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
8#include <net/inet_sock.h>
9#include <net/dsfield.h>
10
11enum {
12 INET_ECN_NOT_ECT = 0,
13 INET_ECN_ECT_1 = 1,
14 INET_ECN_ECT_0 = 2,
15 INET_ECN_CE = 3,
16 INET_ECN_MASK = 3,
17};
18
19extern int sysctl_tunnel_ecn_log;
20
21static inline int INET_ECN_is_ce(__u8 dsfield)
22{
23 return (dsfield & INET_ECN_MASK) == INET_ECN_CE;
24}
25
26static inline int INET_ECN_is_not_ect(__u8 dsfield)
27{
28 return (dsfield & INET_ECN_MASK) == INET_ECN_NOT_ECT;
29}
30
31static inline int INET_ECN_is_capable(__u8 dsfield)
32{
33 return dsfield & INET_ECN_ECT_0;
34}
35
36/*
37 * RFC 3168 9.1.1
38 * The full-functionality option for ECN encapsulation is to copy the
39 * ECN codepoint of the inside header to the outside header on
40 * encapsulation if the inside header is not-ECT or ECT, and to set the
41 * ECN codepoint of the outside header to ECT(0) if the ECN codepoint of
42 * the inside header is CE.
43 */
44static inline __u8 INET_ECN_encapsulate(__u8 outer, __u8 inner)
45{
46 outer &= ~INET_ECN_MASK;
47 outer |= !INET_ECN_is_ce(inner) ? (inner & INET_ECN_MASK) :
48 INET_ECN_ECT_0;
49 return outer;
50}
51
52static inline void INET_ECN_xmit(struct sock *sk)
53{
54 inet_sk(sk)->tos |= INET_ECN_ECT_0;
55 if (inet6_sk(sk) != NULL)
56 inet6_sk(sk)->tclass |= INET_ECN_ECT_0;
57}
58
59static inline void INET_ECN_dontxmit(struct sock *sk)
60{
61 inet_sk(sk)->tos &= ~INET_ECN_MASK;
62 if (inet6_sk(sk) != NULL)
63 inet6_sk(sk)->tclass &= ~INET_ECN_MASK;
64}
65
66#define IP6_ECN_flow_init(label) do { \
67 (label) &= ~htonl(INET_ECN_MASK << 20); \
68 } while (0)
69
70#define IP6_ECN_flow_xmit(sk, label) do { \
71 if (INET_ECN_is_capable(inet6_sk(sk)->tclass)) \
72 (label) |= htonl(INET_ECN_ECT_0 << 20); \
73 } while (0)
74
75static inline int IP_ECN_set_ce(struct iphdr *iph)
76{
77 u32 check = (__force u32)iph->check;
78 u32 ecn = (iph->tos + 1) & INET_ECN_MASK;
79
80 /*
81 * After the last operation we have (in binary):
82 * INET_ECN_NOT_ECT => 01
83 * INET_ECN_ECT_1 => 10
84 * INET_ECN_ECT_0 => 11
85 * INET_ECN_CE => 00
86 */
87 if (!(ecn & 2))
88 return !ecn;
89
90 /*
91 * The following gives us:
92 * INET_ECN_ECT_1 => check += htons(0xFFFD)
93 * INET_ECN_ECT_0 => check += htons(0xFFFE)
94 */
95 check += (__force u16)htons(0xFFFB) + (__force u16)htons(ecn);
96
97 iph->check = (__force __sum16)(check + (check>=0xFFFF));
98 iph->tos |= INET_ECN_CE;
99 return 1;
100}
101
102static inline void IP_ECN_clear(struct iphdr *iph)
103{
104 iph->tos &= ~INET_ECN_MASK;
105}
106
107static inline void ipv4_copy_dscp(unsigned int dscp, struct iphdr *inner)
108{
109 dscp &= ~INET_ECN_MASK;
110 ipv4_change_dsfield(inner, INET_ECN_MASK, dscp);
111}
112
113struct ipv6hdr;
114
115/* Note:
116 * IP_ECN_set_ce() has to tweak IPV4 checksum when setting CE,
117 * meaning both changes have no effect on skb->csum if/when CHECKSUM_COMPLETE
118 * In IPv6 case, no checksum compensates the change in IPv6 header,
119 * so we have to update skb->csum.
