libguestfs/lib/conn-socket.c

/* libguestfs
 * Copyright (C) 2013-2023 Red Hat Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * This file handles connections to the child process where this is
 * done over regular POSIX sockets.
 */

#include <config.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <poll.h>
#include <sys/stat.h>
#include <sys/socket.h>  /* accept4 */
#include <sys/types.h>
#include <assert.h>
#include <libintl.h>

#include "ignore-value.h"
#include "nonblocking.h"

#include "guestfs.h"
#include "guestfs-internal.h"

struct connection_socket {
  const struct connection_ops *ops;

  int console_sock;          /* Appliance console (for debug info). */
  int daemon_sock;           /* Daemon communications socket. */

  /* Socket for accepting a connection from the daemon.  Only used
   * before and during accept_connection.
   */
  int daemon_accept_sock;
};

static int handle_log_message (guestfs_h *g, struct connection_socket *conn);

static int
accept_connection (guestfs_h *g, struct connection *connv)
{
  struct connection_socket *conn = (struct connection_socket *) connv;
  int sock = -1;
  time_t start_t, now_t;
  int timeout_ms;

  time (&start_t);

  if (conn->daemon_accept_sock == -1) {
    error (g, _("accept_connection called twice"));
    return -1;
  }

  while (sock == -1) {
    struct pollfd fds[2];
    nfds_t nfds = 1;
    int r;

    fds[0].fd = conn->daemon_accept_sock;
    fds[0].events = POLLIN;
    fds[0].revents = 0;

    if (conn->console_sock >= 0) {
      fds[1].fd = conn->console_sock;
      fds[1].events = POLLIN;
      fds[1].revents = 0;
      nfds++;
    }

    time (&now_t);
    timeout_ms = 1000 * (APPLIANCE_TIMEOUT - (now_t - start_t));

    r = poll (fds, nfds, timeout_ms);
    if (r == -1) {
      if (errno == EINTR || errno == EAGAIN)
        continue;
      perrorf (g, "accept_connection: poll");
      return -1;
    }

    if (r == 0) {               /* timeout reached */
      guestfs_int_launch_timeout (g);
      return -1;
    }

    /* Log message? */
    if (nfds > 1 && (fds[1].revents & POLLIN) != 0) {
      r = handle_log_message (g, conn);
      if (r <= 0)
        return r;
    }

    /* Accept on socket? */
    if ((fds[0].revents & POLLIN) != 0) {
      sock = accept4 (conn->daemon_accept_sock, NULL, NULL, SOCK_CLOEXEC);
      if (sock == -1) {
        if (errno == EINTR || errno == EAGAIN)
          continue;
        perrorf (g, "accept_connection: accept");
        return -1;
      }
    }
  }

  /* Got a connection and accepted it, so update the connection's
   * internal status.
   */
  close (conn->daemon_accept_sock);
  conn->daemon_accept_sock = -1;
  conn->daemon_sock = sock;

  /* Make sure the new socket is non-blocking. */
  if (set_nonblocking_flag (conn->daemon_sock, 1) == -1) {
    perrorf (g, "accept_connection: set_nonblocking_flag");
    return -1;
  }

  return 1;
}

static ssize_t
read_data (guestfs_h *g, struct connection *connv, void *bufv, size_t len)
{
  char *buf = bufv;
  struct connection_socket *conn = (struct connection_socket *) connv;
  const size_t original_len = len;

  if (conn->daemon_sock == -1) {
    error (g, _("read_data: socket not connected"));
    return -1;
  }

  while (len > 0) {
    struct pollfd fds[2];
    nfds_t nfds = 1;
    int r;

    fds[0].fd = conn->daemon_sock;
    fds[0].events = POLLIN;
    fds[0].revents = 0;

    if (conn->console_sock >= 0) {
      fds[1].fd = conn->console_sock;
      fds[1].events = POLLIN;
      fds[1].revents = 0;
      nfds++;
    }

    r = poll (fds, nfds, -1);
    if (r == -1) {
      if (errno == EINTR || errno == EAGAIN)
        continue;
      perrorf (g, "read_data: poll");
      return -1;
    }

    /* Log message? */
    if (nfds > 1 && (fds[1].revents & POLLIN) != 0) {
      r = handle_log_message (g, conn);
      if (r <= 0)
        return r;
    }

