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gsm/lapdm: Prevent LAPD tx_queue from filling up in polling mode 

If LAPDm receives an I-Frame while there already is an I-Frame in the
tx_queue the code generates an additional RR (to acknowledge the
received I-Frame). Instead, N(R) of the I-Frame in the tx_queue should
be updated to ACK the data.
This commit is contained in:
Daniel Willmann 2014-03-20 19:24:48 +01:00 committed by Daniel Willmann
parent 09129352f9
commit 3dc4e16786
6 changed files with 39 additions and 17 deletions
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2
TODO-RELEASE Normal file
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@ -0,0 +1,2 @@
#library what description / commit summary line
libosmogsm abi-change Prevent LAPD tx_queue from filling up in polling mode

1
include/osmocom/gsm/lapd_core.h
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@ -125,6 +125,7 @@ struct lapd_datalink {
int (*send_dlsap)(struct osmo_dlsap_prim *dp,
struct lapd_msg_ctx *lctx);
int (*send_ph_data_req)(struct lapd_msg_ctx *lctx, struct msgb *msg);
int (*update_pending_frames)(struct lapd_msg_ctx *lctx);
struct {
/*! \brief filled-in once we set the lapd_mode above */
struct lapd_cr_ent loc2rem;

6
src/gsm/lapd_core.c
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@ -1607,6 +1607,12 @@ static int lapd_rx_i(struct msgb *msg, struct lapd_msg_ctx *lctx)
if (!dl->own_busy) {
/* NOTE: V(R) is already set above */
rc = lapd_send_i(lctx, __LINE__);
/* if update_pending_iframe returns 0 it updated
* the lapd header of an iframe in the tx queue */
if (rc && dl->update_pending_frames)
rc = dl->update_pending_frames(lctx);
if (rc) {
LOGP(DLLAPD, LOGL_INFO, "we are not busy and "
"have no pending data, send RR\n");

21
src/gsm/lapdm.c
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@ -114,6 +114,7 @@ enum lapdm_format {
static int lapdm_send_ph_data_req(struct lapd_msg_ctx *lctx, struct msgb *msg);
static int send_rslms_dlsap(struct osmo_dlsap_prim *dp,
struct lapd_msg_ctx *lctx);
static int update_pending_frames(struct lapd_msg_ctx *lctx);
static void lapdm_dl_init(struct lapdm_datalink *dl,
struct lapdm_entity *entity, int t200)
@ -124,6 +125,7 @@ static void lapdm_dl_init(struct lapdm_datalink *dl,
dl->dl.reestablish = 0; /* GSM uses no reestablish */
dl->dl.send_ph_data_req = lapdm_send_ph_data_req;
dl->dl.send_dlsap = send_rslms_dlsap;
dl->dl.update_pending_frames = update_pending_frames;
dl->dl.n200_est_rel = N200_EST_REL;
dl->dl.n200 = N200;
dl->dl.t203_sec = 0; dl->dl.t203_usec = 0;
@ -488,6 +490,25 @@ static int lapdm_send_ph_data_req(struct lapd_msg_ctx *lctx, struct msgb *msg)
23);
}
static int update_pending_frames(struct lapd_msg_ctx *lctx)
{
struct lapd_datalink *dl = lctx->dl;
struct msgb *msg;
int rc = -1;
llist_for_each_entry(msg, &dl->tx_queue, list) {
if (LAPDm_CTRL_is_I(msg->l2h[1])) {
msg->l2h[1] = LAPDm_CTRL_I(dl->v_recv, LAPDm_CTRL_I_Ns(msg->l2h[1]),
LAPDm_CTRL_PF_BIT(msg->l2h[1]));
rc = 0;
} else if (LAPDm_CTRL_is_S(msg->l2h[1])) {
LOGP(DLLAPD, LOGL_ERROR, "Supervisory frame in queue, this shouldn't happen\n");
}
}
return rc;
}
/* input into layer2 (from layer 1) */
static int l2_ph_data_ind(struct msgb *msg, struct lapdm_entity *le,
uint8_t chan_nr, uint8_t link_id)

