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Chapter 41. Capturing network packets
To debug network issues and communications, you can capture network packets. The following sections provide instructions and additional information about capturing network packets.
41.1. Using xdpdump to capture network packets including packets dropped by XDP programs Copiar enlaceEnlace copiado en el portapapeles!
The xdpdump utility captures network packets, including those dropped or modified by XDP programs. Unlike tcpdump, xdpdump uses an eBPF program, allowing it to capture packets that traditional user-space utilities cannot.
You can use xdpdump to debug XDP programs that are already attached to an interface. Therefore, the utility can capture packets before an XDP program is started and after it has finished. In the latter case, xdpdump also captures the XDP action. By default, xdpdump captures incoming packets at the entry of the XDP program.
On other architectures than AMD and Intel 64-bit, the xdpdump utility is provided as a Technology Preview only. Technology Preview features are not supported with Red Hat production Service Level Agreements (SLAs), might not be functionally complete, and Red Hat does not recommend using them for production. These previews provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.
See Technology Preview Features Support Scope on the Red Hat Customer Portal for information about the support scope for Technology Preview features.
Note that xdpdump has no packet filter or decode capabilities. However, you can use it in combination with tcpdump for packet decoding.
If you are a developer and you are interested in the source code of xdpdump, download and install the corresponding source RPM (SRPM) from the Red Hat Customer Portal.
Prerequisites
- A network driver that supports XDP programs.
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An XDP program is loaded to the
enp1s0interface. If no program is loaded,xdpdumpcaptures packets in a similar waytcpdumpdoes, for backward compatibility.
Procedure
To capture packets on the
enp1s0interface and write them to the/root/capture.pcapfile, enter:xdpdump -i enp1s0 -w /root/capture.pcap
# xdpdump -i enp1s0 -w /root/capture.pcapCopy to Clipboard Copied! Toggle word wrap Toggle overflow - To stop capturing packets, press Ctrl+C.