1#include <stddef.h>
2#include <inttypes.h>
3#include <errno.h>
4#include <linux/seg6_local.h>
5#include <linux/bpf.h>
6#include "bpf_helpers.h"
7#include "bpf_endian.h"
8
9
10#define cursor_advance(_cursor, _len) \
11 ({ void *_tmp = _cursor; _cursor += _len; _tmp; })
12
13#define SR6_FLAG_ALERT (1 << 4)
14
15#define BPF_PACKET_HEADER __attribute__((packed))
16
17struct ip6_t {
18 unsigned int ver:4;
19 unsigned int priority:8;
20 unsigned int flow_label:20;
21 unsigned short payload_len;
22 unsigned char next_header;
23 unsigned char hop_limit;
24 unsigned long long src_hi;
25 unsigned long long src_lo;
26 unsigned long long dst_hi;
27 unsigned long long dst_lo;
28} BPF_PACKET_HEADER;
29
30struct ip6_addr_t {
31 unsigned long long hi;
32 unsigned long long lo;
33} BPF_PACKET_HEADER;
34
35struct ip6_srh_t {
36 unsigned char nexthdr;
37 unsigned char hdrlen;
38 unsigned char type;
39 unsigned char segments_left;
40 unsigned char first_segment;
41 unsigned char flags;
42 unsigned short tag;
43
44 struct ip6_addr_t segments[0];
45} BPF_PACKET_HEADER;
46
47struct sr6_tlv_t {
48 unsigned char type;
49 unsigned char len;
50 unsigned char value[0];
51} BPF_PACKET_HEADER;
52
53static __always_inline struct ip6_srh_t *get_srh(struct __sk_buff *skb)
54{
55 void *cursor, *data_end;
56 struct ip6_srh_t *srh;
57 struct ip6_t *ip;
58 uint8_t *ipver;
59
60 data_end = (void *)(long)skb->data_end;
61 cursor = (void *)(long)skb->data;
62 ipver = (uint8_t *)cursor;
63
64 if ((void *)ipver + sizeof(*ipver) > data_end)
65 return NULL;
66
67 if ((*ipver >> 4) != 6)
68 return NULL;
69
70 ip = cursor_advance(cursor, sizeof(*ip));
71 if ((void *)ip + sizeof(*ip) > data_end)
72 return NULL;
73
74 if (ip->next_header != 43)
75 return NULL;
76
77 srh = cursor_advance(cursor, sizeof(*srh));
78 if ((void *)srh + sizeof(*srh) > data_end)
79 return NULL;
80
81 if (srh->type != 4)
82 return NULL;
83
84 return srh;
85}
86
87static __always_inline int update_tlv_pad(struct __sk_buff *skb,
88 uint32_t new_pad, uint32_t old_pad,
89 uint32_t pad_off)
90{
91 int err;
92
93 if (new_pad != old_pad) {
94 err = bpf_lwt_seg6_adjust_srh(skb, pad_off,
95 (int) new_pad - (int) old_pad);
96 if (err)
97 return err;
98 }
99
100 if (new_pad > 0) {
101 char pad_tlv_buf[16] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
102 0, 0, 0};
103 struct sr6_tlv_t *pad_tlv = (struct sr6_tlv_t *) pad_tlv_buf;
104
105 pad_tlv->type = SR6_TLV_PADDING;
106 pad_tlv->len = new_pad - 2;
107
108 err = bpf_lwt_seg6_store_bytes(skb, pad_off,
109 (void *)pad_tlv_buf, new_pad);
110 if (err)
111 return err;
112 }
113
114 return 0;
115}
116
117static __always_inline int is_valid_tlv_boundary(struct __sk_buff *skb,
118 struct ip6_srh_t *srh,
119 uint32_t *tlv_off,
120 uint32_t *pad_size,
121 uint32_t *pad_off)
122{
123 uint32_t srh_off, cur_off;
124 int offset_valid = 0;
125 int err;
126
127 srh_off = (char *)srh - (char *)(long)skb->data;
128
129 cur_off = srh_off + sizeof(*srh) +
130 sizeof(struct ip6_addr_t) * (srh->first_segment + 1);
131
132 *pad_off = 0;
133
134
