rtsp.c

/*
 * RTSP protocol handler. This file is part of Shairport.
 * Copyright (c) James Laird 2013
 * All rights reserved.
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

#include <memory.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <sys/select.h>
#include <signal.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <pthread.h>
#include <poll.h>
#include <sys/stat.h>


#include "config.h"

#ifdef HAVE_LIBSSL
#include <openssl/md5.h>
#endif

#ifdef HAVE_LIBPOLARSSL
#include <polarssl/md5.h>
#endif

#include "common.h"
#include "player.h"
#include "rtp.h"
#include "mdns.h"

#ifdef AF_INET6
#define INETx_ADDRSTRLEN INET6_ADDRSTRLEN
#else
#define INETx_ADDRSTRLEN INET_ADDRSTRLEN
#endif

enum rtsp_read_request_response {
  rtsp_read_request_response_ok,
  rtsp_read_request_response_shutdown_requested,
  rtsp_read_request_response_bad_packet,
  rtsp_read_request_response_error
};

// Mike Brady's part...
static pthread_mutex_t play_lock = PTHREAD_MUTEX_INITIALIZER;

// every time we want to retain or release a reference count, lock it with this
// if a reference count is read as zero, it means the it's being deallocated.
static pthread_mutex_t reference_counter_lock = PTHREAD_MUTEX_INITIALIZER;

// only one thread is allowed to use the player at once.
// it monitors the request variable (at least when interrupted)
static pthread_mutex_t playing_mutex = PTHREAD_MUTEX_INITIALIZER;
static int please_shutdown = 0;
static pthread_t playing_thread = 0;

typedef struct {
  int fd;
  stream_cfg stream;
  SOCKADDR remote;
  int running;
  pthread_t thread;
} rtsp_conn_info;

#ifdef CONFIG_METADATA
typedef struct {
  pthread_mutex_t pc_queue_lock;
  pthread_cond_t pc_queue_item_added_signal;
  pthread_cond_t pc_queue_item_removed_signal;
  size_t item_size;  // number of bytes in each item
  uint32_t count;    // number of items in the queue
  uint32_t capacity; // maximum number of items
  uint32_t toq;      // first item to take
  uint32_t eoq;      // free space at end of queue
  void *items;       // a pointer to where the items are actually stored
} pc_queue;          // producer-consumer queue
#endif

typedef struct {
  uint32_t referenceCount; // we might start using this...
  int nheaders;
  char *name[16];
  char *value[16];

  int contentlength;
  char *content;

  // for requests
  char method[16];

  // for responses
  int respcode;
} rtsp_message;

#ifdef CONFIG_METADATA
typedef struct {
  uint32_t type;
  uint32_t code;
  char *data;
  uint32_t length;
  rtsp_message *carrier;
} metadata_package;

void pc_queue_init(pc_queue *the_queue, char *items, size_t item_size, uint32_t number_of_items) {
  the_queue->item_size = item_size;
  the_queue->items = items;
  the_queue->count = 0;
  the_queue->capacity = number_of_items;
  the_queue->toq = 0;
  the_queue->eoq = 0;
}

int send_metadata(uint32_t type, uint32_t code, char *data, uint32_t length, rtsp_message *carrier,
                  int block);

int send_ssnc_metadata(uint32_t code, char *data, uint32_t length, int block) {
  return send_metadata('ssnc', code, data, length, NULL, block);
}

int pc_queue_add_item(pc_queue *the_queue, const void *the_stuff, int block) {
  int rc;
  if (the_queue) {
    if (block == 0) {
      rc = pthread_mutex_trylock(&the_queue->pc_queue_lock);
      if (rc == EBUSY)
        return EBUSY;
    } else
      rc = pthread_mutex_lock(&the_queue->pc_queue_lock);
    if (rc)
      debug(1, "Error locking for pc_queue_add_item");
    while (the_queue->count == the_queue->capacity) {
      rc = pthread_cond_wait(&the_queue->pc_queue_item_removed_signal, &the_queue->pc_queue_lock);
      if (rc)
        debug(1, "Error waiting for item to be removed");
    }
    uint32_t i = the_queue->eoq;
    void *p = the_queue->items + the_queue->item_size * i;
    //    void * p = &the_queue->qbase + the_queue->item_size*the_queue->eoq;
    memcpy(p, the_stuff, the_queue->item_size);

    // update the pointer
    i++;
    if (i == the_queue->capacity)
      // fold pointer if necessary
      i = 0;
    the_queue->eoq = i;
    the_queue->count++;
    if (the_queue->count == the_queue->capacity)
      debug(1, "pc_queue is full!");
    rc = pthread_cond_signal(&the_queue->pc_queue_item_added_signal);
    if (rc)
      debug(1, "Error signalling after pc_queue_add_item");
    rc = pthread_mutex_unlock(&the_queue->pc_queue_lock);
    if (rc)
      debug(1, "Error unlocking for pc_queue_add_item");
  } else {
    debug(1, "Adding an item to a NULL queue");
  }
  return 0;
}

int pc_queue_get_item(pc_queue *the_queue, void *the_stuff) {
  int rc;
  if (the_queue) {
    rc = pthread_mutex_lock(&the_queue->pc_queue_lock);
    if (rc)
      debug(1, "Error locking for pc_queue_get_item");
    while (the_queue->count == 0) {
      rc = pthread_cond_wait(&the_queue->pc_queue_item_added_signal, &the_queue->pc_queue_lock);
      if (rc)
        debug(1, "Error waiting for item to be added");
    }
    uint32_t i = the_queue->toq;
    //    void * p = &the_queue->qbase + the_queue->item_size*the_queue->toq;
    void *p = the_queue->items + the_queue->item_size * i;
    memcpy(the_stuff, p, the_queue->item_size);

    // update the pointer
    i++;
    if (i == the_queue->capacity)
      // fold pointer if necessary
      i = 0;
    the_queue->toq = i;
    the_queue->count--;
    rc = pthread_cond_signal(&the_queue->pc_queue_item_removed_signal);
    if (rc)
      debug(1, "Error signalling after pc_queue_removed_item");
    rc = pthread_mutex_unlock(&the_queue->pc_queue_lock);
    if (rc)
      debug(1, "Error unlocking for pc_queue_get_item");
  } else {
    debug(1, "Removing an item from a NULL queue");
  }
  return 0;
}

#endif

// determine if we are the currently playing thread
static inline int rtsp_playing(void) {
  if (pthread_mutex_trylock(&playing_mutex)) {
    return pthread_equal(playing_thread, pthread_self());
  } else {
    pthread_mutex_unlock(&playing_mutex);
    return 0;
  }
}

void rtsp_request_shutdown_stream(void) {
  please_shutdown = 1;
  pthread_kill(playing_thread, SIGUSR1);
}

static void rtsp_take_player(void) {
  if (rtsp_playing())
    return;

  if (pthread_mutex_trylock(&playing_mutex)) {
    debug(1, "shutting down playing thread.");
    // XXX minor race condition between please_shutdown and signal delivery
    please_shutdown = 1;
    pthread_kill(playing_thread, SIGUSR1);
    pthread_mutex_lock(&playing_mutex);
  }
  playing_thread = pthread_self(); // make us the currently-playing thread (why?)
}

void rtsp_shutdown_stream(void) {
  rtsp_take_player();
  pthread_mutex_unlock(&playing_mutex);
}

