0

Edit: I ended up using another way of sending an audio stream across the network to a remote Raspberry Pi with Pulseaudio - one that does not involve Avahi... So I lost interest in this question - don't bother answering it unless you find the problem extremely exciting. I'll leave it here anyway, in case my initial forays help anyone.

I am setting up a Rapsberry Pi as a Pulseaudio remote sink. On another host on the same LAN, 'export PULSE_SERVER="[2001:470:ca90:4:ba27:ebff:fee2:ada9]" && mplayer sound.mp3' lets me play music remotely - so far so good. It works well over IPv4 too. Client host is Debian Jessie, server host is Raspbian Jessie.

Pulseaudio works in system mode - a headless sink is one of the few cases where it is preferable. The additions to system.pa are as follow:

load-module module-native-protocol-tcp auth-ip-acl=127.0.0.1;10.4.0.0/24;2001:470:ca90:4:21b:21ff:feaa:99c9
load-module module-zeroconf-publish

I'll remove the 10.4.0.0/24 once in production - but for now I want to be able to test from any station on this subnet.

Selecting a remote Pulseaudio sink requires the server's avahi to advertise that service correctely. This is where we are now.

Locally on the server host, the Pulseaudio service seems advertised correctly:

root@hornwall:~# avahi-browse -a -t
+   eth0 IPv6 pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo PulseAudio Sound Sink local
+   eth0 IPv6 pulse@hornwall: bcm2835 ALSA Analog Stereo    PulseAudio Sound Sink local
+   eth0 IPv4 pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo PulseAudio Sound Sink local
+   eth0 IPv4 pulse@hornwall: bcm2835 ALSA Analog Stereo    PulseAudio Sound Sink local
+   eth0 IPv6 pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo PulseAudio Sound Source local
+   eth0 IPv4 pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo PulseAudio Sound Source local
+   eth0 IPv6 pulse@hornwall                                PulseAudio Sound Server local
+   eth0 IPv4 pulse@hornwall                                PulseAudio Sound Server local
+   eth0 IPv6 hornwall [b8:27:eb:e2:ad:a9]                  Workstation          local
+   eth0 IPv4 hornwall [b8:27:eb:e2:ad:a9]                  Workstation          local

But other hosts on the same network fail to see the Pulseaudio service:

root@Kitandara:/etc/pulse# avahi-browse -a -t
+   eth1 IPv6 amour                                         Remote Disk Management local
+   eth1 IPv4 amour                                         Remote Disk Management local
+   eth1 IPv6 amour [54:04:a6:67:9b:53]                     Workstation          local
+   eth1 IPv6 Kitandara [00:1b:21:aa:99:c9]                 Workstation          local
+   eth1 IPv4 amour [54:04:a6:67:9b:53]                     Workstation          local
+   eth1 IPv4 Kitandara [00:1b:21:aa:99:c9]                 Workstation          local
+   eth2 IPv6 Kitandara [00:1b:21:aa:99:cd]                 Workstation          local
+   eth2 IPv4 Kitandara [00:1b:21:aa:99:cd]                 Workstation          local

root@amour:~# avahi-browse -a -t
+   eth0 IPv6 amour                                         Remote Disk Management local
+   eth0 IPv4 amour                                         Remote Disk Management local
+   eth0 IPv6 amour [54:04:a6:67:9b:53]                     Workstation          local
+   eth0 IPv6 Kitandara [00:1b:21:aa:99:c9]                 Workstation          local
+   eth0 IPv4 amour [54:04:a6:67:9b:53]                     Workstation          local
+   eth0 IPv4 Kitandara [00:1b:21:aa:99:c9]                 Workstation          local

root@waga:~# avahi-browse -a -t
+   eth0 IPv6 waga                                          Remote Disk Management local
+   eth0 IPv4 waga                                          Remote Disk Management local
+   eth0 IPv6 waga [54:04:a6:67:9b:b7]                      Workstation          local
+   eth0 IPv4 waga [54:04:a6:67:9b:b7]                      Workstation          local

Those three examples are other workstations. Strangely, one of them does not even see the other workstations - though I believe it to be similarly configured.

