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osmo-el2tpd
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lapd_switch_altc: allow to switch between timeslot and superchannel 

a special crafted packet can switch between the modes. The packet look like
0x23004200 as magic and 1byte as value (0 = timeslot, 1 = superchannel)
This commit is contained in:
Alexander Couzens 2016-11-11 16:17:54 +01:00
parent 388a33ca9c
commit 95f8ae04bd
1 changed files with 38 additions and 0 deletions
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38
siu/l2tp/l2tpd_lapd.c
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@ -205,6 +205,38 @@ int lapd_ehdlc_to_lapd(struct l2tpd_instance *l2i, struct l2tpd_session *l2s, st
return 0;
}
/*!
* \brief lapd_switch_altc try to parse the msg, if valid it change the ALTC type to the requested
* \param l2i
* \param msg
* \return 1 if valid and parsed, 0 if should passthrough to the siu
*/
int lapd_switch_altc(struct l2tpd_instance *l2i, struct msgb *msg)
{
struct l2tpd_session *l2s = msg->dst;
/* magic 0x23004200 (4 byte) + value (1 byte) */
if (msgb_length(msg) != (4 + 1))
return 0;
/* skip lapd header */
if (osmo_load32be(msgb_data(msg)) != 0x23004200)
return 0;
/* pull data pointer to next object */
msgb_pull(msg, 4);
if (msgb_pull_u8(msg)) {
LOGP(DL2TP, LOGL_INFO, "ALTCRQ -> SuperChannel requested\n");
l2tp_tx_altc_rq_superchannel(l2s->connection);
} else {
LOGP(DL2TP, LOGL_INFO, "ALTCRQ -> TimeSlot requested\n");
l2tp_tx_altc_rq_timeslot(l2s->connection);
}
return 1;
}
/*!
* \brief rsl_oml_cb called when data arrived on the unix socket
@ -243,6 +275,12 @@ int unix_rsl_oml_cb(struct osmo_fd *fd)
return 1;
}
/* check if this packet is for us */
if (lapd_switch_altc(l2i, msg)) {
msgb_free(msg);
return 0;
}
rc = lapd_lapd_to_ehdlc(l2i, msg);
if (rc) {
LOGP(DL2TP, LOGL_NOTICE, "lapd_to_ehlc returned != 0: %d.\n", rc);