"Address family not supported by protocol" error when starting ot-daemon

[MBradbury]

Describe the bug

I am following the instructions to build a Thread network with nRF 52840 DKs.

I have successfully compiled the OT daemon and compiled and flashed the RCP Joiner. I did not follow the nrfjprog instructions and have used nrfutil instead, which has looked like the following:

nrfutil device list
nrfutil device program --serial-number 000683849822 --firmware ot-nrf528xx/build/bin/ot-rcp.hex

When I get to starting the OT daemon I encounter the error below which indicates that SOCK_CLOEXEC at netif.cpp#L2235 is not supported.

To Reproduce

For openthread I am on c11e0f4.
For ot-nrf528xx I am on 2e414b2229ca24f1900eb59aa187bf1c101ce6c7.
OS is Ubuntu 24.04.2 LTS, kernel 6.8.0-60-generic.

Expected behavior

I expected the OT daemon to successfully connect.

Console/log output

sudo ./build/posix/src/posix/ot-daemon -v 'spinel+hdlc+uart:///dev/ttyACM0?uart-baudrate=460800'
./build/posix/src/posix/ot-daemon[31141]: Running OPENTHREAD/thread-reference-20230706-1415-gc11e0f465; POSIX; Jun 18 2025 10:14:05
./build/posix/src/posix/ot-daemon[31141]: Thread version: 5
./build/posix/src/posix/ot-daemon[31141]: 49d.17:56:04.345 [C] P-SpinelDrive-: Software reset co-processor successfully
socket(SOCK_CLOEXEC): Address family not supported by protocol
./build/posix/src/posix/ot-daemon[31141]: 49d.17:56:04.351 [C] Platform------: platformNetifInit() at netif.cpp:2236: Address family not supported by protocol

strace output

socket(AF_INET6, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, IPPROTO_IP) = -1 EAFNOSUPPORT (Address family not supported by protocol)
dup(2)                                  = 6
fcntl(6, F_GETFL)                       = 0x2 (flags O_RDWR)
fstat(6, {st_mode=S_IFCHR|0620, st_rdev=makedev(0x88, 0x2), ...}) = 0
write(6, "socket(SOCK_CLOEXEC): Address fa"..., 63socket(SOCK_CLOEXEC): Address family not supported by protocol
) = 63
close(6)                                = 0
getpid()                                = 50838
write(2, "./build/posix/src/posix/ot-daemo"..., 159./build/posix/src/posix/ot-daemon[50838]: 49d.19:14:01.326 [C] Platform------: platformNetifInit() at netif.cpp:2236: Address family not supported by protocol
) = 159

[MBradbury]

I believe that this may have been caused by my organisation's standard Ubuntu build having IPv6 disabled. I will confirm when I next have access to the machine.

[MBradbury]

Turns out that IPv6 was disabled via GRUB. Removing this allowed the ot-daemon to run.