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libosmocore/src/gsm/gsm23236.c

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/*! \file gsm23236.c
* Utility function implementations related to 3GPP TS 23.236 */
/*
* (C) 2020 sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
* Author: Neels Hofmeyr <nhofmeyr@sysmocom.de>
* All Rights Reserved
*
* SPDX-License-Identifier: GPL-2.0+
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
*/
#include <errno.h>
#include <stdlib.h>
#include <osmocom/core/utils.h>
#include <osmocom/gsm/gsm23236.h>
/*! Validate that the given NRI is valid for a given nri_bitlen range.
* \param[in] nri_v NRI value to validate.
* \param[in] nri_bitlen Valid NRI range in nr of bits used; if nri_bitlen > OSMO_NRI_BITLEN_MAX, nri_v is only
* checked to not be marked invalid.
* \returns 0 if valid, <0 if the NRI is <0, >0 if the NRI surpasses the range.
*/
int osmo_nri_v_validate(int16_t nri_v, uint8_t nri_bitlen)
{
if (nri_v < 0)
return -1;
if (nri_bitlen < OSMO_NRI_BITLEN_MIN)
return 1;
if (nri_bitlen < OSMO_NRI_BITLEN_MAX && (nri_v >> nri_bitlen))
return 1;
return 0;
}
/*! Match NRI value against a list NRI ranges. */
static bool nri_v_matches_range(const struct osmo_nri_range *range, int16_t nri_v)
{
return range && nri_v >= range->first && nri_v <= range->last;
}
/*! Return true if the ranges overlap, i.e. one or more NRI values appear in both ranges. */
static bool nri_range_overlaps_range(const struct osmo_nri_range *a, const struct osmo_nri_range *b)
{
return nri_v_matches_range(b, a->first) || nri_v_matches_range(b, a->last)
|| nri_v_matches_range(a, b->first) || nri_v_matches_range(a, b->last);
}
/*! Return true if the ranges overlap or are directly adjacent to each other. */
static bool nri_range_touches(const struct osmo_nri_range *a, const struct osmo_nri_range *b)
{
/* The first > last check may seem redundant, but ensures integer overflow safety. */
return nri_range_overlaps_range(a, b)
|| (a->first > b->last && a->first == b->last + 1)
|| (b->first > a->last && b->first == a->last + 1);
}
/*! Grow target range to also span range 'add'. Only useful for touching ranges, since all values between the two ranges
* are also included. */
static void nri_range_extend(struct osmo_nri_range *target, const struct osmo_nri_range *add)
{
target->first = OSMO_MIN(target->first, add->first);
target->last = OSMO_MAX(target->last, add->last);
}
/*! Return true when the given NRI value appears in the list of NRI ranges.
* \param[in] nri_v NRI value to look for.
* \param[in] nri_ranges List NRI ranges.
* \returns true iff nri_v appears anywhere in nri_ranges.
*/
bool osmo_nri_v_matches_ranges(int16_t nri_v, const struct osmo_nri_ranges *nri_ranges)
{
struct osmo_nri_range *range;
if (!nri_ranges)
return false;
llist_for_each_entry(range, &nri_ranges->entries, entry) {
if (nri_v_matches_range(range, nri_v))
return true;
}
return false;
}
/*! Modulo and shift the given NRI value so that it becomes a value present in a list of NRI ranges.
* Only range values within nri_bitlen are used.
* \param[inout] nri_v The NRI value to limit, e.g. random bits or an increment counter value.
* \param[in] nri_ranges List of NRI ranges indicating valid NRI values, where no entries may overlap in range values,
* and all entries must be valid (first <= last).
* \returns 0 on success, negative on error.
*/
int osmo_nri_v_limit_by_ranges(int16_t *nri_v, const struct osmo_nri_ranges *nri_ranges, uint32_t nri_bitlen)
{
struct osmo_nri_range *range;
uint32_t total_values = 0;
int16_t v = *nri_v;
int16_t range_max = (((int16_t)1) << nri_bitlen) - 1;
if (v < 0 || !nri_ranges)
return -1;
/* Sum up total amount of range values */
llist_for_each_entry(range, &nri_ranges->entries, entry) {
if (osmo_nri_range_validate(range, 255))
return -1;
if (range->first > range_max)
continue;
total_values += OSMO_MIN(range_max, range->last) - range->first + 1;
}
/* Modulo the given NRI value by that, and pick that nth value from the given ranges.
