/* Copyright 2003-2004 Roger Dingledine.
 * Copyright 2004 Roger Dingledine, Nick Mathewson. */
/* See LICENSE for licensing information */
/* $Id$ */
const char cpuworker_c_id[] = "$Id$";

/**
 * \file cpuworker.c
 * \brief Run computation-intensive tasks (generally for crypto) in
 * a separate execution context. [OR only.]
 *
 * Right now, we only use this for processing onionskins.
 **/

#include "or.h"

/** The maximum number of cpuworker processes we will keep around. */
#define MAX_CPUWORKERS 16
/** The minimum number of cpuworker processes we will keep around. */
#define MIN_CPUWORKERS 1

/** The tag specifies which circuit this onionskin was from. */
#define TAG_LEN 8
/** How many bytes are sent from tor to the cpuworker? */
#define LEN_ONION_QUESTION (1+TAG_LEN+ONIONSKIN_CHALLENGE_LEN)
/** How many bytes are sent from the cpuworker back to tor? */
#define LEN_ONION_RESPONSE (1+TAG_LEN+ONIONSKIN_REPLY_LEN+40+32)

/** How many cpuworkers we have running right now. */
static int num_cpuworkers=0;
/** How many of the running cpuworkers have an assigned task right now. */
static int num_cpuworkers_busy=0;
/** We need to spawn new cpuworkers whenever we rotate the onion keys
 * on platforms where execution contexts==processes.  This variable stores
 * the last time we got a key rotation event. */
static time_t last_rotation_time=0;

static int cpuworker_main(void *data);
static int spawn_cpuworker(void);
static void spawn_enough_cpuworkers(void);
static void process_pending_task(connection_t *cpuworker);

/** Initialize the cpuworker subsystem.
 */
void cpu_init(void) {
  last_rotation_time=time(NULL);
  spawn_enough_cpuworkers();
}

/** Called when we're done sending a request to a cpuworker. */
int connection_cpu_finished_flushing(connection_t *conn) {
  tor_assert(conn);
  tor_assert(conn->type == CONN_TYPE_CPUWORKER);
  connection_stop_writing(conn);
  return 0;
}

/** Pack addr,port,and circ_id; set *tag to the result. (See note on
 * cpuworker_main for wire format.) */
static void tag_pack(char *tag, uint32_t addr, uint16_t port, uint16_t circ_id) {
  *(uint32_t *)tag     = addr;
  *(uint16_t *)(tag+4) = port;
  *(uint16_t *)(tag+6) = circ_id;
}

/** Unpack <b>tag</b> into addr, port, and circ_id.
 */
static void tag_unpack(const char *tag, uint32_t *addr, uint16_t *port, uint16_t *circ_id) {
  struct in_addr in;

  *addr    = *(const uint32_t *)tag;
  *port    = *(const uint16_t *)(tag+4);
  *circ_id = *(const uint16_t *)(tag+6);

  in.s_addr = htonl(*addr);
  log_fn(LOG_DEBUG,"onion was from %s:%d, circ_id %d.", inet_ntoa(in), *port, *circ_id);
}

/** Called when the onion key has changed and we need to spawn new
 * cpuworkers.  Close all currently idle cpuworkers, and mark the last
 * rotation time as now.
 */
void cpuworkers_rotate(void)
{
  connection_t *cpuworker;
  while ((cpuworker = connection_get_by_type_state(CONN_TYPE_CPUWORKER,
                                                   CPUWORKER_STATE_IDLE))) {
    connection_mark_for_close(cpuworker);
    --num_cpuworkers;
  }
  last_rotation_time = time(NULL);
  spawn_enough_cpuworkers();
}

/** If the cpuworker closes the connection,
 * mark it as closed and spawn a new one as needed. */
int connection_cpu_reached_eof(connection_t *conn) {
  log_fn(LOG_WARN,"Read eof. Worker died unexpectedly.");
  if (conn->state != CPUWORKER_STATE_IDLE) {
    /* the circ associated with this cpuworker will have to wait until
     * it gets culled in run_connection_housekeeping(), since we have
     * no way to find out which circ it was. */
    log_fn(LOG_WARN,"...and it left a circuit queued; abandoning circ.");
    num_cpuworkers_busy--;
  }
  num_cpuworkers--;
  spawn_enough_cpuworkers(); /* try to regrow. hope we don't end up spinning. */
  connection_mark_for_close(conn);
  return 0;
}

/** Called when we get data from a cpuworker.  If the answer is not complete,
 * wait for a complete answer. If the answer is complete,
 * process it as appropriate.
 */
int connection_cpu_process_inbuf(connection_t *conn) {
  char success;
  unsigned char buf[LEN_ONION_RESPONSE];
  uint32_t addr;
  uint16_t port;
  uint16_t circ_id;
  connection_t *p_conn;
  circuit_t *circ;

  tor_assert(conn);
  tor_assert(conn->type == CONN_TYPE_CPUWORKER);

  if (!buf_datalen(conn->inbuf))
    return 0;

  if (conn->state == CPUWORKER_STATE_BUSY_ONION) {
    if (buf_datalen(conn->inbuf) < LEN_ONION_RESPONSE) /* entire answer available? */
      return 0; /* not yet */
    tor_assert(buf_datalen(conn->inbuf) == LEN_ONION_RESPONSE);

    connection_fetch_from_buf(&success,1,conn);
    connection_fetch_from_buf(buf,LEN_ONION_RESPONSE-1,conn);

