#include <arpa/inet.h>
#include <stdint.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <unistd.h>

/* changed from 873 to 8733, so it can run as user, the actual port does not
 * matter */
#define RSYNC_PORT (8733)

int main() {
  int so1, so2;
  int32_t optval;

  /* The following code is rewritten from a strace of rsync --daemon. */
  so1 = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

  optval = 1;
  setsockopt(so1, SOL_SOCKET, SO_REUSEADDR, (void *)&optval, sizeof(optval));

  struct sockaddr_in sa1 = {.sin_family = AF_INET,
                            .sin_port = htons(RSYNC_PORT),
                            .sin_addr = inet_addr("0.0.0.0")};
  bind(so1, (struct sockaddr *)&sa1, sizeof(sa1));

  so2 = socket(AF_INET6, SOCK_STREAM, IPPROTO_TCP);

  optval = 1;
  setsockopt(so2, SOL_SOCKET, SO_REUSEADDR, (void *)&optval, sizeof(optval));

  optval = 1;
  setsockopt(so2, SOL_IPV6, IPV6_V6ONLY, (void *)&optval, sizeof(optval));

  struct sockaddr_in6 sa2 = {.sin6_family = AF_INET6,
                             .sin6_port = htons(RSYNC_PORT),
                             .sin6_flowinfo = htonl(0),
                             .sin6_scope_id = 0};
  inet_pton(AF_INET6, "::", &sa2.sin6_addr);
  bind(so2, (struct sockaddr *)&sa2, sizeof(sa2));

  /* WARN_ON() is thrown here: */
  listen(so1, 5);
  /* listen(so2, 5); */
}