Get start with XDP: write a network filter in 10m
summary
Shows how to write a minimal XDP filter that drops IPv6 packets by parsing Ethernet headers, using bounds checks the BPF verifier requires, and returning XDP_DROP vs XDP_PASS; builds the BPF ELF with clang -> xdp_drop.o and inspects sections with llvm-objdump. Loads with ip link or xdp_loader (use XDP_GENERIC to avoid cutting off networking), uses a per-CPU array map to count drops (example output: CPU0=13, CPU1=7) and provides a libbpf/libxdp user-space program that polls the map every 2s and prints totals.
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chapters (6)
- 0:00Start
- 0:16Agenda
- 0:38What and Why We Use Fdp
- 2:48Build the Object
- 4:08Load the Ftp Object
- 10:15Bpf Maps
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