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
10enum {
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
18extern int sysctl_tunnel_ecn_log;
19
20static inline int INET_ECN_is_ce(__u8 dsfield)
21{
22	return (dsfield & INET_ECN_MASK) == INET_ECN_CE;
23}
24
25static inline int INET_ECN_is_not_ect(__u8 dsfield)
26{
27	return (dsfield & INET_ECN_MASK) == INET_ECN_NOT_ECT;
28}
29
30static 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 */
43static 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
51static 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
58static 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
74static 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
101static inline void IP_ECN_clear(struct iphdr *iph)
102{
103	iph->tos &= ~INET_ECN_MASK;
104}
105
106static 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
112struct 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 */
120static 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, from), to);
132	return 1;
133}
134
135static inline void IP6_ECN_clear(struct ipv6hdr *iph)
136{
137	*(__be32*)iph &= ~htonl(INET_ECN_MASK << 20);
138}
139
140static inline void ipv6_copy_dscp(unsigned int dscp, struct ipv6hdr *inner)
141{
142	dscp &= ~INET_ECN_MASK;
143	ipv6_change_dsfield(inner, INET_ECN_MASK, dscp);
144}
145
146static inline int INET_ECN_set_ce(struct sk_buff *skb)
147{
148	switch (skb->protocol) {
149	case cpu_to_be16(ETH_P_IP):
150		if (skb_network_header(skb) + sizeof(struct iphdr) <=
151		    skb_tail_pointer(skb))
152			return IP_ECN_set_ce(ip_hdr(skb));
153		break;
154
155	case cpu_to_be16(ETH_P_IPV6):
156		if (skb_network_header(skb) + sizeof(struct ipv6hdr) <=
157		    skb_tail_pointer(skb))
158			return IP6_ECN_set_ce(skb, ipv6_hdr(skb));
159		break;
160	}
161
162	return 0;
163}
164
165/*
166 * RFC 6040 4.2
167 *  To decapsulate the inner header at the tunnel egress, a compliant
168 *  tunnel egress MUST set the outgoing ECN field to the codepoint at the
169 *  intersection of the appropriate arriving inner header (row) and outer
170 *  header (column) in Figure 4
171 *
172 *      +---------+------------------------------------------------+
173 *      |Arriving |            Arriving Outer Header               |
174 *      |   Inner +---------+------------+------------+------------+
175 *      |  Header | Not-ECT | ECT(0)     | ECT(1)     |     CE     |
176 *      +---------+---------+------------+------------+------------+
177 *      | Not-ECT | Not-ECT |Not-ECT(!!!)|Not-ECT(!!!)| <drop>(!!!)|
178 *      |  ECT(0) |  ECT(0) | ECT(0)     | ECT(1)     |     CE     |
179 *      |  ECT(1) |  ECT(1) | ECT(1) (!) | ECT(1)     |     CE     |
180 *      |    CE   |      CE |     CE     |     CE(!!!)|     CE     |
181 *      +---------+---------+------------+------------+------------+
182 *
183 *             Figure 4: New IP in IP Decapsulation Behaviour
184 *
185 *  returns 0 on success
186 *          1 if something is broken and should be logged (!!! above)
187 *          2 if packet should be dropped
188 */
189static inline int INET_ECN_decapsulate(struct sk_buff *skb,
190				       __u8 outer, __u8 inner)
191{
192	if (INET_ECN_is_not_ect(inner)) {
193		switch (outer & INET_ECN_MASK) {
194		case INET_ECN_NOT_ECT:
195			return 0;
196		case INET_ECN_ECT_0:
197		case INET_ECN_ECT_1:
198			return 1;
199		case INET_ECN_CE:
200			return 2;
201		}
202	}
203
204	if (INET_ECN_is_ce(outer))
205		INET_ECN_set_ce(skb);
206
207	return 0;
208}
209
210static inline int IP_ECN_decapsulate(const struct iphdr *oiph,
211				     struct sk_buff *skb)
212{
213	__u8 inner;
214
215	if (skb->protocol == htons(ETH_P_IP))
216		inner = ip_hdr(skb)->tos;
217	else if (skb->protocol == htons(ETH_P_IPV6))
218		inner = ipv6_get_dsfield(ipv6_hdr(skb));
219	else
220		return 0;
221
222	return INET_ECN_decapsulate(skb, oiph->tos, inner);
223}
224
225static inline int IP6_ECN_decapsulate(const struct ipv6hdr *oipv6h,
226				      struct sk_buff *skb)
227{
228	__u8 inner;
229
230	if (skb->protocol == htons(ETH_P_IP))
231		inner = ip_hdr(skb)->tos;
232	else if (skb->protocol == htons(ETH_P_IPV6))
233		inner = ipv6_get_dsfield(ipv6_hdr(skb));
234	else
235		return 0;
236
237	return INET_ECN_decapsulate(skb, ipv6_get_dsfield(oipv6h), inner);
238}
239#endif
240