tools/testing/selftests/bpf/progs/test_lwt_seg6local.c

   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 /* 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 htonll(x) ((bpf_htonl(1)) == 1 ? (x) : ((uint64_t)bpf_htonl((x) & \
  16                                 0xFFFFFFFF) << 32) | bpf_htonl((x) >> 32))
  17 #define ntohll(x) ((bpf_ntohl(1)) == 1 ? (x) : ((uint64_t)bpf_ntohl((x) & \
  18                                 0xFFFFFFFF) << 32) | bpf_ntohl((x) >> 32))
  19 #define BPF_PACKET_HEADER __attribute__((packed))
  20
  21 struct ip6_t {
  22         unsigned int ver:4;
  23         unsigned int priority:8;
  24         unsigned int flow_label:20;
  25         unsigned short payload_len;
  26         unsigned char next_header;
  27         unsigned char hop_limit;
  28         unsigned long long src_hi;
  29         unsigned long long src_lo;
  30         unsigned long long dst_hi;
  31         unsigned long long dst_lo;
  32 } BPF_PACKET_HEADER;
  33
  34 struct ip6_addr_t {
  35         unsigned long long hi;
  36         unsigned long long lo;
  37 } BPF_PACKET_HEADER;
  38
  39 struct ip6_srh_t {
  40         unsigned char nexthdr;
  41         unsigned char hdrlen;
  42         unsigned char type;
  43         unsigned char segments_left;
  44         unsigned char first_segment;
  45         unsigned char flags;
  46         unsigned short tag;
  47
  48         struct ip6_addr_t segments[0];
  49 } BPF_PACKET_HEADER;
  50
  51 struct sr6_tlv_t {
  52         unsigned char type;
  53         unsigned char len;
  54         unsigned char value[0];
  55 } BPF_PACKET_HEADER;
  56
  57 static __always_inline struct ip6_srh_t *get_srh(struct __sk_buff *skb)
  58 {
  59         void *cursor, *data_end;
  60         struct ip6_srh_t *srh;
  61         struct ip6_t *ip;
  62         uint8_t *ipver;
  63
  64         data_end = (void *)(long)skb->data_end;
  65         cursor = (void *)(long)skb->data;
  66         ipver = (uint8_t *)cursor;
  67
  68         if ((void *)ipver + sizeof(*ipver) > data_end)
  69                 return NULL;
  70
  71         if ((*ipver >> 4) != 6)
  72                 return NULL;
  73
  74         ip = cursor_advance(cursor, sizeof(*ip));
  75         if ((void *)ip + sizeof(*ip) > data_end)
  76                 return NULL;
  77
  78         if (ip->next_header != 43)
  79                 return NULL;
  80
  81         srh = cursor_advance(cursor, sizeof(*srh));
  82         if ((void *)srh + sizeof(*srh) > data_end)
  83                 return NULL;
  84
  85         if (srh->type != 4)
  86                 return NULL;
  87
  88         return srh;
  89 }
  90
  91 static __always_inline
  92 int update_tlv_pad(struct __sk_buff *skb, uint32_t new_pad,
  93                    uint32_t old_pad, uint32_t pad_off)
  94 {
  95         int err;
  96
  97         if (new_pad != old_pad) {
  98                 err = bpf_lwt_seg6_adjust_srh(skb, pad_off,
  99                                           (int) new_pad - (int) old_pad);
 100                 if (err)
 101                         return err;
 102         }
 103
 104         if (new_pad > 0) {
 105                 char pad_tlv_buf[16] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 106                                         0, 0, 0};
 107                 struct sr6_tlv_t *pad_tlv = (struct sr6_tlv_t *) pad_tlv_buf;
 108
 109                 pad_tlv->type = SR6_TLV_PADDING;
 110                 pad_tlv->len = new_pad - 2;
 111
 112                 err = bpf_lwt_seg6_store_bytes(skb, pad_off,
 113                                                (void *)pad_tlv_buf, new_pad);
 114                 if (err)
 115                         return err;
