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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _INET_ECN_H_
3#define _INET_ECN_H_
4
5#include <linux/ip.h>
6#include <linux/skbuff.h>
7#include <linux/if_vlan.h>
8
9#include <net/inet_sock.h>
10#include <net/dsfield.h>
11#include <net/checksum.h>
12
13enum {
14 INET_ECN_NOT_ECT = 0,
15 INET_ECN_ECT_1 = 1,
16 INET_ECN_ECT_0 = 2,
17 INET_ECN_CE = 3,
18 INET_ECN_MASK = 3,
19};
20
21extern int sysctl_tunnel_ecn_log;
22
23static inline int INET_ECN_is_ce(__u8 dsfield)
24{
25 return (dsfield & INET_ECN_MASK) == INET_ECN_CE;
26}
27
28static inline int INET_ECN_is_not_ect(__u8 dsfield)
29{
30 return (dsfield & INET_ECN_MASK) == INET_ECN_NOT_ECT;
31}
32
33static inline int INET_ECN_is_capable(__u8 dsfield)
34{
35 return dsfield & INET_ECN_ECT_0;
36}
37
38/*
39 * RFC 3168 9.1.1
40 * The full-functionality option for ECN encapsulation is to copy the
41 * ECN codepoint of the inside header to the outside header on
42 * encapsulation if the inside header is not-ECT or ECT, and to set the
43 * ECN codepoint of the outside header to ECT(0) if the ECN codepoint of
44 * the inside header is CE.
45 */
46static inline __u8 INET_ECN_encapsulate(__u8 outer, __u8 inner)
47{
48 outer &= ~INET_ECN_MASK;
49 outer |= !INET_ECN_is_ce(inner) ? (inner & INET_ECN_MASK) :
50 INET_ECN_ECT_0;
51 return outer;
52}
53
54/* Apply either ECT(0) or ECT(1) */
55static inline void __INET_ECN_xmit(struct sock *sk, bool use_ect_1)
56{
57 __u8 ect = use_ect_1 ? INET_ECN_ECT_1 : INET_ECN_ECT_0;
58
59 /* Mask the complete byte in case the connection alternates between
60 * ECT(0) and ECT(1).
61 */
62 inet_sk(sk)->tos &= ~INET_ECN_MASK;
63 inet_sk(sk)->tos |= ect;
64 if (inet6_sk(sk)) {
65 inet6_sk(sk)->tclass &= ~INET_ECN_MASK;
66 inet6_sk(sk)->tclass |= ect;
67 }
68}
69
70static inline void INET_ECN_xmit(struct sock *sk)
71{
72 __INET_ECN_xmit(sk, false);
73}
74
75static inline void INET_ECN_dontxmit(struct sock *sk)
76{
77 inet_sk(sk)->tos &= ~INET_ECN_MASK;
78 if (inet6_sk(sk) != NULL)
79 inet6_sk(sk)->tclass &= ~INET_ECN_MASK;
80}
81
82#define IP6_ECN_flow_init(label) do { \
83 (label) &= ~htonl(INET_ECN_MASK << 20); \
84 } while (0)
85
86#define IP6_ECN_flow_xmit(sk, label) do { \
87 if (INET_ECN_is_capable(inet6_sk(sk)->tclass)) \
88 (label) |= htonl(INET_ECN_ECT_0 << 20); \
89 } while (0)
90
91static inline int IP_ECN_set_ce(struct iphdr *iph)
92{
93 u32 ecn = (iph->tos + 1) & INET_ECN_MASK;
94 __be16 check_add;
95
96 /*
97 * After the last operation we have (in binary):
98 * INET_ECN_NOT_ECT => 01
99 * INET_ECN_ECT_1 => 10
100 * INET_ECN_ECT_0 => 11
101 * INET_ECN_CE => 00
102 */
103 if (!(ecn & 2))
104 return !ecn;
105
106 /*
107 * The following gives us:
108 * INET_ECN_ECT_1 => check += htons(0xFFFD)
109 * INET_ECN_ECT_0 => check += htons(0xFFFE)
110 */
111 check_add = (__force __be16)((__force u16)htons(0xFFFB) +
112 (__force u16)htons(ecn));
113
114 iph->check = csum16_add(iph->check, check_add);
115 iph->tos |= INET_ECN_CE;
116 return 1;
117}
118
119static inline int IP_ECN_set_ect1(struct iphdr *iph)
120{
121 if ((iph->tos & INET_ECN_MASK) != INET_ECN_ECT_0)
122 return 0;
123
124 iph->check = csum16_add(iph->check, htons(0x1));
125 iph->tos ^= INET_ECN_MASK;
126 return 1;
127}
128
129static inline void IP_ECN_clear(struct iphdr *iph)
130{
131 iph->tos &= ~INET_ECN_MASK;
132}
133
134static inline void ipv4_copy_dscp(unsigned int dscp, struct iphdr *inner)
135{
136 dscp &= ~INET_ECN_MASK;
137 ipv4_change_dsfield(inner, INET_ECN_MASK, dscp);
138}
139
140struct ipv6hdr;
141
142/* Note:
143 * IP_ECN_set_ce() has to tweak IPV4 checksum when setting CE,
144 * meaning both changes have no effect on skb->csum if/when CHECKSUM_COMPLETE
145 * In IPv6 case, no checksum compensates the change in IPv6 header,
146 * so we have to update skb->csum.
