sock.c

#include "dns.h"
#include "event.h"
#include "log.h"
#include "net.h"
#include "printf.h"
#include "str.h"
#include "timer.h"
#include "tls.h"
#include "url.h"
#include "util.h"

#if MG_ENABLE_SOCKET

#ifndef closesocket
#define closesocket(x) close(x)
#endif

#define FD(c_) ((MG_SOCKET_TYPE) (size_t) (c_)->fd)
#define S2PTR(s_) ((void *) (size_t) (s_))

#ifndef MSG_NONBLOCKING
#define MSG_NONBLOCKING 0
#endif

#ifndef AF_INET6
#define AF_INET6 10
#endif

#ifndef MG_SOCK_ERR
#define MG_SOCK_ERR(errcode) ((errcode) < 0 ? errno : 0)
#endif

#ifndef MG_SOCK_INTR
#define MG_SOCK_INTR(fd) (fd == MG_INVALID_SOCKET && MG_SOCK_ERR(-1) == EINTR)
#endif

#ifndef MG_SOCK_PENDING
#define MG_SOCK_PENDING(errcode) \
  (((errcode) < 0) && (errno == EINPROGRESS || errno == EWOULDBLOCK))
#endif

#ifndef MG_SOCK_RESET
#define MG_SOCK_RESET(errcode) \
  (((errcode) < 0) && (errno == EPIPE || errno == ECONNRESET))
#endif

union usa {
  struct sockaddr sa;
  struct sockaddr_in sin;
#if MG_ENABLE_IPV6
  struct sockaddr_in6 sin6;
#endif
};

static socklen_t tousa(struct mg_addr *a, union usa *usa) {
  socklen_t len = sizeof(usa->sin);
  memset(usa, 0, sizeof(*usa));
  usa->sin.sin_family = AF_INET;
  usa->sin.sin_port = a->port;
  memcpy(&usa->sin.sin_addr, a->addr.ip, sizeof(uint32_t));
#if MG_ENABLE_IPV6
  if (a->is_ip6) {
    usa->sin.sin_family = AF_INET6;
    usa->sin6.sin6_port = a->port;
    usa->sin6.sin6_scope_id = a->scope_id;
    memcpy(&usa->sin6.sin6_addr, a->addr.ip, sizeof(a->addr.ip));
    len = sizeof(usa->sin6);
  }
#endif
  return len;
}

static void tomgaddr(union usa *usa, struct mg_addr *a, bool is_ip6) {
  a->is_ip6 = is_ip6;
#if MG_ENABLE_IPV6
  if (is_ip6) {
    memcpy(a->addr.ip, &usa->sin6.sin6_addr, sizeof(a->addr.ip));
    a->port = usa->sin6.sin6_port;
    a->scope_id = (uint8_t) usa->sin6.sin6_scope_id;
  } else
#endif
  {
    a->port = usa->sin.sin_port;
    memcpy(&a->addr.ip, &usa->sin.sin_addr, sizeof(uint32_t));
  }
}

static void setlocaddr(MG_SOCKET_TYPE fd, struct mg_addr *addr) {
  union usa usa;
  socklen_t n = sizeof(usa);
  if (getsockname(fd, &usa.sa, &n) == 0) {
    tomgaddr(&usa, addr, n != sizeof(usa.sin));
  }
}

// Get the local 'addr' the stack will use to connect to 'to'
void mg_getlocaddr(struct mg_connection *c, struct mg_addr *to, struct mg_addr *addr);
void mg_getlocaddr(struct mg_connection *c, struct mg_addr *to, struct mg_addr *addr) {
  union usa usa;
  socklen_t slen;
  MG_SOCKET_TYPE fd;
  int rc, af = to->is_ip6 ? AF_INET6 : AF_INET;
  fd = socket(af, SOCK_DGRAM, IPPROTO_UDP);
  if (fd == MG_INVALID_SOCKET) {
    mg_error(c, "socket(): %d", MG_SOCK_ERR(-1));
    return;
  }
  // NOTE(): TI-RTOS NDK may require binding
  slen = tousa(to, &usa);
  if ((rc = connect(fd, &usa.sa, slen)) != 0) {
    mg_error(c, "connect: %d", MG_SOCK_ERR(rc));
    return;
  }
  setlocaddr(fd, addr);
  closesocket(fd);
}


