1/* Copyright (c) 2016 PLUMgrid
2 *
3 * This program is free software; you can redistribute it and/or
4 * modify it under the terms of version 2 of the GNU General Public
5 * License as published by the Free Software Foundation.
6 */
7#define KBUILD_MODNAME "foo"
8#include <uapi/linux/bpf.h>
9#include <linux/in.h>
10#include <linux/if_ether.h>
11#include <linux/if_packet.h>
12#include <linux/if_vlan.h>
13#include <linux/ip.h>
14#include <linux/ipv6.h>
15#include <bpf/bpf_helpers.h>
16
17struct {
18	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
19	__type(key, u32);
20	__type(value, long);
21	__uint(max_entries, 256);
22} rxcnt SEC(".maps");
23
24static void swap_src_dst_mac(void *data)
25{
26	unsigned short *p = data;
27	unsigned short dst[3];
28
29	dst[0] = p[0];
30	dst[1] = p[1];
31	dst[2] = p[2];
32	p[0] = p[3];
33	p[1] = p[4];
34	p[2] = p[5];
35	p[3] = dst[0];
36	p[4] = dst[1];
37	p[5] = dst[2];
38}
39
40static int parse_ipv4(void *data, u64 nh_off, void *data_end)
41{
42	struct iphdr *iph = data + nh_off;
43
44	if (iph + 1 > data_end)
45		return 0;
46	return iph->protocol;
47}
48
49static int parse_ipv6(void *data, u64 nh_off, void *data_end)
50{
51	struct ipv6hdr *ip6h = data + nh_off;
52
53	if (ip6h + 1 > data_end)
54		return 0;
55	return ip6h->nexthdr;
56}
57
58SEC("xdp1")
59int xdp_prog1(struct xdp_md *ctx)
60{
61	void *data_end = (void *)(long)ctx->data_end;
62	void *data = (void *)(long)ctx->data;
63	struct ethhdr *eth = data;
64	int rc = XDP_DROP;
65	long *value;
66	u16 h_proto;
67	u64 nh_off;
68	u32 ipproto;
69
70	nh_off = sizeof(*eth);
71	if (data + nh_off > data_end)
72		return rc;
73
74	h_proto = eth->h_proto;
75
76	if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
77		struct vlan_hdr *vhdr;
78
79		vhdr = data + nh_off;
80		nh_off += sizeof(struct vlan_hdr);
81		if (data + nh_off > data_end)
82			return rc;
83		h_proto = vhdr->h_vlan_encapsulated_proto;
84	}
85	if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
86		struct vlan_hdr *vhdr;
87
88		vhdr = data + nh_off;
89		nh_off += sizeof(struct vlan_hdr);
90		if (data + nh_off > data_end)
91			return rc;
92		h_proto = vhdr->h_vlan_encapsulated_proto;
93	}
94
95	if (h_proto == htons(ETH_P_IP))
96		ipproto = parse_ipv4(data, nh_off, data_end);
97	else if (h_proto == htons(ETH_P_IPV6))
98		ipproto = parse_ipv6(data, nh_off, data_end);
99	else
100		ipproto = 0;
101
102	value = bpf_map_lookup_elem(&rxcnt, &ipproto);
103	if (value)
104		*value += 1;
105
106	if (ipproto == IPPROTO_UDP) {
107		swap_src_dst_mac(data);
108		rc = XDP_TX;
109	}
110
111	return rc;
112}
113
114char _license[] SEC("license") = "GPL";
115