147 */
148static inline int IP6_ECN_set_ce(struct sk_buff *skb, struct ipv6hdr *iph)
149{
150 __be32 from, to;
151
152 if (INET_ECN_is_not_ect(ipv6_get_dsfield(iph)))
153 return 0;
154
155 from = *(__be32 *)iph;
156 to = from | htonl(INET_ECN_CE << 20);
157 *(__be32 *)iph = to;
158 if (skb->ip_summed == CHECKSUM_COMPLETE)
159 skb->csum = csum_add(csum_sub(skb->csum, (__force __wsum)from),
160 (__force __wsum)to);
161 return 1;
162}
163
164static inline int IP6_ECN_set_ect1(struct sk_buff *skb, struct ipv6hdr *iph)
165{
166 __be32 from, to;
167
168 if ((ipv6_get_dsfield(iph) & INET_ECN_MASK) != INET_ECN_ECT_0)
169 return 0;
170
171 from = *(__be32 *)iph;
172 to = from ^ htonl(INET_ECN_MASK << 20);
173 *(__be32 *)iph = to;
174 if (skb->ip_summed == CHECKSUM_COMPLETE)
175 skb->csum = csum_add(csum_sub(skb->csum, (__force __wsum)from),
176 (__force __wsum)to);
177 return 1;
178}
179
180static inline void ipv6_copy_dscp(unsigned int dscp, struct ipv6hdr *inner)
181{
182 dscp &= ~INET_ECN_MASK;
183 ipv6_change_dsfield(inner, INET_ECN_MASK, dscp);
184}
185
186static inline int INET_ECN_set_ce(struct sk_buff *skb)
187{
188 switch (skb_protocol(skb, true)) {
189 case cpu_to_be16(ETH_P_IP):
190 if (skb_network_header(skb) + sizeof(struct iphdr) <=
191 skb_tail_pointer(skb))
192 return IP_ECN_set_ce(ip_hdr(skb));
193 break;
194
195 case cpu_to_be16(ETH_P_IPV6):
196 if (skb_network_header(skb) + sizeof(struct ipv6hdr) <=
197 skb_tail_pointer(skb))
198 return IP6_ECN_set_ce(skb, ipv6_hdr(skb));
199 break;
200 }
201
202 return 0;
203}
204
205static inline int skb_get_dsfield(struct sk_buff *skb)
206{
207 switch (skb_protocol(skb, true)) {
208 case cpu_to_be16(ETH_P_IP):
209 if (!pskb_network_may_pull(skb, sizeof(struct iphdr)))
210 break;
211 return ipv4_get_dsfield(ip_hdr(skb));
212
213 case cpu_to_be16(ETH_P_IPV6):
214 if (!pskb_network_may_pull(skb, sizeof(struct ipv6hdr)))
215 break;
216 return ipv6_get_dsfield(ipv6_hdr(skb));
217 }
218
219 return -1;
220}
221
222static inline int INET_ECN_set_ect1(struct sk_buff *skb)
223{
224 switch (skb_protocol(skb, true)) {
225 case cpu_to_be16(ETH_P_IP):
226 if (skb_network_header(skb) + sizeof(struct iphdr) <=
227 skb_tail_pointer(skb))
228 return IP_ECN_set_ect1(ip_hdr(skb));
229 break;
230
231 case cpu_to_be16(ETH_P_IPV6):
232 if (skb_network_header(skb) + sizeof(struct ipv6hdr) <=
233 skb_tail_pointer(skb))
234 return IP6_ECN_set_ect1(skb, ipv6_hdr(skb));
235 break;
236 }
237
238 return 0;
239}
240
241/*
242 * RFC 6040 4.2
243 * To decapsulate the inner header at the tunnel egress, a compliant