12
tests/lapd/lapd_test.c
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@ -621,17 +621,13 @@ const uint8_t gprs_susp[] = {
0xd2, 0x6f, 0x09, 0xf1, 0x07, 0x00, 0x01, 0x00, 0x02
};
const uint8_t gprs_susp_ack[] = {
0x01, 0x41, 0x01
};
const uint8_t cipher_cmd[] = {
0x06, 0x35, 0x01
};
/* The cipher command we send to the MS */
/* The cipher command we send to the MS after updating our N(R) */
const uint8_t cipher_cmd_out[] = {
0x03, 0x20, 0x0d, 0x06, 0x35, 0x01
0x03, 0x40, 0x0d, 0x06, 0x35, 0x01
};
uint8_t cipher_compl[] = {
@ -730,7 +726,7 @@ static void test_lapdm_desync()
rc = dequeue_prim(&bts_to_ms_channel.lapdm_dcch, &pp, "DCCH");
CHECK_RC(rc);
OSMO_ASSERT(memcmp(pp.oph.msg->l2h, gprs_susp_ack, ARRAY_SIZE(gprs_susp_ack)) == 0);
OSMO_ASSERT(memcmp(pp.oph.msg->l2h, cipher_compl_ack, ARRAY_SIZE(cipher_compl_ack)) == 0);
printf("\nEstablishing SAPI=3\n");
send_sabm(&bts_to_ms_channel, 3, NULL, 0);
@ -746,7 +742,7 @@ static void test_lapdm_desync()
rc = dequeue_prim(&bts_to_ms_channel.lapdm_dcch, &pp, "DCCH");
CHECK_RC(rc);
OSMO_ASSERT(memcmp(pp.oph.msg->l2h, cipher_compl_ack, ARRAY_SIZE(cipher_compl_ack)) == 0);
OSMO_ASSERT(memcmp(pp.oph.msg->l2h, cp_data_1_ack, ARRAY_SIZE(cp_data_1_ack)) == 0);
/* clean up */
lapdm_channel_exit(&bts_to_ms_channel);

14
tests/lapd/lapd_test.ok
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@ -68,27 +68,24 @@ Sending GPRS Suspend Request
bts_to_ms_dummy_tx_cb: MS->BTS(us) message 22
Dumping queue:
00 00 17 [L2]> 03 20 0d [L3]> 06 35 01
00 00 17 [L2]> 01 41 01
00 00 17 [L2]> 03 40 0d [L3]> 06 35 01
Took message from DCCH queue: L2 header size 3, L3 size 20, SAP 0x1000000, 0/0, Link 0x00
Message: [L2]> 03 20 0d [L3]> 06 35 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
Message: [L2]> 03 40 0d [L3]> 06 35 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
Sending Cipher Mode Complete
bts_to_ms_dummy_tx_cb: MS->BTS(us) message 11
Dumping queue:
00 00 17 [L2]> 01 41 01
00 00 17 [L2]> 01 61 01
Took message from DCCH queue: L2 header size 23, L3 size 0, SAP 0x1000000, 0/0, Link 0x00
Message: [L2]> 01 41 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
Message: [L2]> 01 61 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
Establishing SAPI=3
bts_to_ms_dummy_tx_cb: MS->BTS(us) message 6
Dumping queue:
00 00 17 [L2]> 01 61 01
Took message from DCCH queue: L2 header size 3, L3 size 20, SAP 0x1000000, 0/0, Link 0x03
Message: [L2]> 0d 73 01 [L3]> 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
@ -96,8 +93,7 @@ Message: [L2]> 0d 73 01 [L3]> 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
Sending CP-DATA
Dumping queue:
00 00 17 [L2]> 01 61 01
Took message from DCCH queue: L2 header size 23, L3 size 0, SAP 0x1000000, 0/0, Link 0x00
Message: [L2]> 01 61 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
Took message from DCCH queue: L2 header size 23, L3 size 0, SAP 0x1000000, 0/0, Link 0x03
Message: [L2]> 0d 21 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
Success.