Loading...
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/bpf_helpers.h>
7#include <bpf/bpf_endian.h>
8
9#include "bpf_compiler.h"
10
11/* Packet parsing state machine helpers. */
12#define cursor_advance(_cursor, _len) \
13 ({ void *_tmp = _cursor; _cursor += _len; _tmp; })
14
15#define SR6_FLAG_ALERT (1 << 4)
16
17#define BPF_PACKET_HEADER __attribute__((packed))
18
19struct ip6_t {
20 unsigned int ver:4;
21 unsigned int priority:8;
22 unsigned int flow_label:20;
23 unsigned short payload_len;
24 unsigned char next_header;
25 unsigned char hop_limit;
26 unsigned long long src_hi;
27 unsigned long long src_lo;
28 unsigned long long dst_hi;
29 unsigned long long dst_lo;
30} BPF_PACKET_HEADER;
31
32struct ip6_addr_t {
33 unsigned long long hi;
34 unsigned long long lo;
35} BPF_PACKET_HEADER;
36
37struct ip6_srh_t {
38 unsigned char nexthdr;
39 unsigned char hdrlen;
40 unsigned char type;
41 unsigned char segments_left;
42 unsigned char first_segment;
43 unsigned char flags;
44 unsigned short tag;
45
46 struct ip6_addr_t segments[0];
47} BPF_PACKET_HEADER;
48
49struct sr6_tlv_t {
50 unsigned char type;
51 unsigned char len;
52 unsigned char value[0];
53} BPF_PACKET_HEADER;
54
55static __always_inline struct ip6_srh_t *get_srh(struct __sk_buff *skb)
56{
57 void *cursor, *data_end;
58 struct ip6_srh_t *srh;
59 struct ip6_t *ip;
60 uint8_t *ipver;
61
62 data_end = (void *)(long)skb->data_end;
63 cursor = (void *)(long)skb->data;
64 ipver = (uint8_t *)cursor;
65
66 if ((void *)ipver + sizeof(*ipver) > data_end)
67 return NULL;
68
69 if ((*ipver >> 4) != 6)
70 return NULL;
71
72 ip = cursor_advance(cursor, sizeof(*ip));
73 if ((void *)ip + sizeof(*ip) > data_end)
74 return NULL;
75
76 if (ip->next_header != 43)
77 return NULL;
78
79 srh = cursor_advance(cursor, sizeof(*srh));
80 if ((void *)srh + sizeof(*srh) > data_end)
81 return NULL;
82
83 if (srh->type != 4)
84 return NULL;
85
86 return srh;
87}
88
89static __always_inline
90int update_tlv_pad(struct __sk_buff *skb, uint32_t new_pad,
91 uint32_t old_pad, uint32_t pad_off)
92{
93 int err;
94
95 if (new_pad != old_pad) {
96 err = bpf_lwt_seg6_adjust_srh(skb, pad_off,
97 (int) new_pad - (int) old_pad);
98 if (err)
99 return err;
100 }
101
102 if (new_pad > 0) {
103 char pad_tlv_buf[16] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
104 0, 0, 0};
105 struct sr6_tlv_t *pad_tlv = (struct sr6_tlv_t *) pad_tlv_buf;
106
107 pad_tlv->type = SR6_TLV_PADDING;
108 pad_tlv->len = new_pad - 2;
109
110 err = bpf_lwt_seg6_store_bytes(skb, pad_off,
111 (void *)pad_tlv_buf, new_pad);
112 if (err)
113 return err;
114 }
115
116 return 0;
117}
118
119static __always_inline
120int is_valid_tlv_boundary(struct __sk_buff *skb, struct ip6_srh_t *srh,
121 uint32_t *tlv_off, uint32_t *pad_size,
122 uint32_t *pad_off)
123{
124 uint32_t srh_off, cur_off;
125 int offset_valid = 0;
126 int err;
127
128 srh_off = (char *)srh - (char *)(long)skb->data;
129 // cur_off = end of segments, start of possible TLVs
130 cur_off = srh_off + sizeof(*srh) +
131 sizeof(struct ip6_addr_t) * (srh->first_segment + 1);
132
133 *pad_off = 0;
134
135 // we can only go as far as ~10 TLVs due to the BPF max stack size
136 __pragma_loop_unroll_full
137 for (int i = 0; i < 10; i++) {
