Re: [Help-smalltalk] [PATCH] Fix multiple binds to the same port

[Paolo Bonzini]

On 01/19/2011 05:24 PM, Holger Hans Peter Freyther wrote:
> Hi,
>
> this is fixing the issue that binding the same port seems to work but in
> reality the socket will be auto bound to another port. Instead of checking for
> soError we will now just check errno.

Ok, now I can reproduce it, but it seems a bug to me.  This is a 
self-contained C reproducer:

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <string.h>

#define PORT 6666

int main()
{
        struct sockaddr_in sin;
        int val;
        socklen_t sz;
        int s1, s2, rc;

        memset(&sin, 0, sizeof(sin));
        sin.sin_family = AF_INET;
        sin.sin_addr.s_addr = INADDR_ANY;
        sin.sin_port = htons(PORT);

        s1 = socket (PF_INET, SOCK_STREAM, IPPROTO_TCP);
        if (s1 == -1) { perror ("socket"); exit (1); }
        s2 = socket (PF_INET, SOCK_STREAM, IPPROTO_TCP);
        if (s2 == -1) { perror ("socket"); exit (1); }

        val = 1;
        setsockopt (s1, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
        val = 1;
        setsockopt (s2, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));

        rc = bind(s1, (struct sockaddr *) &sin, sizeof(sin));
        if (rc == -1) { perror ("bind"); exit (1); }
        rc = listen (s1, 5);
        if (rc == -1) { perror ("listen"); exit (1); }

        errno = 0;
        rc = bind(s2, (struct sockaddr *) &sin, sizeof(sin));
        if (rc != -1) { perror ("bind"); exit (1); }

        printf ("bind (errno): %s\n", strerror (errno));
        sz = sizeof(val);
        getsockopt(s2, SOL_SOCKET, SO_ERROR, &val, &sz);
        printf ("bind (SO_ERROR): %s\n", strerror (val));
        if (val == 0) exit (1);

        exit (0);
}

You're right.  Using errno is thread-unsafe since Smalltalk threads 
share the errno and you could have an interrupt at exactly "that" time.

I'll have to fix it.

Paolo