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Neels Hofmeyr nhofmeyr at sysmocom.deHi Ivan,
as I'm working towards load-based handover and incorporating your patches, I
found that most of it is concerned with libmsc. In contrast, I am currently
working on osmo-bsc, in libbsc, and would like to ask your advice.
Some parts of the patch aren't easy to understand for me, and I'd like to make
sure that I am not dismissing parts of it as non-applicable to libbsc even
though they might be important.
Since your patches were written, the code has changed. Now that we have the
separate osmo-bsc, we will need two layers of handover: intra-BSC and
inter-BSC.
Intra-BSC is a handover between two cells that are serviced by the same BSC,
and the higher layers (MSC) should not even notice that anything has happened
-- MSC has asked the BSC to service a call by BSSAP Assignment, and the BSC is
free to choose and change around the lchans it assigns to that. That is the
layer I'm currently dug into.
Inter-BSC is a handover between cells that are serviced by two different BSCs.
That seems to be the land your patch is improving. The MSC is involved and so
is MNCC.
(Both MSC and BSC levels will need their own DTAP cache, and they are by
definition completely independent -- MSC caches the DTAP coming from MNCC
during Inter-BSC handover, BSC caches DTAP from MSC during Intra-BSC handover.)
Since your patch is applied onto openbsc.git, where all of BSC and MSC are
still one osmo-nitb, I want to make sure that I sort your patch right. Do some
of its semantics apply to osmo-bsc master, even if the code changed?
The smaller patches are either already applied to osmo-bsc master, or I've
submitted them on gerrit just now:
handover_decision: Add more log messages to get more information about HO causes in logs
handover_decision: Fix condition for power budget handover attempt
handover_logic: set correct link to bts for subscriber_connection in case of moving this connection to another bts
Remaining are a small and *the* complex one:
transaction: Add new function trans_find_by_lchan
handover: Implement proper handover procedure handling at any stage of the call
Here is the last one with inline questions, I hope they are not too stupid; or
too long, it ended up being a lot to read. Thanks in advance for taking a look:
> commit f7f4dc5e3b0dd61b8322946597147baef5d0464b
> Author: Ivan Kluchnikov <kluchnikovi at gmail.com>
> Date: Wed Aug 23 18:09:50 2017 +0300
>
> handover: Implement proper handover procedure handling at any stage of the call
>
> Enhancements for each stage of handover procedure should be implemented in order to support handover at any stage of the call.
> For these purposes new in_handover state and ho_queue for call control messages was introduced for gsm_subscriber_connection.
>
> Stage 1: HO-Command is sent to MS
> gsm_subscriber_connection state should be changed to in_handover=1.
> In this state all transmission of signalling layer messages (except RR messages needed for handover procedure)
> should be suspended until resuming is indicated.
> All call control messages for connection received from network side should be buffered in ho_queue.
> All call control messages for connection received from MS side should be ignored.
> Channel mode modification procedures should be also suspended.
>
> Stage 2: HO-Detect is received from MS
> Audio path should be switched on network side.
>
> Stage 3-1: HO-Complete is received from MS
> Resumption procedure after successful handover should be performed:
> - gsm_subscriber_connection state should be changed to normal (in_handover=0).
> - all buffered call control messages (ho_queue) should be sent to MS on new lchan.
> - suspended channel mode modification procedures should be performed on new lchan.
>
> Stage 3-2: HO-Fail is received from MS
> Resumption procedure after failed handover should be performed:
> - gsm_subscriber_connection state should be changed to normal (in_handover=0).
> - all buffered call control messages (ho_queue) should be sent to MS on old lchan.
> - suspended channel mode modification procedures should be performed on old lchan.
>
> Stage 3-3: T3103 expired: Handover has failed without HO-Complete or HO-Fail
> Resumption procedure should not be performed in case of T3103 expired:
> - gsm_subscriber_connection state should be changed to normal (in_handover=0).
> - all buffered call control messages (ho_queue) should be cleaned without sending them to MS.
> - suspended channel mode modification procedures should not be performed.
