include/net/inet_ecn.h

   1 #ifndef _INET_ECN_H_
   2 #define _INET_ECN_H_
   3
   4 #include <linux/ip.h>
   5 #include <linux/skbuff.h>
   6
   7 #include <net/inet_sock.h>
   8 #include <net/dsfield.h>
   9
  10 enum {
  11         INET_ECN_NOT_ECT = 0,
  12         INET_ECN_ECT_1 = 1,
  13         INET_ECN_ECT_0 = 2,
  14         INET_ECN_CE = 3,
  15         INET_ECN_MASK = 3,
  16 };
  17
  18 extern int sysctl_tunnel_ecn_log;
  19
  20 static inline int INET_ECN_is_ce(__u8 dsfield)
  21 {
  22         return (dsfield & INET_ECN_MASK) == INET_ECN_CE;
  23 }
  24
  25 static inline int INET_ECN_is_not_ect(__u8 dsfield)
  26 {
  27         return (dsfield & INET_ECN_MASK) == INET_ECN_NOT_ECT;
  28 }
  29
  30 static inline int INET_ECN_is_capable(__u8 dsfield)
  31 {
  32         return dsfield & INET_ECN_ECT_0;
  33 }
  34
  35 /*
  36  * RFC 3168 9.1.1
  37  *  The full-functionality option for ECN encapsulation is to copy the
  38  *  ECN codepoint of the inside header to the outside header on
  39  *  encapsulation if the inside header is not-ECT or ECT, and to set the
  40  *  ECN codepoint of the outside header to ECT(0) if the ECN codepoint of
  41  *  the inside header is CE.
  42  */
  43 static inline __u8 INET_ECN_encapsulate(__u8 outer, __u8 inner)
  44 {
  45         outer &= ~INET_ECN_MASK;
  46         outer |= !INET_ECN_is_ce(inner) ? (inner & INET_ECN_MASK) :
  47                                           INET_ECN_ECT_0;
  48         return outer;
  49 }
  50
  51 static inline void INET_ECN_xmit(struct sock *sk)
  52 {
  53         inet_sk(sk)->tos |= INET_ECN_ECT_0;
  54         if (inet6_sk(sk) != NULL)
  55                 inet6_sk(sk)->tclass |= INET_ECN_ECT_0;
  56 }
  57
  58 static inline void INET_ECN_dontxmit(struct sock *sk)
  59 {
  60         inet_sk(sk)->tos &= ~INET_ECN_MASK;
  61         if (inet6_sk(sk) != NULL)
  62                 inet6_sk(sk)->tclass &= ~INET_ECN_MASK;
  63 }
  64
  65 #define IP6_ECN_flow_init(label) do {           \
  66       (label) &= ~htonl(INET_ECN_MASK << 20);   \
  67     } while (0)
  68
  69 #define IP6_ECN_flow_xmit(sk, label) do {                               \
  70         if (INET_ECN_is_capable(inet6_sk(sk)->tclass))                  \
  71                 (label) |= htonl(INET_ECN_ECT_0 << 20);                 \
  72     } while (0)
  73
  74 static inline int IP_ECN_set_ce(struct iphdr *iph)
  75 {
  76         u32 check = (__force u32)iph->check;
  77         u32 ecn = (iph->tos + 1) & INET_ECN_MASK;
  78
  79         /*
  80          * After the last operation we have (in binary):
  81          * INET_ECN_NOT_ECT => 01
  82          * INET_ECN_ECT_1   => 10
  83          * INET_ECN_ECT_0   => 11
  84          * INET_ECN_CE      => 00
  85          */
  86         if (!(ecn & 2))
  87                 return !ecn;
  88
  89         /*
  90          * The following gives us:
  91          * INET_ECN_ECT_1 => check += htons(0xFFFD)
  92          * INET_ECN_ECT_0 => check += htons(0xFFFE)
  93          */
  94         check += (__force u16)htons(0xFFFB) + (__force u16)htons(ecn);
  95
  96         iph->check = (__force __sum16)(check + (check>=0xFFFF));
  97         iph->tos |= INET_ECN_CE;
  98         return 1;
  99 }
 100
 101 static inline void IP_ECN_clear(struct iphdr *iph)
 102 {
 103         iph->tos &= ~INET_ECN_MASK;
 104 }
 105
 106 static inline void ipv4_copy_dscp(unsigned int dscp, struct iphdr *inner)
 107 {
 108         dscp &= ~INET_ECN_MASK;
 109         ipv4_change_dsfield(inner, INET_ECN_MASK, dscp);
 110 }
 111
 112 struct ipv6hdr;
 113
 114 /* Note:
 115  * IP_ECN_set_ce() has to tweak IPV4 checksum when setting CE,
 116  * meaning both changes have no effect on skb->csum if/when CHECKSUM_COMPLETE
 117  * In IPv6 case, no checksum compensates the change in IPv6 header,
 118  * so we have to update skb->csum.
