Osmocom test suites in TTCN-3 (Eclipse Titan) https://osmocom.org/projects/core-testing-infra
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osmo-ttcn3-hacks/pcu/GPRS_TBF.ttcn

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module GPRS_TBF {
/* GPRS TBF Routines, intended as minimal MS-Side GPRS implementation
*
* (C) 2018 by Harald Welte <laforge@gnumonks.org>
* All rights reserved.
*
* Released under the terms of GNU General Public License, Version 2 or
* (at your option) any later version.
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
import from GSM_Types all;
import from Osmocom_Types all;
import from General_Types all;
import from RLCMAC_CSN1_Types all;
import from RLCMAC_Types all;
import from RLCMAC_Templates all;
import from LLC_Types all;
import from GPRS_Context all;
private const integer RLC_GPRS_SNS := 128;
private const integer RLC_GPRS_WS := 64;
private const integer RLC_EGPRS_MIN_WS := 64;
private const integer RLC_EGPRS_MAX_WS := 1024;
private const integer RLC_EGPRS_SNS := 2048;
private const integer RLC_EGPRS_MAX_BSN_DELTA := 512;
private const integer RLC_MAX_SNS := RLC_EGPRS_SNS;
private const integer RLC_MAX_WS := RLC_EGPRS_MAX_WS;
private const integer RLC_MAX_LEN := 74 /* MCS-9 data unit */
private const integer sns_half := (RLC_MAX_SNS / 2);
private const integer mod_sns_half := (RLC_MAX_SNS / 2) - 1;
/***********************************************************************
* Uplink TBF handling
***********************************************************************/
/* input parameters into TBF (mostly mode/cs + LLC PDUs */
type record UlTbfPars {
/* Acknowledged mode (true) or unacknowledged (false) */
boolean ack_mode,
/* Coding Scheme for transmission, determines block size */
GprsCodingScheme initial_cs,
/* list of abstract/decoded LLC PDUs */
record of PDU_LLC llc_pdus optional,
/* possibly computed: list of encoded LLC PDUs */
record of octetstring llc_pdus_enc
}
type record RlcEndpointTx {
/* send state variable V(S) (9.1.1): 0 .. SNS-1 */
integer v_s,
/* acknowledge state variable V(A) (9.1.2): BSN value of oldest RLC data block that has not
* been positively acknowledged by peer. */
integer v_a,
/* acknowledge state array V(B) (9.1.3) */
bitstring v_b
}
private function f_RlcEndpointTx_init(inout RlcEndpointTx ep) {
ep.v_s := 0;
ep.v_a := 0;
ep.v_b := int2bit(0, 128); /* FIXME: EGPRS 2048 bits length */
}
type record UlTbfState {
/* "const" input state with TBF Data */
UlTbfPars tbf,
uint8_t num_ts,
RlcEndpointTx et,
integer tfi,
/* total length of all encoded LLC PDUs */
integer llc_pdu_totlen,
/* index of current/next PDU in llc_pdus_enc */
integer cur_pdu,
/* byte offset into current/next PDU; next byte to transmit */
integer cur_index,
/* block sequence number of next block within TBF */
integer bsn_p,
/* total number of bytes remaining in TBF */
integer total_bytes_remain,
/* list of already-sent RLC/MAC Blocks */
record of RlcmacUlBlock rlc_sent
}
function f_UlTbfState_init(inout UlTbfState us, in UlTbfPars utpars) {
var RlcmacUlBlock blk;
us.tbf := utpars;
us.num_ts := 1;
f_RlcEndpointTx_init(us.et);
us.tfi := 0; /* FIXME */
us.cur_pdu := 0;
us.cur_index := 0;
us.bsn_p := 0;
us.total_bytes_remain := 0;
us.rlc_sent := {};
/* encode all LLC PDUs from their abstract type to octetstring */
us.cur_pdu := 0; /* currently processed PDU */
us.cur_index := 0; /* next to-be transmitted index */
if (ispresent(us.tbf.llc_pdus)) {
us.tbf.llc_pdus_enc := {};
us.llc_pdu_totlen := 0;
for (var integer i := 0; i < sizeof(us.tbf.llc_pdus); i := i+1) {
var octetstring cur_enc := enc_PDU_LLC(us.tbf.llc_pdus[i]);