* (nri_ranges is pretty much guaranteed to be sorted and range_max checks thus would no longer be needed, but
* just check them anyway.) */
v %= total_values;
llist_for_each_entry(range, &nri_ranges->entries, entry) {
uint32_t len;
if (range->first > range_max)
continue;
len = OSMO_MIN(range_max, range->last) - range->first + 1;
if (v < len) {
*nri_v = range->first + v;
return 0;
}
v -= len;
}
/* Nothing found -- there are no entires or my math is off. */
return -1;
}
/*! Retrieve the Network Resource Indicator bits from a TMSI or p-TMSI.
* Useful for MSC pooling as described by 3GPP TS 23.236.
* \param[out] nri_v Write the extracted NRI value to this location (if non-NULL). If 0 is returned, it is guaranteed
* that nri_v >= 0. On non-zero return code, nri_v == -1.
* \param[in] tmsi TMSI value containing NRI bits.
* \param[in] nri_bitlen Length of the NRI value in number of bits,
* OSMO_NRI_BITLEN_MIN <= nri_bitlen <= * OSMO_NRI_BITLEN_MAX.
* \return 0 on success, negative on error (i.e. if nri_bitlen is not in the valid range).
*/
int osmo_tmsi_nri_v_get(int16_t *nri_v, uint32_t tmsi, uint8_t nri_bitlen)
{
uint8_t lowest_bit;
if (nri_v)
*nri_v = -1;
if (nri_bitlen < OSMO_NRI_BITLEN_MIN || nri_bitlen > OSMO_NRI_BITLEN_MAX)
return -1;
/* If not interested in the NRI value, exit here. */
if (!nri_v)
return 0;
/* According to 3GPP TS 23.236, the most significant bit of the NRI is always bit 23.
* (So this is not a temporary placeholder 23 we sometimes like to use, it is an actually specified 23!) */
lowest_bit = 23 - (nri_bitlen - 1);
/* ????xxxxxx??????? -> 0000000????xxxxxx tmsi >> lowest_bit
* -> xxxxxx & (bitmask that is nri_bitlen bits wide)
*/
*nri_v = (tmsi >> lowest_bit) & ((((uint32_t)1) << nri_bitlen) - 1);
return 0;
}
/*! Write Network Resource Indicator bits into a TMSI or p-TMSI.
* Overwrite the NRI bits with a given NRI value in a TMSI or p-TMSI.
* Useful for MSC pooling as described by 3GPP TS 23.236.
* \param[inout] tmsi A base TMSI or p-TMSI to replace the NRI value in, result is written back to this location.
* \param[in] nri_v The NRI value to place in the tmsi.
* \param[in] nri_bitlen Length of the NRI value in number of bits,
* OSMO_NRI_BITLEN_MIN <= nri_bitlen <= * OSMO_NRI_BITLEN_MAX.
* \return 0 on success, negative on error (i.e. if nri_bitlen is not in the valid range or if tmsi is NULL).
*/
int osmo_tmsi_nri_v_set(uint32_t *tmsi, int16_t nri_v, uint8_t nri_bitlen)
{
uint8_t lowest_bit;
uint32_t v_mask;
if (nri_bitlen < OSMO_NRI_BITLEN_MIN || nri_bitlen > OSMO_NRI_BITLEN_MAX)
return -1;
if (nri_v < 0)
return -1;
if (!tmsi)
return -1;
lowest_bit = 23 - (nri_bitlen - 1);
v_mask = ((((uint32_t)1) << nri_bitlen) - 1) << lowest_bit;
*tmsi = ((*tmsi) & ~v_mask) | ((((uint32_t)nri_v) << lowest_bit) & v_mask);
return 0;
}
/*! Apply osmo_nri_v_limit_by_ranges() in-place on the NRI value included in a TMSI.
* Extract the NRI value from the TMSI, limit that to be part of the ranges given in 'nri_ranges', and place the
* resulting NRI value back in the TMSI.
* \param[inout] tmsi TMSI value of which to modify the NRI bits, e.g. fresh randomized bits.
* \param[in] nri_ranges List of NRI ranges indicating valid NRI values, where no entries may overlap in range values,
* and all entries must be valid (first <= last).
* \param[in] nri_bitlen Valid NRI range in nr of bits used.
* \returns 0 on success, negative on error.
