src/ndmp/ndml_conn.c

/*
 * Copyright (c) 1998,1999,2000
 *      Traakan, Inc., Los Altos, CA
 *      All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice unmodified, this list of conditions, and the following
 *    disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * Project:  NDMJOB
 * Ident:    $Id: $
 *
 * Description:
 *
 */


#include "ndmlib.h"


#ifndef NDMOS_OPTION_NO_NDMP4
#define MAX_PROTOCOL_VERSION NDMP4VER
#else /* !NDMOS_OPTION_NO_NDMP4 */
#ifndef NDMOS_OPTION_NO_NDMP3
#define MAX_PROTOCOL_VERSION NDMP3VER
#else /* !NDMOS_OPTION_NO_NDMP3 */
#ifndef NDMOS_OPTION_NO_NDMP2
#define MAX_PROTOCOL_VERSION NDMP2VER
#else /* !NDMOS_OPTION_NO_NDMP2 */
#define MAX_PROTOCOL_VERSION 0
#endif /* !NDMOS_OPTION_NO_NDM2 */
#endif /* !NDMOS_OPTION_NO_NDMP3 */
#endif /* !NDMOS_OPTION_NO_NDMP4 */


/*
 * INITIALIZE AND DESTRUCT
 ****************************************************************
 *
 * Initialize an ndmconn. This pretty much amounts to
 * initializing the underlying ndmchan and stuffing
 * the function pointers.
 */

struct ndmconn* ndmconn_initialize(struct ndmconn* aconn, char* name)
{
  struct ndmconn* conn = aconn;

  if (!conn) {
    conn = NDMOS_MACRO_NEW(struct ndmconn);
    if (!conn) return 0;
  }

  NDMOS_MACRO_ZEROFILL(conn);

  if (!name) name = "#?"; /* default */

  ndmchan_initialize(&conn->chan, name);
  conn->was_allocated = aconn == 0;
  conn->next_sequence = 1;
  xdrrec_create(&conn->xdrs, 0, 0, (void*)conn, (void*)ndmconn_readit,
                (void*)ndmconn_writeit);
  conn->unexpected = ndmconn_unexpected;

  conn->call = ndmconn_call;

  conn->time_limit = 0;

  return conn;
}

/*
 * Get rid of an ndmconn.
 */
void ndmconn_destruct(struct ndmconn* conn)
{
  if (conn->chan.fd >= 0) {
    close(conn->chan.fd);
    conn->chan.fd = -1;
  }

  if (conn->xdrs.x_ops) {
    xdr_destroy(&conn->xdrs);
    conn->xdrs.x_ops = NULL;
  }

  if (conn->was_allocated) {
    conn->was_allocated = 0;
    NDMOS_API_FREE(conn);
    conn = 0;
  }
}

/*
 * ESTABLISH CONNECTION
 ****************************************************************
 *
 * The following four routines establish the TCP/IP connection
 * between agents.
 *
 * ndmconn_connect_agent()
 *     make a connection per an ndmagent, uses ..._host_port()
 * ndmconn_connect_host_port ()
 *     make a connection per a hostname and port, uses ..._sockaddr_in()
 * ndmconn_connect_sockaddr_in()
 *     make a connection per sockaddr_in, performs NDMP_CONNECT_
 *     sequences, but no authentication
 * ndmconn_accept()
 *     make a connection (receive it really) from a file descriptor
 *     already accept()ed.
 */

int ndmconn_connect_agent(struct ndmconn* conn, struct ndmagent* agent)
{
  if (agent->conn_type == NDMCONN_TYPE_RESIDENT) {
    conn->conn_type = NDMCONN_TYPE_RESIDENT;
    conn->protocol_version = agent->protocol_version;
    if (conn->protocol_version == 0) {
      /* Let's negotiate......MAX */
      conn->protocol_version = MAX_PROTOCOL_VERSION;
    }
    ndmchan_start_resident(&conn->chan);
    return 0;
  }

  if (agent->port == 0) agent->port = NDMPPORT;

  return ndmconn_connect_host_port(conn, agent->host, agent->port,
                                   agent->protocol_version);
}


