diff options
Diffstat (limited to 'include/net/mld.h')
| -rw-r--r-- | include/net/mld.h | 185 |
1 files changed, 176 insertions, 9 deletions
diff --git a/include/net/mld.h b/include/net/mld.h index c07359808493..23255cc47ced 100644 --- a/include/net/mld.h +++ b/include/net/mld.h @@ -89,29 +89,196 @@ struct mld2_query { #define MLDV2_QQIC_EXP(value) (((value) >> 4) & 0x07) #define MLDV2_QQIC_MAN(value) ((value) & 0x0f) -#define MLD_EXP_MIN_LIMIT 32768UL -#define MLDV1_MRD_MAX_COMPAT (MLD_EXP_MIN_LIMIT - 1) +/* MLDv2 QQIC floating-point exponential field min threshold */ +#define MLD_QQIC_MIN_THRESHOLD 128 +/* MLDv2 QQIC FP max threshold (mant = 0xF, exp = 7) -> 31744 */ +#define MLD_QQIC_MAX_THRESHOLD 31744 +/* MLDv2 MRC floating-point exponential field min threshold */ +#define MLD_MRC_MIN_THRESHOLD 32768UL +/* MLDv2 MRC FP max threshold (mant = 0xFFF, exp = 7) -> 8387584 */ +#define MLD_MRC_MAX_THRESHOLD 8387584 +#define MLDV1_MRD_MAX_COMPAT (MLD_MRC_MIN_THRESHOLD - 1) #define MLD_MAX_QUEUE 8 #define MLD_MAX_SKBS 32 -static inline unsigned long mldv2_mrc(const struct mld2_query *mlh2) +/* V2 exponential field encoding */ + +/* + * Calculate Maximum Response Code from Maximum Response Delay + * + * MRC represents the 16-bit encoded form of Maximum Response Delay (MRD); + * once decoded, the resulting value is in milliseconds. + * + * RFC3810, 5.1.3. defines only the decoding formula: + * Maximum Response Delay = (mant | 0x1000) << (exp + 3) + * + * but does NOT define the encoding procedure. To derive exponent: + * + * For the 16-bit MRC, the "hidden bit" (0x1000) is left shifted by 12 to + * sit above the 12-bit mantissa. The RFC then shifts this entire block + * left by (exp + 3) to reconstruct the value. So, 'hidden bit' is the + * MSB which is shifted by (12 + exp + 3). + * + * Total left shift of the hidden bit = 12 + (exp + 3) = exp + 15. + * This is the MSB at the 0-based bit position: (exp + 15). + * Since fls() is 1-based, fls(value) - 1 = exp + 15. + * + * Therefore: + * exp = fls(value) - 16 + * mant = (value >> (exp + 3)) & 0x0FFF + * + * Final encoding formula: + * 0x8000 | (exp << 12) | mant + * + * Example (value = 1311744): + * 0 1 2 3 + * 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 + * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + * |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 + * | ^-^--------mant---------^ ^...(exp+3)...^| exp=5 + * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + * + * Encoded: + * 0x8000 | (5 << 12) | 0x404 = 0xD404 + */ +static inline u16 mldv2_mrc(unsigned long mrd) +{ + u16 mc_man, mc_exp; + + /* MRC < 32768 is literal */ + if (mrd < MLD_MRC_MIN_THRESHOLD) + return mrd; + + /* Saturate at max representable (mant = 0xFFF, exp = 7) -> 8387584 */ + if (mrd >= MLD_MRC_MAX_THRESHOLD) + return 0xFFFF; + + mc_exp = fls(mrd) - 16; + mc_man = (mrd >> (mc_exp + 3)) & 0x0FFF; + + return 0x8000 | (mc_exp << 12) | mc_man; +} + +/* + * Calculate Querier's Query Interval Code from Querier's Query Interval + * + * QQIC represents the 8-bit encoded form of Querier's Query Interval (QQI); + * once decoded, the resulting value is in seconds. + * + * RFC3810, 5.1.9. defines only the decoding formula: + * QQI = (mant | 0x10) << (exp + 3) + * + * but does NOT define the encoding procedure. To derive exponent: + * + * For any value of mantissa and