summaryrefslogtreecommitdiff
path: root/tools/testing/selftests/bpf/test_xdp_vlan.c
blob: 365a7d2d9f5c46ea4de8848549ada8c28527665d (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
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
/* SPDX-License-Identifier: GPL-2.0
 *  Copyright(c) 2018 Jesper Dangaard Brouer.
 *
 * XDP/TC VLAN manipulation example
 *
 * GOTCHA: Remember to disable NIC hardware offloading of VLANs,
 * else the VLAN tags are NOT inlined in the packet payload:
 *
 *  # ethtool -K ixgbe2 rxvlan off
 *
 * Verify setting:
 *  # ethtool -k ixgbe2 | grep rx-vlan-offload
 *  rx-vlan-offload: off
 *
 */
#include <stddef.h>
#include <stdbool.h>
#include <string.h>
#include <linux/bpf.h>
#include <linux/if_ether.h>
#include <linux/if_vlan.h>
#include <linux/in.h>
#include <linux/pkt_cls.h>

#include "bpf_helpers.h"
#include "bpf_endian.h"

/* linux/if_vlan.h have not exposed this as UAPI, thus mirror some here
 *
 *	struct vlan_hdr - vlan header
 *	@h_vlan_TCI: priority and VLAN ID
 *	@h_vlan_encapsulated_proto: packet type ID or len
 */
struct _vlan_hdr {
	__be16 h_vlan_TCI;
	__be16 h_vlan_encapsulated_proto;
};
#define VLAN_PRIO_MASK		0xe000 /* Priority Code Point */
#define VLAN_PRIO_SHIFT		13
#define VLAN_CFI_MASK		0x1000 /* Canonical Format Indicator */
#define VLAN_TAG_PRESENT	VLAN_CFI_MASK
#define VLAN_VID_MASK		0x0fff /* VLAN Identifier */
#define VLAN_N_VID		4096

struct parse_pkt {
	__u16 l3_proto;
	__u16 l3_offset;
	__u16 vlan_outer;
	__u16 vlan_inner;
	__u8  vlan_outer_offset;
	__u8  vlan_inner_offset;
};

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

static __always_inline
bool parse_eth_frame(struct ethhdr *eth, void *data_end, struct parse_pkt *pkt)
{
	__u16 eth_type;
	__u8 offset;

	offset = sizeof(*eth);
	/* Make sure packet is large enough for parsing eth + 2 VLAN headers */
	if ((void *)eth + offset + (2*sizeof(struct _vlan_hdr)) > data_end)
		return false;

	eth_type = eth->h_proto;

	/* Handle outer VLAN tag */
	if (eth_type == bpf_htons(ETH_P_8021Q)
	    || eth_type == bpf_htons(ETH_P_8021AD)) {
		struct _vlan_hdr *vlan_hdr;

		vlan_hdr = (void *)eth + offset;
		pkt->vlan_outer_offset = offset;
		pkt->vlan_outer = bpf_ntohs(vlan_hdr->h_vlan_TCI)
				& VLAN_VID_MASK;
		eth_type        = vlan_hdr->h_vlan_encapsulated_proto;
		offset += sizeof(*vlan_hdr);
	}

	/* Handle inner (double) VLAN tag */
	if (eth_type == bpf_htons(ETH_P_8021Q)
	    || eth_type == bpf_htons(ETH_P_8021AD)) {
		struct _vlan_hdr *vlan_hdr;

		vlan_hdr = (void *)eth + offset;
		pkt->vlan_inner_offset = offset;
		pkt->vlan_inner = bpf_ntohs(vlan_hdr->h_vlan_TCI)
				& VLAN_VID_MASK;
		eth_type        = vlan_hdr->h_vlan_encapsulated_proto;
		offset += sizeof(*vlan_hdr);
	}

	pkt->l3_proto = bpf_ntohs(eth_type); /* Convert to host-byte-order */
	pkt->l3_offset = offset;

	return true;
}

/* Hint, VLANs are choosen to hit network-byte-order issues */
#define TESTVLAN 4011 /* 0xFAB */
// #define TO_VLAN  4000 /* 0xFA0 (hint 0xOA0 = 160) */

SEC("xdp_drop_vlan_4011")
int  xdp_prognum0(struct xdp_md *ctx)
{
	void *data_end = (void *)(long)ctx->data_end;
	void *data     = (void *)(long)ctx->data;
	struct parse_pkt pkt = { 0 };

	if (!parse_eth_frame(data, data_end, &pkt))
		return XDP_ABORTED;

	/* Drop specific VLAN ID example */
	if (pkt.vlan_outer == TESTVLAN)
		return XDP_ABORTED;
	/*
	 * Using XDP_ABORTED makes it possible to record this event,
	 * via tracepoint xdp:xdp_exception like:
	 *  # perf record -a -e xdp:xdp_exception
	 *  # perf script
	 */
	return XDP_PASS;
}
/*
Commands to setup VLAN on Linux to test packets gets dropped:

 export ROOTDEV=ixgbe2
 export VLANID=4011
 ip link add link $ROOTDEV name $ROOTDEV.$VLANID type vlan id $VLANID
 ip link set dev  $ROOTDEV.$VLANID up

 ip link set dev $ROOTDEV mtu 1508
 ip addr add 100.64.40.11/24 dev $ROOTDEV.$VLANID

