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-rw-r--r--src/libabis/input/lapd.c710
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diff --git a/src/libabis/input/lapd.c b/src/libabis/input/lapd.c
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+/* OpenBSC minimal LAPD implementation */
+
+/* (C) 2009 by oystein@homelien.no
+ * (C) 2009 by Holger Hans Peter Freyther <zecke@selfish.org>
+ * (C) 2010 by Digium and Matthew Fredrickson <creslin@digium.com>
+ * (C) 2011 by Harald Welte <laforge@gnumonks.org>
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+/* TODO:
+ * detect RR timeout and set SAP state back to SABM_RETRANSMIT
+ * use of value_string
+ * further code cleanup (spaghetti)
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+#include <errno.h>
+
+#include "lapd.h"
+
+#include <osmocore/linuxlist.h>
+#include <osmocore/talloc.h>
+#include <osmocore/msgb.h>
+#include <osmocore/timer.h>
+#include <openbsc/debug.h>
+
+#define SABM_INTERVAL 0, 300000
+
+typedef enum {
+ LAPD_TEI_NONE = 0,
+ LAPD_TEI_ASSIGNED,
+ LAPD_TEI_ACTIVE,
+} lapd_tei_state;
+
+const char *lapd_tei_states[] = {
+ "NONE",
+ "ASSIGNED",
+ "ACTIVE",
+};
+
+typedef enum {
+ LAPD_TYPE_NONE = 0,
+
+ LAPD_TYPE_I,
+ LAPD_TYPE_S,
+ LAPD_TYPE_U,
+} lapd_msg_type;
+
+typedef enum {
+ /* commands/responses */
+ LAPD_CMD_NONE = 0,
+
+ LAPD_CMD_I,
+ LAPD_CMD_RR,
+ LAPD_CMD_RNR,
+ LAPD_CMD_REJ,
+
+ LAPD_CMD_SABME,
+ LAPD_CMD_DM,
+ LAPD_CMD_UI,
+ LAPD_CMD_DISC,
+ LAPD_CMD_UA,
+ LAPD_CMD_FRMR,
+ LAPD_CMD_XID,
+} lapd_cmd_type;
+
+const char *lapd_cmd_types[] = {
+ "NONE",
+
+ "I",
+ "RR",
+ "RNR",
+ "REJ",
+
+ "SABME",
+ "DM",
+ "UI",
+ "DISC",
+ "UA",
+ "FRMR",
+ "XID",
+
+};
+
+enum lapd_sap_state {
+ SAP_STATE_INACTIVE,
+ SAP_STATE_SABM_RETRANS,
+ SAP_STATE_ACTIVE,
+};
+
+const char *lapd_sap_states[] = {
+ "INACTIVE",
+ "SABM_RETRANS",
+ "ACTIVE",
+};
+
+const char *lapd_msg_types = "?ISU";
+
+/* structure representing an allocated TEI within a LAPD instance */
+struct lapd_tei {
+ struct llist_head list;
+ struct lapd_instance *li;
+ uint8_t tei;
+ lapd_tei_state state;
+
+ struct llist_head sap_list;
+};
+
+/* Structure representing a SAP within a TEI. We use this for TE-mode to
+ * re-transmit SABM */
+struct lapd_sap {
+ struct llist_head list;
+ struct lapd_tei *tei;
+ uint8_t sapi;
+ enum lapd_sap_state state;
+
+ /* A valid N(R) value is one that is in the range V(A) ≤ N(R) ≤ V(S). */
+ int vs; /* next to be transmitted */
+ int va; /* last acked by peer */
+ int vr; /* next expected to be received */
+
+ struct timer_list sabme_timer; /* timer to re-transmit SABM message */
+};
+
+/* 3.5.2.2 Send state variable V(S)
+ * Each point-to-point data link connection endpoint shall have an associated V(S) when using I frame
+ * commands. V(S) denotes the sequence number of the next I frame to be transmitted. The V(S) can
+ * take on the value 0 through n minus 1. The value of V(S) shall be incremented by 1 with each
+ * successive I frame transmission, and shall not exceed V(A) by more than the maximum number of
+ * outstanding I frames k. The value of k may be in the range of 1 ≤ k ≤ 127.
