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 <sys/poll.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) {
  resp->respcode = 200;
  msg_add_header(resp, "Audio-Latency","88200");
}

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.");
    player_flush(rtptime);
    resp->respcode = 200;
}

static void handle_setup(rtsp_conn_info *conn,
                         rtsp_message *req, rtsp_message *resp) {
    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);
      // debug(1,"Active Remote is %u.",active_remote);
    }
    
    // select 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=88200;
    
    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);
      }
    }
    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)) {
            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' -- the name of the originator -- e.g. "Joe's iPhone" or "iTunes...".
//    
// including a simple base64 encoder to minimise malloc/free activity

// From Stack Overflow, with thanks:
// http:https://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.meta_dir)
        return;

    const char fn[] = "shairport-sync-metadata";
    size_t pl = strlen(config.meta_dir) + 1 + strlen(fn);

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

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

    free(path);      
}

void metadata_open(void) {
    if (!config.meta_dir)
        return;

    const char fn[] = "shairport-sync-metadata";
    size_t pl = strlen(config.meta_dir) + 1 + strlen(fn);

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

    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;
}

ssize_t non_blocking_write(int fd, const void *buf, size_t count) {
  // debug(1,"writing %u to pipe...",count);
  // we are assuming that the count is always smaller than the FIFO's buffer
  struct pollfd ufds[1];
  ssize_t reply;  
  do {
    ufds[0].fd=fd;
    ufds[0].events = POLLOUT;
    int rv = poll(ufds,1,5000);
    if (rv==-1)
      debug(1,"error waiting for pipe to unblock...");
    if (rv==0)
      debug(1,"timeout waiting for pipe to unblock");
    reply=write(fd,buf,count);
    if ((reply==-1) && ((errno == EAGAIN) || (errno == EWOULDBLOCK)))
      debug(1,"writing to pipe will block...");
//    else
//      debug(1,"writing %u to pipe done...",reply);
  } while ((reply==-1) && ((errno == EAGAIN) || (errno == EWOULDBLOCK)));
  return reply;


//  return write(fd,buf,count);
}

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,"<type>%x</type><code>%x</code><length>%u</length>\n",type,code,length);
  ret = non_blocking_write(fd, thestring, strlen(thestring));
  if (ret < 1)
    return;
  if ((data!=NULL) && (length>0)) {
    snprintf(thestring,1024,"<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(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;
      // ret = write(fd,"\r\n",2);
      // if (ret<0)
     	//	return;
    }
    snprintf(thestring,1024,"</data>\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.meta_dir)
      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) {
  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...
    
    // 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 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.
    
    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);
  // send the user some shairport-originated metadata
  // send the name of the player, e.g. "Joe's iPhone" or "iTunes"
  send_metadata('ssnc','sndr',strdup(sender_name),strlen(sender_name),NULL,1);
}

#endif

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) {
  // allow a session to be interrupted if the timeout is set to zero
  if ((config.timeout==0) || (pthread_mutex_trylock(&play_lock) == 0)) {
    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 || !prsaaeskey || !pfmtp) {
      warn("required params missing from announce");
      goto out;
    }

    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) {
    	strncpy(sender_name,hdr,1024);
      debug(1,"Play connection from \"%s\".",hdr);
    } else {
      hdr = msg_get_header(req, "User-Agent");
      if (hdr) {
        debug(1,"Play connection from \"%s\".",hdr);
    		strncpy(sender_name,hdr,1024);
    	} else 
    		sender_name[0]=0;
    } 
    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_ignore},
    {"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(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;
        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);
                mh->handler(conn, req, resp);
                // debug(1,"RTSP Response:");
                // msg_print_debug_headers(resp);
                break;
            }
        }

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");
}