static void iolog(struct mg_connection *c, char *buf, long n, bool r) {
  if (n == MG_IO_WAIT) {
    // Do nothing
  } else if (n <= 0) {
    c->is_closing = 1;  // Termination. Don't call mg_error(): #1529
  } else if (n > 0) {
    if (c->is_hexdumping) {
      MG_INFO(("\n-- %lu %M %s %M %ld", c->id, mg_print_ip_port, &c->loc,
               r ? "<-" : "->", mg_print_ip_port, &c->rem, n));
      mg_hexdump(buf, (size_t) n);
    }
    if (r) {
      c->recv.len += (size_t) n;
      mg_call(c, MG_EV_READ, &n);
    } else {
      mg_iobuf_del(&c->send, 0, (size_t) n);
      // if (c->send.len == 0) mg_iobuf_resize(&c->send, 0);
      if (c->send.len == 0) {
        MG_EPOLL_MOD(c, 0);
      }
      mg_call(c, MG_EV_WRITE, &n);
    }
  }
}

long mg_io_send(struct mg_connection *c, const void *buf, size_t len) {
  long n;
  if (c->is_udp) {
    union usa usa;
    socklen_t slen = tousa(&c->rem, &usa);
    n = sendto(FD(c), (char *) buf, len, 0, &usa.sa, slen);
    if (n > 0) setlocaddr(FD(c), &c->loc);
  } else {
    n = send(FD(c), (char *) buf, len, MSG_NONBLOCKING);
  }
  MG_VERBOSE(("%lu %ld %d", c->id, n, MG_SOCK_ERR(n)));
  if (MG_SOCK_PENDING(n)) return MG_IO_WAIT;
  if (MG_SOCK_RESET(n)) return MG_IO_RESET;  // MbedTLS, see #1507
  if (n <= 0) return MG_IO_ERR;
  return n;
}

bool mg_send(struct mg_connection *c, const void *buf, size_t len) {
  if (c->is_udp) {
    long n = mg_io_send(c, buf, len);
    MG_DEBUG(("%lu %ld %lu:%lu:%lu %ld err %d", c->id, c->fd, c->send.len,
              c->recv.len, c->rtls.len, n, MG_SOCK_ERR(n)));
    iolog(c, (char *) buf, n, false);
    return n > 0;
  } else {
    return len == 0 || mg_iobuf_add(&c->send, c->send.len, buf, len) > 0;
    // returning 0 means an OOM condition (iobuf couldn't resize), yet this is
    // so far recoverable, let the caller decide
  }
}

static void mg_set_non_blocking_mode(MG_SOCKET_TYPE fd) {
#if defined(MG_CUSTOM_NONBLOCK)
  MG_CUSTOM_NONBLOCK(fd);
#elif MG_ARCH == MG_ARCH_WIN32 && MG_ENABLE_WINSOCK
  unsigned long on = 1;
  ioctlsocket(fd, FIONBIO, &on);
#elif MG_ENABLE_RL
  unsigned long on = 1;
  ioctlsocket(fd, FIONBIO, &on);
#elif MG_ENABLE_FREERTOS_TCP
  const BaseType_t off = 0;
  if (setsockopt(fd, 0, FREERTOS_SO_RCVTIMEO, &off, sizeof(off)) != 0) (void) 0;
  if (setsockopt(fd, 0, FREERTOS_SO_SNDTIMEO, &off, sizeof(off)) != 0) (void) 0;
#elif MG_ENABLE_LWIP
  lwip_fcntl(fd, F_SETFL, O_NONBLOCK);
#elif MG_ARCH == MG_ARCH_THREADX
  // NetxDuo fails to send large blocks of data to the non-blocking sockets
  (void) fd;
  // fcntl(fd, F_SETFL, O_NONBLOCK);
#elif MG_ARCH == MG_ARCH_TIRTOS
  int val = 0;
  setsockopt(fd, SOL_SOCKET, SO_BLOCKING, &val, sizeof(val));
  // SPRU524J section 3.3.3 page 63, SO_SNDLOWAT
  int sz = sizeof(val);
  getsockopt(fd, SOL_SOCKET, SO_SNDBUF, &val, &sz);
  val /= 2;  // set send low-water mark at half send buffer size
  setsockopt(fd, SOL_SOCKET, SO_SNDLOWAT, &val, sizeof(val));
#else
  fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) | O_NONBLOCK);  // Non-blocking mode
  fcntl(fd, F_SETFD, FD_CLOEXEC);                          // Set close-on-exec
#endif
}

void mg_multicast_add(struct mg_connection *c, char *ip);
void mg_multicast_add(struct mg_connection *c, char *ip) {
#if MG_ENABLE_RL
  MG_ERROR(("unsupported"));
#elif MG_ENABLE_FREERTOS_TCP
  // TODO(): prvAllowIPPacketIPv4()
#else
  // lwIP, Unix, Windows, Zephyr 4+(, AzureRTOS ?)
#if MG_ENABLE_LWIP && !LWIP_IGMP
  MG_ERROR(("LWIP_IGMP not defined, no multicast support"));
#else
#if defined(__ZEPHYR__) && ZEPHYR_VERSION_CODE < 0x40000
  MG_ERROR(("struct ip_mreq not defined"));
#else
  struct ip_mreq mreq;
  mreq.imr_multiaddr.s_addr = inet_addr(ip);
  mreq.imr_interface.s_addr = mg_htonl(INADDR_ANY);
  setsockopt(FD(c), IPPROTO_IP, IP_ADD_MEMBERSHIP, (char *) &mreq,
             sizeof(mreq));
#endif  // !Zephyr
#endif  // !lwIP
#endif
}

