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
   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(struct sk_buff *skb,
 187                                        __u8 outer, __u8 inner)
 188 {
 189         if (INET_ECN_is_not_ect(inner)) {
 190                 switch (outer & INET_ECN_MASK) {
 191                 case INET_ECN_NOT_ECT:
 192                         return 0;
 193                 case INET_ECN_ECT_0:
 194                 case INET_ECN_ECT_1:
 195                         return 1;
 196                 case INET_ECN_CE:
 197                         return 2;
 198                 }
 199         }
 200
 201         if (INET_ECN_is_ce(outer))
 202                 INET_ECN_set_ce(skb);
 203
 204         return 0;
 205 }
 206
 207 static inline int IP_ECN_decapsulate(const struct iphdr *oiph,
 208                                      struct sk_buff *skb)
 209 {
 210         __u8 inner;
 211
 212         if (skb->protocol == htons(ETH_P_IP))
 213                 inner = ip_hdr(skb)->tos;
 214         else if (skb->protocol == htons(ETH_P_IPV6))
 215                 inner = ipv6_get_dsfield(ipv6_hdr(skb));
 216         else
 217                 return 0;
 218
 219         return INET_ECN_decapsulate(skb, oiph->tos, inner);
 220 }
 221
 222 static inline int IP6_ECN_decapsulate(const struct ipv6hdr *oipv6h,
 223                                       struct sk_buff *skb)
 224 {
 225         __u8 inner;
 226
 227         if (skb->protocol == htons(ETH_P_IP))
 228                 inner = ip_hdr(skb)->tos;
 229         else if (skb->protocol == htons(ETH_P_IPV6))
 230                 inner = ipv6_get_dsfield(ipv6_hdr(skb));
 231         else
 232                 return 0;
 233
 234         return INET_ECN_decapsulate(skb, ipv6_get_dsfield(oipv6h), inner);
 235 }
 236 #endif