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gbproxy: Add SGSN pooling support 

Change-Id: I58b9f55065f6bd43450e4b07cffe7ba132b1fd9b
Related: OS#4472
This commit is contained in:
Daniel Willmann 2020-12-21 18:53:55 +01:00
parent ee834af5d9
commit d4ab1f98bd
3 changed files with 173 additions and 34 deletions
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2
include/osmocom/sgsn/gb_proxy.h
View File

@ -229,5 +229,7 @@ void gbproxy_sgsn_free(struct gbproxy_sgsn *sgsn);
struct gbproxy_sgsn *gbproxy_sgsn_by_nsei(struct gbproxy_config *cfg, uint16_t nsei);
struct gbproxy_sgsn *gbproxy_sgsn_by_nsei_or_new(struct gbproxy_config *cfg, uint16_t nsei);
struct gbproxy_sgsn *gbproxy_sgsn_by_nri(struct gbproxy_config *cfg, uint16_t nri, bool *null_nri);
struct gbproxy_sgsn *gbproxy_sgsn_by_tlli(struct gbproxy_config *cfg, struct gbproxy_sgsn *sgsn_avoid,
uint32_t tlli);
#endif

161
src/gb_proxy.c
View File

@ -38,6 +38,7 @@
#include <osmocom/core/select.h>
#include <osmocom/core/rate_ctr.h>
#include <osmocom/core/stats.h>
#include <osmocom/core/utils.h>
#include <osmocom/gprs/gprs_ns2.h>
#include <osmocom/gprs/gprs_bssgp.h>
@ -45,6 +46,7 @@
#include <osmocom/gprs/gprs_bssgp_bss.h>
#include <osmocom/gprs/bssgp_bvc_fsm.h>
#include <osmocom/gsm/gsm23236.h>
#include <osmocom/gsm/gsm_utils.h>
#include <osmocom/sgsn/signal.h>
@ -201,42 +203,131 @@ int bssgp_prim_cb(struct osmo_prim_hdr *oph, void *ctx)
* PTP BVC handling
***********************************************************************/
/* route an uplink message on a PTP-BVC to a SGSN using the TLLI */
static int gbprox_bss2sgsn_tlli(struct gbproxy_cell *cell, struct msgb *msg, uint32_t tlli,
/* FIXME: Handle the tlli NULL case correctly,
* This function should take a generic selector
* and choose an sgsn based on that
*/
static struct gbproxy_sgsn *gbproxy_select_sgsn(struct gbproxy_config *cfg, const uint32_t *tlli)
{
struct gbproxy_sgsn *sgsn = NULL;
struct gbproxy_sgsn *sgsn_avoid = NULL;
int tlli_type;
int16_t nri;
bool null_nri = false;
if (!tlli) {
sgsn = llist_first_entry(&cfg->sgsns, struct gbproxy_sgsn, list);
if (!sgsn) {
return NULL;
}
LOGPSGSN(sgsn, LOGL_INFO, "Could not get TLLI, using first SGSN\n");
return sgsn;
}
if (cfg->pool.nri_bitlen == 0) {
/* Pooling is disabled */
sgsn = llist_first_entry(&cfg->sgsns, struct gbproxy_sgsn, list);
if (!sgsn) {
return NULL;
}
LOGPSGSN(sgsn, LOGL_INFO, "Pooling disabled, using first configured SGSN\n");
} else {
/* Pooling is enabled, try to use the NRI for routing to an SGSN
* See 3GPP TS 23.236 Ch. 5.3.2 */
tlli_type = gprs_tlli_type(*tlli);
if (tlli_type == TLLI_LOCAL || tlli_type == TLLI_FOREIGN) {
/* Only get/use the NRI if tlli type is local */
osmo_tmsi_nri_v_get(&nri, *tlli, cfg->pool.nri_bitlen);
if (nri >= 0) {
/* Get the SGSN for the NRI */
sgsn = gbproxy_sgsn_by_nri(cfg, nri, &null_nri);
if (sgsn && !null_nri)
return sgsn;
/* If the NRI is the null NRI, we need to avoid the chosen SGSN */
if (null_nri && sgsn) {
sgsn_avoid = sgsn;
}
} else {
/* We couldn't get the NRI from the TLLI */
LOGP(DGPRS, LOGL_ERROR, "Could not extract NRI from local TLLI %u\n", *tlli);
}
}
}
/* If we haven't found an SGSN yet we need to choose one, but avoid the one in sgsn_avoid
* NOTE: This function is not stable if the number of SGSNs or allow_attach changes
* We could implement TLLI tracking here, but 3GPP TS 23.236 Ch. 5.3.2 (see NOTE) argues that
* we can just wait for the MS to reattempt the procedure.
*/
if (!sgsn)
sgsn = gbproxy_sgsn_by_tlli(cfg, sgsn_avoid, *tlli);
if (!sgsn) {
LOGP(DGPRS, LOGL_ERROR, "No suitable SGSN found for TLLI %u\n", *tlli);
return NULL;
}
return sgsn;
}
/*! Find the correct gbproxy_bvc given a cell and an SGSN
* \param[in] cfg The gbproxy configuration
* \param[in] cell The cell the message belongs to
* \param[in] tlli An optional TLLI used for tracking
* \return Returns 0 on success, otherwise a negative value
*/