bool mg_open_listener(struct mg_connection *c, const char *url) {
  MG_SOCKET_TYPE fd = MG_INVALID_SOCKET;
  bool success = false;
  c->loc.port = mg_htons(mg_url_port(url));
  if (!mg_aton(mg_url_host(url), &c->loc)) {
    MG_ERROR(("invalid listening URL: %s", url));
  } else {
    union usa usa;
    socklen_t slen = tousa(&c->loc, &usa);
    int rc, on = 1, af = c->loc.is_ip6 ? AF_INET6 : AF_INET;
    int type = strncmp(url, "udp:", 4) == 0 ? SOCK_DGRAM : SOCK_STREAM;
    int proto = type == SOCK_DGRAM ? IPPROTO_UDP : IPPROTO_TCP;
    (void) on;

    if ((fd = socket(af, type, proto)) == MG_INVALID_SOCKET) {
      MG_ERROR(("socket: %d", MG_SOCK_ERR(-1)));
#if defined(SO_EXCLUSIVEADDRUSE)
    } else if ((rc = setsockopt(fd, SOL_SOCKET, SO_EXCLUSIVEADDRUSE,
                                (char *) &on, sizeof(on))) != 0) {
      // "Using SO_REUSEADDR and SO_EXCLUSIVEADDRUSE"
      MG_ERROR(("setsockopt(SO_EXCLUSIVEADDRUSE): %d %d", on, MG_SOCK_ERR(rc)));
#elif defined(SO_REUSEADDR) && (!defined(LWIP_SOCKET) || SO_REUSE)
    } else if ((rc = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (char *) &on,
                                sizeof(on))) != 0) {
      // 1. SO_REUSEADDR semantics on UNIX and Windows is different.  On
      // Windows, SO_REUSEADDR allows to bind a socket to a port without error
      // even if the port is already open by another program. This is not the
      // behavior SO_REUSEADDR was designed for, and leads to hard-to-track
      // failure scenarios.
      //
      // 2. For LWIP, SO_REUSEADDR should be explicitly enabled by defining
      // SO_REUSE = 1 in lwipopts.h, otherwise the code below will compile but
      // won't work! (setsockopt will return EINVAL)
      MG_ERROR(("setsockopt(SO_REUSEADDR): %d", MG_SOCK_ERR(rc)));
#endif
#if MG_IPV6_V6ONLY
      // Bind only to the V6 address, not V4 address on this port
    } else if (c->loc.is_ip6 &&
               (rc = setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, (char *) &on,
                                sizeof(on))) != 0) {
      // See #2089. Allow to bind v4 and v6 sockets on the same port
      MG_ERROR(("setsockopt(IPV6_V6ONLY): %d", MG_SOCK_ERR(rc)));
#endif
    } else if ((rc = bind(fd, &usa.sa, slen)) != 0) {
      MG_ERROR(("bind: %d", MG_SOCK_ERR(rc)));
    } else if ((type == SOCK_STREAM &&
                (rc = listen(fd, MG_SOCK_LISTEN_BACKLOG_SIZE)) != 0)) {
      // NOTE(lsm): FreeRTOS uses backlog value as a connection limit
      // In case port was set to 0, get the real port number
      MG_ERROR(("listen: %d", MG_SOCK_ERR(rc)));
    } else {
      setlocaddr(fd, &c->loc);
      mg_set_non_blocking_mode(fd);
      c->fd = S2PTR(fd);
      MG_EPOLL_ADD(c);
      success = true;
    }
  }
  if (success == false && fd != MG_INVALID_SOCKET) closesocket(fd);
  return success;
}

static long recv_raw(struct mg_connection *c, void *buf, size_t len) {
  long n = 0;
  if (c->is_udp) {
    union usa usa;
    socklen_t slen = tousa(&c->rem, &usa);
    n = recvfrom(FD(c), (char *) buf, len, 0, &usa.sa, &slen);
    if (n > 0) tomgaddr(&usa, &c->rem, slen != sizeof(usa.sin));
  } else {
    n = recv(FD(c), (char *) buf, len, MSG_NONBLOCKING);
  }
  MG_VERBOSE(("%lu %ld %d", c->id, n, MG_SOCK_ERR(n)));
  if (MG_SOCK_PENDING(n)) return MG_IO_WAIT;
  if (MG_SOCK_RESET(n)) return MG_IO_RESET;  // MbedTLS, see #1507
  if (n <= 0) return MG_IO_ERR;
  return n;
}

