsigned int *)hash_lookup_value_by_key(ip_to_clients, &ip, sizeof(ip));
    if(p_value == NULL)
    {
        unsigned int value = 1;
        hash_add_entry(ip_to_clients, &ip, sizeof(ip), &value, sizeof(value));
        return 1;
    }
    else
    {
        unsigned int value = *p_value;
        ++value;
        *p_value = value;

        return value;
    }
}


void init_hash()
{
    ip_to_clients = hash_alloc(256, hash_func);
    pid_to_ip = hash_alloc(256, hash_func);
}

void add_clients_to_hash(Session_t *sess, uint32_t ip)
{
    ++num_of_clients; //连接数目+1
    sess->curr_clients = num_of_clients;
    sess->curr_ip_clients = add_ip_to_hash(ip);
}

void add_pid_ip_to_hash(pid_t pid, uint32_t ip)
{
    hash_add_entry(pid_to_ip, &pid, sizeof(pid), &ip, sizeof(ip));
}