us.tbf.llc_pdus_enc := us.tbf.llc_pdus_enc & { cur_enc };
us.llc_pdu_totlen := us.llc_pdu_totlen + lengthof(cur_enc);
}
us.total_bytes_remain := us.llc_pdu_totlen;
}
}
private function f_UlTbf_ack_one_block(inout UlTbfState us, integer n) {
/* compute index into v_b */
var integer idx := n - us.et.v_a;
if (idx < 0 or idx > lengthof(us.et.v_b)) {
setverdict(fail, "UlTbf: Cannot ACK ", n, " while V(A) is ", us.et.v_a);
mtc.stop;
}
/* set the bit in the acknowledge state array */
us.et.v_b[idx] := '1'B;
}
/* check if V(B) contains '1' at lower end: if yes, advance V(A) and shift V(B) */
private function f_UlTbf_check_advance_v_a(inout UlTbfState us) {
log("FIXME: Implement this");
}
/* copy 'len' number of bytes from current pending LLC PDU */
private function f_copy_from_llc(inout UlTbfState us, integer len) return octetstring
{
var integer pdu_len := lengthof(us.tbf.llc_pdus_enc[us.cur_pdu])
var octetstring ret;
ret := substr(us.tbf.llc_pdus_enc[us.cur_pdu], us.cur_index, len);
us.cur_index := us.cur_index + len;
us.total_bytes_remain := us.total_bytes_remain - len;
/* if we completed this PDU, move on to the next, resetting the index */
if (us.cur_index >= pdu_len) {
us.cur_pdu := us.cur_pdu +1;
us.cur_index := 0;
log("copy_from_llc (incrementing pdu)");
}
return ret;
}
/* generate one LlcBlock (maximum size 'max_len') */
private function f_ul_tbf_pull_one(out LlcBlock ret, inout LlcBlockHdr prev_hdr,
inout UlTbfState us, integer max_len,
boolean is_final) return boolean
{
/* if we've already pulled all data from all LLC PDUs: nothing to do */
if (us.cur_pdu >= sizeof(us.tbf.llc_pdus_enc)) {
log("pull_one: No more data", us);
return false;
}
var integer pdu_len := lengthof(us.tbf.llc_pdus_enc[us.cur_pdu])
var integer cur_llc_remain_len := pdu_len - us.cur_index;
var integer len;
var LlcBlock lb;
if (us.cur_index == 0) {
/* start of a new LLC PDU */
prev_hdr.more := true;
}
if (cur_llc_remain_len > max_len) {
log("Chunk with length ", cur_llc_remain_len, " larger than space (",
max_len, ") left in block");
len := max_len;
lb := {
hdr := omit,
payload := f_copy_from_llc(us, len)
}
} else if (cur_llc_remain_len == max_len and is_final) {
/* final RLC block of TBF and LLC remainder fits exactly */
len := max_len;
lb := {
hdr := omit,
payload := f_copy_from_llc(us, len)
}
prev_hdr.e := true;
} else if (cur_llc_remain_len == max_len) {
/* LLC remaineder would fit exactly -> "singular case" with L=0 */
len := max_len - 1;
lb := {
hdr := {
length_ind := 0,
more := false,
e := true
},
payload := f_copy_from_llc(us, len)
}
prev_hdr.e := false;
} else {
/* normal case: cur_llc_remain_len < max_len */
len := cur_llc_remain_len;
lb := {
hdr := {
length_ind := len,
more := false,
e := true
},
payload := f_copy_from_llc(us, len)
}
prev_hdr.e := false;
}
ret := lb;
return true;
}
/* return encoded size of one given LlcBlock */
private function f_LlcBlock_enc_len(LlcBlock blk) return integer {
if (isvalue(blk.hdr)) {
return 1 + lengthof(blk.payload);
} else {
return lengthof(blk.payload);
}
}
/* return encoded size of given record of LlcBlock */
private function f_LlcBlocks_enc_len(LlcBlocks blks) return integer {
var integer sum := 0;
for (var integer i := 0; i < sizeof(blks); i := i+1) {
sum := sum + f_LlcBlock_enc_len(blks[i]);
}
return sum;
}
private function f_ul_tbf_pull_multi(out LlcBlocks ret, inout UlTbfState us, integer max_len,
boolean is_final) return boolean
{
var integer space_left;
var boolean rc;
ret := {};
/* loop as long as we have pending LLC data and space left in the current block... */
for (space_left := max_len; space_left > 0; space_left := max_len - f_LlcBlocks_enc_len(ret)) {