static struct gbproxy_bvc *gbproxy_select_sgsn_bvc(struct gbproxy_config *cfg, struct gbproxy_cell *cell, const uint32_t *tlli)
{
struct gbproxy_sgsn *sgsn;
struct gbproxy_bvc *sgsn_bvc = NULL;
sgsn = gbproxy_select_sgsn(cfg, tlli);
if (!sgsn) {
LOGPCELL(cell, LOGL_ERROR, "Could not find any SGSN, dropping message!\n");
return NULL;
}
/* Get the BVC for this SGSN/NSE */
for (int i = 0; i < ARRAY_SIZE(cell->sgsn_bvc); i++) {
sgsn_bvc = cell->sgsn_bvc[i];
if (!sgsn_bvc)
continue;
if (sgsn->nse != sgsn_bvc->nse)
continue;
return sgsn_bvc;
}
/* This shouldn't happen */
LOGPCELL(cell, LOGL_ERROR, "Could not find matching BVC for SGSN, dropping message!\n");
return NULL;
}
/*! Send a message to the next SGSN, possibly ignoring the null SGSN
* route an uplink message on a PTP-BVC to a SGSN using the TLLI
* \param[in] cell The cell the message belongs to
* \param[in] msg The BSSGP message
* \param[in] null_sgsn If not NULL then avoid this SGSN (because this message contains its null NRI)
* \param[in] tlli An optional TLLI used for tracking
* \return Returns 0 on success, otherwise a negative value
*/
static int gbprox_bss2sgsn_tlli(struct gbproxy_cell *cell, struct msgb *msg, const uint32_t *tlli,
bool sig_bvci)
{
struct gbproxy_config *cfg = cell->cfg;
struct gbproxy_bvc *sgsn_bvc;
unsigned int i;
/* FIXME: derive NRI from TLLI */
/* FIXME: find the SGSN for that NRI */
/* HACK: we currently simply pick the first SGSN we find */
for (i = 0; i < ARRAY_SIZE(cell->sgsn_bvc); i++) {
sgsn_bvc = cell->sgsn_bvc[i];
if (sgsn_bvc)
return gbprox_relay2peer(msg, sgsn_bvc, sig_bvci ? 0 : sgsn_bvc->bvci);
sgsn_bvc = gbproxy_select_sgsn_bvc(cfg, cell, tlli);
if (!sgsn_bvc) {
LOGPCELL(cell, LOGL_NOTICE, "Could not find any SGSN for TLLI %u, dropping message!\n", *tlli);
return -EINVAL;
}
return 0;
return gbprox_relay2peer(msg, sgsn_bvc, sig_bvci ? 0 : sgsn_bvc->bvci);
}
static int gbprox_bss2sgsn_null_nri(struct gbproxy_cell *cell, struct msgb *msg)
{
struct gbproxy_bvc *sgsn_bvc;
unsigned int i;
/* FIXME: find the SGSN for that NRI */
/* HACK: we currently simply pick the first SGSN we find */
for (i = 0; i < ARRAY_SIZE(cell->sgsn_bvc); i++) {
sgsn_bvc = cell->sgsn_bvc[i];
if (sgsn_bvc)
return gbprox_relay2peer(msg, sgsn_bvc, sgsn_bvc->bvci);
}
return 0;
}
/* Receive an incoming PTP message from a BSS-side NS-VC */
static int gbprox_rx_ptp_from_bss(struct gbproxy_nse *nse, struct msgb *msg, uint16_t ns_bvci)
{
@ -314,18 +405,20 @@ static int gbprox_rx_ptp_from_bss(struct gbproxy_nse *nse, struct msgb *msg, uin
case BSSGP_PDUT_PS_HO_CANCEL:
/* We can route based on TLLI-NRI */
tlli = osmo_load32be(TLVP_VAL(&tp, BSSGP_IE_TLLI));
rc = gbprox_bss2sgsn_tlli(bss_bvc->cell, msg, tlli, false);
rc = gbprox_bss2sgsn_tlli(bss_bvc->cell, msg, &tlli, false);
break;
case BSSGP_PDUT_RADIO_STATUS:
if (TLVP_PRESENT(&tp, BSSGP_IE_TLLI)) {
tlli = osmo_load32be(TLVP_VAL(&tp, BSSGP_IE_TLLI));
rc = gbprox_bss2sgsn_tlli(bss_bvc->cell, msg, tlli, false);
rc = gbprox_bss2sgsn_tlli(bss_bvc->cell, msg, &tlli, false);
} else if (TLVP_PRESENT(&tp, BSSGP_IE_TMSI)) {
/* we treat the TMSI like a TLLI and extract the NRI from it */
tlli = osmo_load32be(TLVP_VAL(&tp, BSSGP_IE_TMSI));
rc = gbprox_bss2sgsn_tlli(bss_bvc->cell, msg, tlli, false);
rc = gbprox_bss2sgsn_tlli(bss_bvc->cell, msg, &tlli, false);
} else if (TLVP_PRESENT(&tp, BSSGP_IE_IMSI)) {
rc = gbprox_bss2sgsn_null_nri(bss_bvc->cell, msg);
// FIXME: Use the IMSI as selector?
rc = gbprox_bss2sgsn_tlli(bss_bvc->cell, msg, NULL, false);
//rc = gbprox_bss2sgsn_hashed(bss_bvc->cell, msg, NULL);
} else
LOGPBVC(bss_bvc, LOGL_ERROR, "Rx RADIO-STATUS without any of the conditional IEs\n");
break;
@ -828,7 +921,7 @@ static int gbprox_rx_sig_from_bss(struct gbproxy_nse *nse, struct msgb *msg, uin
from_bvc = gbproxy_bvc_by_bvci(nse, ptp_bvci);
if (!from_bvc)
goto err_no_bvc;
gbprox_bss2sgsn_tlli(from_bvc->cell, msg, tlli, true);
gbprox_bss2sgsn_tlli(from_bvc->cell, msg, &tlli, true);
break;
default:
LOGPNSE(nse, LOGL_ERROR, "Rx %s: Implementation missing\n", pdut_name);

