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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef LINUX_MLD_H
3#define LINUX_MLD_H
4
5#include <linux/in6.h>
6#include <linux/icmpv6.h>
7
8/* MLDv1 Query/Report/Done */
9struct mld_msg {
10 struct icmp6hdr mld_hdr;
11 struct in6_addr mld_mca;
12};
13
14#define mld_type mld_hdr.icmp6_type
15#define mld_code mld_hdr.icmp6_code
16#define mld_cksum mld_hdr.icmp6_cksum
17#define mld_maxdelay mld_hdr.icmp6_maxdelay
18#define mld_reserved mld_hdr.icmp6_dataun.un_data16[1]
19
20/* Multicast Listener Discovery version 2 headers */
21/* MLDv2 Report */
22struct mld2_grec {
23 __u8 grec_type;
24 __u8 grec_auxwords;
25 __be16 grec_nsrcs;
26 struct in6_addr grec_mca;
27 struct in6_addr grec_src[];
28};
29
30struct mld2_report {
31 struct icmp6hdr mld2r_hdr;
32 struct mld2_grec mld2r_grec[];
33};
34
35#define mld2r_type mld2r_hdr.icmp6_type
36#define mld2r_resv1 mld2r_hdr.icmp6_code
37#define mld2r_cksum mld2r_hdr.icmp6_cksum
38#define mld2r_resv2 mld2r_hdr.icmp6_dataun.un_data16[0]
39#define mld2r_ngrec mld2r_hdr.icmp6_dataun.un_data16[1]
40
41/* MLDv2 Query */
42struct mld2_query {
43 struct icmp6hdr mld2q_hdr;
44 struct in6_addr mld2q_mca;
45#if defined(__LITTLE_ENDIAN_BITFIELD)
46 __u8 mld2q_qrv:3,
47 mld2q_suppress:1,
48 mld2q_resv2:4;
49#elif defined(__BIG_ENDIAN_BITFIELD)
50 __u8 mld2q_resv2:4,
51 mld2q_suppress:1,
52 mld2q_qrv:3;
53#else
54#error "Please fix <asm/byteorder.h>"
55#endif
56 __u8 mld2q_qqic;
57 __be16 mld2q_nsrcs;
58 struct in6_addr mld2q_srcs[];
59};
60
61#define mld2q_type mld2q_hdr.icmp6_type
62#define mld2q_code mld2q_hdr.icmp6_code
63#define mld2q_cksum mld2q_hdr.icmp6_cksum
64#define mld2q_mrc mld2q_hdr.icmp6_maxdelay
65#define mld2q_resv1 mld2q_hdr.icmp6_dataun.un_data16[1]
66
67/* RFC3810, 5.1.3. Maximum Response Code:
68 *
69 * If Maximum Response Code >= 32768, Maximum Response Code represents a
70 * floating-point value as follows:
71 *
72 * 0 1 2 3 4 5 6 7 8 9 A B C D E F
73 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
74 * |1| exp | mant |
75 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
76 */
77#define MLDV2_MRC_EXP(value) (((value) >> 12) & 0x0007)
78#define MLDV2_MRC_MAN(value) ((value) & 0x0fff)
79
80/* RFC3810, 5.1.9. QQIC (Querier's Query Interval Code):
81 *
82 * If QQIC >= 128, QQIC represents a floating-point value as follows:
83 *
84 * 0 1 2 3 4 5 6 7
85 * +-+-+-+-+-+-+-+-+
86 * |1| exp | mant |
87 * +-+-+-+-+-+-+-+-+
88 */
89#define MLDV2_QQIC_EXP(value) (((value) >> 4) & 0x07)
90#define MLDV2_QQIC_MAN(value) ((value) & 0x0f)
91
92/* MLDv2 QQIC floating-point exponential field min threshold */
93#define MLD_QQIC_MIN_THRESHOLD 128
94/* MLDv2 QQIC FP max threshold (mant = 0xF, exp = 7) -> 31744 */
95#define MLD_QQIC_MAX_THRESHOLD 31744
96/* MLDv2 MRC floating-point exponential field min threshold */
97#define MLD_MRC_MIN_THRESHOLD 32768UL
98/* MLDv2 MRC FP max threshold (mant = 0xFFF, exp = 7) -> 8387584 */
99#define MLD_MRC_MAX_THRESHOLD 8387584
100#define MLDV1_MRD_MAX_COMPAT (MLD_MRC_MIN_THRESHOLD - 1)
101
102#define MLD_MAX_QUEUE 8
103#define MLD_MAX_SKBS 32
104
105/* V2 exponential field encoding */
106
107/*
108 * Calculate Maximum Response Code from Maximum Response Delay
109 *
110 * MRC represents the 16-bit encoded form of Maximum Response Delay (MRD);
111 * once decoded, the resulting value is in milliseconds.
