397 lines
10 KiB
C
397 lines
10 KiB
C
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/*
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* minimal standalone network-side lap-d implementation
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* oystein@homelien.no, 2009
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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 "lapd.h"
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#include "openbsc/debug.h"
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#define DEBUG_LAPD(f, args...) { printf("lapd "); printf(f, ## args); };
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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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const char *lapd_msg_types = "?ISU";
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const int network_side = 1; // 0 for user side
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typedef struct {
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int tei;
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int sapi;
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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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lapd_tei_state state;
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} lapd_tei_t;
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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(teip) (teip->vs)
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#define LAPD_NR(teip) (teip->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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void (*lapd_transmit_cb)(uint8_t *data, int len, void *cbdata);
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static lapd_tei_t tei_list[] = {
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{ 25, 62, },
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{ 1, 0, },
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{ -1 },
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};
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lapd_tei_t *teip_from_tei(int tei) {
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lapd_tei_t *p;
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for (p = tei_list; p->tei != -1; p++) {
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if (p->tei == tei) return p;
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};
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return NULL;
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};
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void lapd_tei_set_state(lapd_tei_t *teip, int newstate) {
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DEBUG_LAPD("state change on tei %d: %s -> %s\n", teip->tei, lapd_tei_states[teip->state], lapd_tei_states[newstate]);
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teip->state = newstate;
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};
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void lapd_tei_receive(uint8_t *data, int len, void *cbdata) {
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//DEBUG_LAPD("tei receive %p, %d\n", data, len);
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int entity = data[0];
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int ref = data[1];
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int mt = data[3];
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int action = data[4] >> 1;
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int e = data[4] & 1;
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//DEBUG_LAPD("tei mgmt: 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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int tei = action;
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DEBUG_LAPD("tei mgmt: identity request, accepting tei %d\n", tei);
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//printf("tei: %d\n", tei);
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uint8_t resp[8];
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memmove(resp, "\xfe\xff\x03\x0f\x00\x00\x02\x00", 8);
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resp[7] = (tei << 1) | 1;
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lapd_transmit_cb(resp, 8, cbdata);
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lapd_tei_t *teip = teip_from_tei (tei);
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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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DEBUG_LAPD("tei mgmt: unknown mt %x action %x\n", mt, action);
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assert(0);
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};
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};
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uint8_t *lapd_receive(uint8_t *data, int len, int *ilen, lapd_mph_type *prim, void *cbdata) {
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#if 0
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DEBUG_LAPD("receive %p, %d\n", data, len);
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hexdump(data, len);
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#endif
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*ilen = 0;
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*prim = 0;
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if (len < 2) {
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DEBUG_LAPD("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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DEBUG_LAPD("address field %x/%x not well formed\n", data[0], data[1]);
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return NULL;
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};
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int sapi = data[0] >> 2;
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int cr = (data[0] >> 1) & 1;
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int tei = data[1] >> 1;
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int command = network_side ^ cr;
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//DEBUG_LAPD(" 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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DEBUG_LAPD("len %d < 4\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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int pf = -1;
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int ns = -1;
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int 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: cmd = LAPD_CMD_RR; break;
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case 0x5: cmd = LAPD_CMD_RNR; break;
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case 0x9: cmd = LAPD_CMD_REJ; break;
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default:
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DEBUG_LAPD("unknown S cmd %x\n", data[2]);
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assert(0);
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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: cmd = LAPD_CMD_SABME; break;
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case 0x0f: cmd = LAPD_CMD_DM; break;
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case 0x03: cmd = LAPD_CMD_UI; break;
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case 0x43: cmd = LAPD_CMD_DISC; break;
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case 0x63: cmd = LAPD_CMD_UA; break;
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case 0x87: cmd = LAPD_CMD_FRMR; break;
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case 0xaf: cmd = LAPD_CMD_XID; break;
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default:
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DEBUG_LAPD("unknown U cmd %x (pf %x data %x)\n", val, pf, data[2]);
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assert(0);
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};
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};
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uint8_t *contents = &data[4];
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if (typ == LAPD_TYPE_U) contents--;
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*ilen = len - (contents - data);
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lapd_tei_t *teip = teip_from_tei(tei);
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if (tei == 127)
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lapd_tei_receive(contents, *ilen, cbdata);
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DEBUG_LAPD("<- %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, teip ? teip->vs : -1, teip ? teip->va : -1, teip ? teip->vr : -1, len);
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if (teip) {
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switch (cmd) {
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case LAPD_CMD_I: {
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if (ns != teip->vr) {
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DEBUG_LAPD("ns %d != vr %d\n", ns, teip->vr);
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if (ns == teip->vr-1) {
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DEBUG_LAPD("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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};
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teip->vr = (ns + 1) & 0x7f; // FIXME: hack!
