[gsm_04_08] Fix gsm48_send_rr_ciph_mode algorithm ID
The algorithm ID used in the GSM 04.08 RR message is
(x-1) for A5/x. In RSL it's (x+1) for A5/x so there is
a difference of 2.
Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/openbsc/src/gsm_04_08.c b/openbsc/src/gsm_04_08.c
index 30c2db3..6eb49c2 100644
--- a/openbsc/src/gsm_04_08.c
+++ b/openbsc/src/gsm_04_08.c
@@ -1699,7 +1699,7 @@
if (lchan->encr.alg_id <= RSL_ENC_ALG_A5(0))
ciph_mod_set = 0;
else
- ciph_mod_set = (lchan->encr.alg_id-1)<<1 | 1;
+ ciph_mod_set = (lchan->encr.alg_id-2)<<1 | 1;
gh = (struct gsm48_hdr *) msgb_put(msg, sizeof(*gh) + 1);
gh->proto_discr = GSM48_PDISC_RR;