// keep track of the threads we have spawned so we can join() them
static rtsp_conn_info **conns = NULL;
static int nconns = 0;
static void track_thread(rtsp_conn_info *conn) {
  conns = realloc(conns, sizeof(rtsp_conn_info *) * (nconns + 1));
  conns[nconns] = conn;
  nconns++;
}

static void cleanup_threads(void) {
  void *retval;
  int i;
  debug(2, "culling threads.");
  for (i = 0; i < nconns;) {
    if (conns[i]->running == 0) {
      pthread_join(conns[i]->thread, &retval);
      free(conns[i]);
      debug(2, "one joined...");
      nconns--;
      if (nconns)
        conns[i] = conns[nconns];
    } else {
      i++;
    }
  }
}

// park a null at the line ending, and return the next line pointer
// accept \r, \n, or \r\n
static char *nextline(char *in, int inbuf) {
  char *out = NULL;
  while (inbuf) {
    if (*in == '\r') {
      *in++ = 0;
      out = in;
    }
    if (*in == '\n') {
      *in++ = 0;
      out = in;
    }

    if (out)
      break;

    in++;
    inbuf--;
  }
  return out;
}

static void msg_retain(rtsp_message *msg) {
  if (msg) {
    int rc = pthread_mutex_lock(&reference_counter_lock);
    if (rc)
      debug(1, "Error %d locking reference counter lock");
    msg->referenceCount++;
    rc = pthread_mutex_unlock(&reference_counter_lock);
    if (rc)
      debug(1, "Error %d unlocking reference counter lock");
  } else {
    debug(1, "null rtsp_message pointer passed to retain");
  }
}

static rtsp_message *msg_init(void) {
  rtsp_message *msg = malloc(sizeof(rtsp_message));
  memset(msg, 0, sizeof(rtsp_message));
  msg->referenceCount = 1; // from now on, any access to this must be protected with the lock
  return msg;
}

static int msg_add_header(rtsp_message *msg, char *name, char *value) {
  if (msg->nheaders >= sizeof(msg->name) / sizeof(char *)) {
    warn("too many headers?!");
    return 1;
  }

  msg->name[msg->nheaders] = strdup(name);
  msg->value[msg->nheaders] = strdup(value);
  msg->nheaders++;

  return 0;
}

static char *msg_get_header(rtsp_message *msg, char *name) {
  int i;
  for (i = 0; i < msg->nheaders; i++)
    if (!strcasecmp(msg->name[i], name))
      return msg->value[i];
  return NULL;
}

static void msg_print_debug_headers(rtsp_message *msg) {
  int i;
  for (i = 0; i < msg->nheaders; i++) {
    debug(1, "  Type: \"%s\", content: \"%s\"", msg->name[i], msg->value[i]);
  }
}

static void msg_free(rtsp_message *msg) {

  if (msg) {
    int rc = pthread_mutex_lock(&reference_counter_lock);
    if (rc)
      debug(1, "Error %d locking reference counter lock during msg_free()", rc);
    msg->referenceCount--;
    rc = pthread_mutex_unlock(&reference_counter_lock);
    if (rc)
      debug(1, "Error %d unlocking reference counter lock during msg_free()", rc);
    if (msg->referenceCount == 0) {
      int i;
      for (i = 0; i < msg->nheaders; i++) {
        free(msg->name[i]);
        free(msg->value[i]);
      }
      if (msg->content)
        free(msg->content);
      free(msg);
    } // else {
      // debug(1,"rtsp_message reference count non-zero: %d!",msg->referenceCount);
      //}
  } else {
    debug(1, "null rtsp_message pointer passed to msg_free()");
  }
}

static int msg_handle_line(rtsp_message **pmsg, char *line) {
  rtsp_message *msg = *pmsg;

  if (!msg) {
    msg = msg_init();
    *pmsg = msg;
    char *sp, *p;

    // debug(1, "received request: %s", line);

    p = strtok_r(line, " ", &sp);
    if (!p)
      goto fail;
    strncpy(msg->method, p, sizeof(msg->method) - 1);

    p = strtok_r(NULL, " ", &sp);
    if (!p)
      goto fail;

    p = strtok_r(NULL, " ", &sp);
    if (!p)
      goto fail;
    if (strcmp(p, "RTSP/1.0"))
      goto fail;

    return -1;
  }

  if (strlen(line)) {
    char *p;
    p = strstr(line, ": ");
    if (!p) {
      warn("bad header: >>%s<<", line);
      goto fail;
    }
    *p = 0;
    p += 2;
    msg_add_header(msg, line, p);
    debug(2, "    %s: %s.", line, p);
    return -1;
  } else {
    char *cl = msg_get_header(msg, "Content-Length");
    if (cl)
      return atoi(cl);
    else
      return 0;
  }

fail:
  *pmsg = NULL;
  msg_free(msg);
  return 0;
}

static enum rtsp_read_request_response rtsp_read_request(int fd, rtsp_message **the_packet) {
  enum rtsp_read_request_response reply = rtsp_read_request_response_ok;
  ssize_t buflen = 512;
  char *buf = malloc(buflen + 1);

  rtsp_message *msg = NULL;

  ssize_t nread;
  ssize_t inbuf = 0;
  int msg_size = -1;

  while (msg_size < 0) {
    if (please_shutdown) {
      debug(1, "RTSP shutdown requested.");
      reply = rtsp_read_request_response_shutdown_requested;
      goto shutdown;
    }
    nread = read(fd, buf + inbuf, buflen - inbuf);
    if (!nread) {
      debug(1, "RTSP connection closed.");
      reply = rtsp_read_request_response_shutdown_requested;
      goto shutdown;
    }
    if (nread < 0) {
      if (errno == EINTR)
        continue;
      perror("read failure");
      reply = rtsp_read_request_response_error;
      goto shutdown;
    }
    inbuf += nread;

    char *next;
    while (msg_size < 0 && (next = nextline(buf, inbuf))) {
      msg_size = msg_handle_line(&msg, buf);

      if (!msg) {
        warn("no RTSP header received");
        reply = rtsp_read_request_response_bad_packet;
        goto shutdown;
      }

      inbuf -= next - buf;
      if (inbuf)
        memmove(buf, next, inbuf);
    }
  }

  if (msg_size > buflen) {
    buf = realloc(buf, msg_size);
    if (!buf) {
      warn("too much content");
      reply = rtsp_read_request_response_error;
      goto shutdown;
    }
    buflen = msg_size;
  }