var LlcBlock lb;
var integer ret_size := sizeof(ret);
if (ret_size > 0) {
rc := f_ul_tbf_pull_one(lb, ret[ret_size-1].hdr, us, space_left, is_final);
} else {
var LlcBlockHdr dummy_hdr;
rc := f_ul_tbf_pull_one(lb, dummy_hdr, us, space_left, is_final);
}
if (rc == false) {
/* we couldn't fill the full RLC block, insufficient LLC Data */
if (sizeof(ret) == 0) {
/* we couldn't obtain any LlcBlocks at all */
return false;
} else {
/* we have some LlcBlocks from earlier iterations */
return true;
}
}
ret := ret & {lb};
}
return true;
}
/* Determine 'K' value for given CS (TS 44.060 9.3.1.1) */
private function f_k_for_cs(GprsCodingScheme cs) return integer {
/* FIXME: EGPRS */
return 1;
}
/* TS 44.060 9.3.1.1 */
private function f_calc_cv(integer nbc, integer bsn_p, integer nts, GprsCodingScheme cs,
integer bs_cv_max) return integer {
var integer dividend := nbc - bsn_p - 1;
var integer k := f_k_for_cs(cs);
var integer divisor := nts * k;
var integer x := f_div_round_up(dividend, divisor);
if (x <= bs_cv_max) {
return x;
} else {
return 15;
}
}
private function f_rlcmac_hdr_size(boolean tlli_needed) return integer {
var integer ret := 2;
if (tlli_needed) {
ret := ret + 4;
}
return ret;
}
/* determine countdown value based on remaining length pending */
private function f_ul_tbf_get_cv(inout UlTbfState us, GprsCodingScheme cs, boolean tlli_needed)
return integer {
var integer hdr_size := f_rlcmac_hdr_size(tlli_needed); /* FIXME: PFI, ... */
var integer blk_len_net := f_gprs_blocksize(cs) - hdr_size;
var integer num_remain := f_div_round_up(us.total_bytes_remain, blk_len_net);
var integer cv := f_calc_cv(num_remain + sizeof(us.rlc_sent), us.bsn_p, us.num_ts, us.tbf.initial_cs, 14 /* FIXME */);
return cv;
}
function f_ul_tbf_get_next_block(out RlcmacUlBlock blk, inout UlTbfState us, inout MmContext mmctx,
boolean tlli_needed := false) return boolean {
var integer hdr_size := f_rlcmac_hdr_size(tlli_needed); /* FIXME: TLLI, PFI, ... */
var integer len_remain := f_gprs_blocksize(us.tbf.initial_cs) - hdr_size;
var octetstring payload;
var integer cv;
var LlcBlocks llc_blocks;
cv := f_ul_tbf_get_cv(us, us.tbf.initial_cs, tlli_needed);
/* potentially get multiple payload chunks of multiple LLC PDUs */
if (f_ul_tbf_pull_multi(llc_blocks, us, len_remain, false) == false) {
return false;
}
/* include TLLI when needed */
if (tlli_needed) {
blk := valueof(t_RLCMAC_UL_DATA_TLLI(CS_1, us.tfi, cv, us.et.v_s,
llc_blocks, false, mmctx.tlli));
} else {
blk := valueof(t_RLCMAC_UL_DATA(CS_1, us.tfi, cv, us.et.v_s, llc_blocks, false));
}
/* Increment Block Sequence Number */
us.bsn_p := us.bsn_p + 1;
us.et.v_s := us.bsn_p mod 128; /* FIXME: EGPRS SNS: 2048 */
/* append to list of sent blocks */
us.rlc_sent := us.rlc_sent & { blk };
return true;
}
function f_ul_tbf_process_acknack(inout UlTbfState us, RlcmacDlCtrlBlock db) {
if (ispresent(db.payload.u.ul_ack_nack.gprs)) {
var UlAckNackGprs uan_gprs := db.payload.u.ul_ack_nack.gprs;
if (ispresent(uan_gprs.cont_res_tlli)) {
/* FIXME: check for contention resolution */
}
var integer i;
/* iterate over received bitmap, ACK each block in our TBF state */
for (i := lengthof(uan_gprs.ack_nack_desc.receive_block_bitmap)-1; i >= 0; i := i-1) {
if (uan_gprs.ack_nack_desc.receive_block_bitmap[i] == '1'B) {
var integer seq := uan_gprs.ack_nack_desc.starting_seq_nr + i;
f_UlTbf_ack_one_block(us, seq);
}
}
f_UlTbf_check_advance_v_a(us);
}
}
/***********************************************************************
* Downlink TBF handling
***********************************************************************/
type record RlcEndpointRx {