>
> Change-Id: Icb9b5c35ef0c894af2ea762e539f1a9216447fb7
>
> diff --git a/openbsc/include/openbsc/bsc_api.h b/openbsc/include/openbsc/bsc_api.h
> index 3a931199..baacbeda 100644
> --- a/openbsc/include/openbsc/bsc_api.h
> +++ b/openbsc/include/openbsc/bsc_api.h
> @@ -51,5 +51,6 @@ int gsm0808_cipher_mode(struct gsm_subscriber_connection *conn, int cipher,
> int gsm0808_page(struct gsm_bts *bts, unsigned int page_group,
> unsigned int mi_len, uint8_t *mi, int chan_type);
> int gsm0808_clear(struct gsm_subscriber_connection *conn);
> +int gsm0808_ho_clear(struct gsm_subscriber_connection *conn);
>
> #endif
> diff --git a/openbsc/include/openbsc/gsm_data.h b/openbsc/include/openbsc/gsm_data.h
> index ac573c49..542b2611 100644
> --- a/openbsc/include/openbsc/gsm_data.h
> +++ b/openbsc/include/openbsc/gsm_data.h
> @@ -138,6 +138,8 @@ struct gsm_subscriber_connection {
> struct gsm_network *network;
>
> int in_release;
> + int in_handover;
> + struct llist_head ho_queue;
> struct gsm_lchan *lchan; /* BSC */
> struct gsm_lchan *ho_lchan; /* BSC */
> struct gsm_bts *bts; /* BSC */
> diff --git a/openbsc/src/libbsc/bsc_api.c b/openbsc/src/libbsc/bsc_api.c
> index 8a4c85ff..71e82d03 100644
> --- a/openbsc/src/libbsc/bsc_api.c
> +++ b/openbsc/src/libbsc/bsc_api.c
> @@ -253,11 +253,14 @@ struct gsm_subscriber_connection *bsc_subscr_con_allocate(struct gsm_lchan *lcha
> conn->bts = lchan->ts->trx->bts;
> lchan->conn = conn;
> llist_add_tail(&conn->entry, &net->subscr_conns);
> + INIT_LLIST_HEAD(&conn->ho_queue);
> return conn;
> }
>
> void bsc_subscr_con_free(struct gsm_subscriber_connection *conn)
> {
> + struct msgb *msg;
> +
> if (!conn)
> return;
>
> @@ -283,6 +286,11 @@ void bsc_subscr_con_free(struct gsm_subscriber_connection *conn)
> conn->secondary_lchan->conn = NULL;
> }
>
> + while (!llist_empty(&conn->ho_queue)) {
> + msg = msgb_dequeue(&conn->ho_queue);
> + msgb_free(msg);
> + }
> +
> llist_del(&conn->entry);
> talloc_free(conn);
> }
> @@ -747,6 +755,17 @@ int gsm0808_clear(struct gsm_subscriber_connection *conn)
> return 0;
> }
>
> +/*
> + * Release handover RF Channel.
> + */
> +int gsm0808_ho_clear(struct gsm_subscriber_connection *conn)
> +{
> + if (conn->ho_lchan)
> + bsc_clear_handover(conn, 1);
> +
> + return 0;
> +}
> +
> static void send_sapi_reject(struct gsm_subscriber_connection *conn, int link_id)
> {
> struct bsc_api *api;
> diff --git a/openbsc/src/libbsc/handover_logic.c b/openbsc/src/libbsc/handover_logic.c
> index af4e8013..b7085c34 100644
> --- a/openbsc/src/libbsc/handover_logic.c
> +++ b/openbsc/src/libbsc/handover_logic.c
> @@ -186,10 +186,17 @@ static void ho_T3103_cb(void *_ho)
> {
> struct bsc_handover *ho = _ho;
> struct gsm_network *net = ho->new_lchan->ts->trx->bts->network;
> + struct msgb *msg;
>
> DEBUGP(DHO, "HO T3103 expired\n");
> rate_ctr_inc(&net->bsc_ctrs->ctr[BSC_CTR_HANDOVER_TIMEOUT]);
>
> + ho->new_lchan->conn->in_handover = 0;
> + while (!llist_empty(&ho->new_lchan->conn->ho_queue)) {
> + msg = msgb_dequeue(&ho->new_lchan->conn->ho_queue);
> + msgb_free(msg);
> + }
> +
(Your ho_queue seems to live in libbsc, while most of the patch seems to be
concerned with libmsc. But nevermind, from jolly's patches I already have a
similar queue in osmo-bsc, and we'll probably use yours for libmsc.)