 116         }
 117
 118         return 0;
 119 }
 120
 121 static __always_inline
 122 int is_valid_tlv_boundary(struct __sk_buff *skb, struct ip6_srh_t *srh,
 123                           uint32_t *tlv_off, uint32_t *pad_size,
 124                           uint32_t *pad_off)
 125 {
 126         uint32_t srh_off, cur_off;
 127         int offset_valid = 0;
 128         int err;
 129
 130         srh_off = (char *)srh - (char *)(long)skb->data;
 131         // cur_off = end of segments, start of possible TLVs
 132         cur_off = srh_off + sizeof(*srh) +
 133                 sizeof(struct ip6_addr_t) * (srh->first_segment + 1);
 134
 135         *pad_off = 0;
 136
 137         // we can only go as far as ~10 TLVs due to the BPF max stack size
 138         #pragma clang loop unroll(full)
 139         for (int i = 0; i < 10; i++) {
 140                 struct sr6_tlv_t tlv;
 141
 142                 if (cur_off == *tlv_off)
 143                         offset_valid = 1;
 144
 145                 if (cur_off >= srh_off + ((srh->hdrlen + 1) << 3))
 146                         break;
 147
 148                 err = bpf_skb_load_bytes(skb, cur_off, &tlv, sizeof(tlv));
 149                 if (err)
 150                         return err;
 151
 152                 if (tlv.type == SR6_TLV_PADDING) {
 153                         *pad_size = tlv.len + sizeof(tlv);
 154                         *pad_off = cur_off;
 155
 156                         if (*tlv_off == srh_off) {
 157                                 *tlv_off = cur_off;
 158                                 offset_valid = 1;
 159                         }
 160                         break;
 161
 162                 } else if (tlv.type == SR6_TLV_HMAC) {
 163                         break;
 164                 }
 165
 166                 cur_off += sizeof(tlv) + tlv.len;
 167         } // we reached the padding or HMAC TLVs, or the end of the SRH
 168
 169         if (*pad_off == 0)
 170                 *pad_off = cur_off;
 171
 172         if (*tlv_off == -1)
 173                 *tlv_off = cur_off;
 174         else if (!offset_valid)
 175                 return -EINVAL;
 176
 177         return 0;
 178 }
 179
 180 static __always_inline
 181 int add_tlv(struct __sk_buff *skb, struct ip6_srh_t *srh, uint32_t tlv_off,
 182             struct sr6_tlv_t *itlv, uint8_t tlv_size)
 183 {
 184         uint32_t srh_off = (char *)srh - (char *)(long)skb->data;
 185         uint8_t len_remaining, new_pad;
 186         uint32_t pad_off = 0;
 187         uint32_t pad_size = 0;
 188         uint32_t partial_srh_len;
 189         int err;
 190
 191         if (tlv_off != -1)
 192                 tlv_off += srh_off;
 193
 194         if (itlv->type == SR6_TLV_PADDING || itlv->type == SR6_TLV_HMAC)
 195                 return -EINVAL;
 196
 197         err = is_valid_tlv_boundary(skb, srh, &tlv_off, &pad_size, &pad_off);
 198         if (err)
 199                 return err;
 200
 201         err = bpf_lwt_seg6_adjust_srh(skb, tlv_off, sizeof(*itlv) + itlv->len);
 202         if (err)
 203                 return err;
 204
 205         err = bpf_lwt_seg6_store_bytes(skb, tlv_off, (void *)itlv, tlv_size);
 206         if (err)
 207                 return err;
 208
 209         // the following can't be moved inside update_tlv_pad because the
 210         // bpf verifier has some issues with it
 211         pad_off += sizeof(*itlv) + itlv->len;
 212         partial_srh_len = pad_off - srh_off;
 213         len_remaining = partial_srh_len % 8;
 214         new_pad = 8 - len_remaining;
 215
 216         if (new_pad == 1) // cannot pad for 1 byte only
 217                 new_pad = 9;
 218         else if (new_pad == 8)