All the four hosts involved (Raspberry Pi and four standard Intel computers) are on the same Ethernet segment with no router in-between. Both IPv6 and IPv4 connectivity are fine. No iptables on either host. All those hosts have a similar Avahi configuration, using both IPv4 and IPv6 on any interface available:

root@Kitandara:/etc/pulse# grep -v ^# /etc/avahi/avahi-daemon.conf

[server]
use-ipv4=yes
use-ipv6=yes
ratelimit-interval-usec=1000000
ratelimit-burst=1000

[wide-area]
enable-wide-area=yes

[publish]

[reflector]

[rlimits]
rlimit-core=0
rlimit-data=4194304
rlimit-fsize=0
rlimit-nofile=768
rlimit-stack=4194304
rlimit-nproc=3

Well... Now I'm stuck - which way should I be prodding ?

On @grawity's suggestion, here is some insight into what goes across the ether...

Listening on the Pulseaudio sink's eth0, restarting the avahi daemon there unleashes a nice burst of the expected MDNS packets:

 56  12.938605 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 450 Standard query 0x0000  ANY hornwall [b8:27:eb:e2:ad:a9]._workstation._tcp.local, "QM" question ANY pulse@hornwall._pulse-server._tcp.local, "QM" question
 57  12.939394   10.4.0.202 -> 224.0.0.251  MDNS 430 Standard query 0x0000  ANY hornwall [b8:27:eb:e2:ad:a9]._workstation._tcp.local, "QM" question ANY pulse@hornwall._pulse-server._tcp.local, "QM" question
 58  12.994690 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 849 Standard query 0x0000  ANY pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local, "QM" question ANY pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local, "QM" question
 59  12.995632   10.4.0.202 -> 224.0.0.251  MDNS 829 Standard query 0x0000  ANY pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local, "QM" question ANY pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local, "QM" question
 60  13.019775 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 652 Standard query 0x0000  ANY pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local, "QM" question ANY pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local, "QM" question
 61  13.020848   10.4.0.202 -> 224.0.0.251  MDNS 632 Standard query 0x0000  ANY pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local, "QM" question ANY pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local, "QM" question
 62  13.049454 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 738 Standard query 0x0000  ANY pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local, "QM" question
 63  13.050227   10.4.0.202 -> 224.0.0.251  MDNS 718 Standard query 0x0000  ANY pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local, "QM" question
 64  13.188819 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 450 Standard query 0x0000  ANY hornwall [b8:27:eb:e2:ad:a9]._workstation._tcp.local, "QM" question ANY pulse@hornwall._pulse-server._tcp.local, "QM" question
 65  13.189735   10.4.0.202 -> 224.0.0.251  MDNS 430 Standard query 0x0000  ANY hornwall [b8:27:eb:e2:ad:a9]._workstation._tcp.local, "QM" question ANY pulse@hornwall._pulse-server._tcp.local, "QM" question
 66  13.245302 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 849 Standard query 0x0000  ANY pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local, "QM" question ANY pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local, "QM" question
 67  13.246325   10.4.0.202 -> 224.0.0.251  MDNS 829 Standard query 0x0000  ANY pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local, "QM" question ANY pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local, "QM" question
 68  13.270384 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 652 Standard query 0x0000  ANY pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local, "QM" question ANY pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local, "QM" question
 69  13.271250   10.4.0.202 -> 224.0.0.251  MDNS 632 Standard query 0x0000  ANY pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local, "QM" question ANY pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local, "QM" question
 70  13.299927 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 738 Standard query 0x0000  ANY pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local, "QM" question
 71  13.300792   10.4.0.202 -> 224.0.0.251  MDNS 718 Standard query 0x0000  ANY pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local, "QM" question
 72  13.439241 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 450 Standard query 0x0000  ANY hornwall [b8:27:eb:e2:ad:a9]._workstation._tcp.local, "QM" question ANY pulse@hornwall._pulse-server._tcp.local, "QM" question
 73  13.440068   10.4.0.202 -> 224.0.0.251  MDNS 430 Standard query 0x0000  ANY hornwall [b8:27:eb:e2:ad:a9]._workstation._tcp.local, "QM" question ANY pulse@hornwall._pulse-server._tcp.local, "QM" question
 74  13.496557 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 849 Standard query 0x0000  ANY pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local, "QM" question ANY pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local, "QM" question
 75  13.497498   10.4.0.202 -> 224.0.0.251  MDNS 829 Standard query 0x0000  ANY pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local, "QM" question ANY pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local, "QM" question
