diff options
Diffstat (limited to 'openbsc/include/openbsc/gprs_llc.h')
| -rw-r--r-- | openbsc/include/openbsc/gprs_llc.h | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/openbsc/include/openbsc/gprs_llc.h b/openbsc/include/openbsc/gprs_llc.h index f905473a1..e3fc82ef9 100644 --- a/openbsc/include/openbsc/gprs_llc.h +++ b/openbsc/include/openbsc/gprs_llc.h @@ -179,4 +179,20 @@ int gprs_llgmm_assign(struct gprs_llc_llme *llme, int gprs_llc_init(const char *cipher_plugin_path); int gprs_llc_vty_init(void); +/** + * \short Check if N(U) should be considered a retransmit + * + * Implements the range check as of GSM 04.64 8.4.2 + * Receipt of unacknowledged information. + * + * @returns Returns 1 if (V(UR)-32) <= N(U) < V(UR) + * @param nu N(U) unconfirmed sequence number of the UI frame + * @param vur V(UR) unconfirmend received state variable + */ +static inline int gprs_llc_is_retransmit(uint16_t nu, uint16_t vur) +{ + int delta = (vur - nu) & 0x1ff; + return 0 < delta && delta < 32; +} + #endif |