static bool ioalloc(struct mg_connection *c, struct mg_iobuf *io) {
  bool res = false;
  if (io->len >= MG_MAX_RECV_SIZE) {
    mg_error(c, "MG_MAX_RECV_SIZE");
  } else if (io->size <= io->len &&
             !mg_iobuf_resize(io, io->size + MG_IO_SIZE)) {
    mg_error(c, "OOM");
  } else {
    res = true;
  }
  return res;
}

// NOTE(lsm): do only one iteration of reads, cause some systems
// (e.g. FreeRTOS stack) return 0 instead of -1/EWOULDBLOCK when no data
static void read_conn(struct mg_connection *c) {
  if (ioalloc(c, &c->recv)) {
    char *buf = (char *) &c->recv.buf[c->recv.len];
    size_t len = c->recv.size - c->recv.len;
    long n = -1;
    if (c->is_tls) {
      // Do not read to the raw TLS buffer if it already has enough.
      // This is to prevent overflowing c->rtls if our reads are slow
      long m;
      if (c->rtls.len < 16 * 1024 + 40) {  // TLS record, header, MAC, padding
        if (!ioalloc(c, &c->rtls)) return;
        n = recv_raw(c, (char *) &c->rtls.buf[c->rtls.len],
                     c->rtls.size - c->rtls.len);
        if (n > 0) c->rtls.len += (size_t) n;
      }
      // there can still be > 16K from last iteration, always mg_tls_recv()
      m = c->is_tls_hs ? (long) MG_IO_WAIT : mg_tls_recv(c, buf, len);
      if (n == MG_IO_ERR || n == MG_IO_RESET) {  // Windows, see #3031
        if (c->rtls.len == 0 || m < 0) {
          // Close only when we have fully drained both rtls and TLS buffers
          c->is_closing = 1;         // or there's nothing we can do about it.
          if (m < 0) m = MG_IO_ERR;  // but return last record data, see #3104
        } else {                     // see #2885
          // TLS buffer is capped to max record size, even though, there can
          // be more than one record, give TLS a chance to process them.
        }
      } else if (c->is_tls_hs) {
        mg_tls_handshake(c);
      }
      n = m;
    } else {
      n = recv_raw(c, buf, len);
    }
    MG_DEBUG(("%lu %ld %lu:%lu:%lu %ld err %d", c->id, c->fd, c->send.len,
              c->recv.len, c->rtls.len, n, MG_SOCK_ERR(n)));
    iolog(c, buf, n, true);
  }
}

static void write_conn(struct mg_connection *c) {
  char *buf = (char *) c->send.buf;
  size_t len = c->send.len;
  long n = c->is_tls ? mg_tls_send(c, buf, len) : mg_io_send(c, buf, len);
  // TODO(): mg_tls_send() may return 0 forever on steady OOM
  MG_DEBUG(("%lu %ld snd %ld/%ld rcv %ld/%ld n=%ld err=%d", c->id, c->fd,
            (long) c->send.len, (long) c->send.size, (long) c->recv.len,
            (long) c->recv.size, n, MG_SOCK_ERR(n)));
  iolog(c, buf, n, false);
}

static void close_conn(struct mg_connection *c) {
  if (FD(c) != MG_INVALID_SOCKET) {
#if MG_ENABLE_EPOLL
    epoll_ctl(c->mgr->epoll_fd, EPOLL_CTL_DEL, FD(c), NULL);
#endif
    closesocket(FD(c));
#if MG_ENABLE_FREERTOS_TCP
    FreeRTOS_FD_CLR(c->fd, c->mgr->ss, eSELECT_ALL);
#endif
  }
  mg_close_conn(c);
}

static void connect_conn(struct mg_connection *c) {
  union usa usa;
  socklen_t n = sizeof(usa);
  // Use getpeername() to test whether we have connected
  if (getpeername(FD(c), &usa.sa, &n) == 0) {
    c->is_connecting = 0;
    setlocaddr(FD(c), &c->loc);
    mg_call(c, MG_EV_CONNECT, NULL);
    MG_EPOLL_MOD(c, 0);
    if (c->is_tls_hs) mg_tls_handshake(c);
    if (!c->is_tls_hs) c->is_tls = 0;  // user did not call mg_tls_init()
  } else {
    mg_error(c, "socket error");
  }
}