 76  13.521724 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 652 Standard query 0x0000  ANY pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local, "QM" question ANY pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local, "QM" question
 77  13.522523   10.4.0.202 -> 224.0.0.251  MDNS 632 Standard query 0x0000  ANY pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local, "QM" question ANY pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local, "QM" question
 78  13.551102 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 738 Standard query 0x0000  ANY pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local, "QM" question
 79  13.551881   10.4.0.202 -> 224.0.0.251  MDNS 718 Standard query 0x0000  ANY pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local, "QM" question
 80  13.640087   10.4.0.202 -> 224.0.0.251  MDNS 243 Standard query response 0x0000  TXT, cache flush PTR hornwall [b8:27:eb:e2:ad:a9]._workstation._tcp.local SRV, cache flush 0 0 9 hornwall.local AAAA, cache flush 2001:470:ca90:4:ba27:ebff:fee2:ada9 A, cache flush 10.4.0.202 PTR _workstation._tcp.local
 81  13.641352 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 247 Standard query response 0x0000  TXT, cache flush PTR hornwall [b8:27:eb:e2:ad:a9]._workstation._tcp.local SRV, cache flush 0 0 9 hornwall.local AAAA, cache flush 2001:470:ca90:4:ba27:ebff:fee2:ada9 PTR _workstation._tcp.local
 82  13.683214   10.4.0.202 -> 224.0.0.251  MDNS 394 Standard query response 0x0000  TXT, cache flush PTR pulse@hornwall._pulse-server._tcp.local SRV, cache flush 0 0 4713 hornwall.local PTR _pulse-server._tcp.local
 83  13.684306 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 414 Standard query response 0x0000  TXT, cache flush PTR pulse@hornwall._pulse-server._tcp.local SRV, cache flush 0 0 4713 hornwall.local PTR _pulse-server._tcp.local
 84  13.700770   10.4.0.202 -> 224.0.0.251  MDNS 849 Standard query response 0x0000  TXT, cache flush PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local SRV, cache flush 0 0 4713 hornwall.local PTR _pulse-source._tcp.local PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local
 85  13.702406 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 869 Standard query response 0x0000  TXT, cache flush PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local SRV, cache flush 0 0 4713 hornwall.local PTR _pulse-source._tcp.local PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local
 86  13.725697   10.4.0.202 -> 224.0.0.251  MDNS 643 Standard query response 0x0000  TXT, cache flush PTR pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local SRV, cache flush 0 0 4713 hornwall.local PTR _pulse-sink._tcp.local PTR pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local
 87  13.727151 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 663 Standard query response 0x0000  TXT, cache flush PTR pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local SRV, cache flush 0 0 4713 hornwall.local PTR _pulse-sink._tcp.local PTR pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local
 88  13.762306   10.4.0.202 -> 224.0.0.251  MDNS 784 Standard query response 0x0000  TXT, cache flush PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local SRV, cache flush 0 0 4713 hornwall.local PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local
 89  13.763689 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 804 Standard query response 0x0000  TXT, cache flush PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local SRV, cache flush 0 0 4713 hornwall.local PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local
 90  13.872390   10.4.0.202 -> 224.0.0.251  MDNS 187 Standard query response 0x0000  PTR, cache flush hornwall.local PTR, cache flush hornwall.local
 91  13.873522 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 174 Standard query response 0x0000  PTR, cache flush hornwall.local
 92  13.895013   10.4.0.202 -> 224.0.0.251  MDNS 93 Standard query response 0x0000  HINFO, cache flush ARMV6L LINUX
 93  13.895711 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 113 Standard query response 0x0000  HINFO, cache flush ARMV6L LINUX
 94  14.685743   10.4.0.202 -> 224.0.0.251  MDNS 243 Standard query response 0x0000  TXT, cache flush PTR hornwall [b8:27:eb:e2:ad:a9]._workstation._tcp.local SRV, cache flush 0 0 9 hornwall.local AAAA, cache flush 2001:470:ca90:4:ba27:ebff:fee2:ada9 A, cache flush 10.4.0.202 PTR _workstation._tcp.local
 95  14.686990 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 247 Standard query response 0x0000  TXT, cache flush PTR hornwall [b8:27:eb:e2:ad:a9]._workstation._tcp.local SRV, cache flush 0 0 9 hornwall.local AAAA, cache flush 2001:470:ca90:4:ba27:ebff:fee2:ada9 PTR _workstation._tcp.local
 96  14.727907   10.4.0.202 -> 224.0.0.251  MDNS 394 Standard query response 0x0000  TXT, cache flush PTR pulse@hornwall._pulse-server._tcp.local SRV, cache flush 0 0 4713 hornwall.local PTR _pulse-server._tcp.local
 97  14.729184 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 414 Standard query response 0x0000  TXT, cache flush PTR pulse@hornwall._pulse-server._tcp.local SRV, cache flush 0 0 4713 hornwall.local PTR _pulse-server._tcp.local