/* receive state variable V(R) (9.1.5): BSN one higher than highest BSN yet received (mod SNS) */
integer v_r,
/* receive window state variable V(Q) (9.1.6): Lowest BSN not yet received (mod SNS) */
integer v_q,
/* receive state array V(N) (9.1.7) */
bitstring v_n
}
private function f_RlcEndpointRx_init(inout RlcEndpointRx ep) {
ep.v_r := 0;
ep.v_q := 0;
ep.v_n := int2bit(0, 128); /* FIXME: EGPRS 2048 bits length */
}
type record DlTbfPars {
/* Acknowledged mode (true) or unacknowledged (false) */
boolean ack_mode,
/* Coding Scheme for transmission, determines block size */
GprsCodingScheme initial_cs,
/* Sequence Number Space */
integer sns,
/* Window Size */
integer ws
}
type record DlTbfState {
/* "const" input state with TBF Data */
DlTbfPars tbf,
uint8_t num_ts,
RlcEndpointRx er,
integer tfi,
/* list of abstract/decoded RLC PDUs */
record of RlcmacDlBlock rlc_received
}
function f_dl_tbf_mod_sns(DlTbfState ds, integer val) return integer
{
return (val mod ds.tbf.sns);
}
function f_dl_tbf_is_in_window(integer bsn) return boolean {
setverdict(fail, "pleaes implement me");
mtc.stop;
}
function f_dl_tbf_is_received(inout DlTbfState ds, integer bsn) return boolean {
var integer offset_v_r;
if (not f_dl_tbf_is_in_window(bsn)) {
return false;
}
/* offset to the end of the received window */
offset_v_r := f_dl_tbf_mod_sns(ds, ds.er.v_r - 1 - bsn);
if (not (offset_v_r < ds.tbf.ws)) {
return false;
}
if (ds.er.v_n[bsn mod sns_half] == '1'B) {
return true;
}
return false;
}
function f_dl_tbf_mark_received(inout DlTbfState ds, integer bsn) {
ds.er.v_n[bsn mod sns_half] := '1'B;
f_dl_tbf_raise_v_r(ds, bsn);
}
/* Raise V(Q) if possible */
function f_dl_tbf_raise_v_q(inout DlTbfState ds, integer bsn) return integer {
var integer count := 0;
while (ds.er.v_q != ds.er.v_r) {
var integer v_q_old := ds.er.v_q;
if (not f_dl_tbf_is_received(ds, v_q_old)) {
break;
}
ds.er.v_q := f_dl_tbf_mod_sns(ds, ds.er.v_q + 1)
log("RLCMAC: Taking block ", v_q_old, " out, raising V(Q) to ", ds.er.v_q);
count := count+1;
}
return count;
}
function f_dl_tbf_raise_v_r(inout DlTbfState ds, integer bsn) {
var integer offset_v_r := f_dl_tbf_mod_sns(ds, bsn + 1 - ds.er.v_r);
if (offset_v_r < (ds.tbf.sns / 2)) {
for (var integer i := offset_v_r; i > 0; i := i-1) {
/* mark as missing */
ds.er.v_n[bsn mod sns_half] := '0'B;
//raise_v_r_to(1);
}
log("RLCMAC: Raising V(R) to ", ds.er.v_r);
}
}
/* process the actual data and update TbfState */
function f_dl_tbf_process_dl_data(inout DlTbfState ds, RlcmacDlDataBlock db) {
var integer bsn := db.mac_hdr.hdr_ext.bsn;
if (db.mac_hdr.hdr_ext.tfi != ds.tfi) {
setverdict(fail, "Unexpected TFI of DL Data Block ", db);
mtc.stop;
}
f_dl_tbf_mark_received(ds, bsn);
if (ds.tbf.ack_mode) {
/* In RLC acknowledged mode, the receive window is defined by the receive window
* state variable V(Q) in the following inequality[ V(Q) ≤ BSN < V(Q)+ WS ] modulo
* SNS */
if (bsn < ds.er.v_q or bsn > ds.er.v_q + ds.tbf.ws) {
setverdict(fail, "Unexpected BSN outside of window ", bsn);
mtc.stop;
}
/* In RLC acknowledged mode, the value of V(Q) shall be updated when the RLC
* receiver receives the RLC data block whose BSN is equal to V(Q). The value of
* V(Q) shall then be set to the BSN value of the next RLC data block in the receive
* window (modulo SNS) that has not yet been received, or it shall be set to V(R) if
* all RLC data blocks in the receive window have been received */
f_dl_tbf_mark_received(ds, bsn);
} else {
/* In RLC unacknowledged mode, if [V(R) - V(Q)] modulo SNS > WS after updating V(R),
* then V(Q) is set to [V(R) - WS] modulo SNS. */
/* FIXME */
}
}
}