112 *
113 * RFC3810, 5.1.3. defines only the decoding formula:
114 * Maximum Response Delay = (mant | 0x1000) << (exp + 3)
115 *
116 * but does NOT define the encoding procedure. To derive exponent:
117 *
118 * For the 16-bit MRC, the "hidden bit" (0x1000) is left shifted by 12 to
119 * sit above the 12-bit mantissa. The RFC then shifts this entire block
120 * left by (exp + 3) to reconstruct the value. So, 'hidden bit' is the
121 * MSB which is shifted by (12 + exp + 3).
122 *
123 * Total left shift of the hidden bit = 12 + (exp + 3) = exp + 15.
124 * This is the MSB at the 0-based bit position: (exp + 15).
125 * Since fls() is 1-based, fls(value) - 1 = exp + 15.
126 *
127 * Therefore:
128 * exp = fls(value) - 16
129 * mant = (value >> (exp + 3)) & 0x0FFF
130 *
131 * Final encoding formula:
132 * 0x8000 | (exp << 12) | mant
133 *
134 * Example (value = 1311744):
135 * 0 1 2 3
136 * 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
137 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
138 * |0 0 0 0 0 0 0 0 0 0 0 1 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0| 1311744
139 * | ^-^--------mant---------^ ^...(exp+3)...^| exp=5
140 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
141 *
142 * Encoded:
143 * 0x8000 | (5 << 12) | 0x404 = 0xD404
144 */
145static inline u16 mldv2_mrc(unsigned long mrd)
146{
147 u16 mc_man, mc_exp;
148
149 /* MRC < 32768 is literal */
150 if (mrd < MLD_MRC_MIN_THRESHOLD)
151 return mrd;
152
153 /* Saturate at max representable (mant = 0xFFF, exp = 7) -> 8387584 */
154 if (mrd >= MLD_MRC_MAX_THRESHOLD)
155 return 0xFFFF;
156
157 mc_exp = fls(mrd) - 16;
158 mc_man = (mrd >> (mc_exp + 3)) & 0x0FFF;
159
160 return 0x8000 | (mc_exp << 12) | mc_man;
161}
162
163/*
164 * Calculate Querier's Query Interval Code from Querier's Query Interval
165 *
166 * QQIC represents the 8-bit encoded form of Querier's Query Interval (QQI);
167 * once decoded, the resulting value is in seconds.
168 *
169 * RFC3810, 5.1.9. defines only the decoding formula:
170 * QQI = (mant | 0x10) << (exp + 3)
171 *
172 * but does NOT define the encoding procedure. To derive exponent:
173 *
174 * For any value of mantissa and exponent, the decoding formula indicates
175 * that the "hidden bit" (0x10) is shifted 4 bits left to sit above the
176 * 4-bit mantissa. The RFC again shifts this entire block left by (exp + 3)
177 * to reconstruct the value. So, 'hidden bit' is the MSB which is shifted
178 * by (4 + exp + 3).
179 *
180 * Total left shift of the 'hidden bit' = 4 + (exp + 3) = exp + 7.