 98  14.745767   10.4.0.202 -> 224.0.0.251  MDNS 849 Standard query response 0x0000  TXT, cache flush PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local SRV, cache flush 0 0 4713 hornwall.local PTR _pulse-source._tcp.local PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local
 99  14.747376 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 869 Standard query response 0x0000  TXT, cache flush PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local SRV, cache flush 0 0 4713 hornwall.local PTR _pulse-source._tcp.local PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local
100  14.769576   10.4.0.202 -> 224.0.0.251  MDNS 629 Standard query response 0x0000  TXT, cache flush SRV, cache flush 0 0 4713 hornwall.local PTR _pulse-sink._tcp.local PTR pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local
101  14.770904 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 649 Standard query response 0x0000  TXT, cache flush SRV, cache flush 0 0 4713 hornwall.local PTR _pulse-sink._tcp.local PTR pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local
102  14.807296   10.4.0.202 -> 224.0.0.251  MDNS 841 Standard query response 0x0000  TXT, cache flush PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local SRV, cache flush 0 0 4713 hornwall.local PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local PTR pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local
103  14.809329 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 861 Standard query response 0x0000  TXT, cache flush PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local SRV, cache flush 0 0 4713 hornwall.local PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local PTR pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local
104  15.917331   10.4.0.202 -> 224.0.0.251  MDNS 231 Standard query response 0x0000  PTR, cache flush hornwall.local A, cache flush 10.4.0.202 PTR, cache flush hornwall.local AAAA, cache flush 2001:470:ca90:4:ba27:ebff:fee2:ada9
105  15.918460 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 202 Standard query response 0x0000  PTR, cache flush hornwall.local AAAA, cache flush 2001:470:ca90:4:ba27:ebff:fee2:ada9
106  15.939179   10.4.0.202 -> 224.0.0.251  MDNS 93 Standard query response 0x0000  HINFO, cache flush ARMV6L LINUX
107  15.942478 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 113 Standard query response 0x0000  HINFO, cache flush ARMV6L LINUX
108  16.730511   10.4.0.202 -> 224.0.0.251  MDNS 243 Standard query response 0x0000  TXT, cache flush PTR hornwall [b8:27:eb:e2:ad:a9]._workstation._tcp.local SRV, cache flush 0 0 9 hornwall.local AAAA, cache flush 2001:470:ca90:4:ba27:ebff:fee2:ada9 A, cache flush 10.4.0.202 PTR _workstation._tcp.local
109  16.731652 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 247 Standard query response 0x0000  TXT, cache flush PTR hornwall [b8:27:eb:e2:ad:a9]._workstation._tcp.local SRV, cache flush 0 0 9 hornwall.local AAAA, cache flush 2001:470:ca90:4:ba27:ebff:fee2:ada9 PTR _workstation._tcp.local
110  16.772372   10.4.0.202 -> 224.0.0.251  MDNS 394 Standard query response 0x0000  TXT, cache flush PTR pulse@hornwall._pulse-server._tcp.local SRV, cache flush 0 0 4713 hornwall.local PTR _pulse-server._tcp.local
111  16.773610 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 414 Standard query response 0x0000  TXT, cache flush PTR pulse@hornwall._pulse-server._tcp.local SRV, cache flush 0 0 4713 hornwall.local PTR _pulse-server._tcp.local
112  16.789610   10.4.0.202 -> 224.0.0.251  MDNS 835 Standard query response 0x0000  TXT, cache flush SRV, cache flush 0 0 4713 hornwall.local PTR _pulse-source._tcp.local PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local
113  16.791221 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 855 Standard query response 0x0000  TXT, cache flush SRV, cache flush 0 0 4713 hornwall.local PTR _pulse-source._tcp.local PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local
114  16.814388   10.4.0.202 -> 224.0.0.251  MDNS 714 Standard query response 0x0000  TXT, cache flush SRV, cache flush 0 0 4713 hornwall.local PTR _pulse-sink._tcp.local PTR pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local
115  16.815894 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 734 Standard query response 0x0000  TXT, cache flush SRV, cache flush 0 0 4713 hornwall.local PTR _pulse-sink._tcp.local PTR pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-source._tcp.local
116  16.850830   10.4.0.202 -> 224.0.0.251  MDNS 827 Standard query response 0x0000  TXT, cache flush SRV, cache flush 0 0 4713 hornwall.local PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local PTR pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local
117  16.852697 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 847 Standard query response 0x0000  TXT, cache flush SRV, cache flush 0 0 4713 hornwall.local PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local PTR pulse@hornwall: bcm2835 ALSA Analog Stereo._pulse-sink._tcp.local
118  16.891486   10.4.0.202 -> 224.0.0.251  MDNS 147 Standard query response 0x0000  PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local
119  16.892429 2001:470:ca90:4:ba27:ebff:fee2:ada9 -> ff02::fb     MDNS 167 Standard query response 0x0000  PTR pulse@hornwall: Sound Blaster X-Fi Go! Pro Analog Stereo._pulse-sink._tcp.local

