Create FIFO for DACP control information

Makefile

@@ -10,7 +10,7 @@ CFLAGS ?= -O2 -Wall
 
 PREFIX ?= /usr/local
 
-SRCS := shairport.c daemon.c rtsp.c mdns.c mdns_external.c mdns_tinysvcmdns.c common.c rtp.c metadata.c player.c alac.c audio.c audio_dummy.c audio_pipe.c tinysvcmdns.c
+SRCS := shairport.c daemon.c rtsp.c mdns.c mdns_external.c mdns_tinysvcmdns.c common.c rtp.c metadata.c dacp.c player.c alac.c audio.c audio_dummy.c audio_pipe.c tinysvcmdns.c
 DEPS := config.mk alac.h audio.h common.h daemon.h getopt_long.h mdns.h metadata.h player.h rtp.h rtsp.h tinysvcmdns.h
 
 ifdef CONFIG_SNDIO

README.md

@@ -82,6 +82,44 @@ An example::
     genre=Rock
     comment=
 
+DACP
+----
+Most devices allow the AirPlay receiver to have basic remote control over the stream. This is done via simple HTTP GET requests from the 
+receiver to the source device. The device sends a `DACP-ID` header to allow the receiver to find hostname and port numbers from mDNS, as well as an
+`Active-Remote` header that must be used as an authentication key for issuing control commands. Similar to the Metadata feature outlined above,
+this information can be read from a fifo after a device announces an audio stream. Using the `-D <directory name>` flag will cause a fifo named
+`dacp` to be created in the directory specified. This fifo will have a similar format as the metadata.
+
+Fields:
+```
+dacp_id=CFAE09D9DA7527E9
+active_remote=3951361179
+```
+
+To issue control commands, you must do an mDNS lookup for `iTunes_Ctrl_<dacp_id>._dacp._tcp.local`. iTunes will always advertise on port 3689 so depending
+on the environment, it may be possible to skip the mDNS lookup if you already know the source IP or hostname. iOS devices seem to choose a random high-numbered 
+port. Once you have found the host and port number, you may issue HTTP GET requests in the following format:
+
+`http://<hostname>:<port>/ctrl-int/1/<cmd>`
+
+Where `<cmd>` may be one of:
+```
+beginff
+beginrew
+mutetoggle
+nextitem
+previtem
+pause
+playpause
+play
+stop
+playresume (after issuing beginff or beginrew)
+shuffle_songs
+volumedown
+volumeup
+```
+Your HTTP request must include an `Active-Remote` header with the value obtained from the fifo.
+
 
 Thanks
 ------

common.h

@@ -31,6 +31,7 @@ typedef struct {
     char *cmd_start, *cmd_stop;
     int cmd_blocking;
     char *meta_dir;
+    char *dacp_dir;
     char *pidfile;
     char *logfile;
     char *errfile;

dacp.c

@@ -0,0 +1,111 @@
+/*
+ * DACP remote methods. This file is part of Shairport.
+ * Copyright (c) 2014 Josh Butts <josh@joshbutts.com>
+ * 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 <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <openssl/md5.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include "common.h"
+#include "dacp.h"
+
+dacpdata player_dacp;
+static int fd = -1;
+static int dirty = 0;
+
+void dacp_set(char** field, const char* value) {
+    if (*field) {
+        if (!strcmp(*field, value))
+            return;
+        free(*field);
+    }
+    *field = strdup(value);
+    dirty = 1;
+}
+
+void dacp_open(void) {
+    if (!config.dacp_dir)
+        return;
+
+    const char fn[] = "dacp";
+    size_t pl = strlen(config.dacp_dir) + 1 + strlen(fn);
+
+    char* path = malloc(pl+1);
+    snprintf(path, pl+1, "%s/%s", config.dacp_dir, fn);
+
+    if (mkfifo(path, 0644) && errno != EEXIST)
+        die("Could not create dacp FIFO %s", path);
+
+    fd = open(path, O_WRONLY | O_NONBLOCK);
+    if (fd < 0)
+        debug(1, "Could not open dacp FIFO %s. Will try again later.", path);
+
+    free(path);
+}
+
+static void dacp_close(void) {
+    close(fd);
+    fd = -1;
+}
+
+static void print_one(const char *name, const char *value) {
+    write_unchecked(fd, name, strlen(name));
+    write_unchecked(fd, "=", 1);
+    if (value)
+        write_unchecked(fd, value, strlen(value));
+    write_unchecked(fd, "\n", 1);
+}
+
+#define write_one(name) \
+   print_one(#name, player_dacp.name)
+
+void dacp_write(void) {
+    int ret;
+
+    // readers may go away and come back
+    if (fd < 0)
+        dacp_open();
+    if (fd < 0)
+        return;
+
+    if (!dirty)
+        return;
+
+    dirty = 0;
+
+    write_one(dacp_id);
+	write_one(active_remote);
+
+    ret = write(fd, "\n", 1);
+    if (ret < 1)    // no reader
+        dacp_close();
+}

