LAPDm: Add a flag to enable suppression of subsequent REJ frame
This behaviour was default in earlier versions of LAPDm/LAPD. Because it
is only required for osmocom-bb, a flag is added to enable it there.
Related: OS#5969
Change-Id: I93994dbbd1fc2c9edb8f3015c6b18ecd0fce0565
diff --git a/include/osmocom/gsm/lapdm.h b/include/osmocom/gsm/lapdm.h
index 08b808c..42ebbce 100644
--- a/include/osmocom/gsm/lapdm.h
+++ b/include/osmocom/gsm/lapdm.h
@@ -50,6 +50,7 @@
#define LAPDM_ENT_F_EMPTY_FRAME 0x0001
#define LAPDM_ENT_F_POLLING_ONLY 0x0002
+#define LAPDM_ENT_F_DROP_2ND_REJ 0x0004
/*! a LAPDm Entity */
struct lapdm_entity {
diff --git a/include/osmocom/isdn/lapd_core.h b/include/osmocom/isdn/lapd_core.h
index 776d4f4..1e010af 100644
--- a/include/osmocom/isdn/lapd_core.h
+++ b/include/osmocom/isdn/lapd_core.h
@@ -86,6 +86,7 @@
/*! lapd_flags */
#define LAPD_F_RTS 0x0001
+#define LAPD_F_DROP_2ND_REJ 0x0002
/*! LAPD T200 state in RTS mode */
enum lapd_t200_rts {
diff --git a/src/gsm/lapdm.c b/src/gsm/lapdm.c
index 28644c2..fb892d2 100644
--- a/src/gsm/lapdm.c
+++ b/src/gsm/lapdm.c
@@ -1637,6 +1637,8 @@
/* Set flags at LAPD. */
if (le->flags & LAPDM_ENT_F_POLLING_ONLY)
dl_flags |= LAPD_F_RTS;
+ if (le->flags & LAPDM_ENT_F_DROP_2ND_REJ)
+ dl_flags |= LAPD_F_DROP_2ND_REJ;
for (i = 0; i < ARRAY_SIZE(le->datalink); i++) {
dl = &le->datalink[i];
diff --git a/src/isdn/lapd_core.c b/src/isdn/lapd_core.c
index 34748a4..d98edae 100644
--- a/src/isdn/lapd_core.c
+++ b/src/isdn/lapd_core.c
@@ -1633,9 +1633,8 @@
ns, dl->v_recv, lapd_state_name(dl->state));
/* discard data */
msgb_free(msg);
- if (dl->seq_err_cond != 1) {
- /* FIXME: help me understand what exactly todo here
- */
+ /* Send reject, but suppress second reject if LAPD_F_DROP_2ND_REJ flag is set. */
+ if (dl->seq_err_cond != 1 || !(dl->lapd_flags & LAPD_F_DROP_2ND_REJ)) {
dl->seq_err_cond = 1;
lapd_send_rej(lctx, lctx->p_f);
} else {