+ *
+ * 3.5.2.3 Acknowledge state variable V(A)
+ * Each point-to-point data link connection endpoint shall have an associated V(A) when using I frame
+ * commands and supervisory frame commands/responses. V(A) identifies the last I frame that has been
+ * acknowledged by its peer [V(A) − 1 equals the N(S) of the last acknowledged I frame]. V(A) can
+ * take on the value 0 through n minus 1. The value of V(A) shall be updated by the valid N(R) values
+ * received from its peer (see 3.5.2.6). A valid N(R) value is one that is in the range V(A) ≤ N(R) ≤
+ * V(S).
+ *
+ * 3.5.2.5 Receive state variable V(R)
+ * Each point-to-point data link connection endpoint shall have an associated V(R) when using I frame
+ * commands and supervisory frame commands/responses. V(R) denotes the sequence number of the
+ * next in-sequence I frame expected to be received. V(R) can take on the value 0 through n minus 1.
+ * The value of V(R) shall be incremented by one with the receipt of an error-free, in-sequence I frame
+ * whose N(S) equals V(R).
+ */
+#define LAPD_NS(sap) (sap->vs)
+#define LAPD_NR(sap) (sap->vr)
+
+/* 3.5.2.4 Send sequence number N(S)
+ * Only I frames contain N(S), the send sequence number of transmitted I frames. At the time that an in-
+ * sequence I frame is designated for transmission, the value of N(S) is set equal to V(S).
+ *
+ * 3.5.2.6 Receive sequence number N(R)
+ * All I frames and supervisory frames contain N(R), the expected send sequence number of the next
+ * received I frame. At the time that a frame of the above types is designated for transmission, the value
+ * of N(R) is set equal to V(R). N(R) indicates that the data link layer entity transmitting the N(R) has
+ * correctly received all I frames numbered up to and including N(R) − 1.
+ */
+
+/* Resolve TEI structure from given numeric TEI */
+static struct lapd_tei *teip_from_tei(struct lapd_instance *li, uint8_t tei)
+{
+ struct lapd_tei *lt;
+
+ llist_for_each_entry(lt, &li->tei_list, list) {
+ if (lt->tei == tei)
+ return lt;
+ }
+ return NULL;
+};
+
+static void lapd_tei_set_state(struct lapd_tei *teip, int newstate)
+{
+ DEBUGP(DMI, "state change on TEI %d: %s -> %s\n", teip->tei,
+ lapd_tei_states[teip->state], lapd_tei_states[newstate]);
+ teip->state = newstate;
+};
+
+/* Allocate a new TEI */
+struct lapd_tei *lapd_tei_alloc(struct lapd_instance *li, uint8_t tei)
+{
+ struct lapd_tei *teip;
+
+ teip = talloc_zero(li, struct lapd_tei);
+ if (!teip)
+ return NULL;
+
+ teip->li = li;
+ teip->tei = tei;
+ llist_add(&teip->list, &li->tei_list);
+ INIT_LLIST_HEAD(&teip->sap_list);
+
+ lapd_tei_set_state(teip, LAPD_TEI_ASSIGNED);
+
+ return teip;
+}
+
+/* Find a SAP within a given TEI */
