LAPDm: Uplink SACCH frames use format B, not format B4

diff --git a/src/gsm/lapdm.c b/src/gsm/lapdm.c
index 242544d..2679ca0 100644 (file)
--- a/src/gsm/lapdm.c
+++ b/src/gsm/lapdm.c
@@ -1592,11 +1592,18 @@ static int l2_ph_data_ind(struct msgb *msg, struct lapdm_entity *le, uint8_t cha
                sapi = 0;
        } else {
                if (mctx.link_id & 0x40) {
-                       /* It was received from network on SACCH, thus
-                        * lapdm_fmt must be B4 */
-                       mctx.lapdm_fmt = LAPDm_FMT_B4;
-                       mctx.n201 = N201_B4;
-                       LOGP(DLLAPDM, LOGL_INFO, "fmt=B4\n");
+                       /* It was received from network on SACCH */
+
+                       /* If sent by BTS, lapdm_fmt must be B4 */
+                       if (le->mode == LAPDM_MODE_MS) {
+                               mctx.lapdm_fmt = LAPDm_FMT_B4;
+                               mctx.n201 = N201_B4;
+                               LOGP(DLLAPDM, LOGL_INFO, "fmt=B4\n");
+                       } else {
+                               mctx.lapdm_fmt = LAPDm_FMT_B;
+                               mctx.n201 = N201_AB_SACCH;
+                               LOGP(DLLAPDM, LOGL_INFO, "fmt=B\n");
+                       }
                        /* SACCH frames have a two-byte L1 header that
                         * OsmocomBB L1 doesn't strip */
                        mctx.tx_power_ind = msg->l2h[0] & 0x1f;