int ndmconn_connect_host_port(struct ndmconn* conn,
                              char* hostname,
                              int port,
                              unsigned want_protocol_version)
{
  struct sockaddr_in sin;
  char* err = "???";

  if (conn->chan.fd >= 0) {
    err = "already-connected";
    return ndmconn_set_err_msg(conn, err);
  }

  if (ndmhost_lookup(hostname, &sin) != 0) {
    err = "bad-host-name";
    return ndmconn_set_err_msg(conn, err);
  }

  if (port == 0) port = NDMPPORT;

  sin.sin_port = htons(port);

  return ndmconn_connect_sockaddr_in(conn, &sin, want_protocol_version);
}

int ndmconn_connect_sockaddr_in(struct ndmconn* conn,
                                struct sockaddr_in* sin,
                                unsigned want_protocol_version)
{
  int fd = -1;
  int rc;
  char* err = "???";
  unsigned max_protocol_version = MAX_PROTOCOL_VERSION;

  if (conn->chan.fd >= 0) {
    err = "already-connected";
    return ndmconn_set_err_msg(conn, err);
  }

  fd = socket(AF_INET, SOCK_STREAM, 0);
  if (fd < 0) {
    err = NDMOS_API_MALLOC(1024);
    if (err) snprintf(err, 1023, "open a socket failed: %s", strerror(errno));
    goto error_out;
  }

  /* reserved port? */
  if (connect(fd, (struct sockaddr*)sin, sizeof *sin) < 0) {
    err = NDMOS_API_MALLOC(1024);
    if (err) snprintf(err, 1023, "connect failed: %s", strerror(errno));
    goto error_out;
  }

  ndmchan_start_readchk(&conn->chan, fd);
  conn->conn_type = NDMCONN_TYPE_REMOTE;

  /*
   * Await the NDMP_NOTIFY_CONNECTED request (no reply)
   * Don't get confused that this client-side is awaiting
   * a "request" from the server.
   */
  NDMC_WITH_NO_REPLY(ndmp0_notify_connected, 0)
  rc = ndmconn_recv_nmb(conn, &xa->request);
  if (rc != 0) {
    err = "recv-notify-connected";
    goto error_out;
  }
  if (xa->request.header.message_type != NDMP0_MESSAGE_REQUEST ||
      xa->request.header.message != NDMP0_NOTIFY_CONNECTED) {
    err = "msg-not-notify-connected";
    goto error_out;
  }

  if (request->reason != NDMP0_CONNECTED) {
    err = "notify-connected-not-connected";
    goto error_out;
  }

  if (max_protocol_version > request->protocol_version) {
    max_protocol_version = request->protocol_version;
  }
  NDMC_ENDWITH

  if (want_protocol_version == 0) {
    want_protocol_version = max_protocol_version;
  } else if (want_protocol_version > max_protocol_version) {
    err = "connect-want/max-version-mismatch";
    goto error_out;
  }

  /*
   * Send the OPEN request
   */
  NDMC_WITH(ndmp0_connect_open, 0)
  request->protocol_version = want_protocol_version;
  rc = NDMC_CALL(conn);
  if (rc) {
    err = "connect-open-failed";
    goto error_out;
  }
  NDMC_ENDWITH

  /* GOOD! */

  conn->protocol_version = want_protocol_version;

  return 0;

error_out:
  if (fd >= 0) {
    close(fd);
    fd = -1;
  }
  conn->chan.fd = -1;
  conn->chan.mode = NDMCHAN_MODE_IDLE;
  conn->conn_type = NDMCONN_TYPE_NONE;

  return ndmconn_set_err_msg(conn, err);
}

int ndmconn_try_open(struct ndmconn* conn, unsigned protocol_version)
{
  int rc;

  /*
   * Send the OPEN request
   */
  NDMC_WITH(ndmp0_connect_open, 0)
  request->protocol_version = protocol_version;
  rc = NDMC_CALL(conn);
  if (rc) { ndmconn_set_err_msg(conn, "connect-open-failed"); }
  NDMC_ENDWITH

  return rc;
}

int ndmconn_accept(struct ndmconn* conn, int sock)
{
  char* err = "???";

  if (conn->chan.fd >= 0) {
    err = "already-connected";
    return ndmconn_set_err_msg(conn, err);
  }

  ndmchan_start_readchk(&conn->chan, sock);
  conn->conn_type = NDMCONN_TYPE_REMOTE;