static void setsockopts(struct mg_connection *c) {
#if MG_ENABLE_FREERTOS_TCP || MG_ARCH == MG_ARCH_THREADX || \
    MG_ARCH == MG_ARCH_TIRTOS
  (void) c;
#else
  int on = 1;
#if !defined(SOL_TCP)
#define SOL_TCP IPPROTO_TCP
#endif
  if (setsockopt(FD(c), SOL_TCP, TCP_NODELAY, (char *) &on, sizeof(on)) != 0)
    (void) 0;
  if (setsockopt(FD(c), SOL_SOCKET, SO_KEEPALIVE, (char *) &on, sizeof(on)) !=
      0)
    (void) 0;
#endif
}

void mg_connect_resolved(struct mg_connection *c) {
  int type = c->is_udp ? SOCK_DGRAM : SOCK_STREAM;
  int proto = type == SOCK_DGRAM ? IPPROTO_UDP : IPPROTO_TCP;
  int rc, af = c->rem.is_ip6 ? AF_INET6 : AF_INET;  // c->rem has resolved IP
  c->fd = S2PTR(socket(af, type, proto));           // Create outbound socket
  c->is_resolving = 0;                              // Clear resolving flag
  if (FD(c) == MG_INVALID_SOCKET) {
    mg_error(c, "socket(): %d", MG_SOCK_ERR(-1));
  } else if (c->is_udp) {
    MG_EPOLL_ADD(c);
#if MG_ARCH == MG_ARCH_TIRTOS
    union usa usa;  // TI-RTOS NDK requires binding to receive on UDP sockets
    socklen_t slen = tousa(&c->loc, &usa);
    if ((rc = bind(c->fd, &usa.sa, slen)) != 0)
      MG_ERROR(("bind: %d", MG_SOCK_ERR(rc)));
#endif
    setlocaddr(FD(c), &c->loc);
    mg_call(c, MG_EV_RESOLVE, NULL);
    mg_call(c, MG_EV_CONNECT, NULL);
  } else {
    union usa usa;
    socklen_t slen = tousa(&c->rem, &usa);
    mg_set_non_blocking_mode(FD(c));
    setsockopts(c);
    MG_EPOLL_ADD(c);
    mg_call(c, MG_EV_RESOLVE, NULL);
    rc = connect(FD(c), &usa.sa, slen);  // Attempt to connect
    if (rc == 0) {                       // Success
      setlocaddr(FD(c), &c->loc);
      mg_call(c, MG_EV_CONNECT, NULL);   // Send MG_EV_CONNECT to the user
      if (!c->is_tls_hs) c->is_tls = 0;  // user did not call mg_tls_init()
    } else if (MG_SOCK_PENDING(rc)) {    // Need to wait for TCP handshake
      MG_DEBUG(("%lu %ld -> %M pend", c->id, c->fd, mg_print_ip_port, &c->rem));
      c->is_connecting = 1;
    } else {
      mg_error(c, "connect: %d", MG_SOCK_ERR(rc));
    }
  }
}

static MG_SOCKET_TYPE raccept(MG_SOCKET_TYPE sock, union usa *usa,
                              socklen_t *len) {
  MG_SOCKET_TYPE fd = MG_INVALID_SOCKET;
  do {
    memset(usa, 0, sizeof(*usa));
    fd = accept(sock, &usa->sa, len);
  } while (MG_SOCK_INTR(fd));
  return fd;
}

static void accept_conn(struct mg_mgr *mgr, struct mg_connection *lsn) {
  struct mg_connection *c = NULL;
  union usa usa;
  socklen_t sa_len = sizeof(usa);
  MG_SOCKET_TYPE fd = raccept(FD(lsn), &usa, &sa_len);
  if (fd == MG_INVALID_SOCKET) {
#if MG_ARCH == MG_ARCH_THREADX || defined(__ECOS)
    // NetxDuo, in non-block socket mode can mark listening socket readable
    // even it is not. See comment for 'select' func implementation in
    // nx_bsd.c That's not an error, just should try later
    if (errno != EAGAIN)
#endif
      MG_ERROR(("%lu accept failed, errno %d", lsn->id, MG_SOCK_ERR(-1)));
#if (MG_ARCH != MG_ARCH_WIN32) && !MG_ENABLE_FREERTOS_TCP && \
    (MG_ARCH != MG_ARCH_TIRTOS) && !MG_ENABLE_POLL && !MG_ENABLE_EPOLL
  } else if ((long) fd >= FD_SETSIZE) {
    MG_ERROR(("%ld > %ld", (long) fd, (long) FD_SETSIZE));
    closesocket(fd);
#endif
  } else if ((c = mg_alloc_conn(mgr)) == NULL) {
    MG_ERROR(("%lu OOM", lsn->id));
    closesocket(fd);
  } else {
    tomgaddr(&usa, &c->rem, sa_len != sizeof(usa.sin));
    LIST_ADD_HEAD(struct mg_connection, &mgr->conns, c);
    c->fd = S2PTR(fd);
    MG_EPOLL_ADD(c);
    mg_set_non_blocking_mode(FD(c));
    setsockopts(c);
    c->is_accepted = 1;
    c->is_hexdumping = lsn->is_hexdumping;
    setlocaddr(fd, &c->loc); // set local addr to where the client connected to
    c->pfn = lsn->pfn;
    c->pfn_data = lsn->pfn_data;
    c->fn = lsn->fn;
    c->fn_data = lsn->fn_data;
    c->is_tls = lsn->is_tls;
    MG_DEBUG(("%lu %ld accepted %M -> %M", c->id, c->fd, mg_print_ip_port,
              &c->rem, mg_print_ip_port, &c->loc));
    mg_call(c, MG_EV_OPEN, NULL);
    mg_call(c, MG_EV_ACCEPT, NULL);
    if (!c->is_tls_hs) c->is_tls = 0;  // user did not call mg_tls_init()
  }
}

