[Dnsmasq-discuss] dnsmasq 2.86 seems to stop reading from one of its dns sockets after a period of time under load

[Tom Keddie]

Hi All,


> I think you're saying that it's not surprising that dnsmasq is not reading
> from the socket because the send queue is also full.
>

As per this thread on netdev (
https://lore.kernel.org/netdev/CABUuw65R3or9HeHsMT_isVx1f-7B6eCPPdr+bNR6f6wbKPnHOQ@mail.gmail.com/)
it seems we were consuming the socket send buffer with pending packets
waiting for ARP responses that were never coming.  This was causing
failures sending to devices that were still live.

As per that thread we increased the /proc/sys/net/core/wmem_default value
so all sockets will have larger send buffers (the device has very few
sockets in use). It might be useful to add dnsmasq config options to
increase SO_SNDBUF on the dhcp and dns sockets to allow more granular
control.

Thanks, Tom Keddie
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