exponent, the decoding formula indicates + * that the "hidden bit" (0x10) is shifted 4 bits left to sit above the + * 4-bit mantissa. The RFC again shifts this entire block left by (exp + 3) + * to reconstruct the value. So, 'hidden bit' is the MSB which is shifted + * by (4 + exp + 3). + * + * Total left shift of the 'hidden bit' = 4 + (exp + 3) = exp + 7. + * This is the MSB at the 0-based bit position: (exp + 7). + * Since fls() is 1-based, fls(value) - 1 = exp + 7. + * + * Therefore: + * exp = fls(value) - 8 + * mant = (value >> (exp + 3)) & 0x0F + * + * Final encoding formula: + * 0x80 | (exp << 4) | mant + * + * Example (value = 3200): + * 0 1 + * 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 + * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + * |0 0 0 0 1 1 0 0 1 0 0 0 0 0 0 0| (value = 3200) + * | ^-^-mant^ ^..(exp+3)..^| exp = 4, mant = 9 + * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + * + * Encoded: + * 0x80 | (4 << 4) | 9 = 0xC9 + */ +static inline u8 mldv2_qqic(unsigned long value) +{ + u8 mc_man, mc_exp; + + /* QQIC < 128 is literal */ + if (value < MLD_QQIC_MIN_THRESHOLD) + return value; + + /* Saturate at max representable (mant = 0xF, exp = 7) -> 31744 */ + if (value >= MLD_QQIC_MAX_THRESHOLD) + return 0xFF; + + mc_exp = fls(value) - 8; + mc_man = (value >> (mc_exp + 3)) & 0x0F; + + return 0x80 | (mc_exp << 4) | mc_man; +} + +/* V2 exponential field decoding */ + +/* Calculate Maximum Response Delay from Maximum Response Code + * + * RFC3810, relevant sections: + * - 5.1.3. Maximum Response Code defines the decoding formula: + * 0 1 2 3 4 5 6 7 8 9 A B C D E F + * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + * |1| exp | mant | + * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + * Maximum Response Delay = (mant | 0x1000) << (exp+3) + * - 9.3. Query Response Interval + * + * After decode, MRC represents the Maximum Response Delay (MRD) in + * units of milliseconds. + */ +static inline unsigned long mldv2_mrd(const struct mld2_query *mlh2) { - /* RFC3810, 5.1.3. Maximum Response Code */ - unsigned long ret, mc_mrc = ntohs(mlh2->mld2q_mrc); + unsigned long mc_mrc = ntohs(mlh2->mld2q_mrc); - if (mc_mrc < MLD_EXP_MIN_LIMIT) { - ret = mc_mrc; + if (mc_mrc < MLD_MRC_MIN_THRESHOLD) { + return mc_mrc; } else { unsigned long mc_man, mc_exp; mc_exp = MLDV2_MRC_EXP(mc_mrc); mc_man = MLDV2_MRC_MAN(mc_mrc); - ret = (mc_man | 0x1000) << (mc_exp + 3); + return (mc_man | 0x1000) << (mc_exp + 3); } +} - return ret; +/* Calculate Querier's Query Interval from Querier's Query Interval Code + * + * RFC3810, relevant sections: + * - 5.1.9. QQIC (Querier's Query Interval Code) defines the decoding formula: + * 0 1 2 3 4 5 6 7 + * +-+-+-+-+-+-+-+-+ + * |1| exp | mant | + * +-+-+-+-+-+-+-+-+ + * QQI = (mant | 0x10) << (exp + 3) + * - 9.2. Query Interval + * - 9.12. Older Version Querier Present Timeout + * (the [Query Interval] in the last Query received) + * + * After decode, QQIC represents the Querier's Query Interval in units + * of seconds. + */ +static inline unsigned long mldv2_qqi(const struct mld2_query *mlh2) +{ + unsigned long qqic = mlh2->mld2q_qqic; + + if (qqic < MLD_QQIC_MIN_THRESHOLD) { + return qqic; + } else { + unsigned long mc_man, mc_exp; + + mc_exp = MLDV2_QQIC_EXP(qqic); + mc_man = MLDV2_QQIC_MAN(qqic); + + return (mc_man | 0x10) << (mc_exp + 3); + } } #endif |