static bool can_read(const struct mg_connection *c) {
  return c->is_full == false;
}

static bool can_write(const struct mg_connection *c) {
  return c->is_connecting || (c->send.len > 0 && c->is_tls_hs == 0);
}

static bool skip_iotest(const struct mg_connection *c) {
  return (c->is_closing || c->is_resolving || FD(c) == MG_INVALID_SOCKET) ||
         (can_read(c) == false && can_write(c) == false);
}

static void mg_iotest(struct mg_mgr *mgr, int ms) {
#if MG_ENABLE_FREERTOS_TCP
  struct mg_connection *c;
  for (c = mgr->conns; c != NULL; c = c->next) {
    c->is_readable = c->is_writable = 0;
    if (skip_iotest(c)) continue;
    if (can_read(c))
      FreeRTOS_FD_SET(c->fd, mgr->ss, eSELECT_READ | eSELECT_EXCEPT);
    if (can_write(c)) FreeRTOS_FD_SET(c->fd, mgr->ss, eSELECT_WRITE);
    if (c->is_closing) ms = 1;
  }
  FreeRTOS_select(mgr->ss, pdMS_TO_TICKS(ms));
  for (c = mgr->conns; c != NULL; c = c->next) {
    EventBits_t bits = FreeRTOS_FD_ISSET(c->fd, mgr->ss);
    c->is_readable = bits & (eSELECT_READ | eSELECT_EXCEPT) ? 1U : 0;
    c->is_writable = bits & eSELECT_WRITE ? 1U : 0;
    if (c->fd != MG_INVALID_SOCKET)
      FreeRTOS_FD_CLR(c->fd, mgr->ss,
                      eSELECT_READ | eSELECT_EXCEPT | eSELECT_WRITE);
  }
#elif MG_ENABLE_EPOLL
  size_t max = 1;
  for (struct mg_connection *c = mgr->conns; c != NULL; c = c->next) {
    c->is_readable = c->is_writable = 0;
    if (c->rtls.len > 0 || mg_tls_pending(c) > 0) ms = 1, c->is_readable = 1;
    if (can_write(c)) MG_EPOLL_MOD(c, 1);
    if (c->is_closing) ms = 1;
    max++;
  }
  struct epoll_event *evs = (struct epoll_event *) alloca(max * sizeof(evs[0]));
  int n = epoll_wait(mgr->epoll_fd, evs, (int) max, ms);
  for (int i = 0; i < n; i++) {
    struct mg_connection *c = (struct mg_connection *) evs[i].data.ptr;
    if (evs[i].events & EPOLLERR) {
      mg_error(c, "socket error");
    } else if (c->is_readable == 0) {
      bool rd = evs[i].events & (EPOLLIN | EPOLLHUP);
      bool wr = evs[i].events & EPOLLOUT;
      c->is_readable = can_read(c) && rd ? 1U : 0;
      c->is_writable = can_write(c) && wr ? 1U : 0;
      if (c->rtls.len > 0 || mg_tls_pending(c) > 0) c->is_readable = 1;
    }
  }
  (void) skip_iotest;
#elif MG_ENABLE_POLL
  nfds_t n = 0;
  for (struct mg_connection *c = mgr->conns; c != NULL; c = c->next) n++;
  struct pollfd *fds = (struct pollfd *) alloca(n * sizeof(fds[0]));
  memset(fds, 0, n * sizeof(fds[0]));
  n = 0;
  for (struct mg_connection *c = mgr->conns; c != NULL; c = c->next) {
    c->is_readable = c->is_writable = 0;
    if (c->is_closing) ms = 1;
    if (skip_iotest(c)) {
      // Socket not valid, ignore
    } else {
      // Don't wait if TLS is ready
      if (c->rtls.len > 0 || mg_tls_pending(c) > 0) ms = 1;
      fds[n].fd = FD(c);
      if (can_read(c)) fds[n].events |= POLLIN;
      if (can_write(c)) fds[n].events |= POLLOUT;
      n++;
    }
  }

