include/net/inet_ecn.h

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