/* This software was written by Dirk Engling <erdgeist@erdgeist.org>
   It is considered beerware. Prost. Skol. Cheers or whatever.

   $id$ */

/* System */
#include <errno.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <poll.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>

/* Opentracker */
#include "ot_ip.h"
#include "ot_socket.h"
#include "test.h"

/* These cases talk to the loopback interface rather than to a mock, because
   what is worth pinning down here is the behaviour of the socket options the
   rest of the tracker relies on, and only the kernel can report that. */

static const char ip_any[16] = {0};
static const char ip_loopback[16] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1};
static const char ip_v4_loopback[16] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff, 127, 0, 0, 1};
/* RFC 3849 reserves 2001:db8::/32 for documentation, so no host carries it */
static const char ip_unassigned[16] = {0x20, 0x01, 0x0d, 0xb8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1};

/* What a socket ended up bound to, which is not always what was asked for: a
   FreeBSD jail, for one, rewrites a loopback bind to the address it was given.
   A datagram a socket sends to itself must come back carrying this, so the
   cases below compare against it rather than against the address they passed
   to the bind. */
static void bound_address(int s, char ip[16], uint16_t *port) {
  struct sockaddr_storage ss;
  socklen_t               len = sizeof(ss);

  memset(&ss, 0, sizeof(ss));
  memset(ip, 0, 16);
  *port = 0;
  if (getsockname(s, (struct sockaddr *)&ss, &len) == -1)
    return;

  /* Spelled out here rather than borrowed from ot_socket.c, so that a wrong
     idea about how a kernel reports an address cannot hide in both at once */
  if (ss.ss_family == AF_INET) {
    const struct sockaddr_in *sa = (const struct sockaddr_in *)&ss;

    memcpy(ip, ip_v4mapped_prefix, sizeof(ip_v4mapped_prefix));
    memcpy(ip + sizeof(ip_v4mapped_prefix), &sa->sin_addr, 4);
    *port = ntohs(sa->sin_port);
  } else {
    const struct sockaddr_in6 *sa = (const struct sockaddr_in6 *)&ss;

    memcpy(ip, &sa->sin6_addr, 16);
    *port = ntohs(sa->sin6_port);
  }
}

static int is_nonblocking(int s) {
  int flags = fcntl(s, F_GETFL, 0);
  return flags != -1 && (flags & O_NONBLOCK) != 0;
}

static int sock_flag(int s, int level, int option) {
  int       value = -1;
  socklen_t len   = sizeof(value);

  if (getsockopt(s, level, option, &value, &len) == -1)
    return -1;
  return value != 0;
}

/* Wait for one event, so a test never blocks forever on a lost packet */
static int wait_for(int s, short events) {
  struct pollfd pfd;

  pfd.fd      = s;
  pfd.events  = events;
  pfd.revents = 0;
  return poll(&pfd, 1, 2000) == 1;
}

/* ------------------------------------------------------------ invariants */

/* Asked for the wildcard address, because a socket bound to one specific
   IPv6 address cannot carry IPv4 traffic anyway and Linux turns IPV6_V6ONLY
   back on in that case. The tracker's own default is the wildcard. */
static void case_socket_options(void) {
  int udp, tcp;

  test_case("a bound udp socket is non blocking and serves both families");
  udp = socket_udp_bind(ip_any, 0, SOCKET_EXCLUSIVE);
  CHECK(udp != -1);
  CHECK_INT(is_nonblocking(udp), 1);
  CHECK_INT(sock_flag(udp, IPPROTO_IPV6, IPV6_V6ONLY), 0);
  close(udp);

  test_case("a listening tcp socket is non blocking and serves both families");
  tcp = socket_tcp_listen(ip_any, 0, SOCKET_EXCLUSIVE);
  CHECK(tcp != -1);
  CHECK_INT(is_nonblocking(tcp), 1);
  CHECK_INT(sock_flag(tcp, IPPROTO_IPV6, IPV6_V6ONLY), 0);
  close(tcp);
}

#ifdef SO_REUSEPORT
static void case_sharing_is_opt_in(void) {
  int s;

  test_case("an address is exclusive unless sharing is asked for");
  s = socket_udp_bind(ip_loopback, 0, SOCKET_EXCLUSIVE);
  CHECK(s != -1);
  CHECK_INT(sock_flag(s, SOL_SOCKET, SO_REUSEPORT), 0);
  close(s);

  test_case("and shared when it is");
  s = socket_udp_bind(ip_loopback, 0, SOCKET_SHARED);
  CHECK(s != -1);
  CHECK_INT(sock_flag(s, SOL_SOCKET, SO_REUSEPORT), 1);
  close(s);
}
#endif

/* ------------------------------------------------------------------- udp */

static void case_udp_roundtrip(void) {
  char     buf[32], ip[16], own_ip[16];
  uint16_t port = 0, own_port = 0;
  int      s;

  test_case("a datagram comes back with the sender's address and port");
  s = socket_udp_bind(ip_loopback, 0, SOCKET_EXCLUSIVE);
  CHECK(s != -1);
  bound_address(s, own_ip, &own_port);
  CHECK(own_port != 0);
  CHECK_INT(socket_send(s, "opentracker", 11, own_ip, own_port), 11);
  CHECK_INT(wait_for(s, POLLIN), 1);
  CHECK_INT(socket_recv(s, buf, sizeof(buf), ip, &port), 11);
  CHECK_MEM(buf, "opentracker", 11);
  CHECK_MEM(ip, own_ip, 16);
  CHECK_INT(port, own_port);
  close(s);
}