    /* Read data on daemon socket? */
    if ((fds[0].revents & POLLIN) != 0) {
      ssize_t n = read (conn->daemon_sock, buf, len);
      if (n == -1) {
        if (errno == EINTR || errno == EAGAIN)
          continue;
        if (errno == ECONNRESET) /* essentially the same as EOF case */
          goto closed;
        perrorf (g, "read_data: read");
        return -1;
      }
      if (n == 0) {
      closed:
        /* Even though qemu has gone away, there could be more log
         * messages in the console socket buffer in the kernel.  Read
         * them out here.
         */
        if (g->verbose && conn->console_sock >= 0) {
          while (handle_log_message (g, conn) == 1)
            ;
        }
        return 0;
      }

      buf += n;
      len -= n;
    }
  }

  return original_len;
}

static int
can_read_data (guestfs_h *g, struct connection *connv)
{
  struct connection_socket *conn = (struct connection_socket *) connv;
  struct pollfd fd;
  int r;

  if (conn->daemon_sock == -1) {
    error (g, _("can_read_data: socket not connected"));
    return -1;
  }

  fd.fd = conn->daemon_sock;
  fd.events = POLLIN;
  fd.revents = 0;

 again:
  r = poll (&fd, 1, 0);
  if (r == -1) {
    if (errno == EINTR || errno == EAGAIN)
      goto again;
    perrorf (g, "can_read_data: poll");
    return -1;
  }

  return (fd.revents & POLLIN) != 0 ? 1 : 0;
}

static ssize_t
write_data (guestfs_h *g, struct connection *connv,
            const void *bufv, size_t len)
{
  const char *buf = bufv;
  struct connection_socket *conn = (struct connection_socket *) connv;
  const size_t original_len = len;

  if (conn->daemon_sock == -1) {
    error (g, _("write_data: socket not connected"));
    return -1;
  }

  while (len > 0) {
    struct pollfd fds[2];
    nfds_t nfds = 1;
    int r;

    fds[0].fd = conn->daemon_sock;
    fds[0].events = POLLOUT;
    fds[0].revents = 0;

    if (conn->console_sock >= 0) {
      fds[1].fd = conn->console_sock;
      fds[1].events = POLLIN;
      fds[1].revents = 0;
      nfds++;
    }

    r = poll (fds, nfds, -1);
    if (r == -1) {
      if (errno == EINTR || errno == EAGAIN)
        continue;
      perrorf (g, "write_data: poll");
      return -1;
    }

    /* Log message? */
    if (nfds > 1 && (fds[1].revents & POLLIN) != 0) {
      r = handle_log_message (g, conn);
      if (r <= 0)
        return r;
    }

    /* Can write data on daemon socket? */
    if ((fds[0].revents & POLLOUT) != 0) {
      ssize_t n = write (conn->daemon_sock, buf, len);
      if (n == -1) {
        if (errno == EINTR || errno == EAGAIN)
          continue;
        if (errno == EPIPE) /* Disconnected from guest (RHBZ#508713). */
          return 0;
        perrorf (g, "write_data: write");
        return -1;
      }

      buf += n;
      len -= n;
    }
  }

  return original_len;
}

/**
 * This is called if C<conn-E<gt>console_sock> becomes ready to read
 * while we are doing one of the connection operations above.  It
 * reads and deals with the log message.
 *
 * Returns:
 *
 * =over 4
 *
 * =item C<1>
 *
 * log message(s) were handled successfully
 *
 * =item C<0>
 *
 * connection to appliance closed
 *
 * =item C<-1>
 *
 * error
 *
 * =back
 */
static int
handle_log_message (guestfs_h *g,
                    struct connection_socket *conn)
{
  CLEANUP_FREE char *buf = safe_malloc (g, BUFSIZ);
  ssize_t n;
  const char dsr_request[] = "\033[6n";
  const char dsr_reply[] = "\033[24;80R";
  const char dsr_reply_padding[] = "\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b";

  /* Carried over from ancient proto.c code.  The comment there was:
   *
   *   "QEMU's console emulates a 16550A serial port.  The real 16550A
   *   device has a small FIFO buffer (16 bytes) which means here we
   *   see lots of small reads of 1-16 bytes in length, usually single
   *   bytes.  Sleeping here for a very brief period groups reads
   *   together (so we usually get a few lines of output at once) and
   *   improves overall throughput, as well as making the event
   *   interface a bit more sane for callers.  With a virtio-serial
   *   based console (not yet implemented) we may be able to remove
   *   this.  XXX"
   */
  usleep (1000);

  n = read (conn->console_sock, buf, BUFSIZ);
  if (n == 0)
    return 0;

  if (n == -1) {
    if (errno == EINTR || errno == EAGAIN)
      return 1; /* not an error */

    perrorf (g, _("error reading console messages from the appliance"));
    return -1;
  }