  uint64_t threshold_time =
      get_absolute_time_in_fp() + ((uint64_t)5 << 32); // i.e. five seconds from now
  int warning_message_sent = 0;

  const size_t max_read_chunk = 50000;
  while (inbuf < msg_size) {

    // we are going to read the stream in chunks and time how long it takes to do so.
    // If it's taking too long, (and we find out about it), we will send an error message as
    // metadata

    if (warning_message_sent == 0) {
      uint64_t time_now = get_absolute_time_in_fp();
      if (time_now > threshold_time) { // it's taking too long
        debug(1, "Error receiving metadata from source -- transmission seems to be stalled.");
#ifdef CONFIG_METADATA
        send_ssnc_metadata('stal', NULL, 0, 1);
#endif
        warning_message_sent = 1;
      }
    }
    ssize_t read_chunk = msg_size - inbuf;
    if (read_chunk > max_read_chunk)
      read_chunk = max_read_chunk;
    nread = read(fd, buf + inbuf, read_chunk);
    if (!nread) {
      reply = rtsp_read_request_response_error;
      goto shutdown;
    }
    if (nread == EINTR)
      continue;
    if (nread < 0) {
      perror("read failure");
      reply = rtsp_read_request_response_error;
      goto shutdown;
    }
    inbuf += nread;
  }

  msg->contentlength = inbuf;
  msg->content = buf;
  *the_packet = msg;
  return reply;

shutdown:
  if (msg) {
    msg_free(msg); // which will free the content and everything else
  }
  // in case the message wasn't formed or wasn't fully initialised
  if ((msg && (msg->content == NULL)) || (!msg))
    free(buf);
  *the_packet = NULL;
  return reply;
}

static void msg_write_response(int fd, rtsp_message *resp) {
  char pkt[1024];
  int pktfree = sizeof(pkt);
  char *p = pkt;
  int i, n;

  n = snprintf(p, pktfree, "RTSP/1.0 %d %s\r\n", resp->respcode,
               resp->respcode == 200 ? "OK" : "Error");
  // debug(1, "sending response: %s", pkt);
  pktfree -= n;
  p += n;

  for (i = 0; i < resp->nheaders; i++) {
    debug(2, "    %s: %s.", resp->name[i], resp->value[i]);
    n = snprintf(p, pktfree, "%s: %s\r\n", resp->name[i], resp->value[i]);
    pktfree -= n;
    p += n;
    if (pktfree <= 0)
      die("Attempted to write overlong RTSP packet");
  }

  if (pktfree < 3)
    die("Attempted to write overlong RTSP packet");

  strcpy(p, "\r\n");
  int ignore = write(fd, pkt, p - pkt + 2);
}

static void handle_record(rtsp_conn_info *conn, rtsp_message *req, rtsp_message *resp) {
  //debug(1,"Handle Record");
  resp->respcode = 200;
   // I think this is for telling the client what the asbsolute minimum latency actually is,
   // and when the client specifies a latency, it should be added to this figure.
   
   // Thus, AirPlay's latency figure of 77175, when added to 11025 gives you exactly 88200
   // and iTunes' latency figure of 88553, when added to 11025 gives you 99578, pretty close to the 99400 we guessed.
   
  msg_add_header(resp, "Audio-Latency", "11025");
  
  char *p;
  uint32_t rtptime = 0;
  char *hdr = msg_get_header(req, "RTP-Info");

  if (hdr) {
    // debug(1,"FLUSH message received: \"%s\".",hdr);
    // get the rtp timestamp
    p = strstr(hdr, "rtptime=");
    if (p) {
      p = strchr(p, '=') + 1;
      if (p) {
        rtptime = uatoi(p); // unsigned integer -- up to 2^32-1
				rtptime--;
				// debug(1,"RTSP Flush Requested by handle_record: %u.",rtptime);
				player_flush(rtptime);
      }
    }
  }
}

static void handle_options(rtsp_conn_info *conn, rtsp_message *req, rtsp_message *resp) {
  resp->respcode = 200;
  msg_add_header(resp, "Public", "ANNOUNCE, SETUP, RECORD, "
                                 "PAUSE, FLUSH, TEARDOWN, "
                                 "OPTIONS, GET_PARAMETER, SET_PARAMETER");
}

static void handle_teardown(rtsp_conn_info *conn, rtsp_message *req, rtsp_message *resp) {
  if (!rtsp_playing())
    return;
  resp->respcode = 200;
  msg_add_header(resp, "Connection", "close");
  please_shutdown = 1;
}

static void handle_flush(rtsp_conn_info *conn, rtsp_message *req, rtsp_message *resp) {
  if (!rtsp_playing())
    return;
  char *p;
  uint32_t rtptime = 0;
  char *hdr = msg_get_header(req, "RTP-Info");

  if (hdr) {
    // debug(1,"FLUSH message received: \"%s\".",hdr);
    // get the rtp timestamp
    p = strstr(hdr, "rtptime=");
    if (p) {
      p = strchr(p, '=') + 1;
      if (p)
        rtptime = uatoi(p); // unsigned integer -- up to 2^32-1
    }
  }
  // debug(1,"RTSP Flush Requested: %u.",rtptime);
  player_flush(rtptime);
  resp->respcode = 200;
}

static void handle_setup(rtsp_conn_info *conn, rtsp_message *req, rtsp_message *resp) {
  // debug(1,"Handle Setup");
  int cport, tport;
  int lsport, lcport, ltport;
  uint32_t active_remote = 0;

  char *ar = msg_get_header(req, "Active-Remote");
  if (ar) {
    debug(1,"Active-Remote string seen: \"%s\".",ar);
    // get the active remote
    char *p;
    active_remote = strtoul(ar, &p, 10);
#ifdef CONFIG_METADATA
    send_metadata('ssnc','acre',ar,strlen(ar),req,1);
#endif
  }

#ifdef CONFIG_METADATA
  ar = msg_get_header(req, "DACP-ID");
  if (ar) {
    debug(1,"DACP-ID string seen: \"%s\".",ar);
    send_metadata('ssnc','daid',ar,strlen(ar),req,1);
  }
#endif

  // This latency-setting mechanism is deprecated and will be removed.
  // If no non-standard latency is chosen, automatic negotiated latency setting is permitted.
  