 219                 new_pad = 0;
 220
 221         return update_tlv_pad(skb, new_pad, pad_size, pad_off);
 222 }
 223
 224 static __always_inline
 225 int delete_tlv(struct __sk_buff *skb, struct ip6_srh_t *srh,
 226                uint32_t tlv_off)
 227 {
 228         uint32_t srh_off = (char *)srh - (char *)(long)skb->data;
 229         uint8_t len_remaining, new_pad;
 230         uint32_t partial_srh_len;
 231         uint32_t pad_off = 0;
 232         uint32_t pad_size = 0;
 233         struct sr6_tlv_t tlv;
 234         int err;
 235
 236         tlv_off += srh_off;
 237
 238         err = is_valid_tlv_boundary(skb, srh, &tlv_off, &pad_size, &pad_off);
 239         if (err)
 240                 return err;
 241
 242         err = bpf_skb_load_bytes(skb, tlv_off, &tlv, sizeof(tlv));
 243         if (err)
 244                 return err;
 245
 246         err = bpf_lwt_seg6_adjust_srh(skb, tlv_off, -(sizeof(tlv) + tlv.len));
 247         if (err)
 248                 return err;
 249
 250         pad_off -= sizeof(tlv) + tlv.len;
 251         partial_srh_len = pad_off - srh_off;
 252         len_remaining = partial_srh_len % 8;
 253         new_pad = 8 - len_remaining;
 254         if (new_pad == 1) // cannot pad for 1 byte only
 255                 new_pad = 9;
 256         else if (new_pad == 8)
 257                 new_pad = 0;
 258
 259         return update_tlv_pad(skb, new_pad, pad_size, pad_off);
 260 }
 261
 262 static __always_inline
 263 int has_egr_tlv(struct __sk_buff *skb, struct ip6_srh_t *srh)
 264 {
 265         int tlv_offset = sizeof(struct ip6_t) + sizeof(struct ip6_srh_t) +
 266                 ((srh->first_segment + 1) << 4);
 267         struct sr6_tlv_t tlv;
 268
 269         if (bpf_skb_load_bytes(skb, tlv_offset, &tlv, sizeof(struct sr6_tlv_t)))
 270                 return 0;
 271
 272         if (tlv.type == SR6_TLV_EGRESS && tlv.len == 18) {
 273                 struct ip6_addr_t egr_addr;
 274
 275                 if (bpf_skb_load_bytes(skb, tlv_offset + 4, &egr_addr, 16))
 276                         return 0;
 277
 278                 // check if egress TLV value is correct
 279                 if (ntohll(egr_addr.hi) == 0xfd00000000000000 &&
 280                                 ntohll(egr_addr.lo) == 0x4)
 281                         return 1;
 282         }
 283
 284         return 0;
 285 }
 286
 287 // This function will push a SRH with segments fd00::1, fd00::2, fd00::3,
 288 // fd00::4
 289 SEC("encap_srh")
 290 int __encap_srh(struct __sk_buff *skb)
 291 {
 292         unsigned long long hi = 0xfd00000000000000;
 293         struct ip6_addr_t *seg;
 294         struct ip6_srh_t *srh;
 295         char srh_buf[72]; // room for 4 segments
 296         int err;
 297
 298         srh = (struct ip6_srh_t *)srh_buf;
 299         srh->nexthdr = 0;
 300         srh->hdrlen = 8;
 301         srh->type = 4;
 302         srh->segments_left = 3;
 303         srh->first_segment = 3;
 304         srh->flags = 0;
 305         srh->tag = 0;
 306
 307         seg = (struct ip6_addr_t *)((char *)srh + sizeof(*srh));
 308
 309         #pragma clang loop unroll(full)
 310         for (unsigned long long lo = 0; lo < 4; lo++) {
 311                 seg->lo = htonll(4 - lo);
 312                 seg->hi = htonll(hi);
 313                 seg = (struct ip6_addr_t *)((char *)seg + sizeof(*seg));
 314         }
 315
 316         err = bpf_lwt_push_encap(skb, 0, (void *)srh, sizeof(srh_buf));
 317         if (err)
 318                 return BPF_DROP;
 319
 320         return BPF_REDIRECT;
 321 }
 322
 323 // Add an Egress TLV fc00::4, add the flag A,
 324 // and apply End.X action to fc42::1
 325 SEC("add_egr_x")
 326 int __add_egr_x(struct __sk_buff *skb)