  /* It's an actual log message. */

  /* SGABIOS tries to query the "serial console" for its size using the
   * ISO/IEC 6429 Device Status Report (ESC [ 6 n).  If it doesn't
   * read anything back, then it unfortunately hangs for 0.26 seconds.
   * Therefore we detect this situation and send back a fake console
   * size.
   */
  if (memmem (buf, n, dsr_request, sizeof dsr_request - 1) != NULL) {
    debug (g, "responding to serial console Device Status Report");

    /* Ignore any error from this write, as it's just an optimization.
     * We can't even be sure that console_sock is a socket or that
     * it's writable.
     */
    ignore_value (write (conn->console_sock, dsr_reply,
                         sizeof dsr_reply - 1));
    /* Additionally, because of a bug in sgabios, it will still pause
     * unless you write at least 14 bytes, so we have to pad the
     * reply.  We can't pad with NULs since sgabios's input routine
     * ignores these, so we have to use some other safe padding
     * characters.  Backspace seems innocuous.
     */
    ignore_value (write (conn->console_sock, dsr_reply_padding,
                         sizeof dsr_reply_padding - 1));
  }

  /* Send it upwards. */
  guestfs_int_log_message_callback (g, buf, n);

  return 1;
}

static int
get_console_sock (guestfs_h *g, struct connection *connv)
{
  struct connection_socket *conn = (struct connection_socket *) connv;

  if (conn->console_sock == -1) {
    error (g, _("console socket not connected"));
    return -1;
  }

  return conn->console_sock;
}

static void
free_conn_socket (guestfs_h *g, struct connection *connv)
{
  struct connection_socket *conn = (struct connection_socket *) connv;

  if (conn->console_sock >= 0)
    close (conn->console_sock);
  if (conn->daemon_sock >= 0)
    close (conn->daemon_sock);
  if (conn->daemon_accept_sock >= 0)
    close (conn->daemon_accept_sock);

  free (conn);
}

static struct connection_ops ops = {
  .free_connection = free_conn_socket,
  .accept_connection = accept_connection,
  .read_data = read_data,
  .write_data = write_data,
  .can_read_data = can_read_data,
  .get_console_sock = get_console_sock,
};

/**
 * Create a new socket connection, listening.
 *
 * Note that it's OK for C<console_sock> to be passed as C<-1>,
 * meaning there's no console available for this appliance.
 *
 * After calling this, C<daemon_accept_sock> is owned by the
 * connection, and will be closed properly either in
 * C<accept_connection> or C<free_connection>.
 */
struct connection *
guestfs_int_new_conn_socket_listening (guestfs_h *g,
				       int daemon_accept_sock,
				       int console_sock)
{
  struct connection_socket *conn;

  assert (daemon_accept_sock >= 0);

  if (set_nonblocking_flag (daemon_accept_sock, 1) == -1) {
    perrorf (g, "new_conn_socket_listening: set_nonblocking_flag");
    return NULL;
  }

  if (console_sock >= 0) {
    if (set_nonblocking_flag (console_sock, 1) == -1) {
      perrorf (g, "new_conn_socket_listening: set_nonblocking_flag");
      return NULL;
    }
  }

  conn = safe_malloc (g, sizeof *conn);

  /* Set the operations. */
  conn->ops = &ops;

  /* Set the internal state. */
  conn->console_sock = console_sock;
  conn->daemon_sock = -1;
  conn->daemon_accept_sock = daemon_accept_sock;

  return (struct connection *) conn;
}

/**
 * Create a new socket connection, connected.
 *
 * As above, but the caller passes us a connected C<daemon_sock> and
 * promises not to call C<accept_connection>.
 */
struct connection *
guestfs_int_new_conn_socket_connected (guestfs_h *g,
				       int daemon_sock,
				       int console_sock)
{
  struct connection_socket *conn;

  assert (daemon_sock >= 0);

  if (set_nonblocking_flag (daemon_sock, 1) == -1) {
    perrorf (g, "new_conn_socket_connected: set_nonblocking_flag");
    return NULL;
  }

  if (console_sock >= 0) {
    if (set_nonblocking_flag (console_sock, 1) == -1) {
      perrorf (g, "new_conn_socket_connected: set_nonblocking_flag");
      return NULL;
    }
  }

  conn = safe_malloc (g, sizeof *conn);

  /* Set the operations. */
  conn->ops = &ops;

  /* Set the internal state. */
  conn->console_sock = console_sock;
  conn->daemon_sock = daemon_sock;
  conn->daemon_accept_sock = -1;

  return (struct connection *) conn;
}