dacp.h

@@ -0,0 +1,17 @@
+#ifndef _DACP_H
+#define _DACP_H
+
+#include <stdio.h>
+
+typedef struct {
+    char *dacp_id;
+    char *active_remote;
+} dacpdata;
+
+void dacp_set(char** field, const char* value);
+void dacp_open(void);
+void dacp_write(void);
+
+extern dacpdata player_dacp;
+
+#endif // _DACP_H

rtsp.c

@@ -46,6 +46,7 @@
 #include "rtp.h"
 #include "mdns.h"
 #include "metadata.h"
+#include "dacp.h"
 
 #ifdef AF_INET6
 #define INETx_ADDRSTRLEN INET6_ADDRSTRLEN
@@ -604,6 +605,16 @@ static void handle_announce(rtsp_conn_info *conn,
     for (i=0; i<sizeof(conn->stream.fmtp)/sizeof(conn->stream.fmtp[0]); i++)
         conn->stream.fmtp[i] = atoi(strsep(&pfmtp, " \t"));
 
+    int c;
+    for (c = 0; c < req->nheaders; c++) {
+        if (!strcmp(req->name[c], "DACP-ID")) {
+            dacp_set(&player_dacp.dacp_id, req->value[c]);
+        } else if (!strcmp(req->name[c], "Active-Remote")) {
+            dacp_set(&player_dacp.active_remote, req->value[c]);
+        }
+    }
+    dacp_write();
+
     resp->respcode = 200;
 }
 

shairport.c

@@ -38,6 +38,7 @@
 #include "mdns.h"
 #include "getopt_long.h"
 #include "metadata.h"
+#include "dacp.h"
 
 static const char *version =
     #include "version.h"
@@ -107,6 +108,7 @@ void usage(char *progname) {
     printf("    -E, --on-stop=COMMAND   run a shell command when playback ends\n");
     printf("    -w, --wait-cmd          block while the shell command(s) run\n");
     printf("    -M, --meta-dir=DIR      set a directory to write metadata and album cover art to\n");
+    printf("    -D, --dacp-dir=DIR      set a directory to write DACP remote control info to\n");
 
     printf("    -o, --output=BACKEND    select audio output method\n");
     printf("    -m, --mdns=BACKEND      force the use of BACKEND to advertise the service\n");
@@ -138,12 +140,13 @@ int parse_options(int argc, char **argv) {
         {"wait-cmd",  no_argument,        NULL, 'w'},
         {"meta-dir",  required_argument,  NULL, 'M'},
         {"mdns",      required_argument,  NULL, 'm'},
+        {"dacp-dir",  required_argument,  NULL, 'D'},
         {NULL,        0,                  NULL,   0}
     };
 
     int opt;
     while ((opt = getopt_long(argc, argv,
-                              "+hdvP:l:e:p:a:k:o:b:B:E:M:wm:",
+                              "+hdvP:l:e:p:a:k:o:b:B:E:M:D:wm:",
                               long_options, NULL)) > 0) {
         switch (opt) {
             default:
@@ -197,6 +200,9 @@ int parse_options(int argc, char **argv) {
             case 'm':
                 config.mdns_name = optarg;
                 break;
+            case 'D':
+                config.dacp_dir = optarg;
+                break;
         }
     }
     return optind;
@@ -315,6 +321,9 @@ int main(int argc, char **argv) {
     if (config.meta_dir)
         metadata_open();
 
+    if (config.dacp_dir)
+	    dacp_open();
+
     rtsp_listen_loop();
 
     // should not.