dhcpd: icmp_echorequest 192.0.2.1: No buffer space available
The kernel has returned an error ENOBUFS to dhcpd in response to the ICMP (ping) message that dhcpd sends with ping-check enabled.
This means that the socket send buffer has overflowed (dhcpd is sending messages faster than the kernel is able to transmit them to the network). This could indicate that there is another problem on the server itself, or it may simply be that you need to increase the buffer size.
We suggest as your next steps:
a) Disable your firewall/iptables. If this solves the problem then your firewall or packet filtering is creating delays on outbound packet transmissions.
b) Review and adjust Linux kernel settings wmem_default and wmem_max.
You will need to restart dhcpd after adjusting Linux kernel settings wmem_default and wmem_max
The dhcpd socket send buffer is allocated when the socket is created; this means that you will need to restart dhcpd for the new settings to take effect.