4 #include <linux/seg6_local.h>
6 #include "bpf_helpers.h"
7 #include "bpf_endian.h"
9 #define bpf_printk(fmt, ...) \
11 char ____fmt[] = fmt; \
12 bpf_trace_printk(____fmt, sizeof(____fmt), \
16 /* Packet parsing state machine helpers. */
17 #define cursor_advance(_cursor, _len) \
18 ({ void *_tmp = _cursor; _cursor += _len; _tmp; })
20 #define SR6_FLAG_ALERT (1 << 4)
22 #define htonll(x) ((bpf_htonl(1)) == 1 ? (x) : ((uint64_t)bpf_htonl((x) & \
23 0xFFFFFFFF) << 32) | bpf_htonl((x) >> 32))
24 #define ntohll(x) ((bpf_ntohl(1)) == 1 ? (x) : ((uint64_t)bpf_ntohl((x) & \
25 0xFFFFFFFF) << 32) | bpf_ntohl((x) >> 32))
26 #define BPF_PACKET_HEADER __attribute__((packed))
30 unsigned int priority:8;
31 unsigned int flow_label:20;
32 unsigned short payload_len;
33 unsigned char next_header;
34 unsigned char hop_limit;
35 unsigned long long src_hi;
36 unsigned long long src_lo;
37 unsigned long long dst_hi;
38 unsigned long long dst_lo;
42 unsigned long long hi;
43 unsigned long long lo;
47 unsigned char nexthdr;
50 unsigned char segments_left;
51 unsigned char first_segment;
55 struct ip6_addr_t segments[0];
61 unsigned char value[0];
64 static __always_inline struct ip6_srh_t *get_srh(struct __sk_buff *skb)
66 void *cursor, *data_end;
67 struct ip6_srh_t *srh;
71 data_end = (void *)(long)skb->data_end;
72 cursor = (void *)(long)skb->data;
73 ipver = (uint8_t *)cursor;
75 if ((void *)ipver + sizeof(*ipver) > data_end)
78 if ((*ipver >> 4) != 6)
81 ip = cursor_advance(cursor, sizeof(*ip));
82 if ((void *)ip + sizeof(*ip) > data_end)
85 if (ip->next_header != 43)
88 srh = cursor_advance(cursor, sizeof(*srh));
89 if ((void *)srh + sizeof(*srh) > data_end)
98 static __always_inline
99 int update_tlv_pad(struct __sk_buff *skb, uint32_t new_pad,
100 uint32_t old_pad, uint32_t pad_off)
104 if (new_pad != old_pad) {
105 err = bpf_lwt_seg6_adjust_srh(skb, pad_off,
106 (int) new_pad - (int) old_pad);
112 char pad_tlv_buf[16] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
114 struct sr6_tlv_t *pad_tlv = (struct sr6_tlv_t *) pad_tlv_buf;
116 pad_tlv->type = SR6_TLV_PADDING;
117 pad_tlv->len = new_pad - 2;
119 err = bpf_lwt_seg6_store_bytes(skb, pad_off,
120 (void *)pad_tlv_buf, new_pad);
128 static __always_inline
129 int is_valid_tlv_boundary(struct __sk_buff *skb, struct ip6_srh_t *srh,
130 uint32_t *tlv_off, uint32_t *pad_size,
133 uint32_t srh_off, cur_off;
134 int offset_valid = 0;
137 srh_off = (char *)srh - (char *)(long)skb->data;
138 // cur_off = end of segments, start of possible TLVs
139 cur_off = srh_off + sizeof(*srh) +
140 sizeof(struct ip6_addr_t) * (srh->first_segment + 1);
144 // we can only go as far as ~10 TLVs due to the BPF max stack size
145 #pragma clang loop unroll(full)
146 for (int i = 0; i < 10; i++) {
147 struct sr6_tlv_t tlv;
149 if (cur_off == *tlv_off)
152 if (cur_off >= srh_off + ((srh->hdrlen + 1) << 3))
155 err = bpf_skb_load_bytes(skb, cur_off, &tlv, sizeof(tlv));
159 if (tlv.type == SR6_TLV_PADDING) {
160 *pad_size = tlv.len + sizeof(tlv);
163 if (*tlv_off == srh_off) {
169 } else if (tlv.type == SR6_TLV_HMAC) {
173 cur_off += sizeof(tlv) + tlv.len;
174 } // we reached the padding or HMAC TLVs, or the end of the SRH
181 else if (!offset_valid)
187 static __always_inline
188 int add_tlv(struct __sk_buff *skb, struct ip6_srh_t *srh, uint32_t tlv_off,
189 struct sr6_tlv_t *itlv, uint8_t tlv_size)
191 uint32_t srh_off = (char *)srh - (char *)(long)skb->data;
192 uint8_t len_remaining, new_pad;
193 uint32_t pad_off = 0;
194 uint32_t pad_size = 0;
195 uint32_t partial_srh_len;
201 if (itlv->type == SR6_TLV_PADDING || itlv->type == SR6_TLV_HMAC)
204 err = is_valid_tlv_boundary(skb, srh, &tlv_off, &pad_size, &pad_off);
208 err = bpf_lwt_seg6_adjust_srh(skb, tlv_off, sizeof(*itlv) + itlv->len);
212 err = bpf_lwt_seg6_store_bytes(skb, tlv_off, (void *)itlv, tlv_size);
216 // the following can't be moved inside update_tlv_pad because the
217 // bpf verifier has some issues with it
218 pad_off += sizeof(*itlv) + itlv->len;
219 partial_srh_len = pad_off - srh_off;
220 len_remaining = partial_srh_len % 8;
221 new_pad = 8 - len_remaining;
223 if (new_pad == 1) // cannot pad for 1 byte only
