falconia has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-bsc/+/42717?usp=email )
Change subject: rsl: don't send legacy Chan Ident IE for Nokia BTS ......................................................................
rsl: don't send legacy Chan Ident IE for Nokia BTS
The description of CHAN ACTIV command message in TS 48.058 section 8.4.1 lists Channel Identification as an optional IE, with a note that reads "Included if compatibility with phase1 is required." This note may have been misinterpreted as referring to compatibility with Phase 1 phones - but since this network-internal Abis detail is invisible to phones, the real intent of GSM spec authors here must have been compatibility with Phase 1 BTS.
Previous versions of OsmoBSC would always include this IE, and it appears that all previously supported BTS models would simply ignore it. However, newer Nokia BTS models (observed on Flexi Multiradio at least) dislike this IE and return CHAN ACTIV NACK with an optional IE error cause if it is included.
To avoid changing OsmoBSC behavior for other users, let us conditionalize removal of this legacy IE on Nokia BTS for now. This change has been tested on InSite, MetroSite and Flexi Multiradio - no adverse effects on previously supported *Site models.
Change-Id: Ibce7a841907ac87ae378ded3ddb174d38b70b7b7 --- M src/osmo-bsc/abis_rsl.c 1 file changed, 46 insertions(+), 19 deletions(-)
git pull ssh://gerrit.osmocom.org:29418/osmo-bsc refs/changes/17/42717/1
diff --git a/src/osmo-bsc/abis_rsl.c b/src/osmo-bsc/abis_rsl.c index 42a164a..4627914 100644 --- a/src/osmo-bsc/abis_rsl.c +++ b/src/osmo-bsc/abis_rsl.c @@ -577,6 +577,31 @@ msgb_put_u8(msg, tsc); }
+static void add_phase1_chan_ident(struct msgb *msg, const struct gsm48_chan_desc *cd) +{ + uint8_t *len; + + /* + * This Channel Identification IE is a Phase1 backward compatibility + * measure. It contains the GSM48 Channel Description and the + * Mobile Allocation. TS 48.058 section 9.3.5 asks for MA + * to have a length of zero. We are using msgb_l3len() to calculate + * the length of both messages. + */ + msgb_v_put(msg, RSL_IE_CHAN_IDENT); + len = msgb_put(msg, 1); + msgb_tv_fixed_put(msg, GSM48_IE_CHANDESC_2, sizeof(*cd), (const uint8_t *) cd); + + /* See 3GPP TS 48.058 (version 15.0.0), section 9.3.5 "Channel Identification". + * The 3GPP TS 24.008 "Mobile Allocation" shall for compatibility reasons + * be included but empty, i.e. the length shall be zero. */ + msgb_tlv_put(msg, GSM48_IE_MA_AFTER, 0, NULL); + + /* update the calculated size */ + msg->l3h = len + 1; + *len = msgb_l3len(msg); +} + /* Chapter 8.4.1 */ int rsl_tx_chan_activ(struct gsm_lchan *lchan, uint8_t act_type, uint8_t ho_ref) { @@ -585,7 +610,6 @@ struct abis_rsl_dchan_hdr *dh; struct msgb *msg; int rc; - uint8_t *len;
struct rsl_ie_chan_mode cm; struct gsm48_chan_desc cd; @@ -625,25 +649,28 @@ msgb_tlv_put(msg, RSL_IE_CHAN_MODE, sizeof(cm), (uint8_t *) &cm);
- /* - * The Channel Identification is needed for Phase1 phones - * and it contains the GSM48 Channel Description and the - * Mobile Allocation. The GSM 08.58 asks for the Mobile - * Allocation to have a length of zero. We are using the - * msgb_l3len to calculate the length of both messages. + /* The description of CHAN ACTIV command message in TS 48.058 + * section 8.4.1 lists Channel Identification as an optional IE, + * with a note that reads "Included if compatibility with phase1 + * is required." This note may have been misinterpreted as + * referring to compatibility with Phase 1 phones - but since + * this network-internal Abis detail is invisible to phones, + * the real intent of GSM spec authors here must have been + * compatibility with Phase 1 BTS. + * + * Previous versions of OsmoBSC would always include this IE, + * and it appears that all previously supported BTS models + * would simply ignore it. However, newer Nokia BTS models + * (observed on Flexi Multiradio at least) dislike this IE + * and return CHAN ACTIV NACK with an optional IE error cause + * if it is included. + * + * To avoid changing OsmoBSC behavior for other users, + * let us conditionalize removal of this legacy IE on + * Nokia BTS for now. */ - msgb_v_put(msg, RSL_IE_CHAN_IDENT); - len = msgb_put(msg, 1); - msgb_tv_fixed_put(msg, GSM48_IE_CHANDESC_2, sizeof(cd), (const uint8_t *) &cd); - - /* See 3GPP TS 48.058 (version 15.0.0), section 9.3.5 "Channel Identification". - * The 3GPP TS 24.008 "Mobile Allocation" shall for compatibility reasons - * be included but empty, i.e. the length shall be zero. */ - msgb_tlv_put(msg, GSM48_IE_MA_AFTER, 0, NULL); - - /* update the calculated size */ - msg->l3h = len + 1; - *len = msgb_l3len(msg); + if (!is_nokia_bts(bts)) + add_phase1_chan_ident(msg, &cd);
if (lchan->encr.alg_a5_n > 0) { uint8_t encr_info[MAX_A5_KEY_LEN+2];