138 struct sr6_tlv_t tlv;
139
140 if (cur_off == *tlv_off)
141 offset_valid = 1;
142
143 if (cur_off >= srh_off + ((srh->hdrlen + 1) << 3))
144 break;
145
146 err = bpf_skb_load_bytes(skb, cur_off, &tlv, sizeof(tlv));
147 if (err)
148 return err;
149
150 if (tlv.type == SR6_TLV_PADDING) {
151 *pad_size = tlv.len + sizeof(tlv);
152 *pad_off = cur_off;
153
154 if (*tlv_off == srh_off) {
155 *tlv_off = cur_off;
156 offset_valid = 1;
157 }
158 break;
159
160 } else if (tlv.type == SR6_TLV_HMAC) {
161 break;
162 }
163
164 cur_off += sizeof(tlv) + tlv.len;
165 } // we reached the padding or HMAC TLVs, or the end of the SRH
166
167 if (*pad_off == 0)
168 *pad_off = cur_off;
169
170 if (*tlv_off == -1)
171 *tlv_off = cur_off;
172 else if (!offset_valid)
173 return -EINVAL;
174
175 return 0;
176}
177
178static __always_inline
179int add_tlv(struct __sk_buff *skb, struct ip6_srh_t *srh, uint32_t tlv_off,
180 struct sr6_tlv_t *itlv, uint8_t tlv_size)
181{
182 uint32_t srh_off = (char *)srh - (char *)(long)skb->data;
183 uint8_t len_remaining, new_pad;
184 uint32_t pad_off = 0;
185 uint32_t pad_size = 0;
186 uint32_t partial_srh_len;
187 int err;
188
189 if (tlv_off != -1)
190 tlv_off += srh_off;
191
192 if (itlv->type == SR6_TLV_PADDING || itlv->type == SR6_TLV_HMAC)
193 return -EINVAL;
194
195 err = is_valid_tlv_boundary(skb, srh, &tlv_off, &pad_size, &pad_off);
196 if (err)
197 return err;
198
199 err = bpf_lwt_seg6_adjust_srh(skb, tlv_off, sizeof(*itlv) + itlv->len);
200 if (err)
201 return err;
202
203 err = bpf_lwt_seg6_store_bytes(skb, tlv_off, (void *)itlv, tlv_size);
204 if (err)
205 return err;
206
207 // the following can't be moved inside update_tlv_pad because the
208 // bpf verifier has some issues with it
209 pad_off += sizeof(*itlv) + itlv->len;
210 partial_srh_len = pad_off - srh_off;
211 len_remaining = partial_srh_len % 8;
212 new_pad = 8 - len_remaining;
213
214 if (new_pad == 1) // cannot pad for 1 byte only
215 new_pad = 9;
216 else if (new_pad == 8)
217 new_pad = 0;
218
219 return update_tlv_pad(skb, new_pad, pad_size, pad_off);
220}
221
222static __always_inline
223int delete_tlv(struct __sk_buff *skb, struct ip6_srh_t *srh,
224 uint32_t tlv_off)
225{
226 uint32_t srh_off = (char *)srh - (char *)(long)skb->data;
227 uint8_t len_remaining, new_pad;
228 uint32_t partial_srh_len;
229 uint32_t pad_off = 0;
230 uint32_t pad_size = 0;
231 struct sr6_tlv_t tlv;
232 int err;
233
234 tlv_off += srh_off;
235
236 err = is_valid_tlv_boundary(skb, srh, &tlv_off, &pad_size, &pad_off);
237 if (err)
238 return err;
239
240 err = bpf_skb_load_bytes(skb, tlv_off, &tlv, sizeof(tlv));
241 if (err)
242 return err;
243
244 err = bpf_lwt_seg6_adjust_srh(skb, tlv_off, -(sizeof(tlv) + tlv.len));
245 if (err)
246 return err;
247
248 pad_off -= sizeof(tlv) + tlv.len;
249 partial_srh_len = pad_off - srh_off;
250 len_remaining = partial_srh_len % 8;
251 new_pad = 8 - len_remaining;
252 if (new_pad == 1) // cannot pad for 1 byte only
253 new_pad = 9;
254 else if (new_pad == 8)
255 new_pad = 0;
256
257 return update_tlv_pad(skb, new_pad, pad_size, pad_off);
258}
259
260static __always_inline
261int has_egr_tlv(struct __sk_buff *skb, struct ip6_srh_t *srh)
262{
263 int tlv_offset = sizeof(struct ip6_t) + sizeof(struct ip6_srh_t) +