+static struct lapd_sap *lapd_sap_find(struct lapd_tei *teip, uint8_t sapi)
+{
+ struct lapd_sap *sap;
+
+ llist_for_each_entry(sap, &teip->sap_list, list) {
+ if (sap->sapi == sapi)
+ return sap;
+ }
+
+ return NULL;
+}
+
+static void sabme_timer_cb(void *_sap);
+
+/* Allocate a new SAP within a given TEI */
+static struct lapd_sap *lapd_sap_alloc(struct lapd_tei *teip, uint8_t sapi)
+{
+ struct lapd_sap *sap = talloc_zero(teip, struct lapd_sap);
+
+ LOGP(DMI, LOGL_INFO, "Allocating SAP for SAPI=%u / TEI=%u\n",
+ sapi, teip->tei);
+
+ sap->sapi = sapi;
+ sap->tei = teip;
+ sap->sabme_timer.cb = &sabme_timer_cb;
+ sap->sabme_timer.data = sap;
+
+ llist_add(&sap->list, &teip->sap_list);
+
+ return sap;
+}
+
+static void lapd_sap_set_state(struct lapd_tei *teip, uint8_t sapi,
+ enum lapd_sap_state newstate)
+{
+ struct lapd_sap *sap = lapd_sap_find(teip, sapi);
+ if (!sap)
+ return;
+
+ DEBUGP(DMI, "state change on TEI %u / SAPI %u: %s -> %s\n", teip->tei,
+ sapi, lapd_sap_states[sap->state], lapd_sap_states[newstate]);
+ switch (sap->state) {
+ case SAP_STATE_SABM_RETRANS:
+ if (newstate != SAP_STATE_SABM_RETRANS)
+ bsc_del_timer(&sap->sabme_timer);
+ break;
+ default:
+ if (newstate == SAP_STATE_SABM_RETRANS)
+ bsc_schedule_timer(&sap->sabme_timer, SABM_INTERVAL);
+ break;
+ }
+
+ sap->state = newstate;
+};
+
+/* Input function into TEI manager */
+static void lapd_tei_receive(struct lapd_instance *li, uint8_t *data, int len)
+{
+ uint8_t entity = data[0];
+ uint8_t ref = data[1];
+ uint8_t mt = data[3];
+ uint8_t action = data[4] >> 1;
+ uint8_t e = data[4] & 1;
+ uint8_t resp[8];
+ struct lapd_tei *teip;
+
+ DEBUGP(DMI, "TEIMGR: entity %x, ref %x, mt %x, action %x, e %x\n", entity, ref, mt, action, e);
+
+ switch (mt) {
+ case 0x01: /* IDENTITY REQUEST */
+ DEBUGP(DMI, "TEIMGR: identity request for TEI %u\n", action);
+
+ teip = teip_from_tei(li, action);
+ if (!teip) {
+ LOGP(DMI, LOGL_INFO, "TEI MGR: New TEI %u\n", action);
+ lapd_tei_alloc(li, action);
+ }
+
+ /* Send ACCEPT */
+ memmove(resp, "\xfe\xff\x03\x0f\x00\x00\x02\x00", 8);
+ resp[7] = (action << 1) | 1;
+ li->transmit_cb(resp, 8, li->cbdata);
+
+ if (teip->state == LAPD_TEI_NONE)
+ lapd_tei_set_state(teip, LAPD_TEI_ASSIGNED);
+ break;
+ default:
+ LOGP(DMI, LOGL_NOTICE, "TEIMGR: unknown mt %x action %x\n",
+ mt, action);
+ break;
+ };
+};
+
+/* General input function for any data received for this LAPD instance */
+uint8_t *lapd_receive(struct lapd_instance *li, uint8_t * data, unsigned int len,
+ int *ilen, lapd_mph_type *prim)
+{
+ uint8_t sapi, cr, tei, command;
+ int pf, ns, nr;
+ uint8_t *contents;
+ struct lapd_tei *teip;
+ struct lapd_sap *sap;
+
+ uint8_t resp[8];
+ int l = 0;