> ho->new_lchan->conn->ho_lchan = NULL;
> ho->new_lchan->conn = NULL;
> lchan_release(ho->new_lchan, 0, RSL_REL_LOCAL_END);
> @@ -214,6 +221,8 @@ static int ho_chan_activ_ack(struct gsm_lchan *new_lchan)
>
> gsm48_send_ho_cmd(ho->old_lchan, new_lchan, 0, ho->ho_ref);
>
> + new_lchan->conn->in_handover = 1;
> +
In current osmo-bsc master, we already set conn->ho_lchan before sending out
the chan activation request. I'd actually assume setting the flag only now,
after the activ ack, is a bit too late?
> /* start T3103. We can continue either with T3103 expiration,
> * 04.08 HANDOVER COMPLETE or 04.08 HANDOVER FAIL */
> ho->T3103.cb = ho_T3103_cb;
> @@ -221,7 +230,8 @@ static int ho_chan_activ_ack(struct gsm_lchan *new_lchan)
> osmo_timer_schedule(&ho->T3103, 10, 0);
>
> /* create a RTP connection */
> - if (is_ipaccess_bts(new_lchan->ts->trx->bts))
> + if (is_ipaccess_bts(new_lchan->ts->trx->bts) &&
> + new_lchan->tch_mode != GSM48_CMODE_SIGN)
> rsl_ipacc_crcx(new_lchan);
Please explain ... what case / behavior is this fixing?
Do we ever see CMODE_SIGN handovers?
Would we also need to check for GSM48_CMODE_DATA_*?
> @@ -273,6 +283,11 @@ static int ho_gsm48_ho_compl(struct gsm_lchan *new_lchan)
> if (is_e1_bts(new_lchan->conn->bts))
> switch_trau_mux(ho->old_lchan, new_lchan);
>
> + if (ho->old_lchan->conn->mncc_rtp_connect_pending) {
> + new_lchan->abis_ip.connect_port = ho->old_lchan->abis_ip.connect_port;
> + new_lchan->abis_ip.connect_ip = ho->old_lchan->abis_ip.connect_ip;
> + }
> +
So if an RTP connect to MNCC is pending, we copy the old lchan's RTP port and
IP? Which is this, the MNCC / call router side IP and port?
Why not set this at the initiation of the HO already?
> @@ -295,27 +310,9 @@ static int ho_gsm48_ho_compl(struct gsm_lchan *new_lchan)
> static int ho_gsm48_ho_fail(struct gsm_lchan *old_lchan)
> {
> struct gsm_network *net = old_lchan->ts->trx->bts->network;
> - struct bsc_handover *ho;
> - struct gsm_lchan *new_lchan;
> -
> - ho = bsc_ho_by_old_lchan(old_lchan);
> - if (!ho) {
> - LOGP(DHO, LOGL_ERROR, "unable to find HO record\n");
> - return -ENODEV;
> - }
>
> rate_ctr_inc(&net->bsc_ctrs->ctr[BSC_CTR_HANDOVER_FAILED]);
>
> - new_lchan = ho->new_lchan;
> -
> - /* release the channel and forget about it */
> - ho->new_lchan->conn->ho_lchan = NULL;
> - ho->new_lchan->conn = NULL;
> - handover_free(ho);
> -
> - lchan_release(new_lchan, 0, RSL_REL_LOCAL_END);
> -
> -
I'm puzzled by this removal. No actions during ho_fail? Is this really
intended, or just some rebase artifact?