264 ((srh->first_segment + 1) << 4);
265 struct sr6_tlv_t tlv;
266
267 if (bpf_skb_load_bytes(skb, tlv_offset, &tlv, sizeof(struct sr6_tlv_t)))
268 return 0;
269
270 if (tlv.type == SR6_TLV_EGRESS && tlv.len == 18) {
271 struct ip6_addr_t egr_addr;
272
273 if (bpf_skb_load_bytes(skb, tlv_offset + 4, &egr_addr, 16))
274 return 0;
275
276 // check if egress TLV value is correct
277 if (bpf_be64_to_cpu(egr_addr.hi) == 0xfd00000000000000 &&
278 bpf_be64_to_cpu(egr_addr.lo) == 0x4)
279 return 1;
280 }
281
282 return 0;
283}
284
285// This function will push a SRH with segments fd00::1, fd00::2, fd00::3,
286// fd00::4
287SEC("encap_srh")
288int __encap_srh(struct __sk_buff *skb)
289{
290 unsigned long long hi = 0xfd00000000000000;
291 struct ip6_addr_t *seg;
292 struct ip6_srh_t *srh;
293 char srh_buf[72]; // room for 4 segments
294 int err;
295
296 srh = (struct ip6_srh_t *)srh_buf;
297 srh->nexthdr = 0;
298 srh->hdrlen = 8;
299 srh->type = 4;
300 srh->segments_left = 3;
301 srh->first_segment = 3;
302 srh->flags = 0;
303 srh->tag = 0;
304
305 seg = (struct ip6_addr_t *)((char *)srh + sizeof(*srh));
306
307 __pragma_loop_unroll_full
308 for (unsigned long long lo = 0; lo < 4; lo++) {
309 seg->lo = bpf_cpu_to_be64(4 - lo);
310 seg->hi = bpf_cpu_to_be64(hi);
311 seg = (struct ip6_addr_t *)((char *)seg + sizeof(*seg));
312 }
313
314 err = bpf_lwt_push_encap(skb, 0, (void *)srh, sizeof(srh_buf));
315 if (err)
316 return BPF_DROP;
317
318 return BPF_REDIRECT;
319}
320
321// Add an Egress TLV fc00::4, add the flag A,
322// and apply End.X action to fc42::1
323SEC("add_egr_x")
324int __add_egr_x(struct __sk_buff *skb)
325{
326 unsigned long long hi = 0xfc42000000000000;
327 unsigned long long lo = 0x1;
328 struct ip6_srh_t *srh = get_srh(skb);
329 uint8_t new_flags = SR6_FLAG_ALERT;
330 struct ip6_addr_t addr;
331 int err, offset;
332
333 if (srh == NULL)
334 return BPF_DROP;
335
336 uint8_t tlv[20] = {2, 18, 0, 0, 0xfd, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
337 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x4};
338
339 err = add_tlv(skb, srh, (srh->hdrlen+1) << 3,
340 (struct sr6_tlv_t *)&tlv, 20);
341 if (err)
342 return BPF_DROP;
343
344 offset = sizeof(struct ip6_t) + offsetof(struct ip6_srh_t, flags);
345 err = bpf_lwt_seg6_store_bytes(skb, offset,
346 (void *)&new_flags, sizeof(new_flags));
347 if (err)
348 return BPF_DROP;
349
350 addr.lo = bpf_cpu_to_be64(lo);
351 addr.hi = bpf_cpu_to_be64(hi);
352 err = bpf_lwt_seg6_action(skb, SEG6_LOCAL_ACTION_END_X,
353 (void *)&addr, sizeof(addr));
354 if (err)
355 return BPF_DROP;
356 return BPF_REDIRECT;
357}
358
359// Pop the Egress TLV, reset the flags, change the tag 2442 and finally do a
360// simple End action
361SEC("pop_egr")
362int __pop_egr(struct __sk_buff *skb)
363{
364 struct ip6_srh_t *srh = get_srh(skb);
365 uint16_t new_tag = bpf_htons(2442);
366 uint8_t new_flags = 0;
367 int err, offset;
368
369 if (srh == NULL)
370 return BPF_DROP;
371
372 if (srh->flags != SR6_FLAG_ALERT)
373 return BPF_DROP;
374
375 if (srh->hdrlen != 11) // 4 segments + Egress TLV + Padding TLV
376 return BPF_DROP;
377
378 if (!has_egr_tlv(skb, srh))
379 return BPF_DROP;
380
381 err = delete_tlv(skb, srh, 8 + (srh->first_segment + 1) * 16);