  // Select a static latency
  // if iTunes V10 or later is detected, use the iTunes latency setting
  // if AirPlay is detected, use the AirPlay latency setting
  // for everything else, use the general latency setting, if given, or
  // else use the default latency setting

  config.latency = -1;

  if (config.userSuppliedLatency)
    config.latency = config.userSuppliedLatency;

  char *ua = msg_get_header(req, "User-Agent");
  if (ua == 0) {
    debug(1, "No User-Agent string found in the SETUP message. Using latency of %d frames.",
          config.latency);
  } else {
    if (strstr(ua, "iTunes") == ua) {
      int iTunesVersion = 0;
      // now check it's version 10 or later
      char *pp = strchr(ua, '/') + 1;
      if (pp)
        iTunesVersion = atoi(pp);
      else
        debug(2, "iTunes Version Number not found.");
      if (iTunesVersion >= 10) {
        debug(2, "User-Agent is iTunes 10 or better, (actual version is %d); selecting the iTunes "
                 "latency of %d frames.",
              iTunesVersion, config.iTunesLatency);
        config.latency = config.iTunesLatency;
      }
    } else if (strstr(ua, "AirPlay") == ua) {
      debug(2, "User-Agent is AirPlay; selecting the AirPlay latency of %d frames.",
            config.AirPlayLatency);
      config.latency = config.AirPlayLatency;
    } else if (strstr(ua, "forked-daapd") == ua) {
      debug(2, "User-Agent is forked-daapd; selecting the forked-daapd latency of %d frames.",
            config.ForkedDaapdLatency);
      config.latency = config.ForkedDaapdLatency;
    } else {
      debug(2, "Unrecognised User-Agent. Using latency of %d frames.", config.latency);
    }
  }
  
  if (config.latency==-1) {
    // this means that no static latency was set, so we'll allow it to be set dynamically
    config.latency=88200; // to be sure, to be sure
    config.use_negotiated_latencies = 1;
  }
  char *hdr = msg_get_header(req, "Transport");
  if (!hdr)
    goto error;

  char *p;
  p = strstr(hdr, "control_port=");
  if (!p)
    goto error;
  p = strchr(p, '=') + 1;
  cport = atoi(p);

  p = strstr(hdr, "timing_port=");
  if (!p)
    goto error;
  p = strchr(p, '=') + 1;
  tport = atoi(p);

  rtsp_take_player();
  rtp_setup(&conn->remote, cport, tport, active_remote, &lsport, &lcport, &ltport);
  if (!lsport)
    goto error;
  char *q;
  p = strstr(hdr, "control_port=");
  if (p) {
    q = strchr(p, ';'); // get past the control port entry
    *p++ = 0;
    if (q++)
      strcat(hdr, q); // should unsplice the control port entry
  }
  p = strstr(hdr, "timing_port=");
  if (p) {
    q = strchr(p, ';'); // get past the timing port entry
    *p++ = 0;
    if (q++)
      strcat(hdr, q); // should unsplice the timing port entry
  }

  player_play(&conn->stream);

  char *resphdr = alloca(200);
  *resphdr = 0;
  sprintf(resphdr, "RTP/AVP/"
                   "UDP;unicast;interleaved=0-1;mode=record;control_port=%d;timing_port=%d;server_"
                   "port=%d",
          lcport, ltport, lsport);

  msg_add_header(resp, "Transport", resphdr);

  msg_add_header(resp, "Session", "1");

  resp->respcode = 200;
  return;

error:
  warn("Error in setup request.");
  pthread_mutex_unlock(&play_lock);
  resp->respcode = 451; // invalid arguments
}

static void handle_ignore(rtsp_conn_info *conn, rtsp_message *req, rtsp_message *resp) {
  resp->respcode = 200;
}

static void handle_set_parameter_parameter(rtsp_conn_info *conn, rtsp_message *req,
                                           rtsp_message *resp) {
  char *cp = req->content;
  int cp_left = req->contentlength;
  char *next;
  while (cp_left && cp) {
    next = nextline(cp, cp_left);
    cp_left -= next - cp;

    if (!strncmp(cp, "volume: ", 8)) {
      if (config.ignore_volume_control == 0) {
        float volume = atof(cp + 8);
        debug(2, "volume: %f\n", volume);
        player_volume(volume);
      }
    } else
#ifdef CONFIG_METADATA
        if (!strncmp(cp, "progress: ", 10)) {
      char *progress = cp + 10;
      debug(2, "progress: \"%s\"\n",
            progress); // rtpstampstart/rtpstampnow/rtpstampend 44100 per second
      send_ssnc_metadata('prgr', strdup(progress), strlen(progress), 1);
    } else
#endif
    {
      debug(1, "unrecognised parameter: \"%s\" (%d)\n", cp, strlen(cp));
    }
    cp = next;
  }
}

#ifdef CONFIG_METADATA
// Metadata is not used by shairport-sync.
// Instead we send all metadata to a fifo pipe, so that other apps can listen to the pipe and use
// the metadata.

// We use two 4-character codes to identify each piece of data and we send the data itself, if any,
// in base64 form.

// The first 4-character code, called the "type", is either:
//    'core' for all the regular metadadata coming from iTunes, etc., or
//    'ssnc' (for 'shairport-sync') for all metadata coming from Shairport Sync itself, such as
//    start/end delimiters, etc.

// For 'core' metadata, the second 4-character code is the 4-character metadata code coming from
// iTunes etc.
// For 'ssnc' metadata, the second 4-character code is used to distinguish the messages.

// Cover art is not tagged in the same way as other metadata, it seems, so is sent as an 'ssnc' type
// metadata message with the code 'PICT'
// Here are the 'ssnc' codes defined so far:
//    'PICT' -- the payload is a picture, either a JPEG or a PNG. Check the first few bytes to see
//    which.
//    'pbeg' -- play stream begin. No arguments
//    'pend' -- play stream end. No arguments
//    'pfls' -- play stream flush. No arguments
//    'prsm' -- play stream resume. No arguments
//    'pvol' -- play volume. The volume is sent as a string --
//    "airplay_volume,volume,lowest_volume,highest_volume,has_true_mute,is_muted"
//              volume, lowest_volume and highest_volume are given in dB
//              is_muted is 1 if [true] mute is enabled, 0 otherwise.
//              The "airplay_volume" is what's sent to the player, and is from 0.00 down to -30.00,
//              with -144.00 meaning mute.
//              This is linear on the volume control slider of iTunes or iOS AirPLay
//    'prgr' -- progress -- this is metadata from AirPlay consisting of RTP timestamps for the start
//    of the current play sequence, the current play point and the end of the play sequence.
//              I guess the timestamps wrap at 2^32.
//    'mdst' -- a sequence of metadata is about to start
//    'mden' -- a sequence of metadata has ended
//    'snam' -- A device -- e.g. "Joe's iPhone" -- has opened a play session. Specifically, it's the "X-Apple-Client-Name" string
//    'snua' -- A "user agent" -- e.g. "iTunes/12..." -- has opened a play session. Specifically, it's the "User-Agent" string
//
// including a simple base64 encoder to minimise malloc/free activity

// From Stack Overflow, with thanks:
// http://stackoverflow.com/questions/342409/how-do-i-base64-encode-decode-in-c
// minor mods to make independent of C99.
// more significant changes make it not malloc memory
// needs to initialise the docoding table first