135 #pragma clang loop unroll(disable)
136 for (int i = 0; i < 100; i++) {
137 struct sr6_tlv_t tlv;
138
139 if (cur_off == *tlv_off)
140 offset_valid = 1;
141
142 if (cur_off >= srh_off + ((srh->hdrlen + 1) << 3))
143 break;
144
145 err = bpf_skb_load_bytes(skb, cur_off, &tlv, sizeof(tlv));
146 if (err)
147 return err;
148
149 if (tlv.type == SR6_TLV_PADDING) {
150 *pad_size = tlv.len + sizeof(tlv);
151 *pad_off = cur_off;
152
153 if (*tlv_off == srh_off) {
154 *tlv_off = cur_off;
155 offset_valid = 1;
156 }
157 break;
158
159 } else if (tlv.type == SR6_TLV_HMAC) {
160 break;
161 }
162
163 cur_off += sizeof(tlv) + tlv.len;
164 }
165
166 if (*pad_off == 0)
167 *pad_off = cur_off;
168
169 if (*tlv_off == -1)
170 *tlv_off = cur_off;
171 else if (!offset_valid)
172 return -EINVAL;
173
174 return 0;
175}
176
177static __always_inline int add_tlv(struct __sk_buff *skb,
178 struct ip6_srh_t *srh, uint32_t tlv_off,
179 struct sr6_tlv_t *itlv, uint8_t tlv_size)
180{
181 uint32_t srh_off = (char *)srh - (char *)(long)skb->data;
182 uint8_t len_remaining, new_pad;
183 uint32_t pad_off = 0;
184 uint32_t pad_size = 0;
185 uint32_t partial_srh_len;
186 int err;
187
188 if (tlv_off != -1)
189 tlv_off += srh_off;
190
191 if (itlv->type == SR6_TLV_PADDING || itlv->type == SR6_TLV_HMAC)
192 return -EINVAL;
193
194 err = is_valid_tlv_boundary(skb, srh, &tlv_off, &pad_size, &pad_off);
195 if (err)
196 return err;
197
198 err = bpf_lwt_seg6_adjust_srh(skb, tlv_off, sizeof(*itlv) + itlv->len);
199 if (err)
200 return err;
201
202 err = bpf_lwt_seg6_store_bytes(skb, tlv_off, (void *)itlv, tlv_size);
203 if (err)
204 return err;
205
206
207
208 pad_off += sizeof(*itlv) + itlv->len;
209 partial_srh_len = pad_off - srh_off;
210 len_remaining = partial_srh_len % 8;
211 new_pad = 8 - len_remaining;
212
213 if (new_pad == 1)
214 new_pad = 9;
215 else if (new_pad == 8)
216 new_pad = 0;
217
218 return update_tlv_pad(skb, new_pad, pad_size, pad_off);
219}
220
221
222
223SEC("lwt_seg6local")
224int __add_egr_x(struct __sk_buff *skb)
225{
226 unsigned long long hi = 0xfc42000000000000;
227 unsigned long long lo = 0x1;
228 struct ip6_srh_t *srh = get_srh(skb);
229 uint8_t new_flags = SR6_FLAG_ALERT;
230 struct ip6_addr_t addr;
231 int err, offset;
232
233 if (srh == NULL)
234 return BPF_DROP;
235
236 uint8_t tlv[20] = {2, 18, 0, 0, 0xfd, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
237 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x4};
238
239 err = add_tlv(skb, srh, (srh->hdrlen+1) << 3,
240 (struct sr6_tlv_t *)&tlv, 20);
241 if (err)
242 return BPF_DROP;
243
244 offset = sizeof(struct ip6_t) + offsetof(struct ip6_srh_t, flags);
245 err = bpf_lwt_seg6_store_bytes(skb, offset,
246 (void *)&new_flags, sizeof(new_flags));
247 if (err)
248 return BPF_DROP;
249
250 addr.lo = bpf_cpu_to_be64(lo);
251 addr.hi = bpf_cpu_to_be64(hi);
252 err = bpf_lwt_seg6_action(skb, SEG6_LOCAL_ACTION_END_X,
253 (void *)&addr, sizeof(addr));
254 if (err)
255 return BPF_DROP;
256 return BPF_REDIRECT;
257}
258char __license[] SEC("license") = "GPL";
259