382 if (err)
383 return BPF_DROP;
384
385 offset = sizeof(struct ip6_t) + offsetof(struct ip6_srh_t, flags);
386 if (bpf_lwt_seg6_store_bytes(skb, offset, (void *)&new_flags,
387 sizeof(new_flags)))
388 return BPF_DROP;
389
390 offset = sizeof(struct ip6_t) + offsetof(struct ip6_srh_t, tag);
391 if (bpf_lwt_seg6_store_bytes(skb, offset, (void *)&new_tag,
392 sizeof(new_tag)))
393 return BPF_DROP;
394
395 return BPF_OK;
396}
397
398// Inspect if the Egress TLV and flag have been removed, if the tag is correct,
399// then apply a End.T action to reach the last segment
400SEC("inspect_t")
401int __inspect_t(struct __sk_buff *skb)
402{
403 struct ip6_srh_t *srh = get_srh(skb);
404 int table = 117;
405 int err;
406
407 if (srh == NULL)
408 return BPF_DROP;
409
410 if (srh->flags != 0)
411 return BPF_DROP;
412
413 if (srh->tag != bpf_htons(2442))
414 return BPF_DROP;
415
416 if (srh->hdrlen != 8) // 4 segments
417 return BPF_DROP;
418
419 err = bpf_lwt_seg6_action(skb, SEG6_LOCAL_ACTION_END_T,
420 (void *)&table, sizeof(table));
421
422 if (err)
423 return BPF_DROP;
424
425 return BPF_REDIRECT;
426}
427
428char __license[] SEC("license") = "GPL";
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/bpf_helpers.h>
7#include <bpf/bpf_endian.h>
8
9/* Packet parsing state machine helpers. */
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
88int update_tlv_pad(struct __sk_buff *skb, uint32_t new_pad,
89 uint32_t old_pad, 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
118int is_valid_tlv_boundary(struct __sk_buff *skb, struct ip6_srh_t *srh,
119 uint32_t *tlv_off, uint32_t *pad_size,
120 uint32_t *pad_off)
121{
122 uint32_t srh_off, cur_off;
123 int offset_valid = 0;
124 int err;
125
126 srh_off = (char *)srh - (char *)(long)skb->data;
127 // cur_off = end of segments, start of possible TLVs
128 cur_off = srh_off + sizeof(*srh) +
129 sizeof(struct ip6_addr_t) * (srh->first_segment + 1);
130
131 *pad_off = 0;
132
133 // we can only go as far as ~10 TLVs due to the BPF max stack size
134 #pragma clang loop unroll(full)
135 for (int i = 0; i < 10; i++) {
136 struct sr6_tlv_t tlv;
137
138 if (cur_off == *tlv_off)
139 offset_valid = 1;
140
141 if (cur_off >= srh_off + ((srh->hdrlen + 1) << 3))
142 break;
143
144 err = bpf_skb_load_bytes(skb, cur_off, &tlv, sizeof(tlv));
145 if (err)
146 return err;
147
148 if (tlv.type == SR6_TLV_PADDING) {
149 *pad_size = tlv.len + sizeof(tlv);
150 *pad_off = cur_off;
151
152 if (*tlv_off == srh_off) {
153 *tlv_off = cur_off;
154 offset_valid = 1;
155 }
156 break;
157
158 } else if (tlv.type == SR6_TLV_HMAC) {
159 break;
160 }
161
162 cur_off += sizeof(tlv) + tlv.len;
163 } // we reached the padding or HMAC TLVs, or the end of the SRH
164
165 if (*pad_off == 0)
166 *pad_off = cur_off;
167
168 if (*tlv_off == -1)
169 *tlv_off = cur_off;
170 else if (!offset_valid)
171 return -EINVAL;
172
173 return 0;
174}
175
176static __always_inline
177int add_tlv(struct __sk_buff *skb, struct ip6_srh_t *srh, uint32_t tlv_off,
178 struct sr6_tlv_t *itlv, uint8_t tlv_size)
179{
180 uint32_t srh_off = (char *)srh - (char *)(long)skb->data;
181 uint8_t len_remaining, new_pad;
182 uint32_t pad_off = 0;
183 uint32_t pad_size = 0;
184 uint32_t partial_srh_len;
185 int err;
186
187 if (tlv_off != -1)