// add _so to end of name to avoid confusion with polarssl's implementation

static char encoding_table[] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
                                'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
                                'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
                                'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
                                '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'};

static int mod_table[] = {0, 2, 1};

// pass in a pointer to the data, its length, a pointer to the output buffer and a pointer to an int
// containing its maximum length
// the actual length will be returned.

char *base64_encode_so(const unsigned char *data, size_t input_length, char *encoded_data,
                       size_t *output_length) {

  size_t calculated_output_length = 4 * ((input_length + 2) / 3);
  if (calculated_output_length > *output_length)
    return (NULL);
  *output_length = calculated_output_length;

  int i, j;
  for (i = 0, j = 0; i < input_length;) {

    uint32_t octet_a = i < input_length ? (unsigned char)data[i++] : 0;
    uint32_t octet_b = i < input_length ? (unsigned char)data[i++] : 0;
    uint32_t octet_c = i < input_length ? (unsigned char)data[i++] : 0;

    uint32_t triple = (octet_a << 0x10) + (octet_b << 0x08) + octet_c;

    encoded_data[j++] = encoding_table[(triple >> 3 * 6) & 0x3F];
    encoded_data[j++] = encoding_table[(triple >> 2 * 6) & 0x3F];
    encoded_data[j++] = encoding_table[(triple >> 1 * 6) & 0x3F];
    encoded_data[j++] = encoding_table[(triple >> 0 * 6) & 0x3F];
  }

  for (i = 0; i < mod_table[input_length % 3]; i++)
    encoded_data[*output_length - 1 - i] = '=';

  return encoded_data;
}

// with thanks!
//

static int fd = -1;
static int dirty = 0;
pc_queue metadata_queue;
#define metadata_queue_size 500
metadata_package metadata_queue_items[metadata_queue_size];

static pthread_t metadata_thread;

void metadata_create(void) {
  if (config.metadata_enabled == 0)
    return;

  size_t pl = strlen(config.metadata_pipename) + 1;

  char *path = malloc(pl + 1);
  snprintf(path, pl + 1, "%s", config.metadata_pipename);

  if (mkfifo(path, 0644) && errno != EEXIST)
    die("Could not create metadata FIFO %s", path);

  free(path);
}

void metadata_open(void) {
  if (config.metadata_enabled == 0)
    return;

  size_t pl = strlen(config.metadata_pipename) + 1;

  char *path = malloc(pl + 1);
  snprintf(path, pl + 1, "%s", config.metadata_pipename);

  fd = open(path, O_WRONLY | O_NONBLOCK);
  // if (fd < 0)
  //    debug(1, "Could not open metadata FIFO %s. Will try again later.", path);

  free(path);
}

static void metadata_close(void) {
  close(fd);
  fd = -1;
}

void metadata_process(uint32_t type, uint32_t code, char *data, uint32_t length) {
  debug(2, "Process metadata with type %x, code %x and length %u.", type, code, length);
  int ret;
  // readers may go away and come back
  if (fd < 0)
    metadata_open();
  if (fd < 0)
    return;
  char thestring[1024];
  snprintf(thestring, 1024, "<item><type>%x</type><code>%x</code><length>%u</length>", type, code,
           length);
  ret = non_blocking_write(fd, thestring, strlen(thestring));
  if (ret < 1)
    return;
  if ((data != NULL) && (length > 0)) {
    snprintf(thestring, 1024, "\n<data encoding=\"base64\">\n");
    ret = non_blocking_write(fd, thestring, strlen(thestring));
    if (ret < 1) // no reader
      return;
    // here, we write the data in base64 form using our nice base64 encoder
    // but, we break it into lines of 76 output characters, except for the last one.
    // thus, we send groups of (76/4)*3 =  57 bytes to the encoder at a time
    size_t remaining_count = length;
    char *remaining_data = data;
    size_t towrite_count;
    char outbuf[76];
    while ((remaining_count) && (ret >= 0)) {
      size_t towrite_count = remaining_count;
      if (towrite_count > 57)
        towrite_count = 57;
      size_t outbuf_size = 76; // size of output buffer on entry, length of result on exit
      if (base64_encode_so((unsigned char *)remaining_data, towrite_count, outbuf, &outbuf_size) == NULL)
        debug(1, "Error encoding base64 data.");
      // debug(1,"Remaining count: %d ret: %d, outbuf_size: %d.",remaining_count,ret,outbuf_size);
      ret = non_blocking_write(fd, outbuf, outbuf_size);
      if (ret < 0)
        return;
      remaining_data += towrite_count;
      remaining_count -= towrite_count;
    }
    snprintf(thestring, 1024, "</data>");
    ret = non_blocking_write(fd, thestring, strlen(thestring));
    if (ret < 1) // no reader
      return;
  }
  snprintf(thestring, 1024, "</item>\n");
  ret = non_blocking_write(fd, thestring, strlen(thestring));
  if (ret < 1) // no reader
    return;
}

void *metadata_thread_function(void *ignore) {
  metadata_create();
  metadata_package pack;
  while (1) {
    pc_queue_get_item(&metadata_queue, &pack);
    if (config.metadata_enabled)
      metadata_process(pack.type, pack.code, pack.data, pack.length);
    if (pack.carrier)
      msg_free(pack.carrier); // release the message
    else if (pack.data)
      free(pack.data);
  }
  pthread_exit(NULL);
}

void metadata_init(void) {
  // create a pc_queue for passing information to a threaded metadata handler
  pc_queue_init(&metadata_queue, (char *)&metadata_queue_items, sizeof(metadata_package),
                metadata_queue_size);
  int ret = pthread_create(&metadata_thread, NULL, metadata_thread_function, NULL);
  if (ret)
    debug(1, "Failed to create metadata thread!");
}

int send_metadata(uint32_t type, uint32_t code, char *data, uint32_t length, rtsp_message *carrier,
                  int block) {

  // parameters: type, code, pointer to data or NULL, length of data or NULL, the rtsp_message or
  // NULL
  // the rtsp_message is sent for 'core' messages, because it contains the data and must not be
  // freed until the data has been read. So, it is passed to send_metadata to be retained,
  // sent to the thread where metadata is processed and released (and probably freed).
  
  // The rtsp_message is also sent for certain non-'core' messages.