> return 0;
> }
>
> diff --git a/openbsc/src/libmsc/gsm_04_08.c b/openbsc/src/libmsc/gsm_04_08.c
> index e5402d0a..84338d72 100644
> --- a/openbsc/src/libmsc/gsm_04_08.c
> +++ b/openbsc/src/libmsc/gsm_04_08.c
> @@ -147,6 +147,15 @@ static int gsm48_conn_sendmsg(struct msgb *msg, struct gsm_subscriber_connection
> sign_link->trx->bts->nr,
> sign_link->trx->nr, msg->lchan->ts->nr,
> gh->proto_discr, gh->msg_type);
> +
> + if (conn->in_handover) {
> + msgb_enqueue(&conn->ho_queue, msg);
> + DEBUGP(DCC, "(bts %d trx %d ts %d) Suspend message sending to MS, "
> + "active HO procedure.\n",
> + sign_link->trx->bts->nr,
> + sign_link->trx->nr, msg->lchan->ts->nr);
> + return 0;
> + }
(here DTAP handled in libmsc ends up in the ho_queue that otherwise seems to
live in libbsc ... as I said above this queue will probably move to libmsc
altogether to become part of osmo-msc master.)
> }
>
> return gsm0808_submit_dtap(conn, msg, 0, 0);
> @@ -1749,11 +1758,8 @@ static int switch_for_handover(struct gsm_lchan *old_lchan,
> struct rtp_socket *old_rs, *new_rs, *other_rs;
>
> /* Ask the new socket to send to the already known port. */
> - if (new_lchan->conn->mncc_rtp_bridge) {
> - LOGP(DHO, LOGL_DEBUG, "Forwarding RTP\n");
> - rsl_ipacc_mdcx(new_lchan,
> - old_lchan->abis_ip.connect_ip,
> - old_lchan->abis_ip.connect_port, 0);
> + if (new_lchan->ts->trx->bts->network->mncc_state) {
> + /* Audio path should be switched after receiving ho detect message.*/
> return 0;
> }
I notice that in the current head, the entire switch_for_handover() has been
dropped; it was doing libbsc lchan stuff from within libmsc. Hence we must have
added similar logic in osmo-bsc.git and completely dropped this.
I think the commit re-implementing handover in osmo-bsc is
http://git.osmocom.org/osmo-bsc/commit/?id=39c609b7c924524172ad311bdf89f92b7ccf175a
It appears that lchan->abis_ip.connect_ip and connect_port aren't used at all
in osmo-bsc master, but are still present in the struct. I'll ask others about
that.
In any case, the code base has changed substantially, and this patch hunk no
longer applies at all.
Am I interpreting this hunk correctly: it moves the ipacc_mdcx to tell the new
lchan about its RTP peer to a later stage?
In current osmo-bsc master, it seems that this ipacc_mdcx happens as soon as
the ipacc_crcx is complete, seen in osmo-bsc/src/osmo-bsc/osmo_bsc_audio.c in
handle_abisip_signal(), always using the IP:port the MSC sent us.
>
> @@ -1821,8 +1827,10 @@ static int handle_abisip_signal(unsigned int subsys, unsigned int signal,
> if (subsys != SS_ABISIP)
> return 0;
>
> + net = lchan->ts->trx->bts->network;
> +
> /* RTP bridge handling */
> - if (lchan->conn && lchan->conn->mncc_rtp_bridge)
> + if (lchan->conn && net->mncc_state)
> return tch_rtp_signal(lchan, signal);
What are the semantics here? It seems odd to move from a check of a
conn-specific state (conn->mncc_rtp_bridge) to a check of a global value
(net->mncc_state).
In any case, this is MNCC related and should not impact Intra-BSC handover,
right?
>
> /* in case we use direct BTS-to-BTS RTP */
> @@ -1851,7 +1859,6 @@ static int handle_abisip_signal(unsigned int subsys, unsigned int signal,
>
> /* check if any transactions on this lchan still have
> * a tch_recv_mncc request pending */
> - net = lchan->ts->trx->bts->network;
> llist_for_each_entry(trans, &net->trans_list, entry) {
> if (trans->conn && trans->conn->lchan == lchan && trans->tch_recv) {
> DEBUGP(DCC, "pending tch_recv_mncc request\n");
> @@ -2017,6 +2024,13 @@ static int tch_recv_mncc(struct gsm_network *net, uint32_t callref, int enable)
> switch (bts->type) {
> case GSM_BTS_TYPE_NANOBTS:
> case GSM_BTS_TYPE_OSMO_SYSMO:
> if (ipacc_rtp_direct) {
> LOGP(DCC, LOGL_ERROR, "Error: RTP proxy is disabled\n");
> return -EINVAL;
> }
> + /* RTP bridge handling */
> + if (lchan->conn && net->mncc_state) {
> + return 0;
> + }
If we have a conn and using external MNCC, don't continue at all? I'm not
following, would be nice if the comment explained why we need to drop out here.