244 * tunnel egress MUST set the outgoing ECN field to the codepoint at the
245 * intersection of the appropriate arriving inner header (row) and outer
246 * header (column) in Figure 4
247 *
248 * +---------+------------------------------------------------+
249 * |Arriving | Arriving Outer Header |
250 * | Inner +---------+------------+------------+------------+
251 * | Header | Not-ECT | ECT(0) | ECT(1) | CE |
252 * +---------+---------+------------+------------+------------+
253 * | Not-ECT | Not-ECT |Not-ECT(!!!)|Not-ECT(!!!)| <drop>(!!!)|
254 * | ECT(0) | ECT(0) | ECT(0) | ECT(1) | CE |
255 * | ECT(1) | ECT(1) | ECT(1) (!) | ECT(1) | CE |
256 * | CE | CE | CE | CE(!!!)| CE |
257 * +---------+---------+------------+------------+------------+
258 *
259 * Figure 4: New IP in IP Decapsulation Behaviour
260 *
261 * returns 0 on success
262 * 1 if something is broken and should be logged (!!! above)
263 * 2 if packet should be dropped
264 */
265static inline int __INET_ECN_decapsulate(__u8 outer, __u8 inner, bool *set_ce)
266{
267 if (INET_ECN_is_not_ect(inner)) {
268 switch (outer & INET_ECN_MASK) {
269 case INET_ECN_NOT_ECT:
270 return 0;
271 case INET_ECN_ECT_0:
272 case INET_ECN_ECT_1:
273 return 1;
274 case INET_ECN_CE:
275 return 2;
276 }
277 }
278
279 *set_ce = INET_ECN_is_ce(outer);
280 return 0;
281}
282
283static inline int INET_ECN_decapsulate(struct sk_buff *skb,
284 __u8 outer, __u8 inner)
285{
286 bool set_ce = false;
287 int rc;
288
289 rc = __INET_ECN_decapsulate(outer, inner, &set_ce);
290 if (!rc) {
291 if (set_ce)
292 INET_ECN_set_ce(skb);
293 else if ((outer & INET_ECN_MASK) == INET_ECN_ECT_1)
294 INET_ECN_set_ect1(skb);
295 }
296
297 return rc;
298}
299
300static inline int IP_ECN_decapsulate(const struct iphdr *oiph,
301 struct sk_buff *skb)
302{
303 __u8 inner;
304
305 switch (skb_protocol(skb, true)) {
306 case htons(ETH_P_IP):
307 inner = ip_hdr(skb)->tos;
308 break;
309 case htons(ETH_P_IPV6):
310 inner = ipv6_get_dsfield(ipv6_hdr(skb));
311 break;
312 default:
313 return 0;
314 }
315
316 return INET_ECN_decapsulate(skb, oiph->tos, inner);
317}
318
319static inline int IP6_ECN_decapsulate(const struct ipv6hdr *oipv6h,
320 struct sk_buff *skb)
321{
322 __u8 inner;
323
324 switch (skb_protocol(skb, true)) {
325 case htons(ETH_P_IP):
326 inner = ip_hdr(skb)->tos;
327 break;
328 case htons(ETH_P_IPV6):
329 inner = ipv6_get_dsfield(ipv6_hdr(skb));
330 break;
331 default:
332 return 0;
333 }
334
335 return INET_ECN_decapsulate(skb, ipv6_get_dsfield(oipv6h), inner);
336}
337#endif