| |
| /* |
| * minimal standalone network-side lap-d implementation |
| * oystein@homelien.no, 2009 |
| */ |
| |
| #include <stdio.h> |
| #include <string.h> |
| #include <assert.h> |
| |
| #include "lapd.h" |
| #include "openbsc/debug.h" |
| |
| #define DEBUG_LAPD(f, args...) { printf("lapd "); printf(f, ## args); }; |
| |
| 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", |
| |
| }; |
| |
| const char *lapd_msg_types = "?ISU"; |
| const int network_side = 1; /* 0 for user side */ |
| |
| typedef struct { |
| int tei; |
| int sapi; |
| /* 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 */ |
| lapd_tei_state state; |
| } lapd_tei_t; |
| |
| /* 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(teip) (teip->vs) |
| #define LAPD_NR(teip) (teip->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. |
| */ |
| void (*lapd_transmit_cb) (uint8_t * data, int len, void *cbdata); |
| |
| static lapd_tei_t tei_list[] = { |
| {25, 62,}, |
| {1, 0,}, |
| {-1}, |
| }; |
| |
| static lapd_tei_t *teip_from_tei(int tei) |
| { |
| lapd_tei_t *p; |
| for (p = tei_list; p->tei != -1; p++) { |
| if (p->tei == tei) |
| return p; |
| }; |
| return NULL; |
| }; |
| |
| static void lapd_tei_set_state(lapd_tei_t * teip, int newstate) |
| { |
| DEBUG_LAPD("state change on tei %d: %s -> %s\n", teip->tei, |
| lapd_tei_states[teip->state], lapd_tei_states[newstate]); |
| teip->state = newstate; |
| }; |
| |
| static void lapd_tei_receive(uint8_t * data, int len, void *cbdata) |
| { |
| //DEBUG_LAPD("tei receive %p, %d\n", data, len); |
| int entity = data[0]; |
| int ref = data[1]; |
| int mt = data[3]; |
| int action = data[4] >> 1; |
| int e = data[4] & 1; |
| //DEBUG_LAPD("tei mgmt: entity %x, ref %x, mt %x, action %x, e %x\n", entity, ref, mt, action, e); |
| |
| switch (mt) { |
| case 0x01:{ // identity request |
| int tei = action; |
| DEBUG_LAPD |
| ("tei mgmt: identity request, accepting tei %d\n", |
| tei); |
| //printf("tei: %d\n", tei); |
| uint8_t resp[8]; |
| memmove(resp, "\xfe\xff\x03\x0f\x00\x00\x02\x00", 8); |
| resp[7] = (tei << 1) | 1; |
| lapd_transmit_cb(resp, 8, cbdata); |
| lapd_tei_t *teip = teip_from_tei(tei); |
| if (teip->state == LAPD_TEI_NONE) |
| lapd_tei_set_state(teip, LAPD_TEI_ASSIGNED); |
| break; |
| } |
| default: |
| DEBUG_LAPD("tei mgmt: unknown mt %x action %x\n", mt, action); |
| assert(0); |
| }; |
| }; |
| |
| uint8_t *lapd_receive(uint8_t * data, int len, int *ilen, lapd_mph_type * prim, |
| void *cbdata) |
| { |
| #if 0 |
| DEBUG_LAPD("receive %p, %d\n", data, len); |
| hexdump(data, len); |
| #endif |
| |
| *ilen = 0; |
| *prim = 0; |
| |
| if (len < 2) { |
| DEBUG_LAPD("len %d < 2\n", len); |
| return NULL; |
| }; |
| |
| if ((data[0] & 1) != 0 || (data[1] & 1) != 1) { |
| DEBUG_LAPD("address field %x/%x not well formed\n", data[0], |
| data[1]); |
| return NULL; |
| }; |
| |
| int sapi = data[0] >> 2; |
| int cr = (data[0] >> 1) & 1; |
| int tei = data[1] >> 1; |
| int command = network_side ^ cr; |
| //DEBUG_LAPD(" address sapi %x tei %d cmd %d cr %d\n", sapi, tei, command, cr); |
| |
| if (len < 3) { |
| DEBUG_LAPD("len %d < 3\n", len); |
| return NULL; |
| }; |
| |
| lapd_msg_type typ = 0; |
| lapd_cmd_type cmd = 0; |
| int pf = -1; |
| int ns = -1; |
| int 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: |
| DEBUG_LAPD("unknown S cmd %x\n", data[2]); |
| assert(0); |
| }; |
| } 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: |
| DEBUG_LAPD("unknown U cmd %x (pf %x data %x)\n", val, |
| pf, data[2]); |
| assert(0); |
| }; |
| }; |
| |
| uint8_t *contents = &data[4]; |
| if (typ == LAPD_TYPE_U) |
| contents--; |
| *ilen = len - (contents - data); |
| |
