summaryrefslogtreecommitdiff
path: root/samples/bpf/xdp_fwd_kern.c
blob: 4a6be0f875050de4e0b450a89d44cfaf47234d51 (plain)
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
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2017-18 David Ahern <dsahern@gmail.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 */
#define KBUILD_MODNAME "foo"
#include <uapi/linux/bpf.h>
#include <linux/in.h>
#include <linux/if_ether.h>
#include <linux/if_packet.h>
#include <linux/if_vlan.h>
#include <linux/ip.h>
#include <linux/ipv6.h>

#include "bpf_helpers.h"

#define IPV6_FLOWINFO_MASK              cpu_to_be32(0x0FFFFFFF)

struct bpf_map_def SEC("maps") tx_port = {
	.type = BPF_MAP_TYPE_DEVMAP,
	.key_size = sizeof(int),
	.value_size = sizeof(int),
	.max_entries = 64,
};

/* from include/net/ip.h */
static __always_inline int ip_decrease_ttl(struct iphdr *iph)
{
	u32 check = (__force u32)iph->check;

	check += (__force u32)htons(0x0100);
	iph->check = (__force __sum16)(check + (check >= 0xFFFF));
	return --iph->ttl;
}

static __always_inline int xdp_fwd_flags(struct xdp_md *ctx, u32 flags)
{
	void *data_end = (void *)(long)ctx->data_end;
	void *data = (void *)(long)ctx->data;
	struct bpf_fib_lookup fib_params;
	struct ethhdr *eth = data;
	struct ipv6hdr *ip6h;
	struct iphdr *iph;
	int out_index;
	u16 h_proto;
	u64 nh_off;

	nh_off = sizeof(*eth);
	if (data + nh_off > data_end)
		return XDP_DROP;

	__builtin_memset(&fib_params, 0, sizeof(fib_params));

	h_proto = eth->h_proto;
	if (h_proto == htons(ETH_P_IP)) {
		iph = data + nh_off;

		if (iph + 1 > data_end)
			return XDP_DROP;

		if (iph->ttl <= 1)
			return XDP_PASS;

		fib_params.family	= AF_INET;
		fib_params.tos		= iph->tos;
		fib_params.l4_protocol	= iph->protocol;
		fib_params.sport	= 0;
		fib_params.dport	= 0;
		fib_params.tot_len	= ntohs(iph->tot_len);
		fib_params.ipv4_src	= iph->saddr;
		fib_params.ipv4_dst	= iph->daddr;
	} else if (h_proto == htons(ETH_P_IPV6)) {
		struct in6_addr *src = (struct in6_addr *) fib_params.ipv6_src;
		struct in6_addr *dst = (struct in6_addr *) fib_params.ipv6_dst;

		ip6h = data + nh_off;
		if (ip6h + 1 > data_end)
			return XDP_DROP;

		if (ip6h->hop_limit <= 1)
			return XDP_PASS;

		fib_params.family	= AF_INET6;
		fib_params.flowlabel	= *(__be32 *)ip6h & IPV6_FLOWINFO_MASK;
		fib_params.l4_protocol	= ip6h->nexthdr;
		fib_params.sport	= 0;
		fib_params.dport	= 0;
		fib_params.tot_len	= ntohs(ip6h->payload_len);
		*src			= ip6h->saddr;
		*dst			= ip6h->daddr;
	} else {
		return XDP_PASS;
	}

	fib_params.ifindex = ctx->ingress_ifindex;

	out_index = bpf_fib_lookup(ctx, &fib_params, sizeof(fib_params), flags);

	/* verify egress index has xdp support
	 * TO-DO bpf_map_lookup_elem(&tx_port, &key) fails with
	 *       cannot pass map_type 14 into func bpf_map_lookup_elem#1:
	 * NOTE: without verification that egress index supports XDP
	 *       forwarding packets are dropped.
	 */
	if (out_index > 0) {
		if (h_proto == htons(ETH_P_IP))
			ip_decrease_ttl(iph);
		else if (h_proto == htons(ETH_P_IPV6))
			ip6h->hop_limit--;

		memcpy(eth->h_dest, fib_params.dmac, ETH_ALEN);
		memcpy(eth->h_source, fib_params.smac, ETH_ALEN);
		return bpf_redirect_map(&tx_port, out_index, 0);
	}

	return XDP_PASS;
}

SEC("xdp_fwd")
int xdp_fwd_prog(struct xdp_md *ctx)
{
	return xdp_fwd_flags(ctx, 0);
}

SEC("xdp_fwd_direct")
int xdp_fwd_direct_prog(struct xdp_md *ctx)
{
	return xdp_fwd_flags(ctx, BPF_FIB_LOOKUP_DIRECT);
}

char _license[] SEC("license") = "GPL";