+
+ *ilen = 0;
+ *prim = 0;
+
+ if (len < 2) {
+ DEBUGP(DMI, "len %d < 2\n", len);
+ return NULL;
+ };
+
+ if ((data[0] & 1) != 0 || (data[1] & 1) != 1) {
+ DEBUGP(DMI, "address field %x/%x not well formed\n", data[0],
+ data[1]);
+ return NULL;
+ };
+
+ sapi = data[0] >> 2;
+ cr = (data[0] >> 1) & 1;
+ tei = data[1] >> 1;
+ command = li->network_side ^ cr;
+ //DEBUGP(DMI, " address sapi %x tei %d cmd %d cr %d\n", sapi, tei, command, cr);
+
+ if (len < 3) {
+ DEBUGP(DMI, "len %d < 3\n", len);
+ return NULL;
+ };
+
+ lapd_msg_type typ = 0;
+ lapd_cmd_type cmd = 0;
+ pf = -1;
+ ns = -1;
+ nr = -1;
+ if ((data[2] & 1) == 0) {
+ typ = LAPD_TYPE_I;
+ assert(len >= 4);
+ ns = data[2] >> 1;
+ nr = data[3] >> 1;
+ pf = data[3] & 1;
+ cmd = LAPD_CMD_I;
+ } else if ((data[2] & 3) == 1) {
+ typ = LAPD_TYPE_S;
+ assert(len >= 4);
+ nr = data[3] >> 1;
+ pf = data[3] & 1;
+ switch (data[2]) {
+ case 0x1:
+ cmd = LAPD_CMD_RR;
+ break;
+ case 0x5:
+ cmd = LAPD_CMD_RNR;
+ break;
+ case 0x9:
+ cmd = LAPD_CMD_REJ;
+ break;
+ default:
+ LOGP(DMI, LOGL_ERROR, "unknown LAPD S cmd %x\n", data[2]);
+ return NULL;
+ };
+ } else if ((data[2] & 3) == 3) {
+ typ = LAPD_TYPE_U;
+ pf = (data[2] >> 4) & 1;
+ int val = data[2] & ~(1 << 4);
+ switch (val) {
+ case 0x6f:
+ cmd = LAPD_CMD_SABME;
+ break;
+ case 0x0f:
+ cmd = LAPD_CMD_DM;
+ break;
+ case 0x03:
+ cmd = LAPD_CMD_UI;
+ break;
+ case 0x43:
+ cmd = LAPD_CMD_DISC;
+ break;
+ case 0x63:
+ cmd = LAPD_CMD_UA;
+ break;
+ case 0x87:
+ cmd = LAPD_CMD_FRMR;
+ break;
+ case 0xaf:
+ cmd = LAPD_CMD_XID;
+ break;
+
+ default:
+ LOGP(DMI, LOGL_ERROR, "unknown U cmd %x "
+ "(pf %x data %x)\n", val, pf, data[2]);
+ return NULL;
+ };
+ };
+
+ contents = &data[4];
+ if (typ == LAPD_TYPE_U)
+ contents--;
+ *ilen = len - (contents - data);
+
+ if (tei == 127)
+ lapd_tei_receive(li, contents, *ilen);
+
+ teip = teip_from_tei(li, tei);
+ if (!teip) {
+ LOGP(DMI, LOGL_NOTICE, "Unknown TEI %u\n", tei);
+ return NULL;
+ }
+
+ sap = lapd_sap_find(teip, sapi);
+ if (!sap) {
+ LOGP(DMI, LOGL_INFO, "No SAP for TEI=%u / SAPI=%u, "
+ "allocating\n", tei, sapi);
+ sap = lapd_sap_alloc(teip, sapi);
+ }
+
+ DEBUGP(DMI, "<- %c %s sapi %x tei %3d cmd %x pf %x ns %3d nr %3d "
+ "ilen %d teip %p vs %d va %d vr %d len %d\n",
+ lapd_msg_types[typ], lapd_cmd_types[cmd], sapi, tei, command, pf,
+ ns, nr, *ilen, teip, sap->vs, sap->va, sap->vr, len);
+
+ switch (cmd) {
+ case LAPD_CMD_I:
+ if (ns != sap->vr) {
+ DEBUGP(DMI, "ns %d != vr %d\n", ns, sap->vr);
+ if (ns == ((sap->vr - 1) & 0x7f)) {
+ DEBUGP(DMI, "DOUBLE FRAME, ignoring\n");
+ cmd = 0; // ignore
+ } else {
+ assert(0);
+ };
+ } else {
+ //printf("IN SEQUENCE\n");
+ sap->vr = (ns + 1) & 0x7f; // FIXME: hack!