/* An IPv4 peer must arrive in the v4 mapped form opentracker stores, however
   the kernel chose to report it. Linux fills a v4 mapped sockaddr_in6 here
   and the BSDs fill a plain sockaddr_in, so this is the case that tells the
   two apart. */
static void case_udp_v4mapped(void) {
  char     buf[32], ip[16], receiver_ip[16], sender_ip[16];
  uint16_t port = 0, receiver_port = 0, sender_port = 0;
  int      receiver, sender;

  test_case("an IPv4 sender is reported in its v4 mapped form");
  receiver = socket_udp_bind(ip_v4_loopback, 0, SOCKET_EXCLUSIVE);
  CHECK(receiver != -1);
  sender = socket_udp_bind(ip_v4_loopback, 0, SOCKET_EXCLUSIVE);
  CHECK(sender != -1);
  bound_address(receiver, receiver_ip, &receiver_port);
  bound_address(sender, sender_ip, &sender_port);
  CHECK_INT(ip_is_v4mapped(sender_ip), 1);

  CHECK_INT(socket_send(sender, "v4", 2, receiver_ip, receiver_port), 2);
  CHECK_INT(wait_for(receiver, POLLIN), 1);
  CHECK_INT(socket_recv(receiver, buf, sizeof(buf), ip, &port), 2);
  CHECK_INT(ip_is_v4mapped(ip), 1);
  CHECK_MEM(ip, sender_ip, 16);
  CHECK_INT(port, sender_port);
  close(sender);
  close(receiver);
}

/* ------------------------------------------------------------------- tcp */

static void case_tcp_roundtrip(void) {
  char     ip[16], listener_ip[16], client_ip[16];
  uint16_t port = 0, listener_port = 0, client_port = 0;
  int      listener, client, accepted;

  test_case("a connection is accepted and carries the caller's address");
  listener = socket_tcp_listen(ip_loopback, 0, SOCKET_EXCLUSIVE);
  CHECK(listener != -1);
  bound_address(listener, listener_ip, &listener_port);
  CHECK(listener_port != 0);

  client = socket_tcp_connect(ip_loopback, 0, listener_ip, listener_port);
  CHECK(client != -1);
  CHECK_INT(wait_for(client, POLLOUT), 1);
  CHECK_INT(socket_is_connected(client), 1);
  bound_address(client, client_ip, &client_port);

  CHECK_INT(wait_for(listener, POLLIN), 1);
  accepted = socket_accept(listener, ip, &port);
  CHECK(accepted != -1);
  CHECK_MEM(ip, client_ip, 16);
  CHECK_INT(port, client_port);

  test_case("the accepted socket is handed over non blocking");
  CHECK_INT(is_nonblocking(accepted), 1);

  close(accepted);
  close(client);
  close(listener);
}

static void case_connect_refused(void) {
  char     listener_ip[16];
  int      listener, client;
  uint16_t port;

  test_case("a refused connection is reported by socket_is_connected");
  /* Take a port, then drop it, so nothing is listening on it any more */
  listener = socket_tcp_listen(ip_loopback, 0, SOCKET_EXCLUSIVE);
  CHECK(listener != -1);
  bound_address(listener, listener_ip, &port);
  close(listener);

  client = socket_tcp_connect(ip_loopback, 0, listener_ip, port);
  CHECK(client != -1);
  CHECK_INT(wait_for(client, POLLOUT), 1);
  CHECK_INT(socket_is_connected(client), 0);
  CHECK_INT(errno, ECONNREFUSED);
  close(client);
}

/* --------------------------------------------------------- failed binds */

/* The lowest free descriptor is handed out first, so a number that stays put
   across a failing call shows the call did not keep a socket behind. */
static int next_descriptor(void) {
  int fd = dup(0);

  if (fd != -1)
    close(fd);
  return fd;
}

static void case_bind_failure(void) {
  int before;

  test_case("binding an address no interface carries fails");
  before = next_descriptor();
  CHECK(before != -1);
  CHECK_INT(socket_tcp_listen(ip_unassigned, 0, SOCKET_EXCLUSIVE), -1);
  CHECK_INT(socket_udp_bind(ip_unassigned, 0, SOCKET_EXCLUSIVE), -1);

  test_case("a failed bind leaves no socket behind");
  CHECK_INT(next_descriptor(), before);
}

#ifdef WANT_SYNC_LIVE
/* Reading an IPv4 multicast option back: Linux answers with an int, the BSDs
   with a single byte, so ask how much was written. */
static int mcast_option(int s, int option) {
  int       value = 0;
  socklen_t len   = sizeof(value);

  if (getsockopt(s, IPPROTO_IP, option, &value, &len) == -1)
    return -1;
  if (len == 1)
    return *(unsigned char *)&value;
  return value;
}

static void case_mcast_sender(void) {
  int s;

  test_case("the sending socket keeps its traffic on the local network");
  s = socket_mcast_bind(ip_v4_loopback, 0, 0);
  CHECK(s != -1);
  CHECK_INT(mcast_option(s, IP_MULTICAST_TTL), 1);

  test_case("and does not hear itself unless it is asked to");
  CHECK_INT(mcast_option(s, IP_MULTICAST_LOOP), 0);

  test_case("whoever sends from it is serving clients too, so it cannot block");
  CHECK_INT(is_nonblocking(s), 1);
  close(s);

  test_case("the proxy asks to hear itself and gets it");
  s = socket_mcast_bind(ip_v4_loopback, 0, 1);
  CHECK(s != -1);
  CHECK_INT(mcast_option(s, IP_MULTICAST_LOOP), 1);
  close(s);
}
#endif

void test_socket(void) {
  case_socket_options();
#ifdef SO_REUSEPORT
  case_sharing_is_opt_in();
#endif
  case_udp_roundtrip();
  case_udp_v4mapped();
  case_tcp_roundtrip();
  case_connect_refused();
  case_bind_failure();
#ifdef WANT_SYNC_LIVE
  case_mcast_sender();
#endif
}