(added some more code context manually)
> /* In case, we don't have a RTP socket to the BTS yet, the BTS
> * will not be connected to our RTP proxy and the socket will
> * not be assigned to the application interface. This method
> * will be called again, once the audio socket is created and
> * connected. */
> if (!lchan->abis_ip.rtp_socket) {
> DEBUGP(DCC, "queue tch_recv_mncc request (%d)\n", enable);
> return 0;
> }
> if (enable) {
> /* connect the TCH's to our RTP proxy */
> rc = rsl_ipacc_mdcx_to_rtpsock(lchan);
> if (rc < 0)
> return rc;
> /* assign socket to application interface */
> rtp_socket_upstream(lchan->abis_ip.rtp_socket,
> net, callref);
> } else
> rtp_socket_upstream(lchan->abis_ip.rtp_socket,
> net, 0);
> break;
>
> @@ -3325,6 +3339,41 @@ static void mncc_recv_rtp_err(struct gsm_network *net, uint32_t callref, int cmd
> return mncc_recv_rtp(net, callref, cmd, 0, 0, 0, 0);
> }
>
> +static void mncc_recv_rtp_modify(struct gsm_lchan *lchan, uint32_t callref)
This is to tell the call router that the payload type has changed, right? I've
asked in the redmine about whether/how we'd convey an RTP payload change to the
MNCC in case of an Intra-BSC handover...
https://osmocom.org/issues/1606#note-45
> +{
> + int msg_type;
> + struct gsm_network *net = lchan->ts->trx->bts->network;
> +
> + LOGP(DMNCC, LOGL_NOTICE, "%s sending pending RTP modify ind.\n",
> + gsm_lchan_name(lchan));
> +
> + switch (lchan->abis_ip.rtp_payload) {
> + case RTP_PT_GSM_FULL:
> + msg_type = GSM_TCHF_FRAME;
> + break;
> + case RTP_PT_GSM_EFR:
> + msg_type = GSM_TCHF_FRAME_EFR;
> + break;
> + case RTP_PT_GSM_HALF:
> + msg_type = GSM_TCHH_FRAME;
> + break;
> + case RTP_PT_AMR:
> + msg_type = GSM_TCH_FRAME_AMR;
> + break;
> + default:
> + LOGP(DMNCC, LOGL_ERROR, "%s unknown payload type %d\n",
> + gsm_lchan_name(lchan), lchan->abis_ip.rtp_payload);
> + msg_type = 0;
> + break;
> + }
> +
> + mncc_recv_rtp(net, callref, MNCC_RTP_MODIFY,
> + lchan->abis_ip.bound_ip,
> + lchan->abis_ip.bound_port,
> + lchan->abis_ip.rtp_payload,
> + msg_type);
> +}
> +
> static int tch_rtp_create(struct gsm_network *net, uint32_t callref)
> {
> struct gsm_bts *bts;
> @@ -3374,6 +3423,9 @@ static int tch_rtp_create(struct gsm_network *net, uint32_t callref)
> LOGP(DMNCC, LOGL_DEBUG, "RTP create: codec=%s, chan_type=%s\n",
> get_value_string(gsm48_chan_mode_names, m),
> get_value_string(gsm_chan_t_names, lchan->type));
> + if (trans->conn->in_handover) {
> + return 0;
> + }
Am I reading right: if we're doing handover, the MSC shouldn't sent another
BSSAP Assignment to the BSC; instead, the BSC level figures out another lchan
and done ... ?