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break; }
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case LAPD_CMD_SABME: {
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teip->vs = 0;
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teip->vr = 0;
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teip->va = 0;
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// ua
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uint8_t resp[8];
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int l = 0;
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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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lapd_transmit_cb(resp, l, cbdata);
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break; }
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case LAPD_CMD_RR: {
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teip->va = (nr & 0x7f);
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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, LAPD_TEI_ACTIVE);
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*prim = LAPD_MPH_ACTIVATE_IND;
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//printf("ASSIGNED and ACTIVE\n");
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} else {
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#if 0
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DEBUG_LAPD("rr in strange state, send rej\n");
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// rej
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uint8_t resp[8];
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int l = 0;
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resp[l++] = (teip->sapi << 2) | (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++] = ((teip->vr+1) << 1) | 0;
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lapd_transmit_cb(resp, l, 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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if (pf) {
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// interrogating us, send rr
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uint8_t resp[8];
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int l = 0;
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resp[l++] = data[0];
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resp[l++] = (tei << 1) | 1;
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resp[l++] = 0x01; // rr
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resp[l++] = (LAPD_NR(teip) << 1) | (data[3] & 1); // pf bit from req
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lapd_transmit_cb(resp, l, cbdata);
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};
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break; }
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case LAPD_CMD_FRMR: { // frame reject
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#if 0
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if (teip->state == LAPD_TEI_ACTIVE)
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*prim = LAPD_MPH_DEACTIVATE_IND;
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lapd_tei_set_state(teip, LAPD_TEI_ASSIGNED);
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#endif
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DEBUG_LAPD("frame reject, ignoring\n");
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assert(0);
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break; }
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case LAPD_CMD_DISC: { // disconnect
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uint8_t resp[8];
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int l = 0;
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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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lapd_transmit_cb(resp, l, cbdata);
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lapd_tei_set_state(teip, LAPD_TEI_NONE);
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break; }
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default:
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DEBUG_LAPD("unknown cmd for tei %d (cmd %x)\n", tei, cmd);
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assert(0);
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};
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};
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//if ((*prim == 0) && (ilen > 0) && (typ != LAPD_TYPE_S)) {
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//if (cmd == LAPD_CMD_I) {
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if (typ == LAPD_TYPE_I) {
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// send rr
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// Thu Jan 22 19:17:13 2009 <4000> sangoma.c:340 read (62/25) 4: fa 33 01 0a
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// 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
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// interrogating us, send rr
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uint8_t resp[8];
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int l = 0;
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resp[l++] = data[0];
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resp[l++] = (tei << 1) | 1;
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resp[l++] = 0x01; // rr
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resp[l++] = (LAPD_NR(teip) << 1) | (data[3] & 1); // pf bit from req
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lapd_transmit_cb(resp, l, cbdata);
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*prim = LAPD_DL_DATA_IND;
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return contents;
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};
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return NULL;
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};
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void lapd_transmit(int tei, uint8_t *data, int len, void *cbdata) {
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//printf("lapd_transmit %d, %d\n", tei, len);
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//hexdump(data, len);
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lapd_tei_t *teip = teip_from_tei(tei);
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//printf("teip %p\n", teip);
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// prepend stuff
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uint8_t buf[10000];
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memset(buf, 0, sizeof(buf));
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memmove(buf+4, data, len);
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len += 4;
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buf[0] = (teip->sapi << 2) | (network_side ? 2 : 0);
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buf[1] = (teip->tei << 1) | 1;
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buf[2] = (LAPD_NS(teip) << 1);
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buf[3] = (LAPD_NR(teip) << 1) | 0;
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teip->vs = (teip->vs + 1) & 0x7f;
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lapd_transmit_cb(buf, len, cbdata);
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};
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