*/
int osmo_tmsi_nri_v_limit_by_ranges(uint32_t *tmsi, const struct osmo_nri_ranges *nri_ranges, uint8_t nri_bitlen)
{
int rc;
int16_t nri_v;
rc = osmo_tmsi_nri_v_get(&nri_v, *tmsi, nri_bitlen);
if (rc)
return rc;
rc = osmo_nri_v_limit_by_ranges(&nri_v, nri_ranges, nri_bitlen);
if (rc)
return rc;
return osmo_tmsi_nri_v_set(tmsi, nri_v, nri_bitlen);
}
/*! Validate that the given NRI range is valid for a given nri_bitlen range.
* \param[in] nri_range NRI value range to validate.
* \param[in] nri_bitlen Valid NRI range in nr of bits used. If nri_bitlen > OSMO_NRI_BITLEN_MAX, the NRI range is only
* validated to be first <= last and non-negative, not checked to fit a bit length range,
* \returns 0 if valid, -1 or 1 if range->first is invalid, -2 or 2 if range->last is invalid, -3 if first > last.
*/
int osmo_nri_range_validate(const struct osmo_nri_range *range, uint8_t nri_bitlen)
{
int rc;
rc = osmo_nri_v_validate(range->first, nri_bitlen);
if (rc)
return rc;
rc = osmo_nri_v_validate(range->last, nri_bitlen);
if (rc)
return 2 * rc;
if (range->first > range->last)
return -3;
return 0;
}
/*! Return true when the given NRI range has at least one NRI value that appears in a list of other NRI ranges.
* \param[in] range NRI range to look for.
* \param[in] nri_ranges List NRI ranges.
* \returns true iff any NRI value from 'range' appears anywhere in nri_ranges.
*/
bool osmo_nri_range_overlaps_ranges(const struct osmo_nri_range *range, const struct osmo_nri_ranges *nri_ranges)
{
struct osmo_nri_range *i;
if (!nri_ranges)
return false;
llist_for_each_entry(i, &nri_ranges->entries, entry) {
if (nri_range_overlaps_range(i, range))
return true;
}
return false;
}
/*! Allocate an empty struct osmo_nri_ranges (list of struct osmo_nri_range).
* \param ctx Talloc context to allocate from.
* \return allocated empty list.
*/
struct osmo_nri_ranges *osmo_nri_ranges_alloc(void *ctx)
{
struct osmo_nri_ranges *nri_ranges;
nri_ranges = talloc_zero(ctx, struct osmo_nri_ranges);
OSMO_ASSERT(nri_ranges);
INIT_LLIST_HEAD(&nri_ranges->entries);
return nri_ranges;
}
/*! Free a struct osmo_nri_ranges.
* \param nri_ranges The list to discard.
*/
void osmo_nri_ranges_free(struct osmo_nri_ranges *nri_ranges)
{
if (nri_ranges)
talloc_free(nri_ranges);
}
/*! Insert a new struct osmo_nri_range in an osmo_nri_ranges list, so that it remains sorted by 'first' values. */
static void nri_ranges_add_entry_sorted(struct osmo_nri_ranges *nri_ranges, struct osmo_nri_range *add)
{
struct osmo_nri_range *r;
struct llist_head *at_pos;
OSMO_ASSERT(nri_ranges);
at_pos = nri_ranges->entries.prev;
llist_for_each_entry(r, &nri_ranges->entries, entry) {
if (r->first <= add->first)
continue;
at_pos = r->entry.prev;
break;
}
llist_add(&add->entry, at_pos);
}
/*! Add a range of NRI values to a list of nri_range structs.
* Intelligently add and/or combine the entries in a list of NRI ranges to also include the NRI range given in 'add'.
* The list remains sorted by 'first' values.
* \param[inout] nri_ranges List of talloc allocated struct osmo_nri_range entries to add the new range to.
* \param[in] add NRI range to add to 'nri_ranges'.
* \returns 0 on success, negative on error (if the range in 'add' is invalid).