Packets directed ff02::fb and 224.0.0.251 on port 5353 are just what should be happening in theory - so that is nice.

But meanwhile, no other station has seen anything - not a single MDNS packet.

A few moments later on a workstation:

root@amour:~# tshark -i eth0 -f "port 5353"
  1   0.000000 2001:470:ca90:4:21b:21ff:feaa:99c9 -> ff02::fb     MDNS 140 Standard query 0x0000  PTR _pulse-sink._tcp.local, "QM" question PTR _non-monitor._sub._pulse-source._tcp.local, "QM" question
  2   0.000031   10.4.0.124 -> 224.0.0.251  MDNS 120 Standard query 0x0000  PTR _pulse-sink._tcp.local, "QM" question PTR _non-monitor._sub._pulse-source._tcp.local, "QM" question

And on the local router:

root@arua:~# tshark -i vlan4 -f "port 5353"
  1   0.000000 2001:470:ca90:4:21b:21ff:feaa:99c9 -> ff02::fb     MDNS 140 Standard query 0x0000  PTR _pulse-sink._tcp.local, "QM" question PTR _non-monitor._sub._pulse-source._tcp.local, "QM" question
  2   0.000135   10.4.0.124 -> 224.0.0.251  MDNS 120 Standard query 0x0000  PTR _pulse-sink._tcp.local, "QM" question PTR _non-monitor._sub._pulse-source._tcp.local, "QM" question

But the Pulseaudio sink avertised here belongs to another station, not to the Raspberry pi that broadcast the large burst above. If I restart avahi on that other sink-advertising station, the correct MDNS burst is seen on both of the preceeding hosts (amour & arua)... But not on the other workstation (waga) nor on the Raspberry Pi (hornwall). This is strange because amour and waga are extremely similarly configured, though something might conceivably have diverged.

Now why doesn't any other station see the MDNS packets that the Raspberry Pi seems to be broadcasting ? Why do only two stations see the sink-advertising MDNS packets broadcast by the other station ? Can there be misconfiguration on the receiving side ?

  • Have you tried checking with Wireshark/tcpdump whether the mDNS packets actually reach you? – grawity May 31 '15 at 17:01
  • I checked cursorily, but after your suggestion I added a more exhaustive description to my post - see above. – Jean-Marc Liotier May 31 '15 at 18:38

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