BDC - eBPF DNS Cache

This project is currently under development

BDC is the eBPF powered DNS caching mechanism in kernel inspired by BMC

Setup

This program depends on 'aya' project, so you have to setup prerequists for using 'aya'

setup nightly rust and related packages

rustup install stable
rustup toolchain install nightly --component rust-src
cargo install --git https://github.com/aya-rs/bpf-linker  --tag v0.9.2 --no-default-features --features rust-llvm -- bpf-linker
cargo +nightly install cargo-generate

Build

First, build eBPF program and generate bytecode

cargo xtask build-ebpf

The bytecode will be located on target/bpfel-unknown-none/debug/bdc and loaded in user program Second, build userspace program

cargo build

The binary file 'bdc' are created and located on target/debug/bdc

Usage

$ ./target/debug/bdc -h
bdc 0.1.0

USAGE:
    bdc [OPTIONS]

FLAGS:
    -h, --help       Prints help information
    -V, --version    Prints version information

OPTIONS:
    -b, --bpftype <bpftype>     [default: xdp]
    -i, --iface <iface>         [default: eth0]

Create list ./bdc/config/block.list of blocking ip and ./bdc/config/cache.list of cache FQDN/IP (Originally, it would match cached DNS requests once they come in, but since it's not implemented yet, we'll warm up the cache from the configuration file for now)

block.list contains the source ip address that is allowed in DNS configuration.
cache.list contains the FQDN and ip address pair list.

for example, if you want to analyze DNS query that requests the A record (192.168.1.2) of FQDN (test.example.com) from a client (192.168.0.2) that is allowed in DNS configuration, then you create block.list and cache.list as follows

$ cat block.list
192.168.0.2

$ cat cache.lsit
test.example.com 192.168.1.2

as mentioned above, cache.list is used to warm up the DNS cache.
block.list is used due to specify the target request by any host. So in this example, a DNS query that is only from 192.168.0.2 will be analyzed. bdc is under development and now it try to parse question section and if success, then print out the result.

# DNS server side execute bdc and wait for request
$ sudo -E ENV_BLOCK_LIST=./block.list ENV_DNS_CACHE=./cache.list ./target/debug/bdc -i <iface>

# Create DNS request to above DNS server from other server that is one of the block.list entry.
$ dig @<DNS Server IP Address> test.example.com

# Then, bdc outputs the cache hit output.
Cache hit ip address = 192.168.1.2

ENV_BLOCK_LIST, ENV_DNS_CACHE environmental variable are used to detect the filepath of block.list and cache.list. If you want to try bdc but don't have your own DNS server, the documents will help you to setup minimal testbed.

Benchmarks

TODO