> return gsm0808_assign_req(trans->conn, m,
> lchan->type != GSM_LCHAN_TCH_H);
> }
> @@ -3420,23 +3472,21 @@ static int tch_rtp_connect(struct gsm_network *net, void *arg)
> * same package!
> */
> trans->conn->mncc_rtp_connect_pending = 1;
> + if (trans->conn->in_handover) {
> + lchan->abis_ip.connect_port = rtp->port;
> + lchan->abis_ip.connect_ip = rtp->ip;
> + return 0;
> + }
> return rsl_ipacc_mdcx(lchan, rtp->ip, rtp->port, 0);
We're not telling the BTS about the call router's IP:port anymore?
Please explain...
> }
>
> static int tch_rtp_signal(struct gsm_lchan *lchan, int signal)
> {
> struct gsm_network *net;
> - struct gsm_trans *tmp, *trans = NULL;
> + struct gsm_trans *trans;
>
> net = lchan->ts->trx->bts->network;
> - llist_for_each_entry(tmp, &net->trans_list, entry) {
> - if (!tmp->conn)
> - continue;
> - if (tmp->conn->lchan != lchan && tmp->conn->ho_lchan != lchan)
> - continue;
> - trans = tmp;
> - break;
> - }
> + trans = trans_find_by_lchan(lchan);
>
> if (!trans) {
> LOGP(DMNCC, LOGL_ERROR, "%s IPA abis signal but no transaction.\n",
> @@ -3459,7 +3509,7 @@ static int tch_rtp_signal(struct gsm_lchan *lchan, int signal)
> maybe_switch_for_handover(lchan);
> break;
> case S_ABISIP_MDCX_ACK:
> - if (lchan->conn->mncc_rtp_connect_pending) {
> + if (lchan->conn->mncc_rtp_connect_pending && !lchan->conn->in_handover) {
if we're in handover, we don't need to tell MNCC that RTP got connected,
because that already happened when the call got established initially?
So mncc_rtp_connect_pending has a second meaning during handover?
> lchan->conn->mncc_rtp_connect_pending = 0;
> LOGP(DMNCC, LOGL_NOTICE, "%s sending pending RTP connect ind.\n",
> gsm_lchan_name(lchan));
> mncc_recv_rtp_sock(net, trans, MNCC_RTP_CONNECT);
> }
> break;
> @@ -3471,6 +3521,134 @@ static int tch_rtp_signal(struct gsm_lchan *lchan, int signal)
> return 0;
> }
>
> +static void ho_queue_clean(struct gsm_subscriber_connection *conn)
> +{
> + struct msgb *msg;
> + while (!llist_empty(&conn->ho_queue)) {
> + msg = msgb_dequeue(&conn->ho_queue);
> + msgb_free(msg);
> + }
> +}
> +
> +static void ho_resumption(struct gsm_lchan *lchan, struct gsm_trans *trans)
> +{
> + struct msgb *msg;
> + enum gsm48_chan_mode m;
> +
> + while (!llist_empty(&lchan->conn->ho_queue)) {
> + msg = msgb_dequeue(&lchan->conn->ho_queue);
> + gsm48_conn_sendmsg(msg, lchan->conn, trans);
> + }
> +
> + if (trans->conn->mncc_rtp_create_pending &&
> + lchan->tch_mode == GSM48_CMODE_SIGN) {
> + m = mncc_codec_for_mode(lchan->type);
> + gsm0808_assign_req(lchan->conn, m, lchan->type != GSM_LCHAN_TCH_H);
Wait, now we *do* send a BSSAP Assignment after all?
(excuse if I'm being noob, I'm still finding my way through handover in general)
shouldn't we rather dequeue the cached DTAP after this instead of before?
