patches and low-level development discussion

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
 // SPDX-License-Identifier: EUPL-1.2+
// SPDX-FileCopyrightText: 2025 Yureka Lilian <yureka@cyberchaos.dev>

#include <vmlinux.h>
#include <bpf/bpf_helpers.h>
#include "parsing_helpers.h"
#include "rewrite_helpers.h"

// The map is actually not used by this program, but just included
// to keep the reference-counted pin alive before any physical interfaces
// are added.
struct {
	__uint(type, BPF_MAP_TYPE_DEVMAP);
	__type(key, int);
	__type(value, int);
	__uint(max_entries, 1);
	__uint(pinning, LIBBPF_PIN_BY_NAME);
} router_iface SEC(".maps");


SEC("xdp")
int router(struct xdp_md *ctx) {
	struct ethhdr *eth;
	int r;
	if (r = parse_ethhdr(ctx, &eth) < 0)
		return XDP_DROP;

	int vlid = vlan_tag_pop(ctx, eth);
	if (vlid < 0) {
		return XDP_DROP;
	}

	return bpf_redirect(vlid, 0);
}