| lapd_tei_t *teip = teip_from_tei(tei); |
| if (tei == 127) |
| lapd_tei_receive(contents, *ilen, cbdata); |
| |
| 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); |
| |
| if (teip) { |
| switch (cmd) { |
| case LAPD_CMD_I:{ |
| if (ns != teip->vr) { |
| DEBUG_LAPD("ns %d != vr %d\n", ns, |
| teip->vr); |
| if (ns == ((teip->vr - 1) & 0x7f)) { |
| DEBUG_LAPD |
| ("DOUBLE FRAME, ignoring\n"); |
| cmd = 0; // ignore |
| } else { |
| assert(0); |
| }; |
| } else { |
| //printf("IN SEQUENCE\n"); |
| teip->vr = (ns + 1) & 0x7f; // FIXME: hack! |
| }; |
| |
| break; |
| } |
| case LAPD_CMD_UI: |
| break; |
| case LAPD_CMD_SABME:{ |
| teip->vs = 0; |
| teip->vr = 0; |
| teip->va = 0; |
| |
| // ua |
| uint8_t resp[8]; |
| int l = 0; |
| resp[l++] = data[0]; |
| resp[l++] = (tei << 1) | 1; |
| resp[l++] = 0x73; |
| lapd_transmit_cb(resp, l, 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 |
| DEBUG_LAPD |
| ("rr in strange state, send rej\n"); |
| |
| // rej |
| uint8_t resp[8]; |
| int l = 0; |
| resp[l++] = |
| (teip-> |
| sapi << 2) | (network_side |
| ? 0 : 2); |
| resp[l++] = (tei << 1) | 1; |
| resp[l++] = 0x09; //rej |
| resp[l++] = |
| ((teip->vr + 1) << 1) | 0; |
| lapd_transmit_cb(resp, l, |
| cbdata); |
| pf = 0; // dont reply |
| #endif |
| }; |
| }; |
| |
| *prim = LAPD_MPH_ACTIVATE_IND; |
| break; |
| } |
| case LAPD_CMD_RR:{ |
| teip->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 |
| DEBUG_LAPD |
| ("rr in strange state, send rej\n"); |
| |
| // rej |
| uint8_t resp[8]; |
| int l = 0; |
| resp[l++] = |
| (teip-> |
| sapi << 2) | (network_side |
| ? 0 : 2); |
| resp[l++] = (tei << 1) | 1; |
| resp[l++] = 0x09; //rej |
| resp[l++] = |
| ((teip->vr + 1) << 1) | 0; |
| lapd_transmit_cb(resp, l, |
| cbdata); |
| pf = 0; // dont reply |
| #endif |
| }; |
| }; |
| #endif |
| if (pf) { |
| // interrogating us, send rr |
| uint8_t resp[8]; |
| int l = 0; |
| resp[l++] = data[0]; |
| resp[l++] = (tei << 1) | 1; |
| resp[l++] = 0x01; // rr |
| resp[l++] = (LAPD_NR(teip) << 1) | (data[3] & 1); // pf bit from req |
| |
| lapd_transmit_cb(resp, l, 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 |
| DEBUG_LAPD("frame reject, ignoring\n"); |
| assert(0); |
| break; |
| } |
| case LAPD_CMD_DISC:{ |
| // disconnect |
| uint8_t resp[8]; |
| int l = 0; |
| resp[l++] = data[0]; |
| resp[l++] = (tei << 1) | 1; |
| resp[l++] = 0x73; |
| lapd_transmit_cb(resp, l, cbdata); |
| lapd_tei_set_state(teip, LAPD_TEI_NONE); |
| break; |
| } |
| default: |
| DEBUG_LAPD("unknown cmd for tei %d (cmd %x)\n", tei, |
| cmd); |
| assert(0); |
| }; |
| }; |
| |
| //if ((*prim == 0) && (ilen > 0) && (typ != LAPD_TYPE_S)) { |
| //if (cmd == LAPD_CMD_I) { |
| 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 |
| DEBUG_LAPD("Sending RR response\n"); |
| uint8_t resp[8]; |
| int l = 0; |
| resp[l++] = data[0]; |
| resp[l++] = (tei << 1) | 1; |
| resp[l++] = 0x01; // rr |
| resp[l++] = (LAPD_NR(teip) << 1) | (data[3] & 1); // pf bit from req |
| |
| lapd_transmit_cb(resp, l, 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; |
| }; |
| |
| void lapd_transmit(int tei, uint8_t * data, int len, void *cbdata) |
| { |
| //printf("lapd_transmit %d, %d\n", tei, len); |
| //hexdump(data, len); |
| lapd_tei_t *teip = teip_from_tei(tei); |
| //printf("teip %p\n", teip); |
| |
| // prepend stuff |
| uint8_t buf[10000]; |
| memset(buf, 0, sizeof(buf)); |
| memmove(buf + 4, data, len); |
| len += 4; |
| |
| buf[0] = (teip->sapi << 2) | (network_side ? 2 : 0); |
| buf[1] = (teip->tei << 1) | 1; |
| buf[2] = (LAPD_NS(teip) << 1); |
| buf[3] = (LAPD_NR(teip) << 1) | 0; |
| |
| teip->vs = (teip->vs + 1) & 0x7f; |
| |
| lapd_transmit_cb(buf, len, cbdata); |
| }; |