188 tlv_off += srh_off;
189
190 if (itlv->type == SR6_TLV_PADDING || itlv->type == SR6_TLV_HMAC)
191 return -EINVAL;
192
193 err = is_valid_tlv_boundary(skb, srh, &tlv_off, &pad_size, &pad_off);
194 if (err)
195 return err;
196
197 err = bpf_lwt_seg6_adjust_srh(skb, tlv_off, sizeof(*itlv) + itlv->len);
198 if (err)
199 return err;
200
201 err = bpf_lwt_seg6_store_bytes(skb, tlv_off, (void *)itlv, tlv_size);
202 if (err)
203 return err;
204
205 // the following can't be moved inside update_tlv_pad because the
206 // bpf verifier has some issues with it
207 pad_off += sizeof(*itlv) + itlv->len;
208 partial_srh_len = pad_off - srh_off;
209 len_remaining = partial_srh_len % 8;
210 new_pad = 8 - len_remaining;
211
212 if (new_pad == 1) // cannot pad for 1 byte only
213 new_pad = 9;
214 else if (new_pad == 8)
215 new_pad = 0;
216
217 return update_tlv_pad(skb, new_pad, pad_size, pad_off);
218}
219
220static __always_inline
221int delete_tlv(struct __sk_buff *skb, struct ip6_srh_t *srh,
222 uint32_t tlv_off)
223{
224 uint32_t srh_off = (char *)srh - (char *)(long)skb->data;
225 uint8_t len_remaining, new_pad;
226 uint32_t partial_srh_len;
227 uint32_t pad_off = 0;
228 uint32_t pad_size = 0;
229 struct sr6_tlv_t tlv;
230 int err;
231
232 tlv_off += srh_off;
233
234 err = is_valid_tlv_boundary(skb, srh, &tlv_off, &pad_size, &pad_off);
235 if (err)
236 return err;
237
238 err = bpf_skb_load_bytes(skb, tlv_off, &tlv, sizeof(tlv));
239 if (err)
240 return err;
241
242 err = bpf_lwt_seg6_adjust_srh(skb, tlv_off, -(sizeof(tlv) + tlv.len));
243 if (err)
244 return err;
245
246 pad_off -= sizeof(tlv) + tlv.len;
247 partial_srh_len = pad_off - srh_off;
248 len_remaining = partial_srh_len % 8;
249 new_pad = 8 - len_remaining;
250 if (new_pad == 1) // cannot pad for 1 byte only
251 new_pad = 9;
252 else if (new_pad == 8)
253 new_pad = 0;
254
255 return update_tlv_pad(skb, new_pad, pad_size, pad_off);
256}
257
258static __always_inline
259int has_egr_tlv(struct __sk_buff *skb, struct ip6_srh_t *srh)
260{
261 int tlv_offset = sizeof(struct ip6_t) + sizeof(struct ip6_srh_t) +
262 ((srh->first_segment + 1) << 4);
263 struct sr6_tlv_t tlv;
264
265 if (bpf_skb_load_bytes(skb, tlv_offset, &tlv, sizeof(struct sr6_tlv_t)))
266 return 0;
267
268 if (tlv.type == SR6_TLV_EGRESS && tlv.len == 18) {
269 struct ip6_addr_t egr_addr;
270
271 if (bpf_skb_load_bytes(skb, tlv_offset + 4, &egr_addr, 16))
272 return 0;
273
274 // check if egress TLV value is correct
275 if (bpf_be64_to_cpu(egr_addr.hi) == 0xfd00000000000000 &&
276 bpf_be64_to_cpu(egr_addr.lo) == 0x4)
277 return 1;
278 }
279
280 return 0;
281}
282
283// This function will push a SRH with segments fd00::1, fd00::2, fd00::3,
284// fd00::4
285SEC("encap_srh")
286int __encap_srh(struct __sk_buff *skb)
287{
288 unsigned long long hi = 0xfd00000000000000;
289 struct ip6_addr_t *seg;
290 struct ip6_srh_t *srh;
291 char srh_buf[72]; // room for 4 segments
292 int err;
293
294 srh = (struct ip6_srh_t *)srh_buf;
295 srh->nexthdr = 0;
296 srh->hdrlen = 8;
297 srh->type = 4;
298 srh->segments_left = 3;
299 srh->first_segment = 3;
300 srh->flags = 0;
301 srh->tag = 0;
302
303 seg = (struct ip6_addr_t *)((char *)srh + sizeof(*srh));
304
305 #pragma clang loop unroll(full)
