17 Nov
2015
17 Nov
'15
2:38 p.m.
The del_cb is now also used for ares (GGSN resolution) timeouts, and expiry is
anyway separated from nr_map, so this comment is void.
Sponsored-by: On-Waves ehi
---
openbsc/include/openbsc/gtphub.h | 2 --
1 file changed, 2 deletions(-)
diff --git a/openbsc/include/openbsc/gtphub.h b/openbsc/include/openbsc/gtphub.h
index 49d685c..68cf90e 100644
--- a/openbsc/include/openbsc/gtphub.h
+++ b/openbsc/include/openbsc/gtphub.h
@@ -248,8 +248,6 @@ int expiry_tick(struct expiry *exq, time_t now);
* Mapping allocation and a del_cb are provided by the caller. If del_cb is
* NULL, no deallocation will be done (allowing statically allocated entries).
*/
-/* TODO at some point I thought the allocation & del_cb complexity was
- * needed/helpful, but by now it seems like overkill. Maybe lose that again. */
typedef int nr_t;
--
2.1.4
17 Nov
17 Nov
2:38 p.m.
New subject: [PATCH 2/3] gtphub: fix number map range for TEIs.
Use unsigned int for nr_map, just large enough to fit the TEI space.
Adjust log output formats and casts accordingly.
Fixes: TEIs are uint32_t, but the nr_map so far used int. This would cause TEIs
from 0x80000000 on to be handled and printed as a negative value.
Sponsored-by: On-Waves ehi
---
openbsc/include/openbsc/gtphub.h | 2 +-
openbsc/src/gprs/gtphub.c | 15 ++++++++-------
openbsc/tests/gtphub/gtphub_test.c | 6 +++---
3 files changed, 12 insertions(+), 11 deletions(-)
diff --git a/openbsc/include/openbsc/gtphub.h b/openbsc/include/openbsc/gtphub.h
index 68cf90e..c43a328 100644
--- a/openbsc/include/openbsc/gtphub.h
+++ b/openbsc/include/openbsc/gtphub.h
@@ -249,7 +249,7 @@ int expiry_tick(struct expiry *exq, time_t now);
* NULL, no deallocation will be done (allowing statically allocated entries).
*/
-typedef int nr_t;
+typedef unsigned int nr_t;
/* Generator for unused numbers. So far this counts upwards from zero, but the
* implementation may change in the future. Treat this like an opaque struct.
diff --git a/openbsc/src/gprs/gtphub.c b/openbsc/src/gprs/gtphub.c
index 22da9a3..7c7f693 100644
--- a/openbsc/src/gprs/gtphub.c
+++ b/openbsc/src/gprs/gtphub.c
@@ -914,10 +914,10 @@ static void gtphub_mapping_del_cb(struct expiring_item *expi)
/* Just for log */
struct gtphub_peer_port *from = nrm->origin;
OSMO_ASSERT(from);
- LOG(LOGL_DEBUG, "expired: %d: nr mapping from %s: %d->%d\n",
+ LOG(LOGL_DEBUG, "expired: %d: nr mapping from %s: %u->%u\n",
(int)nrm->expiry_entry.expiry,
gtphub_port_str(from),
- (int)nrm->orig, (int)nrm->repl);
+ (unsigned int)nrm->orig, (unsigned int)nrm->repl);
gtphub_port_ref_count_dec(from);
@@ -960,10 +960,10 @@ static uint32_t gtphub_tei_mapping_have(struct gtphub *hub,
{
struct nr_mapping *nrm = gtphub_mapping_have(&hub->tei_map[plane_idx],
from, orig_tei, now);
- LOG(LOGL_DEBUG, "New %s TEI: (from %s, TEI %d) <-- TEI %d\n",
+ LOG(LOGL_DEBUG, "New %s TEI: (from %s, TEI %u) <-- TEI %u\n",
gtphub_plane_idx_names[plane_idx],
gtphub_port_str(from),
- (int)orig_tei, (int)nrm->repl);
+ (unsigned int)orig_tei, (unsigned int)nrm->repl);
return (uint32_t)nrm->repl;
}
@@ -1115,8 +1115,9 @@ static int gtphub_unmap_header_tei(struct gtphub_peer_port
**to_port_p,
uint32_t unmapped_tei = nrm->orig;
set_tei(p, unmapped_tei);
- LOG(LOGL_DEBUG, "Unmapped TEI coming from %s: %d -> %d (to %s)\n",
- gtphub_port_str(from_port), tei, unmapped_tei,
+ LOG(LOGL_DEBUG, "Unmapped TEI coming from %s: %u -> %u (to %s)\n",
