分叉的进程一直在监听服务器的端口

Question

This is light version of my code for executing commands:

void close_all_nonestandard_fds()
{
    struct rlimit fds_limit;
    int max_fd = 1024;
    if (getrlimit(RLIMIT_NOFILE, &fds_limit) == 0) max_fd = fds_limit.rlim_cur;
    for(int i = 0; i <= max_fd; ++i) {
        if(i != STDERR_FILENO && i != STDOUT_FILENO && i != STDIN_FILENO) close(i);
    }
}

void exec_command(char* command, char*const* args)
{
    pid_t pid = fork();
    if(pid != 0)
    {
        if(pid == -1) throw_error("Failed to fork: %s", strerror(errno));
        // Parent
    }
    else
    {
        // Child
        close_all_nonestandard_fds();
        if(execv(command, args) == -1) throw_error("Failed to execv: %s", trerror(errno));
    }
}

The exec_command method is used in my server side application for running different kind of processes including daemon processes. But here I noticed a problem:

When server runs a child daemon process, then it (the server) being killed or crashed the child starts to listen to the port server was listening to.

So, how can I execute a command and be sure that it wouldn't keep port of the server busy after servers end (crash, death)?

Answer 1

Just keep track of all server sockets by storing them and then after fork() ing have those close() d in the child.

Those are the listen() ing sockets and the accept() ed sockets.

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Update:

Also you might like to use setsockopt() to set the option SO_REUSEADDR to the socket passed to bind()

SO_REUSEADDR

Indicates that the rules used in validating addresses supplied in a bind(2) call should allow reuse of local addresses. For AF_INET sockets this means that a socket may bind, except when there is an active listening socket bound to the address. When the listening socket is bound to INADDR_ANY with a specific port then it is not possible to bind to this port for any local address. Argument is an integer boolean flag.