LXR linux/tools/testing/selftests/bpf/progs/test_seg6

   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
  21struct 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
  34struct ip6_addr_t {
  35        unsigned long long hi;
  36        unsigned long long lo;
  37} BPF_PACKET_HEADER;
  38
  39struct 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
  51struct sr6_tlv_t {
  52        unsigned char type;
  53        unsigned char len;
  54        unsigned char value[0];
  55} BPF_PACKET_HEADER;
  56
  57static __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
  91static __always_inline int update_tlv_pad(struct __sk_buff *skb,
  92                                          uint32_t new_pad, uint32_t old_pad,
  93                                          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
 121static __always_inline int is_valid_tlv_boundary(struct __sk_buff *skb,
 122                                                 struct ip6_srh_t *srh,
 123                                                 uint32_t *tlv_off,
 124                                                 uint32_t *pad_size,
 125                                                 uint32_t *pad_off)
 126{
 127        uint32_t srh_off, cur_off;
 128        int offset_valid = 0;
 129        int err;
 130
 131        srh_off = (char *)srh - (char *)(long)skb->data;
 132        // cur_off = end of segments, start of possible TLVs
 133        cur_off = srh_off + sizeof(*srh) +
 134                sizeof(struct ip6_addr_t) * (srh->first_segment + 1);
 135
 136        *pad_off = 0;
 137
 138        // we can only go as far as ~10 TLVs due to the BPF max stack size
 139        #pragma clang loop unroll(disable)
 140        for (int i = 0; i < 100; i++) {
 141                struct sr6_tlv_t tlv;
 142
 143                if (cur_off == *tlv_off)
 144                        offset_valid = 1;
 145
 146                if (cur_off >= srh_off + ((srh->hdrlen + 1) << 3))
 147                        break;
 148
 149                err = bpf_skb_load_bytes(skb, cur_off, &tlv, sizeof(tlv));
 150                if (err)
 151                        return err;
 152
 153                if (tlv.type == SR6_TLV_PADDING) {
 154                        *pad_size = tlv.len + sizeof(tlv);
 155                        *pad_off = cur_off;
 156
 157                        if (*tlv_off == srh_off) {
 158                                *tlv_off = cur_off;
 159                                offset_valid = 1;
 160                        }
 161                        break;
 162
 163                } else if (tlv.type == SR6_TLV_HMAC) {
 164                        break;
 165                }
 166
 167                cur_off += sizeof(tlv) + tlv.len;
 168        } // we reached the padding or HMAC TLVs, or the end of the SRH
 169
 170        if (*pad_off == 0)
 171                *pad_off = cur_off;
 172
 173        if (*tlv_off == -1)
 174                *tlv_off = cur_off;
 175        else if (!offset_valid)
 176                return -EINVAL;
 177
 178        return 0;
 179}
 180
 181static __always_inline int add_tlv(struct __sk_buff *skb,
 182                                   struct ip6_srh_t *srh, uint32_t tlv_off,
 183                                   struct sr6_tlv_t *itlv, uint8_t tlv_size)
 184{
 185        uint32_t srh_off = (char *)srh - (char *)(long)skb->data;
 186        uint8_t len_remaining, new_pad;
 187        uint32_t pad_off = 0;
 188        uint32_t pad_size = 0;
 189        uint32_t partial_srh_len;
 190        int err;
 191
 192        if (tlv_off != -1)
 193                tlv_off += srh_off;
 194
 195        if (itlv->type == SR6_TLV_PADDING || itlv->type == SR6_TLV_HMAC)
 196                return -EINVAL;
 197
 198        err = is_valid_tlv_boundary(skb, srh, &tlv_off, &pad_size, &pad_off);
 199        if (err)
 200                return err;
 201
 202        err = bpf_lwt_seg6_adjust_srh(skb, tlv_off, sizeof(*itlv) + itlv->len);
 203        if (err)
 204                return err;
 205
 206        err = bpf_lwt_seg6_store_bytes(skb, tlv_off, (void *)itlv, tlv_size);
 207        if (err)
 208                return err;
 209
 210        // the following can't be moved inside update_tlv_pad because the
 211        // bpf verifier has some issues with it
 212        pad_off += sizeof(*itlv) + itlv->len;
 213        partial_srh_len = pad_off - srh_off;
 214        len_remaining = partial_srh_len % 8;
 215        new_pad = 8 - len_remaining;
 216
 217        if (new_pad == 1) // cannot pad for 1 byte only
 218                new_pad = 9;
 219        else if (new_pad == 8)
 220                new_pad = 0;
 221
 222        return update_tlv_pad(skb, new_pad, pad_size, pad_off);
 223}
 224
 225// Add an Egress TLV fc00::4, add the flag A,
 226// and apply End.X action to fc42::1
 227SEC("lwt_seg6local")
 228int __add_egr_x(struct __sk_buff *skb)
 229{
 230        unsigned long long hi = 0xfc42000000000000;
 231        unsigned long long lo = 0x1;
 232        struct ip6_srh_t *srh = get_srh(skb);
 233        uint8_t new_flags = SR6_FLAG_ALERT;
 234        struct ip6_addr_t addr;
 235        int err, offset;
 236
 237        if (srh == NULL)
 238                return BPF_DROP;
 239
 240        uint8_t tlv[20] = {2, 18, 0, 0, 0xfd, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
 241                           0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x4};
 242
 243        err = add_tlv(skb, srh, (srh->hdrlen+1) << 3,
 244                      (struct sr6_tlv_t *)&tlv, 20);
 245        if (err)
 246                return BPF_DROP;
 247
 248        offset = sizeof(struct ip6_t) + offsetof(struct ip6_srh_t, flags);
 249        err = bpf_lwt_seg6_store_bytes(skb, offset,
 250                                       (void *)&new_flags, sizeof(new_flags));
 251        if (err)
 252                return BPF_DROP;
 253
 254        addr.lo = htonll(lo);
 255        addr.hi = htonll(hi);
 256        err = bpf_lwt_seg6_action(skb, SEG6_LOCAL_ACTION_END_X,
 257                                  (void *)&addr, sizeof(addr));
 258        if (err)
 259                return BPF_DROP;
 260        return BPF_REDIRECT;
 261}
 262char __license[] SEC("license") = "GPL";
 263