+ gtphub_port_str(from_port),
+ (unsigned int)tei, (unsigned int)unmapped_tei,
gtphub_port_str2(to_port));
*to_port_p = to_port;
@@ -1309,7 +1310,7 @@ static int gtphub_unmap(struct gtphub *hub,
gtphub_peer_str(from_peer),
(int)p->seq,
gtphub_port_str(from_seq),
- (int)p->header_tei,
+ (unsigned int)p->header_tei,
gtphub_port_str2(from_tei)
);
}
diff --git a/openbsc/tests/gtphub/gtphub_test.c b/openbsc/tests/gtphub/gtphub_test.c
index 8434f61..4e22ac7 100644
--- a/openbsc/tests/gtphub/gtphub_test.c
+++ b/openbsc/tests/gtphub/gtphub_test.c
@@ -233,9 +233,9 @@ static int nr_map_is(struct nr_map *map, const char *str)
size_t len = sizeof(buf);
struct nr_mapping *m;
llist_for_each_entry(m, &map->mappings, entry) {
- size_t wrote = snprintf(pos, len, "(%d->%d@%d), ",
- (int)m->orig,
- (int)m->repl,
+ size_t wrote = snprintf(pos, len, "(%u->%u@%d), ",
+ m->orig,
+ m->repl,
(int)m->expiry_entry.expiry);
OSMO_ASSERT(wrote < len);
pos += wrote;
--
2.1.4
25 Nov
25 Nov
8:53 p.m.
New subject: [PATCH 2/3] gtphub: fix number map range for TEIs.
On 17 Nov 2015, at 14:38, Neels Hofmeyr
<nhofmeyr(a)sysmocom.de> wrote:
Use unsigned int for nr_map, just large enough to fit the TEI space.
Adjust log output formats and casts accordingly.
Fixes: TEIs are uint32_t, but the nr_map so far used int. This would cause TEIs
from 0x80000000 on to be handled and printed as a negative value.
good!
-typedef int nr_t;
+typedef unsigned int nr_t;
use uint32_t here then? and "nr_t" is that clear it refers to a tei?
+ (unsigned int)nrm->orig, (unsigned
int)nrm->repl);
What is the explicit casting about?
holger
26 Nov
26 Nov
5:29 p.m.
New subject: [PATCH 2/3] gtphub: fix number map range for TEIs.
On Wed, Nov 25, 2015 at 08:53:45PM +0100, Holger Freyther wrote:
nr_map is used for both sequence numbers and TEIs with different range
settings. Sequence numbers range from 0..ffff and TEIs from 1..ffffffff.
So nr_t is intended to be more general, but since gtphub is the only scope
using it, unsigned int is enough to fit both number spaces (assuming int
size will never be less than 32 bits...). So nr_t refers to a TEI as soon
as a nr_pool is *used* for a TEI.
To print values 80000000..ffffffff as positive numbers, the printf format
is using '%u'. Casting to unsigned int it is my preferred way of making
sure the argument matches the printf format...
Might not be necessary, but erases all doubt about intention or type
sizes.
~Neels
-typedef int
nr_t;
+typedef unsigned int nr_t;
use uint32_t here then? and "nr_t" is that clear it refers to a tei? +
(unsigned int)nrm->orig, (unsigned int)nrm->repl);
What is the explicit casting about? 
27 Nov
27 Nov
9:38 a.m.
New subject: [PATCH 2/3] gtphub: fix number map range for TEIs.
On 26.11.2015 17:29, Neels Hofmeyr wrote:
On Wed, Nov 25, 2015 at 08:53:45PM +0100, Holger
Freyther wrote:
To print values 80000000..ffffffff as positive numbers, the printf format
is using '%u'. Casting to unsigned int it is my preferred way of making
sure the argument matches the printf format...
Might not be necessary, but erases all doubt about intention or type
sizes.
As far as I understand the C99 specification, this not necessary. IMO
the make the code less readable and the hinder the compiler and tools
like coverity to find certain bugs, e.g. if someone raised the type of
nmr->orig to 'long long' for some reason, he/she wouldn't get a warning
from the tools.