 327 {
 328         unsigned long long hi = 0xfc42000000000000;
 329         unsigned long long lo = 0x1;
 330         struct ip6_srh_t *srh = get_srh(skb);
 331         uint8_t new_flags = SR6_FLAG_ALERT;
 332         struct ip6_addr_t addr;
 333         int err, offset;
 334
 335         if (srh == NULL)
 336                 return BPF_DROP;
 337
 338         uint8_t tlv[20] = {2, 18, 0, 0, 0xfd, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
 339                            0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x4};
 340
 341         err = add_tlv(skb, srh, (srh->hdrlen+1) << 3,
 342                       (struct sr6_tlv_t *)&tlv, 20);
 343         if (err)
 344                 return BPF_DROP;
 345
 346         offset = sizeof(struct ip6_t) + offsetof(struct ip6_srh_t, flags);
 347         err = bpf_lwt_seg6_store_bytes(skb, offset,
 348                                        (void *)&new_flags, sizeof(new_flags));
 349         if (err)
 350                 return BPF_DROP;
 351
 352         addr.lo = htonll(lo);
 353         addr.hi = htonll(hi);
 354         err = bpf_lwt_seg6_action(skb, SEG6_LOCAL_ACTION_END_X,
 355                                   (void *)&addr, sizeof(addr));
 356         if (err)
 357                 return BPF_DROP;
 358         return BPF_REDIRECT;
 359 }
 360
 361 // Pop the Egress TLV, reset the flags, change the tag 2442 and finally do a
 362 // simple End action
 363 SEC("pop_egr")
 364 int __pop_egr(struct __sk_buff *skb)
 365 {
 366         struct ip6_srh_t *srh = get_srh(skb);
 367         uint16_t new_tag = bpf_htons(2442);
 368         uint8_t new_flags = 0;
 369         int err, offset;
 370
 371         if (srh == NULL)
 372                 return BPF_DROP;
 373
 374         if (srh->flags != SR6_FLAG_ALERT)
 375                 return BPF_DROP;
 376
 377         if (srh->hdrlen != 11) // 4 segments + Egress TLV + Padding TLV
 378                 return BPF_DROP;
 379
 380         if (!has_egr_tlv(skb, srh))
 381                 return BPF_DROP;
 382
 383         err = delete_tlv(skb, srh, 8 + (srh->first_segment + 1) * 16);
 384         if (err)
 385                 return BPF_DROP;
 386
 387         offset = sizeof(struct ip6_t) + offsetof(struct ip6_srh_t, flags);
 388         if (bpf_lwt_seg6_store_bytes(skb, offset, (void *)&new_flags,
 389                                      sizeof(new_flags)))
 390                 return BPF_DROP;
 391
 392         offset = sizeof(struct ip6_t) + offsetof(struct ip6_srh_t, tag);
 393         if (bpf_lwt_seg6_store_bytes(skb, offset, (void *)&new_tag,
 394                                      sizeof(new_tag)))
 395                 return BPF_DROP;
 396
 397         return BPF_OK;
 398 }
 399
 400 // Inspect if the Egress TLV and flag have been removed, if the tag is correct,
 401 // then apply a End.T action to reach the last segment
 402 SEC("inspect_t")
 403 int __inspect_t(struct __sk_buff *skb)
 404 {
 405         struct ip6_srh_t *srh = get_srh(skb);
 406         int table = 117;
 407         int err;
 408
 409         if (srh == NULL)
 410                 return BPF_DROP;
 411
 412         if (srh->flags != 0)
 413                 return BPF_DROP;
 414
 415         if (srh->tag != bpf_htons(2442))
 416                 return BPF_DROP;
 417
 418         if (srh->hdrlen != 8) // 4 segments
 419                 return BPF_DROP;
 420
 421         err = bpf_lwt_seg6_action(skb, SEG6_LOCAL_ACTION_END_T,
 422                                   (void *)&table, sizeof(table));
 423
 424         if (err)
 425                 return BPF_DROP;
 426
 427         return BPF_REDIRECT;
 428 }
 429
 430 char __license[] SEC("license") = "GPL";