laforge has submitted this change. ( https://gerrit.osmocom.org/c/osmo-bsc/+/28019 )

Change subject: cbsp: Reject CBSP WRITE for emergency if emergency already active ......................................................................

cbsp: Reject CBSP WRITE for emergency if emergency already active

From 3GPP TS 48.018:

If only the New Serial Number IE, and not the Old Serial Number IE, is included in the WRITE-REPLACE message,then the BSC shall interpret the message as a write request, i.e. a broadcast request of a new emergency message without replacing an ongoing emergency message broadcast.

Only one emergency message at the time can be broadcasted in a cell. If a write request is received for a cell where an emergency message broadcast is currently ongoing, the write request is considered as failed.

Change-Id: I376c9e796f3a2d26b22d0451f15ef1debbd7f656 Closes: OS#5539 Related: SYS#5906 (cherry picked from commit 24567cfeed0ba9c0422e88f65cd1a9a489a197b6) --- M src/osmo-bsc/smscb.c 1 file changed, 28 insertions(+), 3 deletions(-)

Approvals: laforge: Looks good to me, approved Jenkins Builder: Verified

diff --git a/src/osmo-bsc/smscb.c b/src/osmo-bsc/smscb.c index 8ec239a..8a6a705 100644 --- a/src/osmo-bsc/smscb.c +++ b/src/osmo-bsc/smscb.c @@ -494,13 +494,37 @@ etws_pn_stop(bts, true); }

-static void etws_primary_to_bts(struct gsm_bts *bts, const struct osmo_cbsp_write_replace *wrepl) +static int etws_primary_to_bts(struct gsm_bts *bts, const struct osmo_cbsp_write_replace *wrepl) { struct bts_etws_state *bes = &bts->etws; struct gsm_bts_trx *trx; unsigned int count = 0; int i, j;

+ if (bes->active) { + /* we were already broadcasting emergency before receiving this WRITE-REPLACE */ + + /* If only the New Serial Number IE, and not the Old Serial Number IE, is included in the + * WRITE-REPLACE message, then the BSC shall interpret the message as a write request, i.e. a + * broadcast request of a new emergency message without replacing an ongoing emergency message + * broadcast. */ + if (!wrepl->old_serial_nr) { + /* If a write request is received for a cell where an emergency message broadcast is + * currently ongoing, the write request is considered as failed */ + LOG_BTS(bts, DCBS, LOGL_NOTICE, "Rx CBSP WRITE rejected due to ongoing emergency " + "while no Old Serial Nr IE present in CBSP WRITE\n"); + return -CBSP_CAUSE_BSC_CAPACITY_EXCEEDED; + } + + if (!etws_msg_id_matches(*wrepl->old_serial_nr, bes->input.serial_nr)) { + LOG_BTS(bts, DCBS, LOGL_NOTICE, "Rx CBSP WRITE-REPLACE old_serial 0x%04x doesn't match " + "current serial 0x%04x. Is the CBC confused?\n", + *wrepl->old_serial_nr, bes->input.serial_nr); + /* we allow the WRITE-REPLACE to continue, TS 48.049 doesn't specify how to + * handle situations like this */ + } + } + if (bes->input.sec_info) { talloc_free(bes->input.sec_info); bes->input.sec_info = NULL; @@ -553,6 +577,8 @@ } else LOG_BTS(bts, DCBS, LOGL_NOTICE, "Unlimited ETWS PN broadcast, this breaks " "normal network operation due to PCH blockage\n"); + + return 0; }

/*! Try to execute a write-replace operation; roll-back if it fails. @@ -624,8 +650,7 @@ int rc;

if (!wrepl->is_cbs) { - etws_primary_to_bts(bts, wrepl); - return 0; + return etws_primary_to_bts(bts, wrepl); }

/* check if cell has a CBCH at all */