> + }
> +
> + if (trans->conn->mncc_rtp_connect_pending) {
> + rsl_ipacc_mdcx(lchan, lchan->abis_ip.connect_ip, lchan->abis_ip.connect_port, 0);
> + }
> +}
> +
> +static int ho_complete(struct gsm_lchan *new_lchan)
> +{
> + struct gsm_trans *trans;
> +
> + new_lchan->conn->in_handover = 0;
> + trans = trans_find_by_lchan(new_lchan);
> + if (!trans) {
> + LOGP(DHO, LOGL_ERROR, "%s HO detected, but no transaction for new_lchan.\n",
> + gsm_lchan_name(new_lchan));
> + ho_queue_clean(new_lchan->conn);
> + return 0;
> + }
> +
> + ho_resumption(new_lchan, trans);
> + return 0;
> +}
> +
> +static int ho_fail(struct gsm_lchan *old_lchan)
> +{
> + struct gsm_trans *trans;
> +
> + old_lchan->conn->in_handover = 0;
> + trans = trans_find_by_lchan(old_lchan);
> + if (trans)
> + ho_resumption(old_lchan, trans);
> + else {
> + LOGP(DHO, LOGL_ERROR, "%s HO fail, but no transaction for old_lchan.\n",
> + gsm_lchan_name(old_lchan));
> + ho_queue_clean(old_lchan->conn);
> + }
> +
> + gsm0808_ho_clear(old_lchan->conn);
> + return 0;
> +}
> +
> +static int ho_detect(struct gsm_lchan *new_lchan)
> +{
> + struct gsm_trans *trans;
> + struct gsm_lchan *old_lchan;
> +
> + trans = trans_find_by_lchan(new_lchan);
> +
> + if (!trans) {
> + LOGP(DHO, LOGL_ERROR, "%s HO detected, but no transaction for new_lchan"
> + " with enabled tch_recv.\n",
> + gsm_lchan_name(new_lchan));
> + return 0;
> + }
> +
> + if (!new_lchan->conn->mncc_rtp_bridge) {
> + LOGP(DHO, LOGL_ERROR, "%s HO detected, but connection not in mncc_rtp_bridge mode.\n",
> + gsm_lchan_name(new_lchan));
> + return 0;
> + }
> +
> + old_lchan = bsc_handover_pending(new_lchan);
> + if (!old_lchan) {
> + LOGP(DHO, LOGL_ERROR, "%s HO detected, but no old_lchan for handover.\n",
> + gsm_lchan_name(new_lchan));
> + return 0;
> + }
> +
> + LOGP(DHO, LOGL_DEBUG, "HO detected, forwarding RTP\n");
> + rsl_ipacc_mdcx(new_lchan,
> + old_lchan->abis_ip.connect_ip,
> + old_lchan->abis_ip.connect_port, 0);
> +
> + mncc_recv_rtp_modify(new_lchan, trans->callref);
> +
> + return 0;
> +}
> +
> +/* some other part of the code sends us a signal */
> +static int handle_lchan_signal(unsigned int subsys, unsigned int signal,
> + void *handler_data, void *signal_data)
> +{
> + struct lchan_signal_data *lchan_data;
> + struct gsm_lchan *lchan;
> +
> + lchan_data = signal_data;
> + switch (subsys) {
> + case SS_LCHAN:
> + lchan = lchan_data->lchan;
> + if (!lchan->conn)
> + return 0;
> + switch (signal) {
> + case S_LCHAN_HANDOVER_DETECT:
> + return ho_detect(lchan);
> + case S_LCHAN_HANDOVER_COMPL:
> + return ho_complete(lchan);
> + case S_LCHAN_HANDOVER_FAIL:
> + return ho_fail(lchan);
> + }
> + break;
> + }
> +
> + return 0;
> +}
>
> static struct downstate {
> uint32_t states;
> @@ -3853,6 +4031,11 @@ static int gsm0408_rcv_cc(struct gsm_subscriber_connection *conn, struct msgb *m
> gsm48_cc_msg_name(msg_type), trans?(trans->cc.state):0,
> gsm48_cc_state_name(trans?(trans->cc.state):0));
>
> + if (conn->in_handover) {
> + DEBUGP(DCC, "Message unhandled, handover procedure.\n");
> + return 0;
> + }
> +
If in handover, drop all CC on the floor?
How about a call release, i.e. I hang up while I'm coincidentally being
handovered?
> /* Create transaction */
> if (!trans) {
> DEBUGP(DCC, "Unknown transaction ID %x, "
>
>
>
Thanks again!
~N
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