lathiat
A lot of annoying sendmsg() to ff02::fb (iface #1) failed: Network is unreachable is generated
It seems this is related to issue #125 implementation. I think it is failing, because destination address used on loopback lo interface does not have MULTICAST flag. Therefore sending multicast destination packet cannot succeed.
This could in theory be fixed by using dest address as our own address. But it does not make sense to send packets to our own loopback addresses, unless we expect other mdns stacks are listening there as well.
(gdb) bt
#0 avahi_send_dns_packet_ipv6 (fd=12, interface=1, p=0x4717e0, src_address=0x432cdc, dst_address=0x0, dst_port=0)
at socket.c:581
#1 0x00007ffff7f75273 in avahi_interface_send_packet_unicast (i=0x432ca0, p=0x4717e0, a=0x0, port=0) at iface.c:604
#2 0x00007ffff7f75303 in avahi_interface_send_packet (i=0x432ca0, p=0x4717e0) at iface.c:611
#3 0x00007ffff7f889b8 in append_known_answers_and_send (s=0x4335d0, p=0x4717e0) at query-sched.c:269
#4 0x00007ffff7f88b44 in elapse_callback (e=0x4632d0, data=0x463280) at query-sched.c:310
#5 0x00007ffff7f72a2b in expiration_event (timeout=0x430190, userdata=0x436970) at timeeventq.c:94
#6 0x00007ffff7fba561 in timeout_callback (t=0x430190) at simple-watch.c:447
#7 0x00007ffff7fba972 in avahi_simple_poll_dispatch (s=0x42d490) at simple-watch.c:570
#8 0x00007ffff7fbaae9 in avahi_simple_poll_iterate (s=0x42d490, timeout=-1) at simple-watch.c:605
#9 0x0000000000409d85 in run_server (c=0x427a40 <config>) at main.c:1279
#10 0x000000000040aa13 in main (argc=2, argv=0x7fffffffe368) at main.c:1708
(gdb) frame 2
#2 0x00007ffff7f75303 in avahi_interface_send_packet (i=0x432ca0, p=0x4717e0) at iface.c:611
611 avahi_interface_send_packet_unicast(i, p, NULL, 0);
(gdb) p *i
$4 = {monitor = 0x431ed0, hardware = 0x437030, interface_next = 0x432330, interface_prev = 0x433680,
by_hardware_next = 0x432330, by_hardware_prev = 0x0, protocol = 1, announcing = 1, local_mcast_address = {
proto = 1, data = {ipv6 = {address = '\000' <repeats 15 times>, "\001"}, ipv4 = {address = 0}, data = ""}},
mcast_joined = 1, cache = 0x433150, query_scheduler = 0x4335d0, response_scheduler = 0x4335a0,
probe_scheduler = 0x433610, addresses = 0x44aac0, announcers = 0x460050, queriers_by_key = 0x432d40,
queriers = 0x46b9d0}
(gdb) p *i->hardware
$5 = {monitor = 0x431ed0, hardware_next = 0x0, hardware_prev = 0x4377d0, name = 0x42da30 "lo", index = 1,
flags_ok = 1, mtu = 65536, mac_address = "\000\000\000\000\000\000,\"parameters\":{\"userName\":",
mac_address_size = 6, entry_group = 0x0, ratelimit_begin = {tv_sec = 1706365099, tv_usec = 11741},
ratelimit_counter = 1, interfaces = 0x432ca0}
Strange is it has mcast_joined==1 on interface structure, which is very likely wrong. It seems to me we should detect if interface has MULTICAST feature in ip link and skip attempts to send multicast to this interface. We want services there, but not multicast usage.
For me sendmsg() to ff02::fb (iface #1) failed: Network is unreachable is also getting logged WITHOUT --debug. When I start avahi-discover-standalone from a terminal.
Interface #1 is lo, so the assumption above about it being caused by the Multicast flag not being set for it appear to be true. (It should be noted however that this issue persists even after ip link set dev lo multicast on though).
[user@PC-001 tmp]$ avahi-discover-standalone
*** WARNING: Detected another IPv4 mDNS stack running on this host. This makes mDNS unreliable and is thus not recommended. ***
*** WARNING: Detected another IPv6 mDNS stack running on this host. This makes mDNS unreliable and is thus not recommended. ***
Joining mDNS multicast group on interface vlan30.IPv4 with address 192.168.*****.
New relevant interface vlan30.IPv4 for mDNS.
Joining mDNS multicast group on interface vlan20.IPv6 with address fe80::*****.
New relevant interface vlan20.IPv6 for mDNS.
Joining mDNS multicast group on interface vlan10.IPv6 with address fd0c:*****.
New relevant interface vlan10.IPv6 for mDNS.
Joining mDNS multicast group on interface vlan10.IPv4 with address 192.168.*****.
New relevant interface vlan10.IPv4 for mDNS.
Joining mDNS multicast group on interface lo.IPv6 with address ::1.
New relevant interface lo.IPv6 for mDNS.
Joining mDNS multicast group on interface lo.IPv4 with address 127.0.0.1.
New relevant interface lo.IPv4 for mDNS.
Network interface enumeration completed.
sendmsg() to ff02::fb (iface #1) failed: Network is unreachable
sendmsg() to ff02::fb (iface #1) failed: Network is unreachable
sendmsg() to ff02::fb (iface #1) failed: Network is unreachable
sendmsg() to ff02::fb (iface #1) failed: Network is unreachable
sendmsg() to ff02::fb (iface #1) failed: Network is unreachable
sendmsg() to ff02::fb (iface #1) failed: Network is unreachable
sendmsg() to ff02::fb (iface #1) failed: Network is unreachable
sendmsg() to ff02::fb (iface #1) failed: Network is unreachable
sendmsg() to ff02::fb (iface #1) failed: Network is unreachable
sendmsg() to ff02::fb (iface #1) failed: Network is unreachable
sendmsg() to ff02::fb (iface #1) failed: Network is unreachable
sendmsg() to ff02::fb (iface #1) failed: Network is unreachable
sendmsg() to ff02::fb (iface #1) failed: Network is unreachable
sendmsg() to ff02::fb (iface #1) failed: Network is unreachable
sendmsg() to ff02::fb (iface #1) failed: Network is unreachable
sendmsg() to ff02::fb (iface #1) failed: Network is unreachable
[user@PC-001 tmp]$ ip link show lo
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
