Quintin:
>> Do you reach your server's conntrack limit?
>
> The word conntrack never appears in my logs, so I don't think it's that.
> The ISP also requires this from tor exits: net.netfilter.nf_conntrack_max =
> 10000

How many conntrack entries do you actually have when you get
sendto failed: Operation not permitted
log entries?

sysctl net.netfilter.nf_conntrack_count
or
cat /proc/sys/net/netfilter/nf_conntrack_count

Regardless of whether this is the root-cause or not,
nf_conntrack_max = 10k is probably to low for an exit relay.

If nf_conntrack_count is near nf_conntrack_max, does the problem
go away when you temporarily increase nf_conntrack_max?

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