laforge has submitted this change. ( 
https://gerrit.osmocom.org/c/osmo-bsc/+/23574 )

Change subject: Ignore CHANnel ReQuireD with Access Delay IE > 63
......................................................................

Ignore CHANnel ReQuireD with Access Delay IE > 63

It is observed that a CHANnel ReQuireD with access delay
greater than 63 can be received from the Ericsson RBS.
This results in osmo-bsc sending back a CHANnel ACTIVation with
a Timing Advance IE containing the access delay value.
The RBS NACKs this, leading to a BORKEN Channel.

This patch makes the maximum acceptable access delay vty-configurable
and Ignores CHANnel ReQuireD RSL Messages with Access Delay IE greater
than that configured. Default value is 63.

Related: OS#5096
Change-Id: Ie8987bcc0e43921bc753162b77a0efc68799b3ce
---
M include/osmocom/bsc/bts.h
M src/osmo-bsc/abis_rsl.c
M src/osmo-bsc/bsc_vty.c
M src/osmo-bsc/bts.c
4 files changed, 33 insertions(+), 0 deletions(-)

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



diff --git a/include/osmocom/bsc/bts.h b/include/osmocom/bsc/bts.h
index f40aa3e..c8cf8b3 100644
--- a/include/osmocom/bsc/bts.h
+++ b/include/osmocom/bsc/bts.h
@@ -28,6 +28,7 @@
        BTS_CTR_CHREQ_ATTEMPTED_UNKNOWN,
        BTS_CTR_CHREQ_SUCCESSFUL,
        BTS_CTR_CHREQ_NO_CHANNEL,
+       BTS_CTR_CHREQ_MAX_DELAY_EXCEEDED,
        BTS_CTR_CHAN_RF_FAIL,
        BTS_CTR_CHAN_RF_FAIL_TCH,
        BTS_CTR_CHAN_RF_FAIL_SDCCH,
@@ -529,6 +530,9 @@
        /* MS/BS Power Control parameters */
        struct gsm_power_ctrl_params ms_power_ctrl;
        struct gsm_power_ctrl_params bs_power_ctrl;
+
+       /* We will ignore CHAN RQD with access delay greater than 
rach_max_delay */
+       uint8_t rach_max_delay;
 };

 #define GSM_BTS_SI2Q(bts, i)   (struct gsm48_system_information_type_2quater 
*)((bts)->si_buf[SYSINFO_TYPE_2quater][i])
diff --git a/src/osmo-bsc/abis_rsl.c b/src/osmo-bsc/abis_rsl.c
index 67e7d27..6445b6d 100644
--- a/src/osmo-bsc/abis_rsl.c
+++ b/src/osmo-bsc/abis_rsl.c
@@ -1526,6 +1526,13 @@
                return -EINVAL;
        }
        rqd->ta = rqd_hdr->data[sizeof(struct gsm48_req_ref)+2];
+       if (rqd->ta > bts->rach_max_delay) {
+               LOG_BTS(bts, DRSL, LOGL_INFO, "Ignoring CHAN RQD: Access 
Delay(%d) greater than %u\n",
+                       rqd->ta, bts->rach_max_delay);
+               
rate_ctr_inc(&bts->bts_ctrs->ctr[BTS_CTR_CHREQ_MAX_DELAY_EXCEEDED]);
+               talloc_free(rqd);
+               return -EINVAL;
+       }