+ };
+
+ break;
+ case LAPD_CMD_UI:
+ break;
+ case LAPD_CMD_SABME:
+ sap->vs = 0;
+ sap->vr = 0;
+ sap->va = 0;
+
+ // ua
+ resp[l++] = data[0];
+ resp[l++] = (tei << 1) | 1;
+ resp[l++] = 0x73;
+ li->transmit_cb(resp, l, li->cbdata);
+ if (teip->state != LAPD_TEI_ACTIVE) {
+ if (teip->state == LAPD_TEI_ASSIGNED) {
+ lapd_tei_set_state(teip,
+ LAPD_TEI_ACTIVE);
+ //printf("ASSIGNED and ACTIVE\n");
+ } else {
+#if 0
+ DEBUGP(DMI, "rr in strange state, send rej\n");
+
+ // rej
+ resp[l++] = (sap-> sapi << 2) | (li->network_side ? 0 : 2);
+ resp[l++] = (tei << 1) | 1;
+ resp[l++] = 0x09; //rej
+ resp[l++] = ((sap->vr + 1) << 1) | 0;
+ li->transmit_cb(resp, l, li->cbdata);
+ pf = 0; // dont reply
+#endif
+ };
+ };
+
+ *prim = LAPD_MPH_ACTIVATE_IND;
+ break;
+ case LAPD_CMD_UA:
+ sap->vs = 0;
+ sap->vr = 0;
+ sap->va = 0;
+ lapd_tei_set_state(teip, LAPD_TEI_ACTIVE);
+ lapd_sap_set_state(teip, sapi, SAP_STATE_ACTIVE);
+ *prim = LAPD_MPH_ACTIVATE_IND;
+ break;
+ case LAPD_CMD_RR:
+ sap->va = (nr & 0x7f);
+#if 0
+ if (teip->state != LAPD_TEI_ACTIVE) {
+ if (teip->state == LAPD_TEI_ASSIGNED) {
+ lapd_tei_set_state(teip, LAPD_TEI_ACTIVE);
+ *prim = LAPD_MPH_ACTIVATE_IND;
+ //printf("ASSIGNED and ACTIVE\n");
+ } else {
+#if 0
+ DEBUGP(DMI, "rr in strange " "state, send rej\n");
+
+ // rej
+ resp[l++] = (sap-> sapi << 2) | (li->network_side ? 0 : 2);
+ resp[l++] = (tei << 1) | 1;
+ resp[l++] = 0x09; //rej
+ resp[l++] =
+ ((sap->vr + 1) << 1) | 0;
+ li->transmit_cb(resp, l, li->cbdata);
+ pf = 0; // dont reply
+#endif
+ };
+ };
+#endif
+ if (pf) {
+ // interrogating us, send rr
+ resp[l++] = data[0];
+ resp[l++] = (tei << 1) | 1;
+ resp[l++] = 0x01; // rr
+ resp[l++] = (LAPD_NR(sap) << 1) | (data[3] & 1); // pf bit from req
+
+ li->transmit_cb(resp, l, li->cbdata);
+
+ };
+ break;
+ case LAPD_CMD_FRMR:
+ // frame reject
+#if 0
+ if (teip->state == LAPD_TEI_ACTIVE)
+ *prim = LAPD_MPH_DEACTIVATE_IND;
+ lapd_tei_set_state(teip, LAPD_TEI_ASSIGNED);
+#endif
+ LOGP(DMI, LOGL_NOTICE, "frame reject, ignoring\n");
+ break;
+ case LAPD_CMD_DISC:
+ // disconnect
+ resp[l++] = data[0];
+ resp[l++] = (tei << 1) | 1;
+ resp[l++] = 0x73;
+ li->transmit_cb(resp, l, li->cbdata);
+ lapd_tei_set_state(teip, LAPD_TEI_NONE);
+ break;
+ default:
+ LOGP(DMI, LOGL_NOTICE, "unknown cmd for tei %d (cmd %x)\n",
+ tei, cmd);
+ break;
+ }
+
+ if (typ == LAPD_TYPE_I) {
+ /* send rr
+ * Thu Jan 22 19:17:13 2009 <4000> sangoma.c:340 read (62/25) 4: fa 33 01 0a
+ * lapd <- S RR sapi 3e tei 25 cmd 0 pf 0 ns -1 nr 5 ilen 0 teip 0x613800 vs 7 va 5 vr 2 len 4
+ */
+
+ /* interrogating us, send rr */
+ DEBUGP(DMI, "Sending RR response\n");
+ resp[l++] = data[0];
+ resp[l++] = (tei << 1) | 1;
+ resp[l++] = 0x01; // rr
+ resp[l++] = (LAPD_NR(sap) << 1) | (data[3] & 1); // pf bit from req
+
+ li->transmit_cb(resp, l, li->cbdata);
+
+ if (cmd != 0) {
+ *prim = LAPD_DL_DATA_IND;
+ return contents;
+ }
+ } else if (tei != 127 && typ == LAPD_TYPE_U && cmd == LAPD_CMD_UI) {
+ *prim = LAPD_DL_UNITDATA_IND;
+ return contents;
+ }
+
+ return NULL;
+};
+
