# Networking: netstat -su: packet receive errors, receive buffer errors — UDP datagrams dropped by a full socket buffer

**Code:** `UDP RcvbufErrors / packet receive errors` · **Category:** Networking · **Seen on:** Linux, Networking

UDP packets arrive faster than the application reads them, so the kernel throws the extras away.

## Meaning

UDP has no flow control: when the socket buffer is full, `RcvbufErrors` rises and data is lost (logs, metrics, VoIP, DNS, syslog). Read faster or in more threads, increase `net.core.rmem_max` and the socket's `SO_RCVBUF`, and reduce the sender's rate.

## Common causes

- Receiver slower than the sender
- Small `rmem_default`/`rmem_max`
- Burst traffic (syslog, StatsD, video)
- Single-threaded reader
- CPU starvation

## Quick fix

1. Check counters: `nstat -az UdpRcvbufErrors`
2. Raise `net.core.rmem_max` and set SO_RCVBUF
3. Add reader threads or slow the sender

## Detailed fix by platform

### Linux

1. 

```bash
nstat -az UdpInErrors UdpRcvbufErrors
sudo sysctl -w net.core.rmem_max=26214400 net.core.rmem_default=26214400
```


## How to diagnose

1. **RcvbufErrors** — Rising?
2. **Buffer** — Large enough?
3. **Reader** — Fast enough?

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Source: [WhatIsMyError](https://whatismyerror.com/errors/networking/udp-receive-buffer-errors-packet-loss)