  /*
   * Send the NDMP_NOTIFY_CONNECTED message, no reply
   * The connect()er is waiting for it.
   */
  NDMC_WITH_NO_REPLY(ndmp0_notify_connected, 0)
  request->reason = NDMP0_CONNECTED;
  request->protocol_version = MAX_PROTOCOL_VERSION;
  request->text_reason = "Hello";
  NDMC_SEND(conn);
  NDMC_ENDWITH

  /* assume connection is running in offered protocol_version */
  conn->protocol_version = MAX_PROTOCOL_VERSION;

  return 0;
}


/*
 * TERMINATE CONNECTION
 ****************************************************************
 *
 * These two routines are about terminating a connection.
 * They are incomplete.
 */

/* hangup */
int ndmconn_abort(struct ndmconn* conn) { return 0; }

/* orderly close */
int ndmconn_close(struct ndmconn* conn) { return 0; }


/*
 * Return the underlying fd of the ndmconn.
 * This is no longer used since the ndmchan stuff was done.
 */

int ndmconn_fileno(struct ndmconn* conn) { return conn->chan.fd; }


/*
 * AUTHENTICATION
 *
 * The following three routines do the NDMP_CONNECT_AUTH sequences.
 */

int ndmconn_auth_agent(struct ndmconn* conn, struct ndmagent* agent)
{
  int rc;

  if (conn->conn_type == NDMCONN_TYPE_RESIDENT) return 0;

  switch (agent->auth_type) {
    case 'n': /* NDMP_AUTH_NONE */
      rc = ndmconn_auth_none(conn);
      break;

    case 't': /* NDMP_AUTH_TEXT */
      rc = ndmconn_auth_text(conn, agent->account, agent->password);
      break;

    case 'm': /* NDMP_AUTH_MD5 */
      rc = ndmconn_auth_md5(conn, agent->account, agent->password);
      break;

    case 'v': /* void (don't auth) */
      rc = 0;
      break;

    default:
      ndmconn_set_err_msg(conn, "connect-auth-unknown");
      rc = -1;
      break;
  }

  return rc;
}

int ndmconn_auth_none(struct ndmconn* conn)
{
  int rc;

  switch (conn->protocol_version) {
    default:
      ndmconn_set_err_msg(conn, "connect-auth-none-vers-botch");
      return -1;

#ifndef NDMOS_OPTION_NO_NDMP2
    case NDMP2VER:
      NDMC_WITH(ndmp2_connect_client_auth, NDMP2VER)
      request->auth_data.auth_type = NDMP2_AUTH_NONE;
      rc = NDMC_CALL(conn);
      NDMC_ENDWITH
      break;
#endif /* !NDMOS_OPTION_NO_NDMP2 */

#ifndef NDMOS_OPTION_NO_NDMP3
    case NDMP3VER:
      NDMC_WITH(ndmp3_connect_client_auth, NDMP3VER)
      request->auth_data.auth_type = NDMP3_AUTH_NONE;
      rc = NDMC_CALL(conn);
      NDMC_ENDWITH
      break;
#endif /* !NDMOS_OPTION_NO_NDMP3 */

#ifndef NDMOS_OPTION_NO_NDMP4
    case NDMP4VER:
      NDMC_WITH(ndmp4_connect_client_auth, NDMP4VER)
      request->auth_data.auth_type = NDMP4_AUTH_NONE;
      rc = NDMC_CALL(conn);
      NDMC_ENDWITH
      break;
#endif /* !NDMOS_OPTION_NO_NDMP4 */
  }

  if (rc) {
    ndmconn_set_err_msg(conn, "connect-auth-none-failed");
    return -1;
  }

  return 0;
}

int ndmconn_auth_text(struct ndmconn* conn, char* id, char* pw)
{
  int rc;

  switch (conn->protocol_version) {
    default:
      ndmconn_set_err_msg(conn, "connect-auth-text-vers-botch");
      return -1;

