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