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Linux/include/net/inet_ecn.h

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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 
  8 #include <net/inet_sock.h>
  9 #include <net/dsfield.h>
 10 
 11 enum {
 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 
 19 extern int sysctl_tunnel_ecn_log;
 20 
 21 static inline int INET_ECN_is_ce(__u8 dsfield)
 22 {
 23         return (dsfield & INET_ECN_MASK) == INET_ECN_CE;
 24 }
 25 
 26 static inline int INET_ECN_is_not_ect(__u8 dsfield)
 27 {
 28         return (dsfield & INET_ECN_MASK) == INET_ECN_NOT_ECT;
 29 }
 30 
 31 static 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  */
 44 static 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 
 52 static 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 
 59 static 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 
 75 static 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 
102 static inline void IP_ECN_clear(struct iphdr *iph)
103 {
104         iph->tos &= ~INET_ECN_MASK;
105 }
106 
107 static 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 
113 struct 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  */
121 static 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 
137 static 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 
143 static 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  */
186 static 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 
204 static 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 
217 static 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 
232 static 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 

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