  // The reading of the parameters is a bit complex
  // If the rtsp_message field is non-null, then it represents an rtsp_message which should be freed
  // in the thread handler when the parameter pointed to by the pointer and specified by the length
  // is finished with
  // If the rtsp_message is NULL, then if the pointer is non-null, it points to a malloc'ed block
  // and should be freed when the thread is finished with it. The length of the data in the block is
  // given in length
  // If the rtsp_message is NULL and the pointer is also NULL, nothing further is done.

  metadata_package pack;
  pack.type = type;
  pack.code = code;
  pack.data = data;
  pack.length = length;
  if (carrier)
    msg_retain(carrier);
  pack.carrier = carrier;
  int rc = pc_queue_add_item(&metadata_queue, &pack, block);
  if ((rc == EBUSY) && (carrier))
    msg_free(carrier);
  if (rc == EBUSY)
    warn("Metadata queue is busy, dropping message of type 0x%08X, code 0x%08X.", type, code);
  return rc;
}

static void handle_set_parameter_metadata(rtsp_conn_info *conn, rtsp_message *req,
                                          rtsp_message *resp) {
  char *cp = req->content;
  int cl = req->contentlength;

  unsigned int off = 8;

  // inform the listener that a set of metadata is starting
  // this doesn't include the cover art though...

  send_metadata('ssnc', 'mdst', NULL, 0, NULL, 1);

  while (off < cl) {
    // pick up the metadata tag as an unsigned longint
    uint32_t itag = ntohl(*(uint32_t *)(cp + off));
    off += sizeof(uint32_t);

    // pick up the length of the data
    uint32_t vl = ntohl(*(uint32_t *)(cp + off));
    off += sizeof(uint32_t);

    // pass the data over
    if (vl == 0)
      send_metadata('core', itag, NULL, 0, NULL, 1);
    else
      send_metadata('core', itag, (char *)(cp + off), vl, req, 1);

    // move on to the next item
    off += vl;
  }

  // inform the listener that a set of metadata is ending
  send_metadata('ssnc', 'mden', NULL, 0, NULL, 1);
}

#endif

static void handle_get_parameter(rtsp_conn_info *conn, rtsp_message *req, rtsp_message *resp) {
  debug(1, "received GET_PARAMETER request.");
  resp->respcode = 200;
}


static void handle_set_parameter(rtsp_conn_info *conn, rtsp_message *req, rtsp_message *resp) {
  // if (!req->contentlength)
  //    debug(1, "received empty SET_PARAMETER request.");

  char *ct = msg_get_header(req, "Content-Type");

  if (ct) {
    debug(2, "SET_PARAMETER Content-Type:\"%s\".", ct);
#ifdef CONFIG_METADATA
    if (!strncmp(ct, "application/x-dmap-tagged", 25)) {
      debug(2, "received metadata tags in SET_PARAMETER request.");
      handle_set_parameter_metadata(conn, req, resp);
    } else if (!strncmp(ct, "image", 5)) {
      // debug(1, "received image in SET_PARAMETER request.");
      // note: the image/type tag isn't reliable, so it's not being sent
      // -- best look at the first few bytes of the image
      send_metadata('ssnc', 'PICT', req->content, req->contentlength, req, 1);
    } else
#endif
        if (!strncmp(ct, "text/parameters", 15)) {
      debug(2, "received parameters in SET_PARAMETER request.");
      handle_set_parameter_parameter(conn, req, resp);
    } else {
      debug(1, "received unknown Content-Type \"%s\" in SET_PARAMETER request.", ct);
    }
  } else {
    debug(1, "missing Content-Type header in SET_PARAMETER request.");
  }

  resp->respcode = 200;
}

static void handle_announce(rtsp_conn_info *conn, rtsp_message *req, rtsp_message *resp) {
  // interrupt session if permitted
  if ((config.allow_session_interruption == 1) || (pthread_mutex_trylock(&play_lock) == 0)) {
    resp->respcode = 456; // 456 - Header Field Not Valid for Resource
    char *paesiv = NULL;
    char *prsaaeskey = NULL;
    char *pfmtp = NULL;
    char *cp = req->content;
    int cp_left = req->contentlength;
    char *next;
    while (cp_left && cp) {
      next = nextline(cp, cp_left);
      cp_left -= next - cp;

      if (!strncmp(cp, "a=fmtp:", 7))
        pfmtp = cp + 7;

      if (!strncmp(cp, "a=aesiv:", 8))
        paesiv = cp + 8;

      if (!strncmp(cp, "a=rsaaeskey:", 12))
        prsaaeskey = cp + 12;

      cp = next;
    }
    
    if ((paesiv==NULL) && (prsaaeskey==NULL)) {
      //debug(1,"Unencrypted session requested?");
      conn->stream.encrypted = 0;
    } else {
      conn->stream.encrypted = 1;
      //debug(1,"Encrypted session requested");
    }
    
    if (!pfmtp) {
      warn("FMTP params missing from the following ANNOUNCE message:");
      // print each line of the request content
      // the problem is that nextline has replace all returns, newlines, etc. by NULLs
      char *cp = req->content;
      int cp_left = req->contentlength;
      while (cp_left>1) {
        if (strlen(cp)!=0)
          warn("    %s",cp);
        cp+=strlen(cp)+1;
        cp_left-=strlen(cp)+1;
      }
      goto out;
    }
    
    if (conn->stream.encrypted) {
      int len, keylen;
      uint8_t *aesiv = base64_dec(paesiv, &len);
      if (len != 16) {
        warn("client announced aeskey of %d bytes, wanted 16", len);
        free(aesiv);
        goto out;
      }
      memcpy(conn->stream.aesiv, aesiv, 16);
      free(aesiv);

      uint8_t *rsaaeskey = base64_dec(prsaaeskey, &len);
      uint8_t *aeskey = rsa_apply(rsaaeskey, len, &keylen, RSA_MODE_KEY);
      free(rsaaeskey);
      if (keylen != 16) {
        warn("client announced rsaaeskey of %d bytes, wanted 16", keylen);
        free(aeskey);
        goto out;
      }
      memcpy(conn->stream.aeskey, aeskey, 16);
      free(aeskey);
    }
    int i;
    for (i = 0; i < sizeof(conn->stream.fmtp) / sizeof(conn->stream.fmtp[0]); i++)
      conn->stream.fmtp[i] = atoi(strsep(&pfmtp, " \t"));

    char *hdr = msg_get_header(req, "X-Apple-Client-Name");
    if (hdr) {
      debug(1, "Play connection from device named \"%s\".", hdr);
      #ifdef CONFIG_METADATA
      send_metadata('ssnc','snam',hdr,strlen(hdr),req,1);
      #endif
    }
    hdr = msg_get_header(req, "User-Agent");
    if (hdr) {
      debug(1, "Play connection from user agent \"%s\".", hdr);
      #ifdef CONFIG_METADATA
      send_metadata('ssnc','snua',hdr,strlen(hdr),req,1);
      #endif
    }
    resp->respcode = 200;
  } else {
    resp->respcode = 453;
    debug(1, "Already playing.");
  }

out:
  if (resp->respcode != 200 && resp->respcode != 453) {
    pthread_mutex_unlock(&play_lock);
  }
}

static struct method_handler {
  char *method;
  void (*handler)(rtsp_conn_info *conn, rtsp_message *req, rtsp_message *resp);
} method_handlers[] = {{"OPTIONS", handle_options},
                       {"ANNOUNCE", handle_announce},
                       {"FLUSH", handle_flush},
                       {"TEARDOWN", handle_teardown},
                       {"SETUP", handle_setup},
                       {"GET_PARAMETER", handle_get_parameter},
                       {"SET_PARAMETER", handle_set_parameter},
                       {"RECORD", handle_record},
                       {NULL, NULL}};

static void apple_challenge(int fd, rtsp_message *req, rtsp_message *resp) {
  char *hdr = msg_get_header(req, "Apple-Challenge");
  if (!hdr)
    return;

