// SPDX-License-Identifier: GPL-2.0

#include <arpa/inet.h>
#include <error.h>
#include <errno.h>
#include <unistd.h>

int main(void)
{
        int fd1, fd2, one = 1;
        struct sockaddr_in6 bind_addr = {
                .sin6_family = AF_INET6,
                .sin6_port = htons(20000),
                .sin6_flowinfo = htonl(0),
                .sin6_addr = {},
                .sin6_scope_id = 0,
        };

        inet_pton(AF_INET6, "::", &bind_addr.sin6_addr);

        fd1 = socket(AF_INET6, SOCK_STREAM, IPPROTO_IP);
        if (fd1 < 0) {
                error(1, errno, "socket fd1");
                return -1;
        }

        if (setsockopt(fd1, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one))) {
                error(1, errno, "setsockopt(SO_REUSEADDR) fd1");
                goto out_err1;
        }

        if (bind(fd1, (struct sockaddr *)&bind_addr, sizeof(bind_addr))) {
                error(1, errno, "bind fd1");
                goto out_err1;
        }

        if (listen(fd1, 0)) {
                error(1, errno, "listen");
                goto out_err1;
        }

        fd2 = socket(AF_INET6, SOCK_STREAM, IPPROTO_IP);
        if (fd2 < 0) {
                error(1, errno, "socket fd2");
                goto out_err1;
        }

        if (connect(fd2, (struct sockaddr *)&bind_addr, sizeof(bind_addr))) {
                error(1, errno, "bind fd2");
                goto out_err2;
        }

        close(fd2);
        close(fd1);
        return 0;

out_err2:
        close(fd2);
out_err1:
        close(fd1);
        return -1;
}