diff options
| author | Harald Welte <laforge@osmocom.org> | 2021-01-25 17:59:06 +0100 |
|---|---|---|
| committer | laforge <laforge@osmocom.org> | 2021-01-29 21:24:36 +0000 |
| commit | 5e01039d79674171d20c5ea40266635a576eee56 (patch) | |
| tree | 7309fb5d50ad727f93060c181a4a0bdc89a042eb /src | |
| parent | 6d32c92e4fbc67e09f77157baef72ea3044ab534 (diff) | |
select_best_cipher(): Prefer A5/1 over A5/2
We cannot simply use the highest 'x' in A5/x codecs.
For A5/7 through A5/3, larger 'x' means better.
But: A5/1 is better than A5/2, so we need to prefer the former
over the latter.
Change-Id: I399fff8d07d1bfcbc6b385e90914ff6d9e00eb73
Closes: OS#4975
Diffstat (limited to 'src')
| -rw-r--r-- | src/osmo-bsc/osmo_bsc_bssap.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/src/osmo-bsc/osmo_bsc_bssap.c b/src/osmo-bsc/osmo_bsc_bssap.c index 63dee9e3d..9d7815314 100644 --- a/src/osmo-bsc/osmo_bsc_bssap.c +++ b/src/osmo-bsc/osmo_bsc_bssap.c @@ -402,12 +402,16 @@ int bsc_paging_start(struct bsc_paging_params *params) /* select the best cipher permitted by the intersection of both masks */ static int select_best_cipher(uint8_t msc_mask, uint8_t bsc_mask) { + /* A5/7 ... A5/3: We assume higher is better, + * but: A5/1 is better than A5/2, which is better than A5/0 */ + const uint8_t codec_strength[8] = { 7, 6, 5, 4, 3, 1, 2, 0 }; uint8_t intersection = msc_mask & bsc_mask; int i; - for (i = 7; i >= 0; i--) { - if (intersection & (1 << i)) - return i; + for (i = 0; i < ARRAY_SIZE(codec_strength); i++) { + uint8_t codec = codec_strength[i]; + if (intersection & (1 << codec)) + return codec; } return -1; } |