  SOCKADDR fdsa;
  socklen_t sa_len = sizeof(fdsa);
  getsockname(fd, (struct sockaddr *)&fdsa, &sa_len);

  int chall_len;
  uint8_t *chall = base64_dec(hdr, &chall_len);
  uint8_t buf[48], *bp = buf;
  int i;
  memset(buf, 0, sizeof(buf));

  if (chall_len > 16) {
    warn("oversized Apple-Challenge!");
    free(chall);
    return;
  }
  memcpy(bp, chall, chall_len);
  free(chall);
  bp += chall_len;

#ifdef AF_INET6
  if (fdsa.SAFAMILY == AF_INET6) {
    struct sockaddr_in6 *sa6 = (struct sockaddr_in6 *)(&fdsa);
    memcpy(bp, sa6->sin6_addr.s6_addr, 16);
    bp += 16;
  } else
#endif
  {
    struct sockaddr_in *sa = (struct sockaddr_in *)(&fdsa);
    memcpy(bp, &sa->sin_addr.s_addr, 4);
    bp += 4;
  }

  for (i = 0; i < 6; i++)
    *bp++ = config.hw_addr[i];

  int buflen, resplen;
  buflen = bp - buf;
  if (buflen < 0x20)
    buflen = 0x20;

  uint8_t *challresp = rsa_apply(buf, buflen, &resplen, RSA_MODE_AUTH);
  char *encoded = base64_enc(challresp, resplen);

  // strip the padding.
  char *padding = strchr(encoded, '=');
  if (padding)
    *padding = 0;

  msg_add_header(resp, "Apple-Response", encoded);
  free(challresp);
  free(encoded);
}

static char *make_nonce(void) {
  uint8_t random[8];
  int fd = open("/dev/random", O_RDONLY);
  if (fd < 0)
    die("could not open /dev/random!");
  int ignore = read(fd, random, sizeof(random));
  close(fd);
  return base64_enc(random, 8);
}

static int rtsp_auth(char **nonce, rtsp_message *req, rtsp_message *resp) {

  if (!config.password)
    return 0;
  if (!*nonce) {
    *nonce = make_nonce();
    goto authenticate;
  }

  char *hdr = msg_get_header(req, "Authorization");
  if (!hdr || strncmp(hdr, "Digest ", 7))
    goto authenticate;

  char *realm = strstr(hdr, "realm=\"");
  char *username = strstr(hdr, "username=\"");
  char *response = strstr(hdr, "response=\"");
  char *uri = strstr(hdr, "uri=\"");

  if (!realm || !username || !response || !uri)
    goto authenticate;

  char *quote;
  realm = strchr(realm, '"') + 1;
  if (!(quote = strchr(realm, '"')))
    goto authenticate;
  *quote = 0;
  username = strchr(username, '"') + 1;
  if (!(quote = strchr(username, '"')))
    goto authenticate;
  *quote = 0;
  response = strchr(response, '"') + 1;
  if (!(quote = strchr(response, '"')))
    goto authenticate;
  *quote = 0;
  uri = strchr(uri, '"') + 1;
  if (!(quote = strchr(uri, '"')))
    goto authenticate;
  *quote = 0;

  uint8_t digest_urp[16], digest_mu[16], digest_total[16];

#ifdef HAVE_LIBSSL
  MD5_CTX ctx;

  MD5_Init(&ctx);
  MD5_Update(&ctx, username, strlen(username));
  MD5_Update(&ctx, ":", 1);
  MD5_Update(&ctx, realm, strlen(realm));
  MD5_Update(&ctx, ":", 1);
  MD5_Update(&ctx, config.password, strlen(config.password));
  MD5_Final(digest_urp, &ctx);
  MD5_Init(&ctx);
  MD5_Update(&ctx, req->method, strlen(req->method));
  MD5_Update(&ctx, ":", 1);
  MD5_Update(&ctx, uri, strlen(uri));
  MD5_Final(digest_mu, &ctx);
#endif

#ifdef HAVE_LIBPOLARSSL
  md5_context tctx;
  md5_starts(&tctx);
  md5_update(&tctx, (const unsigned char *)username, strlen(username));
  md5_update(&tctx, (unsigned char *)":", 1);
  md5_update(&tctx, (const unsigned char *)realm, strlen(realm));
  md5_update(&tctx, (unsigned char *)":", 1);
  md5_update(&tctx, (const unsigned char *)config.password, strlen(config.password));
  md5_finish(&tctx, digest_urp);
  md5_starts(&tctx);
  md5_update(&tctx, (const unsigned char *)req->method, strlen(req->method));
  md5_update(&tctx, (unsigned char *)":", 1);
  md5_update(&tctx, (const unsigned char *)uri, strlen(uri));
  md5_finish(&tctx, digest_mu);
#endif

  int i;
  unsigned char buf[33];
  for (i = 0; i < 16; i++)
    sprintf((char *)buf + 2 * i, "%02X", digest_urp[i]);

#ifdef HAVE_LIBSSL
  MD5_Init(&ctx);
  MD5_Update(&ctx, buf, 32);
  MD5_Update(&ctx, ":", 1);
  MD5_Update(&ctx, *nonce, strlen(*nonce));
  MD5_Update(&ctx, ":", 1);
  for (i = 0; i < 16; i++)
    sprintf((char *)buf + 2 * i, "%02X", digest_mu[i]);
  MD5_Update(&ctx, buf, 32);
  MD5_Final(digest_total, &ctx);
#endif