Here is the definition of "integer promotions":
§6.3.1.1 (2): "If an int can represent all values of the original
type, the value is converted to an int; otherwise, it is converted to an
unsigned int. These are called the integer promotions. All other types
are unchanged by the integer promotions."
Here is the definition of "default argument promotions":
§6.5.2.2 (6): "If the expression that denotes the called function has
a type that does not include a prototype, the integer promotions are
performed on each argument, and arguments that have type float are
promoted to double. These are called the default argument promotions. ..."
And finally, these have to be applied to the trailing arguments or printf:
§6.5.2.2 (7): "... The ellipsis notation in a function prototype
declarator causes argument type conversion to stop after the last
declared parameter. The default argument promotions are performed on
trailing arguments."
Jacob
--
- Jacob Erlbeck <jerlbeck(a)sysmocom.de> http://www.sysmocom.de/
=======================================================================
* sysmocom - systems for mobile communications GmbH
* Alt-Moabit 93
* 10559 Berlin, Germany
* Sitz / Registered office: Berlin, HRB 134158 B
* Geschaeftsfuehrer / Managing Directors: Holger Freyther, Harald Welte
+
(unsigned int)nrm->orig, (unsigned int)nrm->repl);
What is the explicit casting about?
17 Nov
17 Nov
2:38 p.m.
New subject: [PATCH 3/3] gtphub: nr_map: add min,max and wrap.
Implement min/max bounds for nr_pool, adjust nr_pool_init() and current tests,
and create unit tests for nr_map wrapping.
Sequence numbers range from 0 to 65535, while TEIs range from 1 to 0xffffffff.
Both cause problems when the nr_pool surpasses the range: seq exit their valid
range, causing unmappings to fail, and a TEI would be mapped as zero (invalid).
Add a comment about TEI wrapping, and lose the comment about random TEIs (not
really important).
Sponsored-by: On-Waves ehi
---
openbsc/include/openbsc/gtphub.h | 11 +++++++--
openbsc/src/gprs/gtphub.c | 21 +++++++++-------
openbsc/tests/gtphub/gtphub_test.c | 49 ++++++++++++++++++++++++++++++++++++--
3 files changed, 68 insertions(+), 13 deletions(-)
diff --git a/openbsc/include/openbsc/gtphub.h b/openbsc/include/openbsc/gtphub.h
index c43a328..77e43e4 100644
--- a/openbsc/include/openbsc/gtphub.h
+++ b/openbsc/include/openbsc/gtphub.h
@@ -256,7 +256,8 @@ typedef unsigned int nr_t;
* If this becomes random, the tests need to be fixed. */
struct nr_pool {
nr_t last_nr;
- /* TODO add min, max, for safe wrapping */
+ nr_t nr_min;
+ nr_t nr_max;
};
struct nr_mapping {
@@ -275,7 +276,7 @@ struct nr_map {
};
-void nr_pool_init(struct nr_pool *pool);
+void nr_pool_init(struct nr_pool *pool, nr_t nr_min, nr_t nr_max);
/* Return the next unused number from the nr_pool. */
nr_t nr_pool_next(struct nr_pool *pool);
@@ -398,6 +399,12 @@ struct gtphub {
/* pointers to an entry of to_ggsns[x].peers */
struct gtphub_peer_port *ggsn_proxy[GTPH_PLANE_N];
+ /* The TEI numbers will simply wrap and be reused, which will work out
+ * in practice. Problems would arise if one given peer maintained the
+ * same TEI for a time long enough for the TEI nr map to wrap an entire
+ * uint32_t; if a new TEI were mapped every second, this would take
+ * more than 100 years (in which a single given TEI must not time out)