*/
int osmo_nri_ranges_add(struct osmo_nri_ranges *nri_ranges, const struct osmo_nri_range *add)
{
struct osmo_nri_range *range;
struct osmo_nri_range *range_next;
struct osmo_nri_range *target = NULL;
if (osmo_nri_range_validate(add, 255))
return -1;
if (!nri_ranges)
return -1;
/* Is there an entry overlapping this range? */
llist_for_each_entry(range, &nri_ranges->entries, entry) {
if (!nri_range_touches(range, add))
continue;
target = range;
}
if (!target) {
/* No overlaps with existing ranges, create a new one. */
target = talloc_zero(nri_ranges, struct osmo_nri_range);
OSMO_ASSERT(target);
*target = *add;
nri_ranges_add_entry_sorted(nri_ranges, target);
return 0;
}
/* Overlap found, join into existing entry */
nri_range_extend(target, add);
/* Remove redundant entries */
llist_for_each_entry_safe(range, range_next, &nri_ranges->entries, entry) {
if (range == target)
continue;
if (!nri_range_touches(target, range))
continue;
nri_range_extend(target, range);
llist_del(&range->entry);
talloc_free(range);
}
return 0;
}
/*! Remove a range of NRI values from a list of nri_range structs.
* Intelligently drop and/or cut or split the entries in a list of NRI ranges to no longer include the NRI range given
* in 'del'. Note that after this, the list may have more entries than before, if a range was split into two smaller
* ranges.
* \param[inout] nri_ranges List of talloc allocated struct osmo_nri_range entries to remove values from.
* \param[in] del NRI range to remove from 'nri_ranges'.
* \returns 0 on success, negative on error (if the range in 'del' is invalid).
*/
int osmo_nri_ranges_del(struct osmo_nri_ranges *nri_ranges, const struct osmo_nri_range *del)
{
struct osmo_nri_range *range;
struct osmo_nri_range *range_next;
if (osmo_nri_range_validate(del, 255))
return -1;
if (!nri_ranges)
return -1;
llist_for_each_entry_safe(range, range_next, &nri_ranges->entries, entry) {
bool head;
bool tail;
if (!nri_range_overlaps_range(range, del))
continue;
head = nri_v_matches_range(range, del->first) && (del->first > range->first);
tail = nri_v_matches_range(range, del->last) && (del->last < range->last);
if (head && tail) {
/* Range cut in two */
struct osmo_nri_range *new_tail;
/* Add a new entry for the tail section */
new_tail = talloc_zero(nri_ranges, struct osmo_nri_range);
OSMO_ASSERT(new_tail);
*new_tail = (struct osmo_nri_range){
.first = del->last + 1,
.last = range->last,
};
llist_add(&new_tail->entry, &range->entry);
/* Existing entry becomes the head section */
range->last = del->first - 1;
} else if (head) {
/* Range reduced, a head remains */
range->last = del->first - 1;
} else if (tail) {
/* Range reduced, a tail remains */
range->first = del->last + 1;
} else {
/* nothing remains */
llist_del(&range->entry);
talloc_free(range);
}
}
return 0;
}
/*! Compose a human readable representation of a list of NRI ranges in a buffer, like "23..42,123..142".
* \param[out] buf Target buffer.
* \param[in] buflen sizeof(buf).
* \param[in] nri_ranges List NRI ranges.
* \returns strlen() of string that would be written if the buffer is large enough, like snprintf().
*/
int osmo_nri_ranges_to_str_buf(char *buf, size_t buflen, const struct osmo_nri_ranges *nri_ranges)
{
struct osmo_nri_range *range;
struct osmo_strbuf sb = { .buf = buf, .len = buflen };
bool first = true;
if (!nri_ranges || llist_empty(&nri_ranges->entries)) {
OSMO_STRBUF_PRINTF(sb, "empty");
return sb.chars_needed;
}
llist_for_each_entry(range, &nri_ranges->entries, entry) {
OSMO_STRBUF_PRINTF(sb, "%s%d..%d", first ? "" : ",", range->first, range->last);
}
return sb.chars_needed;
}
/*! Compose a human readable representation of a list of NRI ranges in a talloc buffer, like "23..42,123..142".
* \param[in] ctx Talloc context.
* \param[in] nri_ranges List of NRI ranges.
* \returns a talloc allocated string.
*/
char *osmo_nri_ranges_to_str_c(void *ctx, const struct osmo_nri_ranges *nri_ranges)
{
OSMO_NAME_C_IMPL(ctx, 16, "ERROR", osmo_nri_ranges_to_str_buf, nri_ranges);
}
/*! Parse a string to an NRI value, allowing both decimal and hexadecimal formats; useful for VTY config
* implementations.
* \param[out] dst Write the resulting NRI value to this location.
* \param[in] str Decimal "511" or hex "0x1ff" string to parse.
* \returns 0 on success, negative on error.
