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
|
// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2020 Jesper Dangaard Brouer */
#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>
#include <linux/if_ether.h>
#include <stddef.h>
#include <stdint.h>
char _license[] SEC("license") = "GPL";
/* Userspace will update with MTU it can see on device */
static volatile const int GLOBAL_USER_MTU;
static volatile const __u32 GLOBAL_USER_IFINDEX;
/* BPF-prog will update these with MTU values it can see */
__u32 global_bpf_mtu_xdp = 0;
__u32 global_bpf_mtu_tc = 0;
SEC("xdp")
int xdp_use_helper_basic(struct xdp_md *ctx)
{
__u32 mtu_len = 0;
if (bpf_check_mtu(ctx, 0, &mtu_len, 0, 0))
return XDP_ABORTED;
return XDP_PASS;
}
SEC("xdp")
int xdp_use_helper(struct xdp_md *ctx)
{
int retval = XDP_PASS; /* Expected retval on successful test */
__u32 mtu_len = 0;
__u32 ifindex = 0;
int delta = 0;
/* When ifindex is zero, save net_device lookup and use ctx netdev */
if (GLOBAL_USER_IFINDEX > 0)
ifindex = GLOBAL_USER_IFINDEX;
if (bpf_check_mtu(ctx, ifindex, &mtu_len, delta, 0)) {
/* mtu_len is also valid when check fail */
retval = XDP_ABORTED;
goto out;
}
if (mtu_len != GLOBAL_USER_MTU)
retval = XDP_DROP;
out:
global_bpf_mtu_xdp = mtu_len;
return retval;
}
SEC("xdp")
int xdp_exceed_mtu(struct xdp_md *ctx)
{
void *data_end = (void *)(long)ctx->data_end;
void *data = (void *)(long)ctx->data;
__u32 ifindex = GLOBAL_USER_IFINDEX;
__u32 data_len = data_end - data;
int retval = XDP_ABORTED; /* Fail */
__u32 mtu_len = 0;
int delta;
int err;
/* Exceed MTU with 1 via delta adjust */
delta = GLOBAL_USER_MTU - (data_len - ETH_HLEN) + 1;
err = bpf_check_mtu(ctx, ifindex, &mtu_len, delta, 0);
if (err) {
retval = XDP_PASS; /* Success in exceeding MTU check */
if (err != BPF_MTU_CHK_RET_FRAG_NEEDED)
retval = XDP_DROP;
}
global_bpf_mtu_xdp = mtu_len;
return retval;
}
SEC("xdp")
int xdp_minus_delta(struct xdp_md *ctx)
{
int retval = XDP_PASS; /* Expected retval on successful test */
void *data_end = (void *)(long)ctx->data_end;
void *data = (void *)(long)ctx->data;
__u32 ifindex = GLOBAL_USER_IFINDEX;
__u32 data_len = data_end - data;
__u32 mtu_len = 0;
int delta;
/* Borderline test case: Minus delta exceeding packet length allowed */
delta = -((data_len - ETH_HLEN) + 1);
/* Minus length (adjusted via delta) still pass MTU check, other helpers
* are responsible for catching this, when doing actual size adjust
*/
if (bpf_check_mtu(ctx, ifindex, &mtu_len, delta, 0))
retval = XDP_ABORTED;
global_bpf_mtu_xdp = mtu_len;
return retval;
}
SEC("classifier")
int tc_use_helper(struct __sk_buff *ctx)
{
int retval = BPF_OK; /* Expected retval on successful test */
__u32 mtu_len = 0;
int delta = 0;
if (bpf_check_mtu(ctx, 0, &mtu_len, delta, 0)) {
retval = BPF_DROP;
goto out;
}
if (mtu_len != GLOBAL_USER_MTU)
retval = BPF_REDIRECT;
out:
global_bpf_mtu_tc = mtu_len;
return retval;
}
SEC("classifier")
int tc_exceed_mtu(struct __sk_buff *ctx)
{
__u32 ifindex = GLOBAL_USER_IFINDEX;
int retval = BPF_DROP; /* Fail */
__u32 skb_len = ctx->len;
__u32 mtu_len = 0;
int delta;
int err;
/* Exceed MTU with 1 via delta adjust */
delta = GLOBAL_USER_MTU - (skb_len - ETH_HLEN) + 1;
err = bpf_check_mtu(ctx, ifindex, &mtu_len, delta, 0);
if (err) {
retval = BPF_OK; /* Success in exceeding MTU check */
if (err != BPF_MTU_CHK_RET_FRAG_NEEDED)
retval = BPF_DROP;
}
global_bpf_mtu_tc = mtu_len;
return retval;
}
SEC("classifier")
int tc_exceed_mtu_da(struct __sk_buff *ctx)
{
/* SKB Direct-Access variant */
void *data_end = (void *)(long)ctx->data_end;
void *data = (void *)(long)ctx->data;
__u32 ifindex = GLOBAL_USER_IFINDEX;
__u32 data_len = data_end - data;
int retval = BPF_DROP; /* Fail */
__u32 mtu_len = 0;
int delta;
int err;
/* Exceed MTU with 1 via delta adjust */
delta = GLOBAL_USER_MTU - (data_len - ETH_HLEN) + 1;
err = bpf_check_mtu(ctx, ifindex, &mtu_len, delta, 0);
if (err) {
retval = BPF_OK; /* Success in exceeding MTU check */
if (err != BPF_MTU_CHK_RET_FRAG_NEEDED)
retval = BPF_DROP;
}
global_bpf_mtu_tc = mtu_len;
return retval;
}
SEC("classifier")
int tc_minus_delta(struct __sk_buff *ctx)
{
int retval = BPF_OK; /* Expected retval on successful test */
__u32 ifindex = GLOBAL_USER_IFINDEX;
__u32 skb_len = ctx->len;
__u32 mtu_len = 0;
int delta;
/* Borderline test case: Minus delta exceeding packet length allowed */
delta = -((skb_len - ETH_HLEN) + 1);
/* Minus length (adjusted via delta) still pass MTU check, other helpers
* are responsible for catching this, when doing actual size adjust
*/
if (bpf_check_mtu(ctx, ifindex, &mtu_len, delta, 0))
retval = BPF_DROP;
global_bpf_mtu_xdp = mtu_len;
return retval;
}
|