#ifndef NDMOS_OPTION_NO_NDMP2
    case NDMP2VER:
      NDMC_WITH(ndmp2_connect_client_auth, NDMP2VER)
      struct ndmp2_auth_text* at;

      request->auth_data.auth_type = NDMP2_AUTH_TEXT;
      at = &request->auth_data.ndmp2_auth_data_u.auth_text;
      at->auth_id = id;
      at->auth_password = pw;
      rc = NDMC_CALL(conn);
      NDMC_ENDWITH
      break;
#endif /* !NDMOS_OPTION_NO_NDMP2 */

#ifndef NDMOS_OPTION_NO_NDMP3
    case NDMP3VER:
      NDMC_WITH(ndmp3_connect_client_auth, NDMP3VER)
      struct ndmp3_auth_text* at;

      request->auth_data.auth_type = NDMP3_AUTH_TEXT;
      at = &request->auth_data.ndmp3_auth_data_u.auth_text;
      at->auth_id = id;
      at->auth_password = pw;
      rc = NDMC_CALL(conn);
      NDMC_ENDWITH
      break;
#endif /* !NDMOS_OPTION_NO_NDMP3 */

#ifndef NDMOS_OPTION_NO_NDMP4
    case NDMP4VER:
      NDMC_WITH(ndmp4_connect_client_auth, NDMP4VER)
      struct ndmp4_auth_text* at;

      request->auth_data.auth_type = NDMP4_AUTH_TEXT;
      at = &request->auth_data.ndmp4_auth_data_u.auth_text;
      at->auth_id = id;
      at->auth_password = pw;
      rc = NDMC_CALL(conn);
      NDMC_ENDWITH
      break;
#endif /* !NDMOS_OPTION_NO_NDMP4 */
  }

  if (rc) {
    ndmconn_set_err_msg(conn, "connect-auth-text-failed");
    return -1;
  }

  return 0;
}

int ndmconn_auth_md5(struct ndmconn* conn, char* id, char* pw)
{
  int rc;
  char challenge[NDMP_MD5_CHALLENGE_LENGTH];
  char digest[NDMP_MD5_DIGEST_LENGTH];

  switch (conn->protocol_version) {
    default:
      ndmconn_set_err_msg(conn, "connect-auth-md5-vers-botch");
      return -1;

#ifndef NDMOS_OPTION_NO_NDMP2
    case NDMP2VER:
      NDMC_WITH(ndmp2_config_get_auth_attr, NDMP2VER)
      request->auth_type = NDMP2_AUTH_MD5;
      rc = NDMC_CALL(conn);
      if (rc == 0) {
        if (reply->server_attr.auth_type != NDMP2_AUTH_MD5) {
          ndmconn_set_err_msg(conn, "connect-auth-md5-attr-type-botch");
          return -1;
        }
        NDMOS_API_BCOPY(reply->server_attr.ndmp2_auth_attr_u.challenge,
                        challenge, sizeof challenge);
      }
      NDMC_ENDWITH
      break;
#endif /* !NDMOS_OPTION_NO_NDMP2 */

#ifndef NDMOS_OPTION_NO_NDMP3
    case NDMP3VER:
      NDMC_WITH(ndmp3_config_get_auth_attr, NDMP3VER)
      request->auth_type = NDMP3_AUTH_MD5;
      rc = NDMC_CALL(conn);
      if (rc == 0) {
        if (reply->server_attr.auth_type != NDMP3_AUTH_MD5) {
          ndmconn_set_err_msg(conn, "connect-auth-md5-attr-type-botch");
          return -1;
        }
        NDMOS_API_BCOPY(reply->server_attr.ndmp3_auth_attr_u.challenge,
                        challenge, sizeof challenge);
      }
      NDMC_ENDWITH
      break;
#endif /* !NDMOS_OPTION_NO_NDMP3 */

