[REGRESSION] v6.1+ bind() does not fail with EADDRINUSE if dual stack is bound

[Paul Holzinger <pholzing@xxxxxxxxxx>]

Hi all,

there seems to be a regression which allows you to bind the same port 
twice when the first bind call bound to all ip addresses (i. e. dual stack).

A second bind call for the same port will succeed if you try to bind to 
a specific ipv4 (e. g. 127.0.0.1), binding to 0.0.0.0 or an ipv6 address 
fails correctly with EADDRINUSE.

I included a small c program below to show the issue. Normally the 
second bind call should fail, this was the case before v6.1.


I bisected the regression to commit 5456262d2baa ("net: Fix incorrect 
address comparison when searching for a bind2 bucket").

I also checked that the issue is still present in v6.3-rc1.


Original report: https://github.com/containers/podman/issues/17719

#regzbot introduced: 5456262d2baa


```

#include <sys/socket.h>
#include <sys/un.h>
#include <stdlib.h>
#include <stdio.h>
#include <netinet/in.h>
#include <unistd.h>

int main(int argc, char *argv[])
{
    int ret, sock1, sock2;
    struct sockaddr_in6 addr;
    struct sockaddr_in addr2;

    sock1 = socket(AF_INET6, SOCK_STREAM, 0);
    if (sock1 == -1)
    {
        perror("socket1");
        exit(1);
    }
    sock2 = socket(AF_INET, SOCK_STREAM, 0);
    if (sock2 == -1)
    {
        perror("socket2");
        exit(1);
    }

    memset(&addr, 0, sizeof(addr));
    addr.sin6_family = AF_INET6;
    addr.sin6_addr = in6addr_any;
    addr.sin6_port = htons(8080);

    memset(&addr2, 0, sizeof(addr2));
    addr2.sin_family = AF_INET;
    addr2.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
    addr2.sin_port = htons(8080);

    ret = bind(sock1, (struct sockaddr *)&addr, sizeof(addr));
    if (ret == -1)
    {
        perror("bind1");
        exit(1);
    }
    printf("bind1 ret: %d\n", ret);

    if ((listen(sock1, 5)) != 0)
    {
        perror("listen1");
        exit(1);
    }

    ret = bind(sock2, (struct sockaddr *)&addr2, sizeof(addr2));
    if (ret == -1)
    {
        perror("bind2");
        exit(1);
    }
    printf("bind2 ret: %d\n", ret);

    if ((listen(sock2, 5)) != 0)
    {
        perror("listen2");
        exit(1);
    }

    // uncomment pause() to see with ss -tlpn the bound ports
    // pause();

    return 0;
}

```


Best regards,

Paul