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Linux/include/net/inet_ecn.h

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  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 IP6_ECN_clear(struct ipv6hdr *iph)
137 {
138         *(__be32*)iph &= ~htonl(INET_ECN_MASK << 20);
139 }
140 
141 static inline void ipv6_copy_dscp(unsigned int dscp, struct ipv6hdr *inner)
142 {
143         dscp &= ~INET_ECN_MASK;
144         ipv6_change_dsfield(inner, INET_ECN_MASK, dscp);
145 }
146 
147 static inline int INET_ECN_set_ce(struct sk_buff *skb)
148 {
149         switch (skb->protocol) {
150         case cpu_to_be16(ETH_P_IP):
151                 if (skb_network_header(skb) + sizeof(struct iphdr) <=
152                     skb_tail_pointer(skb))
153                         return IP_ECN_set_ce(ip_hdr(skb));
154                 break;
155 
156         case cpu_to_be16(ETH_P_IPV6):
157                 if (skb_network_header(skb) + sizeof(struct ipv6hdr) <=
158                     skb_tail_pointer(skb))
159                         return IP6_ECN_set_ce(skb, ipv6_hdr(skb));
160                 break;
161         }
162 
163         return 0;
164 }
165 
166 /*
167  * RFC 6040 4.2
168  *  To decapsulate the inner header at the tunnel egress, a compliant
169  *  tunnel egress MUST set the outgoing ECN field to the codepoint at the
170  *  intersection of the appropriate arriving inner header (row) and outer
171  *  header (column) in Figure 4
172  *
173  *      +---------+------------------------------------------------+
174  *      |Arriving |            Arriving Outer Header               |
175  *      |   Inner +---------+------------+------------+------------+
176  *      |  Header | Not-ECT | ECT(0)     | ECT(1)     |     CE     |
177  *      +---------+---------+------------+------------+------------+
178  *      | Not-ECT | Not-ECT |Not-ECT(!!!)|Not-ECT(!!!)| <drop>(!!!)|
179  *      |  ECT(0) |  ECT(0) | ECT(0)     | ECT(1)     |     CE     |
180  *      |  ECT(1) |  ECT(1) | ECT(1) (!) | ECT(1)     |     CE     |
181  *      |    CE   |      CE |     CE     |     CE(!!!)|     CE     |
182  *      +---------+---------+------------+------------+------------+
183  *
184  *             Figure 4: New IP in IP Decapsulation Behaviour
185  *
186  *  returns 0 on success
187  *          1 if something is broken and should be logged (!!! above)
188  *          2 if packet should be dropped
189  */
190 static inline int INET_ECN_decapsulate(struct sk_buff *skb,
191                                        __u8 outer, __u8 inner)
192 {
193         if (INET_ECN_is_not_ect(inner)) {
194                 switch (outer & INET_ECN_MASK) {
195                 case INET_ECN_NOT_ECT:
196                         return 0;
197                 case INET_ECN_ECT_0:
198                 case INET_ECN_ECT_1:
199                         return 1;
200                 case INET_ECN_CE:
201                         return 2;
202                 }
203         }
204 
205         if (INET_ECN_is_ce(outer))
206                 INET_ECN_set_ce(skb);
207 
208         return 0;
209 }
210 
211 static inline int IP_ECN_decapsulate(const struct iphdr *oiph,
212                                      struct sk_buff *skb)
213 {
214         __u8 inner;
215 
216         if (skb->protocol == htons(ETH_P_IP))
217                 inner = ip_hdr(skb)->tos;
218         else if (skb->protocol == htons(ETH_P_IPV6))
219                 inner = ipv6_get_dsfield(ipv6_hdr(skb));
220         else
221                 return 0;
222 
223         return INET_ECN_decapsulate(skb, oiph->tos, inner);
224 }
225 
226 static inline int IP6_ECN_decapsulate(const struct ipv6hdr *oipv6h,
227                                       struct sk_buff *skb)
228 {
229         __u8 inner;
230 
231         if (skb->protocol == htons(ETH_P_IP))
232                 inner = ip_hdr(skb)->tos;
233         else if (skb->protocol == htons(ETH_P_IPV6))
234                 inner = ipv6_get_dsfield(ipv6_hdr(skb));
235         else
236                 return 0;
237 
238         return INET_ECN_decapsulate(skb, ipv6_get_dsfield(oipv6h), inner);
239 }
240 #endif
241 

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