4 #include <linux/seg6_local.h>
6 #include "bpf_helpers.h"
7 #include "bpf_endian.h"
9 /* Packet parsing state machine helpers. */
10 #define cursor_advance(_cursor, _len) \
11 ({ void *_tmp = _cursor; _cursor += _len; _tmp; })
13 #define SR6_FLAG_ALERT (1 << 4)
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))
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;
35 unsigned long long hi;
36 unsigned long long lo;
40 unsigned char nexthdr;
43 unsigned char segments_left;
44 unsigned char first_segment;
48 struct ip6_addr_t segments[0];
54 unsigned char value[0];
57 static __always_inline struct ip6_srh_t *get_srh(struct __sk_buff *skb)
59 void *cursor, *data_end;
60 struct ip6_srh_t *srh;
64 data_end = (void *)(long)skb->data_end;
65 cursor = (void *)(long)skb->data;
66 ipver = (uint8_t *)cursor;
68 if ((void *)ipver + sizeof(*ipver) > data_end)
71 if ((*ipver >> 4) != 6)
74 ip = cursor_advance(cursor, sizeof(*ip));
75 if ((void *)ip + sizeof(*ip) > data_end)
78 if (ip->next_header != 43)
81 srh = cursor_advance(cursor, sizeof(*srh));
82 if ((void *)srh + sizeof(*srh) > data_end)
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)
97 if (new_pad != old_pad) {
98 err = bpf_lwt_seg6_adjust_srh(skb, pad_off,
99 (int) new_pad - (int) old_pad);
105 char pad_tlv_buf[16] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
107 struct sr6_tlv_t *pad_tlv = (struct sr6_tlv_t *) pad_tlv_buf;
109 pad_tlv->type = SR6_TLV_PADDING;
110 pad_tlv->len = new_pad - 2;
112 err = bpf_lwt_seg6_store_bytes(skb, pad_off,
113 (void *)pad_tlv_buf, new_pad);
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,
126 uint32_t srh_off, cur_off;
127 int offset_valid = 0;
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);
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;
142 if (cur_off == *tlv_off)
145 if (cur_off >= srh_off + ((srh->hdrlen + 1) << 3))
148 err = bpf_skb_load_bytes(skb, cur_off, &tlv, sizeof(tlv));
152 if (tlv.type == SR6_TLV_PADDING) {
153 *pad_size = tlv.len + sizeof(tlv);
156 if (*tlv_off == srh_off) {
162 } else if (tlv.type == SR6_TLV_HMAC) {
166 cur_off += sizeof(tlv) + tlv.len;
167 } // we reached the padding or HMAC TLVs, or the end of the SRH
174 else if (!offset_valid)
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)
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;
194 if (itlv->type == SR6_TLV_PADDING || itlv->type == SR6_TLV_HMAC)
197 err = is_valid_tlv_boundary(skb, srh, &tlv_off, &pad_size, &pad_off);
201 err = bpf_lwt_seg6_adjust_srh(skb, tlv_off, sizeof(*itlv) + itlv->len);
205 err = bpf_lwt_seg6_store_bytes(skb, tlv_off, (void *)itlv, tlv_size);
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;
216 if (new_pad == 1) // cannot pad for 1 byte only
218 else if (new_pad == 8)
221 return update_tlv_pad(skb, new_pad, pad_size, pad_off);
224 static __always_inline
225 int delete_tlv(struct __sk_buff *skb, struct ip6_srh_t *srh,
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;
238 err = is_valid_tlv_boundary(skb, srh, &tlv_off, &pad_size, &pad_off);
242 err = bpf_skb_load_bytes(skb, tlv_off, &tlv, sizeof(tlv));
246 err = bpf_lwt_seg6_adjust_srh(skb, tlv_off, -(sizeof(tlv) + tlv.len));
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
256 else if (new_pad == 8)
259 return update_tlv_pad(skb, new_pad, pad_size, pad_off);
262 static __always_inline
263 int has_egr_tlv(struct __sk_buff *skb, struct ip6_srh_t *srh)
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;
269 if (bpf_skb_load_bytes(skb, tlv_offset, &tlv, sizeof(struct sr6_tlv_t)))
272 if (tlv.type == SR6_TLV_EGRESS && tlv.len == 18) {
273 struct ip6_addr_t egr_addr;
275 if (bpf_skb_load_bytes(skb, tlv_offset + 4, &egr_addr, 16))
278 // check if egress TLV value is correct
279 if (ntohll(egr_addr.hi) == 0xfd00000000000000 &&
280 ntohll(egr_addr.lo) == 0x4)
287 // This function will push a SRH with segments fd00::1, fd00::2, fd00::3,
290 int __encap_srh(struct __sk_buff *skb)
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
298 srh = (struct ip6_srh_t *)srh_buf;
302 srh->segments_left = 3;
303 srh->first_segment = 3;
307 seg = (struct ip6_addr_t *)((char *)srh + sizeof(*srh));
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));
316 err = bpf_lwt_push_encap(skb, 0, (void *)srh, sizeof(srh_buf));
323 // Add an Egress TLV fc00::4, add the flag A,
324 // and apply End.X action to fc42::1
326 int __add_egr_x(struct __sk_buff *skb)
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;
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};
341 err = add_tlv(skb, srh, (srh->hdrlen+1) << 3,
342 (struct sr6_tlv_t *)&tlv, 20);
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));
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));
361 // Pop the Egress TLV, reset the flags, change the tag 2442 and finally do a
364 int __pop_egr(struct __sk_buff *skb)
366 struct ip6_srh_t *srh = get_srh(skb);
367 uint16_t new_tag = bpf_htons(2442);
368 uint8_t new_flags = 0;
374 if (srh->flags != SR6_FLAG_ALERT)
377 if (srh->hdrlen != 11) // 4 segments + Egress TLV + Padding TLV
380 if (!has_egr_tlv(skb, srh))
383 err = delete_tlv(skb, srh, 8 + (srh->first_segment + 1) * 16);
387 offset = sizeof(struct ip6_t) + offsetof(struct ip6_srh_t, flags);
388 if (bpf_lwt_seg6_store_bytes(skb, offset, (void *)&new_flags,
392 offset = sizeof(struct ip6_t) + offsetof(struct ip6_srh_t, tag);
393 if (bpf_lwt_seg6_store_bytes(skb, offset, (void *)&new_tag,
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
403 int __inspect_t(struct __sk_buff *skb)
405 struct ip6_srh_t *srh = get_srh(skb);
415 if (srh->tag != bpf_htons(2442))
418 if (srh->hdrlen != 8) // 4 segments
421 err = bpf_lwt_seg6_action(skb, SEG6_LOCAL_ACTION_END_T,
422 (void *)&table, sizeof(table));
430 char __license[] SEC("license") = "GPL";