    /* parse out the circ it was talking about */
    tag_unpack(buf, &addr, &port, &circ_id);
    circ = NULL;
    /* (Here we use connection_exact_get_by_addr_port rather than
     * get_by_identity_digest: we want a specific port here in
     * case there are multiple connections.) */
    p_conn = connection_exact_get_by_addr_port(addr,port);
    if (p_conn)
      circ = circuit_get_by_circ_id_conn(circ_id, p_conn);

    if (success == 0) {
      log_fn(LOG_WARN,"decoding onionskin failed. Closing.");
      if (circ)
        circuit_mark_for_close(circ);
      goto done_processing;
    }
    if (!circ) {
      log_fn(LOG_INFO,"processed onion for a circ that's gone. Dropping.");
      goto done_processing;
    }
    tor_assert(circ->p_conn);
    if (onionskin_answer(circ, buf+TAG_LEN, buf+TAG_LEN+ONIONSKIN_REPLY_LEN) < 0) {
      log_fn(LOG_WARN,"onionskin_answer failed. Closing.");
      circuit_mark_for_close(circ);
      goto done_processing;
    }
    log_fn(LOG_DEBUG,"onionskin_answer succeeded. Yay.");
  } else {
    tor_assert(0); /* don't ask me to do handshakes yet */
  }

done_processing:
  conn->state = CPUWORKER_STATE_IDLE;
  num_cpuworkers_busy--;
  if (conn->timestamp_created < last_rotation_time) {
    connection_mark_for_close(conn);
    num_cpuworkers--;
    spawn_enough_cpuworkers();
  } else {
    process_pending_task(conn);
  }
  return 0;
}

/** Implement a cpuworker.  'data' is an fdarray as returned by socketpair.
 * Read and writes from fdarray[1].  Reads requests, writes answers.
 *
 *   Request format:
 *          Task type           [1 byte, always CPUWORKER_TASK_ONION]
 *          Opaque tag          TAG_LEN
 *          Onionskin challenge ONIONSKIN_CHALLENGE_LEN
 *   Response format:
 *          Success/failure     [1 byte, boolean.]
 *          Opaque tag          TAG_LEN
 *          Onionskin challenge ONIONSKIN_REPLY_LEN
 *          Negotiated keys     KEY_LEN*2+DIGEST_LEN*2
 *
 *  (Note: this _should_ be by addr/port, since we're concerned with specific
 * connections, not with routers (where we'd use identity).)
 */
static int cpuworker_main(void *data) {
  unsigned char question[ONIONSKIN_CHALLENGE_LEN];
  unsigned char question_type;
  int *fdarray = data;
  int fd;

  /* variables for onion processing */
  unsigned char keys[40+32];
  unsigned char reply_to_proxy[ONIONSKIN_REPLY_LEN];
  unsigned char buf[LEN_ONION_RESPONSE];
  char tag[TAG_LEN];
  crypto_pk_env_t *onion_key = NULL, *last_onion_key = NULL;

  fd = fdarray[1]; /* this side is ours */
#ifndef TOR_IS_MULTITHREADED
  tor_close_socket(fdarray[0]); /* this is the side of the socketpair the parent uses */
  connection_free_all(); /* so the child doesn't hold the parent's fd's open */
#endif
  handle_signals(0); /* ignore interrupts from the keyboard, etc */

  dup_onion_keys(&onion_key, &last_onion_key);

  for (;;) {

    if (recv(fd, &question_type, 1, 0) != 1) {
//      log_fn(LOG_ERR,"read type failed. Exiting.");
      log_fn(LOG_INFO,"cpuworker exiting because tor process closed connection (either rotated keys or died).");
      goto end;
    }
    tor_assert(question_type == CPUWORKER_TASK_ONION);

    if (read_all(fd, tag, TAG_LEN, 1) != TAG_LEN) {
      log_fn(LOG_ERR,"read tag failed. Exiting.");
      goto end;
    }

    if (read_all(fd, question, ONIONSKIN_CHALLENGE_LEN, 1) != ONIONSKIN_CHALLENGE_LEN) {
      log_fn(LOG_ERR,"read question failed. Exiting.");
      goto end;
    }