306 for (unsigned long long lo = 0; lo < 4; lo++) {
307 seg->lo = bpf_cpu_to_be64(4 - lo);
308 seg->hi = bpf_cpu_to_be64(hi);
309 seg = (struct ip6_addr_t *)((char *)seg + sizeof(*seg));
310 }
311
312 err = bpf_lwt_push_encap(skb, 0, (void *)srh, sizeof(srh_buf));
313 if (err)
314 return BPF_DROP;
315
316 return BPF_REDIRECT;
317}
318
319// Add an Egress TLV fc00::4, add the flag A,
320// and apply End.X action to fc42::1
321SEC("add_egr_x")
322int __add_egr_x(struct __sk_buff *skb)
323{
324 unsigned long long hi = 0xfc42000000000000;
325 unsigned long long lo = 0x1;
326 struct ip6_srh_t *srh = get_srh(skb);
327 uint8_t new_flags = SR6_FLAG_ALERT;
328 struct ip6_addr_t addr;
329 int err, offset;
330
331 if (srh == NULL)
332 return BPF_DROP;
333
334 uint8_t tlv[20] = {2, 18, 0, 0, 0xfd, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
335 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x4};
336
337 err = add_tlv(skb, srh, (srh->hdrlen+1) << 3,
338 (struct sr6_tlv_t *)&tlv, 20);
339 if (err)
340 return BPF_DROP;
341
342 offset = sizeof(struct ip6_t) + offsetof(struct ip6_srh_t, flags);
343 err = bpf_lwt_seg6_store_bytes(skb, offset,
344 (void *)&new_flags, sizeof(new_flags));
345 if (err)
346 return BPF_DROP;
347
348 addr.lo = bpf_cpu_to_be64(lo);
349 addr.hi = bpf_cpu_to_be64(hi);
350 err = bpf_lwt_seg6_action(skb, SEG6_LOCAL_ACTION_END_X,
351 (void *)&addr, sizeof(addr));
352 if (err)
353 return BPF_DROP;
354 return BPF_REDIRECT;
355}
356
357// Pop the Egress TLV, reset the flags, change the tag 2442 and finally do a
358// simple End action
359SEC("pop_egr")
360int __pop_egr(struct __sk_buff *skb)
361{
362 struct ip6_srh_t *srh = get_srh(skb);
363 uint16_t new_tag = bpf_htons(2442);
364 uint8_t new_flags = 0;
365 int err, offset;
366
367 if (srh == NULL)
368 return BPF_DROP;
369
370 if (srh->flags != SR6_FLAG_ALERT)
371 return BPF_DROP;
372
373 if (srh->hdrlen != 11) // 4 segments + Egress TLV + Padding TLV
374 return BPF_DROP;
375
376 if (!has_egr_tlv(skb, srh))
377 return BPF_DROP;
378
379 err = delete_tlv(skb, srh, 8 + (srh->first_segment + 1) * 16);
380 if (err)
381 return BPF_DROP;
382
383 offset = sizeof(struct ip6_t) + offsetof(struct ip6_srh_t, flags);
384 if (bpf_lwt_seg6_store_bytes(skb, offset, (void *)&new_flags,
385 sizeof(new_flags)))
386 return BPF_DROP;
387
388 offset = sizeof(struct ip6_t) + offsetof(struct ip6_srh_t, tag);
389 if (bpf_lwt_seg6_store_bytes(skb, offset, (void *)&new_tag,
390 sizeof(new_tag)))
391 return BPF_DROP;
392
393 return BPF_OK;
394}
395
396// Inspect if the Egress TLV and flag have been removed, if the tag is correct,
397// then apply a End.T action to reach the last segment
398SEC("inspect_t")
399int __inspect_t(struct __sk_buff *skb)
400{
401 struct ip6_srh_t *srh = get_srh(skb);
402 int table = 117;
403 int err;
404
405 if (srh == NULL)
406 return BPF_DROP;
407
408 if (srh->flags != 0)
409 return BPF_DROP;
410
411 if (srh->tag != bpf_htons(2442))
412 return BPF_DROP;
413
414 if (srh->hdrlen != 8) // 4 segments
415 return BPF_DROP;
416
417 err = bpf_lwt_seg6_action(skb, SEG6_LOCAL_ACTION_END_T,
418 (void *)&table, sizeof(table));
419
420 if (err)
421 return BPF_DROP;
422
423 return BPF_REDIRECT;
424}
425
426char __license[] SEC("license") = "GPL";