#ifndef NDMOS_OPTION_NO_NDMP4
    case NDMP4VER:
      NDMC_WITH(ndmp4_config_get_auth_attr, NDMP4VER)
      request->auth_type = NDMP4_AUTH_MD5;
      rc = NDMC_CALL(conn);
      if (rc == 0) {
        if (reply->server_attr.auth_type != NDMP4_AUTH_MD5) {
          ndmconn_set_err_msg(conn, "connect-auth-md5-attr-type-botch");
          return -1;
        }
        NDMOS_API_BCOPY(reply->server_attr.ndmp4_auth_attr_u.challenge,
                        challenge, sizeof challenge);
      }
      NDMC_ENDWITH
      break;
#endif /* !NDMOS_OPTION_NO_NDMP4 */
  }

  if (rc) {
    ndmconn_set_err_msg(conn, "connect-auth-md5-attr-failed");
    return -1;
  }

  ndmmd5_digest(challenge, pw, digest);

  switch (conn->protocol_version) {
    default:
      ndmconn_set_err_msg(conn, "connect-auth-text-vers-botch");
      return -1;

#ifndef NDMOS_OPTION_NO_NDMP2
    case NDMP2VER:
      NDMC_WITH(ndmp2_connect_client_auth, NDMP2VER)
      struct ndmp2_auth_md5* am;

      request->auth_data.auth_type = NDMP2_AUTH_MD5;
      am = &request->auth_data.ndmp2_auth_data_u.auth_md5;
      am->auth_id = id;
      NDMOS_API_BCOPY(digest, am->auth_digest, sizeof digest);
      rc = NDMC_CALL(conn);
      NDMC_ENDWITH
      break;
#endif /* !NDMOS_OPTION_NO_NDMP2 */

#ifndef NDMOS_OPTION_NO_NDMP3
    case NDMP3VER:
      NDMC_WITH(ndmp3_connect_client_auth, NDMP3VER)
      struct ndmp3_auth_md5* am;

      request->auth_data.auth_type = NDMP3_AUTH_MD5;
      am = &request->auth_data.ndmp3_auth_data_u.auth_md5;
      am->auth_id = id;
      NDMOS_API_BCOPY(digest, am->auth_digest, sizeof digest);
      rc = NDMC_CALL(conn);
      NDMC_ENDWITH
      break;
#endif /* !NDMOS_OPTION_NO_NDMP3 */

#ifndef NDMOS_OPTION_NO_NDMP4
    case NDMP4VER:
      NDMC_WITH(ndmp4_connect_client_auth, NDMP4VER)
      struct ndmp4_auth_md5* am;

      request->auth_data.auth_type = NDMP4_AUTH_MD5;
      am = &request->auth_data.ndmp4_auth_data_u.auth_md5;
      am->auth_id = id;
      NDMOS_API_BCOPY(digest, am->auth_digest, sizeof digest);
      rc = NDMC_CALL(conn);
      NDMC_ENDWITH
      break;
#endif /* !NDMOS_OPTION_NO_NDMP4 */
  }

  if (rc) {
    ndmconn_set_err_msg(conn, "connect-auth-md5-failed");
    return -1;
  }

  return 0;
}


/*
 * CALL (REQUEST/REPLY), SEND, and RECEIVE
 ****************************************************************
 */

int ndmconn_call(struct ndmconn* conn, struct ndmp_xa_buf* xa)
{
  unsigned protocol_version = conn->protocol_version;
  unsigned msg = xa->request.header.message;
  int rc;
  struct ndmp_xdr_message_table* xmte;

  conn->last_message = msg;
  conn->last_call_status = NDMCONN_CALL_STATUS_BOTCH;
  conn->last_header_error = -1; /* invalid */
  conn->last_reply_error = -1;  /* invalid */

  if (protocol_version != xa->request.protocol_version) {
    ndmconn_set_err_msg(conn, "protocol-version-mismatch");
    return NDMCONN_CALL_STATUS_BOTCH;
  }

  xmte = ndmp_xmt_lookup(protocol_version, msg);
  if (!xmte) {
    ndmconn_set_err_msg(conn, "no-xdr-found");
    return NDMCONN_CALL_STATUS_BOTCH;
  }

  xa->request.header.message_type = NDMP0_MESSAGE_REQUEST;

  if (!xmte->xdr_reply) {
    /* no reply expected, just a send (eg NOTIFY) */
    return ndmconn_send_nmb(conn, &xa->request);
  }

  rc = ndmconn_exchange_nmb(conn, &xa->request, &xa->reply);
  if (rc) {
    ndmconn_set_err_msg(conn, "exchange-failed");
    return NDMCONN_CALL_STATUS_BOTCH;
  }

  if (xa->reply.header.message != msg) {
    ndmconn_set_err_msg(conn, "msg-mismatch");
    return NDMCONN_CALL_STATUS_BOTCH;
  }

