squid on 9.2: No buffer space available

[Stephen Borrill <netbsd%precedence.co.uk@localhost>]

I'm running squid 4.16 on NetBSD 9.2_STABLE.

Under heavy use, I see frequent pairs of log messages along the lines of:

comm_udp_sendto FD 22, (family=2) 127.0.0.1:53: (55) No buffer space available
idnsSendQuery FD 22: sendto: (55) No buffer space available


# sysctl kern.mbuf.nmbclusters
kern.mbuf.nmbclusters = 1038373

# netstat -m
18381 mbufs in use:
        5746 mbufs allocated to data
        12631 mbufs allocated to packet headers
        4 mbufs allocated to socket names and addresses
0 calls to protocol drain routines

# sysctl net.inet.udp
net.inet.udp.checksum = 1
net.inet.udp.sendspace = 9216
net.inet.udp.recvspace = 41600
net.inet.udp.do_loopback_cksum = 0

I tried increasing net.inet.udp.sendspace to 32768, but it hasn't made any 
difference. Any ideas of other tweaks?

As an aside, I have seen similar messages when trying to do a UDP 
bandwidth test with netio.

--
Stephen