Cellular Network Infrastructure

I submitted a WIP patch with might solve the problem, but I am not 100% sure:

https://gerrit.osmocom.org/c/osmo-bsc/+/32090 nm_channel_fsm: do not send SET CHAN ATTR before SET BTS ATTR [WIP]

keith please give it a try. Thanks!

Relevant code in osmo-bts:

static int oml_rx_set_bts_attr(struct gsm_bts *bts, struct msgb *msg)
    /* 9.4.9 BSIC */
    if (TLVP_PRES_LEN(&tp, NM_ATT_BSIC, 1))
        bts->bsic = *TLVP_VAL(&tp, NM_ATT_BSIC);

#define BTS_TSC(bts) BSIC2BCC((bts)->bsic)

        
static int oml_rx_set_chan_attr(struct gsm_bts_trx_ts *ts, struct msgb *msg)
{
    /* 9.4.60 TSC */
    if (TLVP_PRES_LEN(&tp, NM_ATT_TSC, 1)) {
        ts->tsc_oml = ts->tsc = *TLVP_VAL(&tp, NM_ATT_TSC);
        if (ts->tsc != BTS_TSC(bts) &&
            !osmo_bts_has_feature(bts->features, BTS_FEAT_MULTI_TSC)) {
            LOGPFOH(DOML, LOGL_ERROR, foh, "SET CHAN ATTR: this BTS model does not " 
                "support TSC %u != BSIC-BCC %u\n", ts->tsc, BTS_TSC(bts));
            talloc_free(tp_merged);
            return oml_fom_ack_nack(msg, NM_NACK_PARAM_RANGE);
        }
    } else {
        /* If there is no TSC specified, use the BCC */
        ts->tsc_oml = ts->tsc = BTS_TSC(bts);
    }
    LOGPFOH(DOML, LOGL_INFO, foh, "SET CHAN ATTR (TSC=%u pchan=%s",
        ts->tsc, gsm_pchan_name(ts->pchan));
    if (ts->hopping.enabled)
        LOGPC(DOML, LOGL_INFO, " hsn=%u maio=%u chan_num=%u",
              ts->hopping.hsn, ts->hopping.maio, ts->hopping.arfcn_num);
    LOGPC(DOML, LOGL_INFO, ")\n");

    /* call into BTS driver to apply new attributes to hardware */
    return bts_model_apply_oml(bts, msg, tp_merged, NM_OC_CHANNEL, ts);

It might be some days, or weeks until I get around to testing this in the high latency/VPN scenario I described.