    if (question_type == CPUWORKER_TASK_ONION) {
      if (onion_skin_server_handshake(question, onion_key, last_onion_key,
          reply_to_proxy, keys, 40+32) < 0) {
        /* failure */
        log_fn(LOG_WARN,"onion_skin_server_handshake failed.");
        memset(buf,0,LEN_ONION_RESPONSE); /* send all zeros for failure */
      } else {
        /* success */
        log_fn(LOG_DEBUG,"onion_skin_server_handshake succeeded.");
        buf[0] = 1; /* 1 means success */
        memcpy(buf+1,tag,TAG_LEN);
        memcpy(buf+1+TAG_LEN,reply_to_proxy,ONIONSKIN_REPLY_LEN);
        memcpy(buf+1+TAG_LEN+ONIONSKIN_REPLY_LEN,keys,40+32);
      }
      if (write_all(fd, buf, LEN_ONION_RESPONSE, 1) != LEN_ONION_RESPONSE) {
        log_fn(LOG_ERR,"writing response buf failed. Exiting.");
        spawn_exit();
      }
      log_fn(LOG_DEBUG,"finished writing response.");
    }
  }
 end:
  if (onion_key)
    crypto_free_pk_env(onion_key);
  if (last_onion_key)
    crypto_free_pk_env(last_onion_key);
  spawn_exit();
  return 0; /* windows wants this function to return an int */
}

/** Launch a new cpuworker.
 */
static int spawn_cpuworker(void) {
  int fd[2];
  connection_t *conn;

  if (tor_socketpair(AF_UNIX, SOCK_STREAM, 0, fd) < 0) {
    log(LOG_ERR, "Couldn't construct socketpair: %s",
        tor_socket_strerror(tor_socket_errno(-1)));
    tor_cleanup();
    exit(1);
  }

  spawn_func(cpuworker_main, (void*)fd);
  log_fn(LOG_DEBUG,"just spawned a worker.");
#ifndef TOR_IS_MULTITHREADED
  tor_close_socket(fd[1]); /* we don't need the worker's side of the pipe */
#endif

  conn = connection_new(CONN_TYPE_CPUWORKER);

  set_socket_nonblocking(fd[0]);

  /* set up conn so it's got all the data we need to remember */
  conn->s = fd[0];
  conn->address = tor_strdup("localhost");

  if (connection_add(conn) < 0) { /* no space, forget it */
    log_fn(LOG_WARN,"connection_add failed. Giving up.");
    connection_free(conn); /* this closes fd[0] */
    return -1;
  }

  conn->state = CPUWORKER_STATE_IDLE;
  connection_start_reading(conn);

  return 0; /* success */
}

/** If we have too few or too many active cpuworkers, try to spawn new ones
 * or kill idle ones.
 */
static void spawn_enough_cpuworkers(void) {
  int num_cpuworkers_needed = get_options()->NumCpus;

  if (num_cpuworkers_needed < MIN_CPUWORKERS)
    num_cpuworkers_needed = MIN_CPUWORKERS;
  if (num_cpuworkers_needed > MAX_CPUWORKERS)
    num_cpuworkers_needed = MAX_CPUWORKERS;

  while (num_cpuworkers < num_cpuworkers_needed) {
    if (spawn_cpuworker() < 0) {
      log_fn(LOG_WARN,"spawn failed!");
      return;
    }
    num_cpuworkers++;
  }
}

/** Take a pending task from the queue and assign it to 'cpuworker'. */
static void process_pending_task(connection_t *cpuworker) {
  circuit_t *circ;

  tor_assert(cpuworker);

  /* for now only process onion tasks */

  circ = onion_next_task();
  if (!circ)
    return;
  if (assign_to_cpuworker(cpuworker, CPUWORKER_TASK_ONION, circ) < 0)
    log_fn(LOG_WARN,"assign_to_cpuworker failed. Ignoring.");
}

/** if cpuworker is defined, assert that he's idle, and use him. else,
 * look for an idle cpuworker and use him. if none idle, queue task onto
 * the pending onion list and return.
 * If question_type is CPUWORKER_TASK_ONION then task is a circ.
 * No other question_types are allowed.
 */
int assign_to_cpuworker(connection_t *cpuworker, unsigned char question_type,
                        void *task) {
  circuit_t *circ;
  char tag[TAG_LEN];

  tor_assert(question_type == CPUWORKER_TASK_ONION);

  if (question_type == CPUWORKER_TASK_ONION) {
    circ = task;

    if (num_cpuworkers_busy == num_cpuworkers) {
      log_fn(LOG_DEBUG,"No idle cpuworkers. Queuing.");
      if (onion_pending_add(circ) < 0)
        return -1;
      return 0;
    }

    if (!cpuworker)
      cpuworker = connection_get_by_type_state(CONN_TYPE_CPUWORKER, CPUWORKER_STATE_IDLE);

    tor_assert(cpuworker);

    if (!circ->p_conn) {
      log_fn(LOG_INFO,"circ->p_conn gone. Failing circ.");
      return -1;
    }
    tag_pack(tag, circ->p_conn->addr, circ->p_conn->port, circ->p_circ_id);

    cpuworker->state = CPUWORKER_STATE_BUSY_ONION;
    num_cpuworkers_busy++;

    connection_write_to_buf(&question_type, 1, cpuworker);
    connection_write_to_buf(tag, sizeof(tag), cpuworker);
    connection_write_to_buf(circ->onionskin, ONIONSKIN_CHALLENGE_LEN, cpuworker);
  }
  return 0;
}