        /* Determine channel request cause code */
        rqd->reason = get_reason_by_chreq(rqd->ref.ra, bts->network->neci);
diff --git a/src/osmo-bsc/bsc_vty.c b/src/osmo-bsc/bsc_vty.c
index 280fe9f..91eaee0 100644
--- a/src/osmo-bsc/bsc_vty.c
+++ b/src/osmo-bsc/bsc_vty.c
@@ -433,6 +433,8 @@
        vty_out(vty, "  RACH Max transmissions: %u%s",
                rach_max_trans_raw2val(bts->si_common.rach_control.max_trans),
                VTY_NEWLINE);
+       vty_out(vty, "  RACH Max Delay (Max Access Delay IE in CHANnel 
ReQuireD): %u%s",
+               bts->rach_max_delay, VTY_NEWLINE);
        if (bts->si_common.rach_control.cell_bar)
                vty_out(vty, "  CELL IS BARRED%s", VTY_NEWLINE);
        if (bts->dtxu != GSM48_DTX_SHALL_NOT_BE_USED)
@@ -1041,6 +1043,7 @@
        vty_out(vty, "  rach max transmission %u%s",
                rach_max_trans_raw2val(bts->si_common.rach_control.max_trans),
                VTY_NEWLINE);
+       vty_out(vty, "  rach max-delay %u%s", bts->rach_max_delay, VTY_NEWLINE);

        vty_out(vty, "  channel-description attach %u%s",
                bts->si_common.chan_desc.att, VTY_NEWLINE);
@@ -2746,6 +2749,19 @@
        return CMD_SUCCESS;
 }

+DEFUN_ATTR(cfg_bts_rach_max_delay,
+          cfg_bts_rach_max_delay_cmd,
+          "rach max-delay <1-127>",
+          RACH_STR
+          "Set the max Access Delay IE value to accept in CHANnel ReQuireD\n"
+          "Maximum Access Delay IE value to accept in CHANnel ReQuireD\n",
+          CMD_ATTR_IMMEDIATE)
+{
+       struct gsm_bts *bts = vty->index;
+       bts->rach_max_delay = atoi(argv[0]);
+       return CMD_SUCCESS;
+}
+
 #define REP_ACCH_STR "FACCH/SACCH repetition\n"

 DEFUN_USRATTR(cfg_bts_rep_dl_facch,
@@ -7668,6 +7684,7 @@
        install_element(BTS_NODE, &cfg_bts_challoc_cmd);
        install_element(BTS_NODE, &cfg_bts_rach_tx_integer_cmd);
        install_element(BTS_NODE, &cfg_bts_rach_max_trans_cmd);
+       install_element(BTS_NODE, &cfg_bts_rach_max_delay_cmd);
        install_element(BTS_NODE, &cfg_bts_chan_desc_att_cmd);
        install_element(BTS_NODE, &cfg_bts_chan_dscr_att_cmd);
        install_element(BTS_NODE, &cfg_bts_chan_desc_bs_pa_mfrms_cmd);
diff --git a/src/osmo-bsc/bts.c b/src/osmo-bsc/bts.c
index 398f26f..b5b7136 100644
--- a/src/osmo-bsc/bts.c
+++ b/src/osmo-bsc/bts.c
@@ -357,6 +357,8 @@
        bts->bs_power_ctrl = power_ctrl_params_def;
        bts->bs_power_ctrl.dir = GSM_PWR_CTRL_DIR_DL;

+       bts->rach_max_delay = 63;
+
        return bts;
 }

@@ -767,6 +769,9 @@
        [BTS_CTR_CHREQ_NO_CHANNEL] = \
                { "chreq:no_channel",
                  "Sent to MS no channel available" },
+       [BTS_CTR_CHREQ_MAX_DELAY_EXCEEDED] = \
+               { "chreq:max_delay_exceeded",
+                 "Received channel requests with greater than permitted access 
delay" },
        [BTS_CTR_CHAN_RF_FAIL] = \
                { "chan:rf_fail",
                  "Received a RF failure indication from BTS" },

--
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Gerrit-Project: osmo-bsc
Gerrit-Branch: master
Gerrit-Change-Id: Ie8987bcc0e43921bc753162b77a0efc68799b3ce
Gerrit-Change-Number: 23574
Gerrit-PatchSet: 8
Gerrit-Owner: keith <ke...@rhizomatica.org>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: fixeria <vyanits...@sysmocom.de>
Gerrit-Reviewer: laforge <lafo...@osmocom.org>
Gerrit-MessageType: merged

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