the default value on the machines seems to be 262144 but on some larger
experiments dmesg will sometimes show the following logs:
[Fri Aug  8 05:01:42 2025] TCP: too many orphaned sockets
[Fri Aug  8 05:01:42 2025] TCP: too many orphaned sockets
[Fri Aug  8 05:01:42 2025] TCP: too many orphaned sockets
[Fri Aug  8 05:01:42 2025] TCP: too many orphaned sockets
[Fri Aug  8 05:01:42 2025] TCP: too many orphaned sockets
[Fri Aug  8 05:01:42 2025] TCP: too many orphaned sockets
[Fri Aug  8 05:01:42 2025] TCP: too many orphaned sockets
[Fri Aug  8 05:01:42 2025] TCP: too many orphaned sockets
[Fri Aug  8 05:01:42 2025] TCP: too many orphaned sockets
[Fri Aug  8 05:01:42 2025] TCP: too many orphaned sockets

hopefully increasing this limit will fix that.
https://serverfault.com/questions/624911/what-does-tcp-too-many-orphaned-sockets-mean
the second answer on server faul also says it could be due to tcp memory
limits:
```
The possible cause of this error is system run out of socket memory.Either you need to increase the socket memory(net.ipv4.tcp_mem) or find out the cause of memory consumption

        [root@test ~]# cat /proc/sys/net/ipv4/tcp_mem
         362688  483584  725376
So here in my system you can see 725376(pages)*4096=2971140096bytes/1024*1024=708 megabyte

So this 708 megabyte of memory is used by application for sending and receiving data as well as utilized by my loopback interface.If at any stage this value reached no further socket can be made until this memory is released from the application which are holding socket open which you can determine using netstat -antulp.
```
but for now I will just increase the max orphans and see if that is
enough.

dmesg was showing this messages:
[Thu Aug  7 14:05:26 2025] net_ratelimit: 4328 callbacks suppressed
[Thu Aug  7 14:05:26 2025] neighbour: arp_cache: neighbor table overflow!
[Thu Aug  7 14:05:26 2025] neighbour: arp_cache: neighbor table overflow!
[Thu Aug  7 14:05:26 2025] neighbour: arp_cache: neighbor table overflow!
[Thu Aug  7 14:05:26 2025] neighbour: arp_cache: neighbor table overflow!

and the machines were becoming inaccessible. increase the arp cache size
fixes this.

we were hitting conntrack limits when opening lots of connections and
sending UDP packets to many different hosts. this resulted in TCP
packets getting dropped which would manifest itself as errors when
connecting or timeouts and when sending UDP packets using `sendto` it
would fail with permission denied error. disabling conntrack fixes all
of these problems.

there were messages similar to:
HTB: quantum of class 10020 is small. Consider r2q change.
that showed up when brining up the network. this commit fixes that.