120 */
121static inline int IP6_ECN_set_ce(struct sk_buff *skb, struct ipv6hdr *iph)
122{
123 __be32 from, to;
124
125 if (INET_ECN_is_not_ect(ipv6_get_dsfield(iph)))
126 return 0;
127
128 from = *(__be32 *)iph;
129 to = from | htonl(INET_ECN_CE << 20);
130 *(__be32 *)iph = to;
131 if (skb->ip_summed == CHECKSUM_COMPLETE)
132 skb->csum = csum_add(csum_sub(skb->csum, (__force __wsum)from),
133 (__force __wsum)to);
134 return 1;
135}
136
137static inline void ipv6_copy_dscp(unsigned int dscp, struct ipv6hdr *inner)
138{
139 dscp &= ~INET_ECN_MASK;
140 ipv6_change_dsfield(inner, INET_ECN_MASK, dscp);
141}
142
143static inline int INET_ECN_set_ce(struct sk_buff *skb)
144{
145 switch (skb->protocol) {
146 case cpu_to_be16(ETH_P_IP):
147 if (skb_network_header(skb) + sizeof(struct iphdr) <=
148 skb_tail_pointer(skb))
149 return IP_ECN_set_ce(ip_hdr(skb));
150 break;
151
152 case cpu_to_be16(ETH_P_IPV6):
153 if (skb_network_header(skb) + sizeof(struct ipv6hdr) <=
154 skb_tail_pointer(skb))
155 return IP6_ECN_set_ce(skb, ipv6_hdr(skb));
156 break;
157 }
158
159 return 0;
160}
161
162/*
163 * RFC 6040 4.2
164 * To decapsulate the inner header at the tunnel egress, a compliant
165 * tunnel egress MUST set the outgoing ECN field to the codepoint at the
166 * intersection of the appropriate arriving inner header (row) and outer
167 * header (column) in Figure 4
168 *
169 * +---------+------------------------------------------------+
170 * |Arriving | Arriving Outer Header |
171 * | Inner +---------+------------+------------+------------+
172 * | Header | Not-ECT | ECT(0) | ECT(1) | CE |
173 * +---------+---------+------------+------------+------------+
174 * | Not-ECT | Not-ECT |Not-ECT(!!!)|Not-ECT(!!!)| <drop>(!!!)|
175 * | ECT(0) | ECT(0) | ECT(0) | ECT(1) | CE |
176 * | ECT(1) | ECT(1) | ECT(1) (!) | ECT(1) | CE |
177 * | CE | CE | CE | CE(!!!)| CE |
178 * +---------+---------+------------+------------+------------+
179 *
180 * Figure 4: New IP in IP Decapsulation Behaviour
181 *
182 * returns 0 on success
183 * 1 if something is broken and should be logged (!!! above)
184 * 2 if packet should be dropped
185 */
186static inline int __INET_ECN_decapsulate(__u8 outer, __u8 inner, bool *set_ce)
187{
188 if (INET_ECN_is_not_ect(inner)) {
189 switch (outer & INET_ECN_MASK) {
190 case INET_ECN_NOT_ECT:
191 return 0;
192 case INET_ECN_ECT_0:
193 case INET_ECN_ECT_1:
194 return 1;
195 case INET_ECN_CE:
196 return 2;
197 }
198 }
199
200 *set_ce = INET_ECN_is_ce(outer);
201 return 0;
202}
203
204static inline int INET_ECN_decapsulate(struct sk_buff *skb,
205 __u8 outer, __u8 inner)
206{
207 bool set_ce = false;
208 int rc;
209
210 rc = __INET_ECN_decapsulate(outer, inner, &set_ce);
211 if (!rc && set_ce)
212 INET_ECN_set_ce(skb);
213
214 return rc;
215}
216
217static inline int IP_ECN_decapsulate(const struct iphdr *oiph,
218 struct sk_buff *skb)
219{
220 __u8 inner;
221
222 if (skb->protocol == htons(ETH_P_IP))
223 inner = ip_hdr(skb)->tos;
224 else if (skb->protocol == htons(ETH_P_IPV6))
225 inner = ipv6_get_dsfield(ipv6_hdr(skb));
226 else
227 return 0;
228
229 return INET_ECN_decapsulate(skb, oiph->tos, inner);
230}
231
232static inline int IP6_ECN_decapsulate(const struct ipv6hdr *oipv6h,
233 struct sk_buff *skb)
234{
235 __u8 inner;
236
237 if (skb->protocol == htons(ETH_P_IP))
238 inner = ip_hdr(skb)->tos;
239 else if (skb->protocol == htons(ETH_P_IPV6))
240 inner = ipv6_get_dsfield(ipv6_hdr(skb));
241 else
242 return 0;
243
244 return INET_ECN_decapsulate(skb, ipv6_get_dsfield(oipv6h), inner);
245}
246#endif
247