Load prog with ip tool:

 ip link set $ROOTDEV xdp off
 ip link set $ROOTDEV xdp object xdp_vlan01_kern.o section xdp_drop_vlan_4011

*/

/* Changing VLAN to zero, have same practical effect as removing the VLAN. */
#define TO_VLAN	0

SEC("xdp_vlan_change")
int  xdp_prognum1(struct xdp_md *ctx)
{
	void *data_end = (void *)(long)ctx->data_end;
	void *data     = (void *)(long)ctx->data;
	struct parse_pkt pkt = { 0 };

	if (!parse_eth_frame(data, data_end, &pkt))
		return XDP_ABORTED;

	/* Change specific VLAN ID */
	if (pkt.vlan_outer == TESTVLAN) {
		struct _vlan_hdr *vlan_hdr = data + pkt.vlan_outer_offset;

		/* Modifying VLAN, preserve top 4 bits */
		vlan_hdr->h_vlan_TCI =
			bpf_htons((bpf_ntohs(vlan_hdr->h_vlan_TCI) & 0xf000)
				  | TO_VLAN);
	}

	return XDP_PASS;
}

/*
 * Show XDP+TC can cooperate, on creating a VLAN rewriter.
 * 1. Create a XDP prog that can "pop"/remove a VLAN header.
 * 2. Create a TC-bpf prog that egress can add a VLAN header.
 */

#ifndef ETH_ALEN /* Ethernet MAC address length */
#define ETH_ALEN	6	/* bytes */
#endif
#define VLAN_HDR_SZ	4	/* bytes */

SEC("xdp_vlan_remove_outer")
int  xdp_prognum2(struct xdp_md *ctx)
{
	void *data_end = (void *)(long)ctx->data_end;
	void *data     = (void *)(long)ctx->data;
	struct parse_pkt pkt = { 0 };
	char *dest;

	if (!parse_eth_frame(data, data_end, &pkt))
		return XDP_ABORTED;

	/* Skip packet if no outer VLAN was detected */
	if (pkt.vlan_outer_offset == 0)
		return XDP_PASS;

	/* Moving Ethernet header, dest overlap with src, memmove handle this */
	dest = data;
	dest+= VLAN_HDR_SZ;
	/*
	 * Notice: Taking over vlan_hdr->h_vlan_encapsulated_proto, by
	 * only moving two MAC addrs (12 bytes), not overwriting last 2 bytes
	 */
	__builtin_memmove(dest, data, ETH_ALEN * 2);
	/* Note: LLVM built-in memmove inlining require size to be constant */

	/* Move start of packet header seen by Linux kernel stack */
	bpf_xdp_adjust_head(ctx, VLAN_HDR_SZ);

	return XDP_PASS;
}

static __always_inline
void shift_mac_4bytes_16bit(void *data)
{
	__u16 *p = data;

	p[7] = p[5]; /* delete p[7] was vlan_hdr->h_vlan_TCI */
	p[6] = p[4]; /* delete p[6] was ethhdr->h_proto */
	p[5] = p[3];
	p[4] = p[2];
	p[3] = p[1];
	p[2] = p[0];
}

static __always_inline
void shift_mac_4bytes_32bit(void *data)
{
	__u32 *p = data;

	/* Assuming VLAN hdr present. The 4 bytes in p[3] that gets
	 * overwritten, is ethhdr->h_proto and vlan_hdr->h_vlan_TCI.
	 * The vlan_hdr->h_vlan_encapsulated_proto take over role as
	 * ethhdr->h_proto.
	 */
	p[3] = p[2];
	p[2] = p[1];
	p[1] = p[0];
}

SEC("xdp_vlan_remove_outer2")
int  xdp_prognum3(struct xdp_md *ctx)
{
	void *data_end = (void *)(long)ctx->data_end;
	void *data     = (void *)(long)ctx->data;
	struct ethhdr *orig_eth = data;
	struct parse_pkt pkt = { 0 };

	if (!parse_eth_frame(orig_eth, data_end, &pkt))
		return XDP_ABORTED;

	/* Skip packet if no outer VLAN was detected */
	if (pkt.vlan_outer_offset == 0)
		return XDP_PASS;

	/* Simply shift down MAC addrs 4 bytes, overwrite h_proto + TCI */
	shift_mac_4bytes_32bit(data);

	/* Move start of packet header seen by Linux kernel stack */
	bpf_xdp_adjust_head(ctx, VLAN_HDR_SZ);

	return XDP_PASS;
}

/*=====================================
 *  BELOW: TC-hook based ebpf programs
 * ====================================
 * The TC-clsact eBPF programs (currently) need to be attach via TC commands
 */

SEC("tc_vlan_push")
int _tc_progA(struct __sk_buff *ctx)
{
	bpf_skb_vlan_push(ctx, bpf_htons(ETH_P_8021Q), TESTVLAN);

	return TC_ACT_OK;
}
/*
Commands to setup TC to use above bpf prog:

export ROOTDEV=ixgbe2
export FILE=xdp_vlan01_kern.o

# Re-attach clsact to clear/flush existing role
tc qdisc del dev $ROOTDEV clsact 2> /dev/null ;\
tc qdisc add dev $ROOTDEV clsact

# Attach BPF prog EGRESS
tc filter add dev $ROOTDEV egress \
  prio 1 handle 1 bpf da obj $FILE sec tc_vlan_push

tc filter show dev $ROOTDEV egress
*/