vtun 中的__io_canceled变量和相关函数

1、__io_canceled在lib.h中定义，

/* IO cancelation */
extern volatile sig_atomic_t __io_canceled;

 

__io_canceled变量影响下列函数，

static inline int read_n(int fd, char *buf, int len)
{
    register int t=0, w;

    while (!__io_canceled && len > 0)
    {
        if( (w = read(fd, buf, len)) < 0 )
        {
        if( errno == EINTR || errno == EAGAIN )
        continue;
        return -1;
        }
        if( !w )
            return 0;
        len -= w; buf += w; t += w;
    }

    return t;
}  

static inline int write_n(int fd, char *buf, int len)
{
    register int t=0, w;

    while (!__io_canceled && len > 0)
    {
        if( (w = write(fd, buf, len)) < 0 )
        {
            if( errno == EINTR || errno == EAGAIN )
                continue;
            return -1;
        }
        if( !w ) return 0;
        len -= w; buf += w; t += w;
    }

    return t;
}

2、下面的函数改变__io_canceled变量，

static inline void io_init(void)
{
    __io_canceled = 0;
}

static inline void io_cancel(void)
{
    __io_canceled = 1;
}

3、

而io_cancel函数在下面函数中调用，

static void sig_term(int sig)
{
    vtun_syslog(LOG_INFO, "Closing connection");
    io_cancel();
    linker_term = VTUN_SIG_TERM;
}

static void sig_hup(int sig)
{
    vtun_syslog(LOG_INFO, "Reestablishing connection");
    io_cancel();
    linker_term = VTUN_SIG_HUP;
}

4、

当内核发出退出或挂起等信号时，会调用sig_term或sig_hup函数，从而改变__io_canceled的值，从而停止read_n  write_n.