 119  */
 120 static inline int IP6_ECN_set_ce(struct sk_buff *skb, struct ipv6hdr *iph)
 121 {
 122         __be32 from, to;
 123
 124         if (INET_ECN_is_not_ect(ipv6_get_dsfield(iph)))
 125                 return 0;
 126
 127         from = *(__be32 *)iph;
 128         to = from | htonl(INET_ECN_CE << 20);
 129         *(__be32 *)iph = to;
 130         if (skb->ip_summed == CHECKSUM_COMPLETE)
 131                 skb->csum = csum_add(csum_sub(skb->csum, (__force __wsum)from),
 132                                      (__force __wsum)to);
 133         return 1;
 134 }
 135
 136 static inline void ipv6_copy_dscp(unsigned int dscp, struct ipv6hdr *inner)
 137 {
 138         dscp &= ~INET_ECN_MASK;
 139         ipv6_change_dsfield(inner, INET_ECN_MASK, dscp);
 140 }
 141
 142 static inline int INET_ECN_set_ce(struct sk_buff *skb)
 143 {
 144         switch (skb->protocol) {
 145         case cpu_to_be16(ETH_P_IP):
 146                 if (skb_network_header(skb) + sizeof(struct iphdr) <=
 147                     skb_tail_pointer(skb))
 148                         return IP_ECN_set_ce(ip_hdr(skb));
 149                 break;
 150
 151         case cpu_to_be16(ETH_P_IPV6):
 152                 if (skb_network_header(skb) + sizeof(struct ipv6hdr) <=
 153                     skb_tail_pointer(skb))
 154                         return IP6_ECN_set_ce(skb, ipv6_hdr(skb));
 155                 break;
 156         }
 157
 158         return 0;
 159 }
 160
 161 /*
 162  * RFC 6040 4.2
 163  *  To decapsulate the inner header at the tunnel egress, a compliant
 164  *  tunnel egress MUST set the outgoing ECN field to the codepoint at the
 165  *  intersection of the appropriate arriving inner header (row) and outer
 166  *  header (column) in Figure 4
 167  *
 168  *      +---------+------------------------------------------------+
 169  *      |Arriving |            Arriving Outer Header               |
 170  *      |   Inner +---------+------------+------------+------------+
 171  *      |  Header | Not-ECT | ECT(0)     | ECT(1)     |     CE     |
 172  *      +---------+---------+------------+------------+------------+
 173  *      | Not-ECT | Not-ECT |Not-ECT(!!!)|Not-ECT(!!!)| <drop>(!!!)|
 174  *      |  ECT(0) |  ECT(0) | ECT(0)     | ECT(1)     |     CE     |
 175  *      |  ECT(1) |  ECT(1) | ECT(1) (!) | ECT(1)     |     CE     |
 176  *      |    CE   |      CE |     CE     |     CE(!!!)|     CE     |
 177  *      +---------+---------+------------+------------+------------+
 178  *
 179  *             Figure 4: New IP in IP Decapsulation Behaviour
 180  *
 181  *  returns 0 on success
 182  *          1 if something is broken and should be logged (!!! above)
 183  *          2 if packet should be dropped
 184  */
 185 static inline int INET_ECN_decapsulate(struct sk_buff *skb,
 186                                        __u8 outer, __u8 inner)
 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         if (INET_ECN_is_ce(outer))
 201                 INET_ECN_set_ce(skb);
 202
 203         return 0;
 204 }
 205
 206 static inline int IP_ECN_decapsulate(const struct iphdr *oiph,
 207                                      struct sk_buff *skb)
 208 {
 209         __u8 inner;
 210
 211         if (skb->protocol == htons(ETH_P_IP))
 212                 inner = ip_hdr(skb)->tos;
 213         else if (skb->protocol == htons(ETH_P_IPV6))
 214                 inner = ipv6_get_dsfield(ipv6_hdr(skb));
 215         else
 216                 return 0;
 217
 218         return INET_ECN_decapsulate(skb, oiph->tos, inner);
 219 }
 220
 221 static inline int IP6_ECN_decapsulate(const struct ipv6hdr *oipv6h,
 222                                       struct sk_buff *skb)
 223 {
 224         __u8 inner;
 225
 226         if (skb->protocol == htons(ETH_P_IP))
 227                 inner = ip_hdr(skb)->tos;
 228         else if (skb->protocol == htons(ETH_P_IPV6))
 229                 inner = ipv6_get_dsfield(ipv6_hdr(skb));
 230         else
 231                 return 0;
 232
 233         return INET_ECN_decapsulate(skb, ipv6_get_dsfield(oipv6h), inner);
 234 }
 235 #endif