I guess this is an easy way to reproduce the issue:
https://openwrt.org/docs/guide-user/perf_and_log/statistic.collectd#ping_check
Then customize the hosts:
uci set luci_statistics.collectd_ping.Hosts="openwrt.org"
uci commit luci_statistics
/etc/init.d/luci_statistics restart
And check the logs:
# logread -l 3 -e collectd
Mon Mar 8 21:05:42 2021 daemon.err collectd[30196]: Initialization complete, entering read-loop.
Mon Mar 8 21:05:43 2021 daemon.err collectd[30196]: ping_sendto: Permission denied
Mon Mar 8 21:05:43 2021 daemon.err collectd[30196]: ping plugin: ping_send failed: Permission denied
# ping -q -c 1 openwrt.org
PING openwrt.org (139.59.209.225): 56 data bytes
--- openwrt.org ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max = 90.241/90.241/90.241 ms
# ping6 -q -c 1 openwrt.org
PING openwrt.org (2a03:b0c0:3:d0::1af1:1): 56 data bytes
ping6: sendto: Permission denied
Looks like getaddrinfo prefers IPv6, so it fails when we have no IPv6 connectivity.
@hnyman, any idea?