  // MG_INFO(("poll n=%d ms=%d", (int) n, ms));
  if (poll(fds, n, ms) < 0) {
#if MG_ARCH == MG_ARCH_WIN32
    if (n == 0) Sleep(ms);  // On Windows, poll fails if no sockets
#endif
    memset(fds, 0, n * sizeof(fds[0]));
  }
  n = 0;
  for (struct mg_connection *c = mgr->conns; c != NULL; c = c->next) {
    if (skip_iotest(c)) {
      // Socket not valid, ignore
    } else {
      if (fds[n].revents & POLLERR) {
        mg_error(c, "socket error");
      } else {
        c->is_readable =
            (unsigned) (fds[n].revents & (POLLIN | POLLHUP) ? 1 : 0);
        c->is_writable = (unsigned) (fds[n].revents & POLLOUT ? 1 : 0);
        if (c->rtls.len > 0 || mg_tls_pending(c) > 0) c->is_readable = 1;
      }
      n++;
    }
  }
#else
  struct timeval tv = {ms / 1000, (ms % 1000) * 1000}, tv_1ms = {0, 1000}, *tvp;
  struct mg_connection *c;
  fd_set rset, wset, eset;
  MG_SOCKET_TYPE maxfd = 0;
  int rc;

  FD_ZERO(&rset);
  FD_ZERO(&wset);
  FD_ZERO(&eset);
  tvp = ms < 0 ? NULL : &tv;
  for (c = mgr->conns; c != NULL; c = c->next) {
    c->is_readable = c->is_writable = 0;
    if (skip_iotest(c)) continue;
    FD_SET(FD(c), &eset);
    if (can_read(c)) FD_SET(FD(c), &rset);
    if (can_write(c)) FD_SET(FD(c), &wset);
    if (c->rtls.len > 0 || mg_tls_pending(c) > 0) tvp = &tv_1ms;
    if (FD(c) > maxfd) maxfd = FD(c);
    if (c->is_closing) tvp = &tv_1ms;
  }

  if ((rc = select((int) maxfd + 1, &rset, &wset, &eset, tvp)) <= 0) {
#if MG_ARCH == MG_ARCH_WIN32
    if (maxfd == 0) Sleep(ms);  // On Windows, select fails if no sockets
#else
    if (rc < 0) MG_ERROR(("select: %d %d", rc, MG_SOCK_ERR(rc)));
#endif
    FD_ZERO(&rset);
    FD_ZERO(&wset);
    FD_ZERO(&eset);
  }

  for (c = mgr->conns; c != NULL; c = c->next) {
    if (FD(c) != MG_INVALID_SOCKET && FD_ISSET(FD(c), &eset)) {
#if MG_ARCH == MG_ARCH_THREADX
      // NetxDuo stack returns exceptions for listening connection after accept
      if (c->is_listening == 0) mg_error(c, "socket error");
#else
      mg_error(c, "socket error");
#endif
    } else {
      c->is_readable = FD(c) != MG_INVALID_SOCKET && FD_ISSET(FD(c), &rset);
      c->is_writable = FD(c) != MG_INVALID_SOCKET && FD_ISSET(FD(c), &wset);
      if (c->rtls.len > 0 || mg_tls_pending(c) > 0) c->is_readable = 1;
    }
  }
#endif
}

static bool mg_socketpair(MG_SOCKET_TYPE sp[2], union usa usa[2]) {
  socklen_t n = sizeof(usa[0].sin);
  bool success = false;

  sp[0] = sp[1] = MG_INVALID_SOCKET;
  (void) memset(&usa[0], 0, sizeof(usa[0]));
  usa[0].sin.sin_family = AF_INET;
  *(uint32_t *) &usa->sin.sin_addr = mg_htonl(0x7f000001U);  // 127.0.0.1
  usa[1] = usa[0];

  if ((sp[0] = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) != MG_INVALID_SOCKET &&
      (sp[1] = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) != MG_INVALID_SOCKET &&
      bind(sp[0], &usa[0].sa, n) == 0 &&          //
      bind(sp[1], &usa[1].sa, n) == 0 &&          //
      getsockname(sp[0], &usa[0].sa, &n) == 0 &&  //
      getsockname(sp[1], &usa[1].sa, &n) == 0 &&  //
      connect(sp[0], &usa[1].sa, n) == 0 &&       //
      connect(sp[1], &usa[0].sa, n) == 0) {       //
    success = true;
  }
  if (!success) {
    if (sp[0] != MG_INVALID_SOCKET) closesocket(sp[0]);
    if (sp[1] != MG_INVALID_SOCKET) closesocket(sp[1]);
    sp[0] = sp[1] = MG_INVALID_SOCKET;
  }
  return success;
}

