Using NGINX as UDP load balancer at high rate

Hi, I’m running nginx on Kubernetes and I want to use it as a UDP load balancer at high rate.

nginx.conf:

user  root;

worker_processes  auto;



events {

  worker_connections  1024;

}


stream {

  upstream app_node {

  server <receiver_ip>:<receiver_port> fail_timeout=60s weight=1;

  }


  server {

  listen <nginx_port> udp;

  proxy_pass app_node;

  proxy_protocol on;

  set_real_ip_from 0.0.0.0/0;

  proxy_bind $server_addr:$remote_port;

  }

}

Code (markup):

I try to test it by generating high traffic, such as 30,000 packets per second on average for 5 minutes, and each packet size is 1 KB.

I use tcpdump for monitoring packets that nginx receives and sends.

Tcpdump command for receiving packets:

tcpdump -i <receiving_inteface> dst <nginx_pod_ip> and port <nginx_port> -w receceived_30000.pcap

Code (markup):

Tcpdump command for sending packets:

tcpdump -i <sending_inteface> src <nginx_pod_ip> and dst <receiver_ip> and port <receiver_port> -w sent_30000.pcap

Code (markup):

But the count of packets captured by the two commands is not the same. It seems that nginx drops packets:

Result of first tcpdump command:

9000000 packets captured

9000000 packets received by filter

0 packets dropped by kernel

Code (markup):

Result of second tcpdump command:

8997898 packets captured

8997898 packets received by filter

0 packets dropped by kernel

Code (markup):

And this difference will increase if we increase the rate of sending packets.

So what is the problem here? Is our configuration wrong, or has something else happened?