181 * This is the MSB at the 0-based bit position: (exp + 7).
182 * Since fls() is 1-based, fls(value) - 1 = exp + 7.
183 *
184 * Therefore:
185 * exp = fls(value) - 8
186 * mant = (value >> (exp + 3)) & 0x0F
187 *
188 * Final encoding formula:
189 * 0x80 | (exp << 4) | mant
190 *
191 * Example (value = 3200):
192 * 0 1
193 * 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
194 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
195 * |0 0 0 0 1 1 0 0 1 0 0 0 0 0 0 0| (value = 3200)
196 * | ^-^-mant^ ^..(exp+3)..^| exp = 4, mant = 9
197 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
198 *
199 * Encoded:
200 * 0x80 | (4 << 4) | 9 = 0xC9
201 */
202static inline u8 mldv2_qqic(unsigned long value)
203{
204 u8 mc_man, mc_exp;
205
206 /* QQIC < 128 is literal */
207 if (value < MLD_QQIC_MIN_THRESHOLD)
208 return value;
209
210 /* Saturate at max representable (mant = 0xF, exp = 7) -> 31744 */
211 if (value >= MLD_QQIC_MAX_THRESHOLD)
212 return 0xFF;
213
214 mc_exp = fls(value) - 8;
215 mc_man = (value >> (mc_exp + 3)) & 0x0F;
216
217 return 0x80 | (mc_exp << 4) | mc_man;
218}
219
220/* V2 exponential field decoding */
221
222/* Calculate Maximum Response Delay from Maximum Response Code
223 *
224 * RFC3810, relevant sections:
225 * - 5.1.3. Maximum Response Code defines the decoding formula:
226 * 0 1 2 3 4 5 6 7 8 9 A B C D E F
227 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
228 * |1| exp | mant |
229 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
230 * Maximum Response Delay = (mant | 0x1000) << (exp+3)
231 * - 9.3. Query Response Interval
232 *
233 * After decode, MRC represents the Maximum Response Delay (MRD) in
234 * units of milliseconds.
235 */
236static inline unsigned long mldv2_mrd(const struct mld2_query *mlh2)
237{
238 unsigned long mc_mrc = ntohs(mlh2->mld2q_mrc);
239
240 if (mc_mrc < MLD_MRC_MIN_THRESHOLD) {
241 return mc_mrc;
242 } else {
243 unsigned long mc_man, mc_exp;
244
245 mc_exp = MLDV2_MRC_EXP(mc_mrc);
246 mc_man = MLDV2_MRC_MAN(mc_mrc);
247
248 return (mc_man | 0x1000) << (mc_exp + 3);
249 }
250}
251
252/* Calculate Querier's Query Interval from Querier's Query Interval Code
253 *
254 * RFC3810, relevant sections:
255 * - 5.1.9. QQIC (Querier's Query Interval Code) defines the decoding formula:
256 * 0 1 2 3 4 5 6 7
257 * +-+-+-+-+-+-+-+-+
258 * |1| exp | mant |
259 * +-+-+-+-+-+-+-+-+
260 * QQI = (mant | 0x10) << (exp + 3)
261 * - 9.2. Query Interval
262 * - 9.12. Older Version Querier Present Timeout
263 * (the [Query Interval] in the last Query received)
264 *
265 * After decode, QQIC represents the Querier's Query Interval in units
266 * of seconds.
267 */
268static inline unsigned long mldv2_qqi(const struct mld2_query *mlh2)
269{
270 unsigned long qqic = mlh2->mld2q_qqic;
271
272 if (qqic < MLD_QQIC_MIN_THRESHOLD) {
273 return qqic;
274 } else {
275 unsigned long mc_man, mc_exp;
276
277 mc_exp = MLDV2_QQIC_EXP(qqic);
278 mc_man = MLDV2_QQIC_MAN(qqic);
279
280 return (mc_man | 0x10) << (mc_exp + 3);
281 }
282}
283
284#endif