  /* TODO: this should be converted ndmp_xto9_error(....) */
  conn->last_header_error = xa->reply.header.error;

  if (xa->reply.header.error) {
    conn->last_call_status = NDMCONN_CALL_STATUS_HDR_ERROR;
    ndmconn_set_err_msg(conn, "reply-error-hdr");
    return NDMCONN_CALL_STATUS_HDR_ERROR;
  }

  conn->last_reply_error = ndmnmb_get_reply_error(&xa->reply);

  switch (conn->last_reply_error) {
    case NDMP9_NO_ERR:
    case NDMP9_DEV_NOT_OPEN_ERR:
      /*
       * We allow NDMP9_DEV_NOT_OPEN_ERR as answer to NDMP4_TAPE_GET_STATE
       * This always happens during ndmca_monitor_shutdown()
       */
      break;
    default:
      conn->last_call_status = NDMCONN_CALL_STATUS_REPLY_ERROR;
      ndmconn_set_err_msg(conn, "reply-error");
      return NDMCONN_CALL_STATUS_REPLY_ERROR;
  }

  return NDMCONN_CALL_STATUS_OK;
}

int ndmconn_exchange_nmb(struct ndmconn* conn,
                         struct ndmp_msg_buf* request_nmb,
                         struct ndmp_msg_buf* reply_nmb)
{
  int rc;

  if ((rc = ndmconn_send_nmb(conn, request_nmb)) != 0) return rc;
  conn->received_time = 0;
  conn->sent_time = time(0);

  for (;;) {
    if ((rc = ndmconn_recv_nmb(conn, reply_nmb)) != 0) return rc;

    if (reply_nmb->header.message_type == NDMP0_MESSAGE_REPLY &&
        reply_nmb->header.reply_sequence == request_nmb->header.sequence) {
      conn->received_time = time(0);
      return 0;
    }

    (*conn->unexpected)(conn, reply_nmb);
  }
}

int ndmconn_send_nmb(struct ndmconn* conn, struct ndmp_msg_buf* nmb)
{
  return ndmconn_xdr_nmb(conn, nmb, XDR_ENCODE);
}

int ndmconn_recv_nmb(struct ndmconn* conn, struct ndmp_msg_buf* nmb)
{
  NDMOS_MACRO_ZEROFILL(nmb);
  nmb->protocol_version = conn->protocol_version;

  return ndmconn_xdr_nmb(conn, nmb, XDR_DECODE);
}

void ndmconn_free_nmb(struct ndmconn* conn, struct ndmp_msg_buf* nmb)
{
  ndmnmb_free(nmb);
}


int ndmconn_xdr_nmb(struct ndmconn* conn,
                    struct ndmp_msg_buf* nmb,
                    enum xdr_op x_op)
{
  xdrproc_t xdr_body = 0;

  assert(conn->conn_type == NDMCONN_TYPE_REMOTE);

  if (conn->chan.fd < 0) { return ndmconn_set_err_msg(conn, "not-open"); }

  conn->xdrs.x_op = x_op;

  if (x_op == XDR_ENCODE) {
    xdr_body = ndmnmb_find_xdrproc(nmb);

    if (nmb->header.error == NDMP0_NO_ERR && !xdr_body) {
      return ndmconn_set_err_msg(conn, "unknown-body");
    }
    nmb->header.sequence = conn->next_sequence++;
    nmb->header.time_stamp = time(0);
    ndmconn_snoop_nmb(conn, nmb, "Send");
  }
  if (x_op == XDR_DECODE) {
    if (!xdrrec_skiprecord(&conn->xdrs)) {
      return ndmconn_set_err_msg(conn, "xdr-get-next");
    }
  }

