Grab Packets in a Fresh Network Namespace

Case

• Capture traffic that originates inside network namespaces created on the fly—useful for debugging isolated test environments.
• The test_netns_newly_exec.sh script provisions two namespaces and runs curl through them while ptcpdump follows along.
• Debug applications that create temporary, isolated network environments for specific tasks.
• Analyze network behavior of sandboxed processes or containers that utilize fresh network namespaces.
• Verify the network configuration and isolation of newly provisioned network namespaces.

Command

sudo ptcpdump -i any --netns newly -- bash testdata/create_netns.sh netns30 veth30 netns31 veth31

Run this from the repository root so the helper script under testdata/ is available, or swap in your own setup logic. ptcpdump keeps up with the namespaces as they appear and disappear, annotating packets with the originating interface. Combine --netns with additional filters (like specific subnets) to focus on just the flows you care about.