#ifdef HAVE_LIBPOLARSSL
  md5_starts(&tctx);
  md5_update(&tctx, buf, 32);
  md5_update(&tctx, (unsigned char *)":", 1);
  md5_update(&tctx, (const unsigned char *)*nonce, strlen(*nonce));
  md5_update(&tctx, (unsigned char *)":", 1);
  for (i = 0; i < 16; i++)
    sprintf((char *)buf + 2 * i, "%02X", digest_mu[i]);
  md5_update(&tctx, buf, 32);
  md5_finish(&tctx, digest_total);
#endif

  for (i = 0; i < 16; i++)
    sprintf((char *)buf + 2 * i, "%02X", digest_total[i]);

  if (!strcmp(response, (const char *)buf))
    return 0;
  warn("auth failed");

authenticate:
  resp->respcode = 401;
  int hdrlen = strlen(*nonce) + 40;
  char *authhdr = malloc(hdrlen);
  snprintf(authhdr, hdrlen, "Digest realm=\"taco\", nonce=\"%s\"", *nonce);
  msg_add_header(resp, "WWW-Authenticate", authhdr);
  free(authhdr);
  return 1;
}

static void *rtsp_conversation_thread_func(void *pconn) {
  // SIGUSR1 is used to interrupt this thread if blocked for read
  sigset_t set;
  sigemptyset(&set);
  sigaddset(&set, SIGUSR1);
  pthread_sigmask(SIG_UNBLOCK, &set, NULL);

  rtsp_conn_info *conn = pconn;

  rtsp_message *req, *resp;
  char *hdr, *auth_nonce = NULL;

  enum rtsp_read_request_response reply;

  do {
    reply = rtsp_read_request(conn->fd, &req);
    if (reply == rtsp_read_request_response_ok) {
      resp = msg_init();
      resp->respcode = 400;

      apple_challenge(conn->fd, req, resp);
      hdr = msg_get_header(req, "CSeq");
      if (hdr)
        msg_add_header(resp, "CSeq", hdr);
      msg_add_header(resp, "Audio-Jack-Status", "connected; type=analog");

      if (rtsp_auth(&auth_nonce, req, resp))
        goto respond;

      struct method_handler *mh;
      int method_selected = 0;
      for (mh = method_handlers; mh->method; mh++) {
        if (!strcmp(mh->method, req->method)) {
          //debug(1,"RTSP Packet received of type \"%s\":",mh->method),
          //msg_print_debug_headers(req);
          method_selected = 1;
          mh->handler(conn, req, resp);
          //debug(1,"RTSP Response:");
          //msg_print_debug_headers(resp);
          break;
        }
      }
    if (method_selected==0)
      debug(1,"Unrecognised and unhandled rtsp request \"%s\".",req->method);

    respond:
      msg_write_response(conn->fd, resp);
      msg_free(req);
      msg_free(resp);
    } else {
      if (reply != rtsp_read_request_response_shutdown_requested)
        debug(1, "rtsp_read_request error %d, packet ignored.", (int)reply);
    }
  } while (reply != rtsp_read_request_response_shutdown_requested);

  debug(1, "closing RTSP connection.");
  if (conn->fd > 0)
    close(conn->fd);
  if (rtsp_playing()) {
    rtp_shutdown();
    player_stop();
    pthread_mutex_unlock(&play_lock);
    please_shutdown = 0;
    pthread_mutex_unlock(&playing_mutex);
  }
  if (auth_nonce)
    free(auth_nonce);
  conn->running = 0;
  debug(2, "terminating RTSP thread.");
  return NULL;
}

// this function is not thread safe.
static const char *format_address(struct sockaddr *fsa) {
  static char string[INETx_ADDRSTRLEN];
  void *addr;
#ifdef AF_INET6
  if (fsa->sa_family == AF_INET6) {
    struct sockaddr_in6 *sa6 = (struct sockaddr_in6 *)(fsa);
    addr = &(sa6->sin6_addr);
  } else
#endif
  {
    struct sockaddr_in *sa = (struct sockaddr_in *)(fsa);
    addr = &(sa->sin_addr);
  }
  return inet_ntop(fsa->sa_family, addr, string, sizeof(string));
}

void rtsp_listen_loop(void) {
  struct addrinfo hints, *info, *p;
  char portstr[6];
  int *sockfd = NULL;
  int nsock = 0;
  int i, ret;

  memset(&hints, 0, sizeof(hints));
  hints.ai_family = AF_UNSPEC;
  hints.ai_socktype = SOCK_STREAM;
  hints.ai_flags = AI_PASSIVE;

  snprintf(portstr, 6, "%d", config.port);

  // debug(1,"listen socket port request is \"%s\".",portstr);

  ret = getaddrinfo(NULL, portstr, &hints, &info);
  if (ret) {
    die("getaddrinfo failed: %s", gai_strerror(ret));
  }

  for (p = info; p; p = p->ai_next) {
    int fd = socket(p->ai_family, p->ai_socktype, IPPROTO_TCP);
    int yes = 1;

    // Handle socket open failures if protocol unavailable (or IPV6 not handled)
    if (fd == -1) {
      // debug(1, "Failed to get socket: fam=%d, %s\n", p->ai_family, strerror(errno));
      continue;
    }

    ret = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes));

#ifdef IPV6_V6ONLY
    // some systems don't support v4 access on v6 sockets, but some do.
    // since we need to account for two sockets we might as well
    // always.
    if (p->ai_family == AF_INET6) {
      ret |= setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &yes, sizeof(yes));
    }
#endif

    if (!ret)
      ret = bind(fd, p->ai_addr, p->ai_addrlen);

    // one of the address families will fail on some systems that
    // report its availability. do not complain.
    if (ret) {
      debug(1, "Failed to bind to address %s.", format_address(p->ai_addr));
      continue;
    }

    listen(fd, 5);
    nsock++;
    sockfd = realloc(sockfd, nsock * sizeof(int));
    sockfd[nsock - 1] = fd;
  }

  freeaddrinfo(info);

  if (!nsock)
    die("could not bind any listen sockets!");

  int maxfd = -1;
  fd_set fds;
  FD_ZERO(&fds);
  for (i = 0; i < nsock; i++) {
    if (sockfd[i] > maxfd)
      maxfd = sockfd[i];
  }

  mdns_register();

  // printf("Listening for connections.");
  // shairport_startup_complete();

  int acceptfd;
  struct timeval tv;
  while (1) {
    tv.tv_sec = 300;
    tv.tv_usec = 0;

    for (i = 0; i < nsock; i++)
      FD_SET(sockfd[i], &fds);

    ret = select(maxfd + 1, &fds, 0, 0, &tv);
    if (ret < 0) {
      if (errno == EINTR)
        continue;
      break;
    }

    cleanup_threads();

    acceptfd = -1;
    for (i = 0; i < nsock; i++) {
      if (FD_ISSET(sockfd[i], &fds)) {
        acceptfd = sockfd[i];
        break;
      }
    }
    if (acceptfd < 0) // timeout
      continue;

    rtsp_conn_info *conn = malloc(sizeof(rtsp_conn_info));
    memset(conn, 0, sizeof(rtsp_conn_info));
    socklen_t slen = sizeof(conn->remote);

    debug(1, "new RTSP connection.");
    conn->fd = accept(acceptfd, (struct sockaddr *)&conn->remote, &slen);
    if (conn->fd < 0) {
      perror("failed to accept connection");
      free(conn);
    } else {
      pthread_t rtsp_conversation_thread;
      ret = pthread_create(&rtsp_conversation_thread, NULL, rtsp_conversation_thread_func, conn);
      if (ret)
        die("Failed to create RTSP receiver thread!");

      conn->thread = rtsp_conversation_thread;
      conn->running = 1;
      track_thread(conn);
    }
  }
  perror("select");
  die("fell out of the RTSP select loop");
}