44
src/gb_proxy_peer.c
View File

@ -443,3 +443,47 @@ struct gbproxy_sgsn *gbproxy_sgsn_by_nri(struct gbproxy_config *cfg, uint16_t nr
return NULL;
}
/*! Seleect a pseudo-random SGSN for a given TLLI, ignoring any SGSN that is not accepting connections
* \param[in] cfg The gbproxy configuration
* \param[in] sgsn_avoid If not NULL then avoid this SGSN when selecting a new one. Use for load redistribution
* \param[in] tlli The tlli to choose an SGSN for. The same tlli will map to the same SGSN as long as no SGSN is
* added/removed or allow_attach changes.
* \return Returns the sgsn on success, NULL if no SGSN that allows new connections could be found
*/
struct gbproxy_sgsn *gbproxy_sgsn_by_tlli(struct gbproxy_config *cfg, struct gbproxy_sgsn *sgsn_avoid,
uint32_t tlli)
{
uint32_t i = 0;
uint32_t index, num_sgsns;
struct gbproxy_sgsn *sgsn;
OSMO_ASSERT(cfg);
// TODO: We should keep track of count in cfg
num_sgsns = llist_count(&cfg->sgsns);
if (num_sgsns == 0)
return NULL;
// FIXME: 256 SGSNs ought to be enough for everyone
index = hash_32(tlli, 8) % num_sgsns;
// Get the first enabled SGSN after index
llist_for_each_entry(sgsn, &cfg->sgsns, list) {
if (i >= index && sgsn->pool.allow_attach) {
return sgsn;
}
i++;
}
// Start again from the beginning
llist_for_each_entry(sgsn, &cfg->sgsns, list) {
if (i > index) {
break;
} else if (sgsn->pool.allow_attach) {
return sgsn;
}
i++;
}
return NULL;
}