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c9b2ce08eb
In case the 53 UDP port is not an option to bind then we hijack the DNS traffic with eBPF, and we forward the traffic to the listener on a custom port. With this implementation, we should be able to listen to DNS queries on any address and still set the local host system to send queries to the custom address on port 53. Because we tried to attach multiple XDP programs to the same interface, I did a refactor in the WG traffic forward code also.
54 lines
1.2 KiB
C
54 lines
1.2 KiB
C
const __u32 map_key_proxy_port = 0;
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const __u32 map_key_wg_port = 1;
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struct bpf_map_def SEC("maps") nb_wg_proxy_settings_map = {
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.type = BPF_MAP_TYPE_ARRAY,
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.key_size = sizeof(__u32),
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.value_size = sizeof(__u16),
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.max_entries = 10,
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};
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__u16 proxy_port = 0;
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__u16 wg_port = 0;
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bool read_port_settings() {
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__u16 *value;
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value = bpf_map_lookup_elem(&nb_wg_proxy_settings_map, &map_key_proxy_port);
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if (!value) {
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return false;
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}
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proxy_port = *value;
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value = bpf_map_lookup_elem(&nb_wg_proxy_settings_map, &map_key_wg_port);
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if (!value) {
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return false;
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}
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wg_port = htons(*value);
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return true;
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}
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int xdp_wg_proxy(struct iphdr *ip, struct udphdr *udp) {
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if (proxy_port == 0 || wg_port == 0) {
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if (!read_port_settings()){
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return XDP_PASS;
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}
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bpf_printk("proxy port: %d, wg port: %d", proxy_port, wg_port);
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}
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// 2130706433 = 127.0.0.1
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if (ip->daddr != htonl(2130706433)) {
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return XDP_PASS;
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}
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if (udp->source != wg_port){
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return XDP_PASS;
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}
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__be16 new_src_port = udp->dest;
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__be16 new_dst_port = htons(proxy_port);
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udp->dest = new_dst_port;
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udp->source = new_src_port;
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return XDP_PASS;
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} |