*/
static int osmo_nri_parse(int16_t *dst, const char *str)
{
int val;
int base = 10;
if (osmo_str_startswith(str, "0x"))
base = 16;
if (osmo_str_to_int(&val, str, base, 0, INT16_MAX))
return -1;
*dst = (int16_t)val;
return 0;
}
/*! Parse string arguments to a struct osmo_nri_range; useful for VTY config implementations.
* Validate and parse 'first' and optional 'last' string arguments into struct osmo_nri_range values.
* The strings may be in decimal format ("511") or hexadecimal with leading "0x" ("0x1ff").
* If only one of 'first'/'last' is provided, the resulting range will have only that value (first == last).
* \param[out] nri_range Target for parsed values.
* \param[in] first_str Decimal or hex string, representing the first value in the range, or NULL if omitted.
* \param[in] last_str Decimal or hex string, representing the last value in the range, or NULL if omitted.
* \returns 0 on success, negative on error.
*/
static int osmo_nri_parse_range(struct osmo_nri_range *nri_range, const char *first_str, const char *last_str)
{
if (!nri_range)
return -1;
if (!first_str) {
first_str = last_str;
last_str = NULL;
if (!first_str)
return -1;
}
if (osmo_nri_parse(&nri_range->first, first_str))
return -1;
nri_range->last = nri_range->first;
if (last_str) {
if (osmo_nri_parse(&nri_range->last, last_str))
return -1;
}
return 0;
}
/*! VTY implementation for adding an NRI range to a list of ranges.
* Parse one or, if present, two argv arguments, which must be numbers representing the first and last value to add to
* the list of NRI ranges, in decimal format ("511") or hexadecimal with leading "0x" ("0x1ff"). If the range values
* surpass the nri_bitlen, return a warning in 'message', but still add the values to the list.
* \param[out] message Returned string constant to alert the user with, or NULL if all is well.
* \param[out] added_range If not NULL, write the range parsing result to this location.
* \param[in] nri_ranges List NRI ranges to add to.
* \param[in] argc Argument count.
* \param[in] argv Argument list.
* \param[in] nri_bitlen Valid NRI range in nr of bits used.
* \returns 0 on success, -1 on error, 1 for a warning (if adding was successful but the added range surpasses
* nri_bitlen).
*/
int osmo_nri_ranges_vty_add(const char **message, struct osmo_nri_range *added_range,
struct osmo_nri_ranges *nri_ranges, int argc, const char **argv, uint8_t nri_bitlen)
{
struct osmo_nri_range add_range;
if (osmo_nri_parse_range(&add_range, argv[0], argc > 1 ? argv[1] : NULL)) {
*message = "Error: cannot parse NRI range";
return -1;
}
if (added_range)
*added_range = add_range;
if (osmo_nri_ranges_add(nri_ranges, &add_range)) {
*message = "Error: failed to add NRI range";
return -1;
}
if (nri_bitlen <= OSMO_NRI_BITLEN_MAX && osmo_nri_range_validate(&add_range, nri_bitlen)) {
*message = "Warning: NRI range surpasses current NRI bitlen";
return 1;
}
*message = NULL;
return 0;
}
/*! VTY implementation for removing an NRI range from a list of ranges.
* Parse one or, if present, two argv arguments, which must be numbers representing the first and last value to remove
* from the list of NRI ranges, in decimal format ("511") or hexadecimal with leading "0x" ("0x1ff").
* \param[out] message Returned string constant to alert the user with, or NULL if all is well.
* \param[out] removed_range If not NULL, write the range parsing result to this location.
* \param[in] nri_ranges List of NRI ranges to remove from.
* \param[in] argc Argument count.
* \param[in] argv Argument list.
* \returns 0 on success, -1 on error, 1 for a warning.
*/
int osmo_nri_ranges_vty_del(const char **message, struct osmo_nri_range *removed_range,
struct osmo_nri_ranges *nri_ranges, int argc, const char **argv)
{
struct osmo_nri_range del_range;
if (osmo_nri_parse_range(&del_range, argv[0], argc > 1 ? argv[1] : NULL)) {
*message = "Error: cannot parse NRI range";
return -1;
}
if (removed_range)
*removed_range = del_range;
if (osmo_nri_ranges_del(nri_ranges, &del_range)) {
*message = "Error: failed to remove NRI range";
return -1;
}
*message = NULL;
return 0;
}
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