  if (!xdr_ndmp0_header(&conn->xdrs, &nmb->header)) {
    ndmconn_abort(conn);
    if (x_op == XDR_DECODE && conn->chan.eof && !conn->chan.error) {
      return ndmconn_set_err_msg(conn, "EOF");
    } else {
      return ndmconn_set_err_msg(conn, "xdr-hdr");
    }
  }

  if (x_op == XDR_DECODE) {
    xdr_body = ndmnmb_find_xdrproc(nmb);

    if (nmb->header.error == NDMP0_NO_ERR && !xdr_body) {
      return ndmconn_set_err_msg(conn, "unknown-body");
    }
  }
  if (nmb->header.error == NDMP0_NO_ERR) {
    if (!(*xdr_body)(&conn->xdrs, &nmb->body, 0)) {
      ndmconn_abort(conn);
      return ndmconn_set_err_msg(conn, "xdr-body");
    }
  }

  if (x_op == XDR_ENCODE) {
    if (!xdrrec_endofrecord(&conn->xdrs, 1)) {
      ndmconn_abort(conn);
      return ndmconn_set_err_msg(conn, "xdr-send");
    }
  }
  if (x_op == XDR_DECODE) { ndmconn_snoop_nmb(conn, nmb, "Recv"); }

  return 0;
}


/*
 * XDR READ/WRITE CALLBACKS
 ****************************************************************
 *
 * ndmconn_readit() and ndmconn_writeit() are the XDR callbacks
 * used by xdrrec_create(). They are fundamentally wrappers
 * around read() and write(), and have very similar parameters.
 * See the xdr(3) manual page (or try "man xdrrec_create").
 *
 * ndmconn_readit() tracks the XDR record marks, and never
 * reads across a record boundary. This keeps select() an
 * indicator of when there is a (single) request pending.
 * Otherwise, we have to check buffers internal to XDR
 * as well as the file descriptor (via select) to determine
 * if a request is pending.
 */

int ndmconn_readit(void* a_conn, char* buf, int len)
{
  struct ndmconn* conn = (struct ndmconn*)a_conn;
  int rc, i, c;

  /* could impose timeout here */
  if (conn->chan.fd < 0 || conn->chan.eof) return -1;

  ndmconn_snoop(conn, 8, "frag_resid=%d fhb_off=%d", conn->frag_resid,
                conn->fhb_off);

  if (conn->frag_resid == 0) {
    i = 0;
    while (i < 4) {
      c = 4 - i;

      rc = ndmconn_sys_read(conn, (void*)(conn->frag_hdr_buf + i), c);
      if (rc <= 0) { return rc; }
      i += rc;
    }
    conn->frag_resid = conn->frag_hdr_buf[0] << 24;
    conn->frag_resid |= conn->frag_hdr_buf[1] << 16;
    conn->frag_resid |= conn->frag_hdr_buf[2] << 8;
    conn->frag_resid |= conn->frag_hdr_buf[3];
    conn->frag_resid &= 0xFFFFFF;
    conn->fhb_off = 0;
  }
  if (conn->fhb_off < 4) {
    i = 0;
    while (conn->fhb_off < 4 && len > 0) {
      buf[i++] = conn->frag_hdr_buf[conn->fhb_off++];
      len--;
    }
    return i;
  }

  if ((unsigned int)len > conn->frag_resid)
    len = (unsigned int)conn->frag_resid;

  rc = ndmconn_sys_read(conn, buf, len);

  if (rc > 0) { conn->frag_resid -= rc; }

  return rc;
}

int ndmconn_writeit(void* a_conn, char* buf, int len)
{
  struct ndmconn* conn = (struct ndmconn*)a_conn;

