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
 58#define XDPBUFSIZE	64
 59SEC("xdp.frags")
 60int xdp_prog1(struct xdp_md *ctx)
 61{
 62	__u8 pkt[XDPBUFSIZE] = {};
 63	void *data_end = &pkt[XDPBUFSIZE-1];
 64	void *data = pkt;
 65	struct ethhdr *eth = data;
 66	int rc = XDP_DROP;
 67	long *value;
 68	u16 h_proto;
 69	u64 nh_off;
 70	u32 ipproto;
 71
 72	if (bpf_xdp_load_bytes(ctx, 0, pkt, sizeof(pkt)))
 73		return rc;
 74
 75	nh_off = sizeof(*eth);
 76	if (data + nh_off > data_end)
 77		return rc;
 78
 79	h_proto = eth->h_proto;
 80
 81	/* Handle VLAN tagged packet */
 82	if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
 83		struct vlan_hdr *vhdr;
 84
 85		vhdr = data + nh_off;
 86		nh_off += sizeof(struct vlan_hdr);
 87		if (data + nh_off > data_end)
 88			return rc;
 89		h_proto = vhdr->h_vlan_encapsulated_proto;
 90	}
 91	/* Handle double VLAN tagged packet */
 92	if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
 93		struct vlan_hdr *vhdr;
 94
 95		vhdr = data + nh_off;
 96		nh_off += sizeof(struct vlan_hdr);
 97		if (data + nh_off > data_end)
 98			return rc;
 99		h_proto = vhdr->h_vlan_encapsulated_proto;
100	}
101
102	if (h_proto == htons(ETH_P_IP))
103		ipproto = parse_ipv4(data, nh_off, data_end);
104	else if (h_proto == htons(ETH_P_IPV6))
105		ipproto = parse_ipv6(data, nh_off, data_end);
106	else
107		ipproto = 0;
108
109	value = bpf_map_lookup_elem(&rxcnt, &ipproto);
110	if (value)
111		*value += 1;
112
113	if (ipproto == IPPROTO_UDP) {
114		swap_src_dst_mac(data);
115
116		if (bpf_xdp_store_bytes(ctx, 0, pkt, sizeof(pkt)))
117			return rc;
118
119		rc = XDP_TX;
120	}
121
122	return rc;
123}
124
125char _license[] SEC("license") = "GPL";