+/* low-level function to send a single SABM message */
+static int lapd_send_sabm(struct lapd_instance *li, uint8_t tei, uint8_t sapi)
+{
+ struct msgb *msg = msgb_alloc_headroom(1024, 128, "LAPD SABM");
+ if (!msg)
+ return -ENOMEM;
+
+ DEBUGP(DMI, "Sending SABM for TEI=%u, SAPI=%u\n", tei, sapi);
+
+ msgb_put_u8(msg, (sapi << 2) | (li->network_side ? 2 : 0));
+ msgb_put_u8(msg, (tei << 1) | 1);
+ msgb_put_u8(msg, 0x7F);
+
+ li->transmit_cb(msg->data, msg->len, li->cbdata);
+
+ msgb_free(msg);
+
+ return 0;
+}
+
+/* timer call-back function for SABM re-transmission */
+static void sabme_timer_cb(void *_sap)
+{
+ struct lapd_sap *sap = _sap;
+
+ lapd_send_sabm(sap->tei->li, sap->tei->tei, sap->sapi);
+
+ if (sap->state == SAP_STATE_SABM_RETRANS)
+ bsc_schedule_timer(&sap->sabme_timer, SABM_INTERVAL);
+}
+
+/* Start a (user-side) SAP for the specified TEI/SAPI on the LAPD instance */
+int lapd_sap_start(struct lapd_instance *li, uint8_t tei, uint8_t sapi)
+{
+ struct lapd_sap *sap;
+ struct lapd_tei *teip;
+
+ teip = teip_from_tei(li, tei);
+ if (!teip)
+ teip = lapd_tei_alloc(li, tei);
+
+ sap = lapd_sap_find(teip, sapi);
+ if (sap)
+ return -EEXIST;
+
+ sap = lapd_sap_alloc(teip, sapi);
+
+ lapd_sap_set_state(teip, sapi, SAP_STATE_SABM_RETRANS);
+
+ return 0;
+}
+
+/* Stop a (user-side) SAP for the specified TEI/SAPI on the LAPD instance */
+int lapd_sap_stop(struct lapd_instance *li, uint8_t tei, uint8_t sapi)
+{
+ struct lapd_tei *teip;
+ struct lapd_sap *sap;
+
+ teip = teip_from_tei(li, tei);
+ if (!teip)
+ return -ENODEV;
+
+ sap = lapd_sap_find(teip, sapi);
+ if (!sap)
+ return -ENODEV;
+
+ lapd_sap_set_state(teip, sapi, SAP_STATE_INACTIVE);
+
+ llist_del(&sap->list);
+ talloc_free(sap);
+
+ return 0;
+}
+
+/* Transmit Data (I-Frame) on the given LAPD Instance / TEI / SAPI */
+void lapd_transmit(struct lapd_instance *li, uint8_t tei, uint8_t sapi,
+ uint8_t *data, unsigned int len)
+{
+ struct lapd_tei *teip = teip_from_tei(li, tei);
+ struct lapd_sap *sap;
+
+ if (!teip) {
+ LOGP(DMI, LOGL_ERROR, "Cannot transmit on non-existing "
+ "TEI %u\n", tei);
+ return;
+ }
+
+ sap = lapd_sap_find(teip, sapi);
+ if (!sap) {
+ LOGP(DMI, LOGL_INFO, "Tx on unknown SAPI=%u in TEI=%u, "
+ "allocating\n", sapi, tei);
+ sap = lapd_sap_alloc(teip, sapi);
+ }
+
+ /* prepend stuff */
+ uint8_t buf[10000];
+ memset(buf, 0, sizeof(buf));
+ memmove(buf + 4, data, len);
+ len += 4;
+
+ buf[0] = (sapi << 2) | (li->network_side ? 2 : 0);
+ buf[1] = (tei << 1) | 1;
+ buf[2] = (LAPD_NS(sap) << 1);
+ buf[3] = (LAPD_NR(sap) << 1) | 0;
+
+ sap->vs = (sap->vs + 1) & 0x7f;
+
+ li->transmit_cb(buf, len, li->cbdata);
+};
+
+/* Allocate a new LAPD instance */
+struct lapd_instance *lapd_instance_alloc(int network_side,
+ void (*tx_cb)(uint8_t *data, int len,
+ void *cbdata), void *cbdata)
+{
+ struct lapd_instance *li;
+
+ li = talloc_zero(NULL, struct lapd_instance);
+ if (!li)
+ return NULL;
+
+ li->transmit_cb = tx_cb;
+ li->cbdata = cbdata;
+ li->network_side = network_side;
+ INIT_LLIST_HEAD(&li->tei_list);
+
+ return li;
+}