// mg_wakeup() event handler
static void wufn(struct mg_connection *c, int ev, void *ev_data) {
  if (ev == MG_EV_READ) {
    unsigned long *id = (unsigned long *) c->recv.buf;
    // MG_INFO(("Got data"));
    // mg_hexdump(c->recv.buf, c->recv.len);
    if (c->recv.len >= sizeof(*id)) {
      struct mg_connection *t;
      for (t = c->mgr->conns; t != NULL; t = t->next) {
        if (t->id == *id) {
          struct mg_str data = mg_str_n((char *) c->recv.buf + sizeof(*id),
                                        c->recv.len - sizeof(*id));
          mg_call(t, MG_EV_WAKEUP, &data);
        }
      }
    }
    c->recv.len = 0;  // Consume received data
  } else if (ev == MG_EV_CLOSE) {
    closesocket(c->mgr->pipe);         // When we're closing, close the other
    c->mgr->pipe = MG_INVALID_SOCKET;  // side of the socketpair, too
  }
  (void) ev_data;
}

bool mg_wakeup_init(struct mg_mgr *mgr) {
  bool ok = false;
  if (mgr->pipe == MG_INVALID_SOCKET) {
    union usa usa[2];
    MG_SOCKET_TYPE sp[2] = {MG_INVALID_SOCKET, MG_INVALID_SOCKET};
    struct mg_connection *c = NULL;
    if (!mg_socketpair(sp, usa)) {
      MG_ERROR(("Cannot create socket pair"));
    } else if ((c = mg_wrapfd(mgr, (int) sp[1], wufn, NULL)) == NULL) {
      closesocket(sp[0]);
      closesocket(sp[1]);
      sp[0] = sp[1] = MG_INVALID_SOCKET;
    } else {
      tomgaddr(&usa[0], &c->rem, false);
      MG_DEBUG(("%lu %p pipe %lu", c->id, c->fd, (unsigned long) sp[0]));
      mgr->pipe = sp[0];
      ok = true;
    }
  }
  return ok;
}

bool mg_wakeup(struct mg_mgr *mgr, unsigned long conn_id, const void *buf,
               size_t len) {
  if (mgr->pipe != MG_INVALID_SOCKET && conn_id > 0) {
    char *extended_buf = (char *) alloca(len + sizeof(conn_id));
    memcpy(extended_buf, &conn_id, sizeof(conn_id));
    memcpy(extended_buf + sizeof(conn_id), buf, len);
    send(mgr->pipe, extended_buf, len + sizeof(conn_id), MSG_NONBLOCKING);
    return true;
  }
  return false;
}

void mg_mgr_poll(struct mg_mgr *mgr, int ms) {
  struct mg_connection *c, *tmp;
  uint64_t now;

  mg_iotest(mgr, ms);
  now = mg_millis();
  mg_timer_poll(&mgr->timers, now);

  for (c = mgr->conns; c != NULL; c = tmp) {
    bool is_resp = c->is_resp;
    tmp = c->next;
    mg_call(c, MG_EV_POLL, &now);
    if (is_resp && !c->is_resp) {
      long n = 0;
      mg_call(c, MG_EV_READ, &n);
    }
    MG_VERBOSE(("%lu %c%c %c%c%c%c%c %lu %lu", c->id,
                c->is_readable ? 'r' : '-', c->is_writable ? 'w' : '-',
                c->is_tls ? 'T' : 't', c->is_connecting ? 'C' : 'c',
                c->is_tls_hs ? 'H' : 'h', c->is_resolving ? 'R' : 'r',
                c->is_closing ? 'C' : 'c', mg_tls_pending(c), c->rtls.len));
    if (c->is_resolving || c->is_closing) {
      // Do nothing
    } else if (c->is_listening && c->is_udp == 0) {
      if (c->is_readable) accept_conn(mgr, c);
    } else if (c->is_connecting) {
      if (c->is_readable || c->is_writable) connect_conn(c);
    } else {
      if (c->is_readable) read_conn(c);
      if (c->is_writable) write_conn(c);
      if (c->is_tls && !c->is_tls_hs && c->send.len == 0) mg_tls_flush(c);
    }

    if (c->is_draining && c->send.len == 0) c->is_closing = 1;
    if (c->is_closing) close_conn(c);
  }
}
#endif