225 else if (new_pad == 8)
228 return update_tlv_pad(skb, new_pad, pad_size, pad_off);
231 static __always_inline
232 int delete_tlv(struct __sk_buff *skb, struct ip6_srh_t *srh,
235 uint32_t srh_off = (char *)srh - (char *)(long)skb->data;
236 uint8_t len_remaining, new_pad;
237 uint32_t partial_srh_len;
238 uint32_t pad_off = 0;
239 uint32_t pad_size = 0;
240 struct sr6_tlv_t tlv;
245 err = is_valid_tlv_boundary(skb, srh, &tlv_off, &pad_size, &pad_off);
249 err = bpf_skb_load_bytes(skb, tlv_off, &tlv, sizeof(tlv));
253 err = bpf_lwt_seg6_adjust_srh(skb, tlv_off, -(sizeof(tlv) + tlv.len));
257 pad_off -= sizeof(tlv) + tlv.len;
258 partial_srh_len = pad_off - srh_off;
259 len_remaining = partial_srh_len % 8;
260 new_pad = 8 - len_remaining;
261 if (new_pad == 1) // cannot pad for 1 byte only
263 else if (new_pad == 8)
266 return update_tlv_pad(skb, new_pad, pad_size, pad_off);
269 static __always_inline
270 int has_egr_tlv(struct __sk_buff *skb, struct ip6_srh_t *srh)
272 int tlv_offset = sizeof(struct ip6_t) + sizeof(struct ip6_srh_t) +
273 ((srh->first_segment + 1) << 4);
274 struct sr6_tlv_t tlv;
276 if (bpf_skb_load_bytes(skb, tlv_offset, &tlv, sizeof(struct sr6_tlv_t)))
279 if (tlv.type == SR6_TLV_EGRESS && tlv.len == 18) {
280 struct ip6_addr_t egr_addr;
282 if (bpf_skb_load_bytes(skb, tlv_offset + 4, &egr_addr, 16))
285 // check if egress TLV value is correct
286 if (ntohll(egr_addr.hi) == 0xfd00000000000000 &&
287 ntohll(egr_addr.lo) == 0x4)
294 // This function will push a SRH with segments fd00::1, fd00::2, fd00::3,
297 int __encap_srh(struct __sk_buff *skb)
299 unsigned long long hi = 0xfd00000000000000;
300 struct ip6_addr_t *seg;
301 struct ip6_srh_t *srh;
302 char srh_buf[72]; // room for 4 segments
305 srh = (struct ip6_srh_t *)srh_buf;
309 srh->segments_left = 3;
310 srh->first_segment = 3;
314 seg = (struct ip6_addr_t *)((char *)srh + sizeof(*srh));
316 #pragma clang loop unroll(full)
317 for (unsigned long long lo = 0; lo < 4; lo++) {
318 seg->lo = htonll(4 - lo);
319 seg->hi = htonll(hi);
320 seg = (struct ip6_addr_t *)((char *)seg + sizeof(*seg));
323 err = bpf_lwt_push_encap(skb, 0, (void *)srh, sizeof(srh_buf));
330 // Add an Egress TLV fc00::4, add the flag A,
331 // and apply End.X action to fc42::1
333 int __add_egr_x(struct __sk_buff *skb)
335 unsigned long long hi = 0xfc42000000000000;
336 unsigned long long lo = 0x1;
337 struct ip6_srh_t *srh = get_srh(skb);
338 uint8_t new_flags = SR6_FLAG_ALERT;
339 struct ip6_addr_t addr;
345 uint8_t tlv[20] = {2, 18, 0, 0, 0xfd, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
346 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x4};
348 err = add_tlv(skb, srh, (srh->hdrlen+1) << 3,
349 (struct sr6_tlv_t *)&tlv, 20);
353 offset = sizeof(struct ip6_t) + offsetof(struct ip6_srh_t, flags);
354 err = bpf_lwt_seg6_store_bytes(skb, offset,
355 (void *)&new_flags, sizeof(new_flags));
359 addr.lo = htonll(lo);
360 addr.hi = htonll(hi);
361 err = bpf_lwt_seg6_action(skb, SEG6_LOCAL_ACTION_END_X,
362 (void *)&addr, sizeof(addr));
368 // Pop the Egress TLV, reset the flags, change the tag 2442 and finally do a
371 int __pop_egr(struct __sk_buff *skb)
373 struct ip6_srh_t *srh = get_srh(skb);
374 uint16_t new_tag = bpf_htons(2442);
375 uint8_t new_flags = 0;
381 if (srh->flags != SR6_FLAG_ALERT)
384 if (srh->hdrlen != 11) // 4 segments + Egress TLV + Padding TLV
387 if (!has_egr_tlv(skb, srh))
390 err = delete_tlv(skb, srh, 8 + (srh->first_segment + 1) * 16);
394 offset = sizeof(struct ip6_t) + offsetof(struct ip6_srh_t, flags);
395 if (bpf_lwt_seg6_store_bytes(skb, offset, (void *)&new_flags,
399 offset = sizeof(struct ip6_t) + offsetof(struct ip6_srh_t, tag);
400 if (bpf_lwt_seg6_store_bytes(skb, offset, (void *)&new_tag,
407 // Inspect if the Egress TLV and flag have been removed, if the tag is correct,
408 // then apply a End.T action to reach the last segment
410 int __inspect_t(struct __sk_buff *skb)
412 struct ip6_srh_t *srh = get_srh(skb);
422 if (srh->tag != bpf_htons(2442))
425 if (srh->hdrlen != 8) // 4 segments
428 err = bpf_lwt_seg6_action(skb, SEG6_LOCAL_ACTION_END_T,
429 (void *)&table, sizeof(table));
437 char __license[] SEC("license") = "GPL";