  /* could impose timeout here */
  if (conn->chan.fd < 0) return -1;

  return ndmconn_sys_write(conn, buf, len);
}

/*
 * ndmconn_sys_read() and ndmconn_sys_write() are simply
 * wrappers around read() and write(). They implement
 * the low-level snooping.
 */

int ndmconn_sys_read(struct ndmconn* conn, char* buf, unsigned len)
{
  int rc;

  ndmconn_snoop(conn, 9, "reading %d ...", len);

  rc = read(conn->chan.fd, buf, len);

  ndmconn_snoop(conn, 8, "read=%d len=%d", rc, len);

  if (rc <= 0) {
    conn->chan.eof = 1;
    if (rc < 0) conn->chan.error = 1;
  } else {
    ndmconn_hex_dump(conn, buf, rc);
  }

  return rc;
}

int ndmconn_sys_write(struct ndmconn* conn, char* buf, unsigned len)
{
  int rc;

  ndmconn_snoop(conn, 9, "writing %d ...", len);
  ndmconn_hex_dump(conn, buf, len);

  rc = write(conn->chan.fd, buf, len);

  ndmconn_snoop(conn, 8, "write=%d len=%d", rc, len);

  if (rc != (int)len) {
    conn->chan.eof = 1;
    conn->chan.error = 1;
  }

  return rc;
}


/*
 * UNEXPECTED
 ****************************************************************
 *
 * The default unexpected() handler for a connection. It is
 * called when ndmconn_exchange_nmb() receives something
 * other than the reply for which it is waiting.
 * This default routine silently dumps the message.
 */

void ndmconn_unexpected(struct ndmconn* conn, struct ndmp_msg_buf* nmb)
{
  xdrproc_t xdr_body = ndmnmb_find_xdrproc(nmb);

  if (xdr_body) { xdr_free(xdr_body, (void*)&nmb->body); }
}


/*
 * SNOOP
 ****************************************************************
 *
 * The ndmconn snoop stuff. The cool part. This pretty prints
 * NDMP messages as they go flying by this end-point.
 */

int ndmconn_set_snoop(struct ndmconn* conn, struct ndmlog* log, int level)
{
  conn->snoop_log = log;
  conn->snoop_level = level;
  return 0;
}

void ndmconn_clear_snoop(struct ndmconn* conn)
{
  conn->snoop_log = 0;
  conn->snoop_level = 0;
}

void ndmconn_snoop_nmb(struct ndmconn* conn,
                       struct ndmp_msg_buf* nmb,
                       char* whence)
{
  if (!conn->snoop_log) { return; }

  ndmnmb_snoop(conn->snoop_log, conn->chan.name, conn->snoop_level, nmb,
               whence);
}

void ndmconn_snoop(struct ndmconn* conn, int level, char* fmt, ...)
{
  va_list ap;

  if (conn->snoop_log && conn->snoop_level >= level) {
    va_start(ap, fmt);
    ndmlogfv(conn->snoop_log, conn->chan.name, level, fmt, ap);
    va_end(ap);
  }
}

/* used by ndmconn_sys_read() and ndmconn_sys_write() to show low-level */
void ndmconn_hex_dump(struct ndmconn* conn, char* buf, unsigned len)
{
  struct ndmlog* log = conn->snoop_log;
  char* tag = conn->chan.name;
  char linebuf[16 * 3 + 3];
  char* p = linebuf;
  int b;
  unsigned i;

  if (log && conn->snoop_level > 8) {
    for (i = 0; i < len; i++) {
      b = buf[i] & 0xFF;
      sprintf(p, " %02x", b);
      while (*p) p++;
      if ((i & 0xF) == 0xF) {
        ndmlogf(log, tag, 9, "%s", linebuf + 1);
        p = linebuf;
      }
    }
    if (p > linebuf) { ndmlogf(log, tag, 9, "%s", linebuf + 1); }
  }
}


/*
 * ERRORS
 ****************************************************************
 *
 * Possible errors for ndmconn are not enumerated.
 * Instead, errors are indicated by a -1 return, and
 * a simple string error message is available for details.
 * Appologies for the english-centric design, but it
 * is quick and easy, and better than using printf().
 */

int ndmconn_set_err_msg(struct ndmconn* conn, char* err_msg)
{
  conn->last_err_msg = err_msg;
  ndmconn_snoop(conn, 4, "ERR=%s", err_msg);
  return -1;
}

char* ndmconn_get_err_msg(struct ndmconn* conn)
{
  if (!conn->last_err_msg)
    return "-no-error-";
  else
    return conn->last_err_msg;
}