DRAFT: Using Linux BPF Filter in DHCP Client - Blog of Gris
Blog of GrisDuring DHCP discovery process, the DHCP network flow is based on UDP when lower IP stack is not ready yet. The user space DHCP client program will need ethernet RAW socket(AF_PACKET, SOCK_RAW) to receive UDP package otherwise kernel will drop the UDP package as IP mismatch.Hooking on Ethernet RAW socket requires DHCP client filter out non-DHCP network package in user space which could result a large CPU overhead. The Linux kernel is providing BPF (Berkeley Packet Filter) facility for filtering packages in kernel space before sending to user space.
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