+ * to cause a problem. */
struct nr_map tei_map[GTPH_PLANE_N];
struct nr_pool tei_pool[GTPH_PLANE_N];
diff --git a/openbsc/src/gprs/gtphub.c b/openbsc/src/gprs/gtphub.c
index 7c7f693..155024b 100644
--- a/openbsc/src/gprs/gtphub.c
+++ b/openbsc/src/gprs/gtphub.c
@@ -577,18 +577,21 @@ void expiring_item_del(struct expiring_item *item)
/* nr_map, nr_pool */
-void nr_pool_init(struct nr_pool *pool)
+void nr_pool_init(struct nr_pool *pool, nr_t nr_min, nr_t nr_max)
{
- *pool = (struct nr_pool){};
+ *pool = (struct nr_pool){
+ .nr_min = nr_min,
+ .nr_max = nr_max,
+ .last_nr = nr_max
+ };
}
nr_t nr_pool_next(struct nr_pool *pool)
{
- pool->last_nr ++;
-
- OSMO_ASSERT(pool->last_nr > 0);
- /* TODO: gracefully handle running out of TEIs. */
- /* TODO: random TEIs. */
+ if (pool->last_nr >= pool->nr_max)
+ pool->last_nr = pool->nr_min;
+ else
+ pool->last_nr ++;
return pool->last_nr;
}
@@ -1806,7 +1809,7 @@ void gtphub_init(struct gtphub *hub)
int plane_idx;
for (plane_idx = 0; plane_idx < GTPH_PLANE_N; plane_idx++) {
- nr_pool_init(&hub->tei_pool[plane_idx]);
+ nr_pool_init(&hub->tei_pool[plane_idx], 1, 0xffffffff);
nr_map_init(&hub->tei_map[plane_idx],
&hub->tei_pool[plane_idx],
&hub->expire_tei_maps);
@@ -1974,7 +1977,7 @@ static struct gtphub_peer *gtphub_peer_new(struct gtphub *hub,
INIT_LLIST_HEAD(&peer->addresses);
- nr_pool_init(&peer->seq_pool);
+ nr_pool_init(&peer->seq_pool, 0, 0xffff);
nr_map_init(&peer->seq_map, &peer->seq_pool,
&hub->expire_seq_maps);
/* TODO use something random to pick the initial sequence nr.
diff --git a/openbsc/tests/gtphub/gtphub_test.c b/openbsc/tests/gtphub/gtphub_test.c
index 4e22ac7..b1ebb40 100644
--- a/openbsc/tests/gtphub/gtphub_test.c
+++ b/openbsc/tests/gtphub/gtphub_test.c
@@ -157,7 +157,7 @@ static void test_nr_map_basic(void)
struct nr_map _map;
struct nr_map *map = &_map;
- nr_pool_init(pool);
+ nr_pool_init(pool, 1, 1000);
nr_map_init(map, pool, NULL);
OSMO_ASSERT(llist_empty(&map->mappings));
@@ -253,6 +253,50 @@ static int nr_map_is(struct nr_map *map, const char *str)
return 1;
}
+static int test_nr_map_wrap_with(nr_t nr_min, nr_t nr_max, nr_t repl_last,
+ nr_t orig_start, int orig_n,
+ const char *expect)
+{
+ struct nr_pool _pool;
+ struct nr_pool *pool = &_pool;
+ struct nr_map _map;
+ struct nr_map *map = &_map;
+
+ nr_pool_init(pool, nr_min, nr_max);
+ nr_map_init(map, pool, NULL);
+
+ pool->last_nr = repl_last;
+
+ void *origin = (void*)0x1234;
+
+ int i;
+ for (i = 0; i < orig_n; i++)
+ LVL2_ASSERT(nr_map_have(map, origin, orig_start + i, 0));
+
+ LVL2_ASSERT(nr_map_is(map, expect));
+
+ nr_map_clear(map);
+ return 1;
+}
+
+static void test_nr_map_wrap(void)
+{
+ OSMO_ASSERT(test_nr_map_wrap_with(
+ 0, UINT_MAX, UINT_MAX - 2,
+ 1, 5,
+ "(1->4294967294@0), "
+ "(2->4294967295@0), "
+ "(3->0@0), "
+ "(4->1@0), "
+ "(5->2@0), "
+ ));
+ OSMO_ASSERT(test_nr_map_wrap_with(
+ 5, 10, 8,
+ 1, 5,
+ "(1->9@0), (2->10@0), (3->5@0), (4->6@0), (5->7@0), "
+ ));
+}
+
static void test_expiry(void)
{
struct expiry expiry;
@@ -261,7 +305,7 @@ static void test_expiry(void)
int i;
expiry_init(&expiry, 30);
- nr_pool_init(&pool);
+ nr_pool_init(&pool, 1, 1000);
nr_map_init(&map, &pool, &expiry);
OSMO_ASSERT(nr_map_is(&map, ""));
@@ -947,6 +991,7 @@ int main(int argc, char **argv)
osmo_gtphub_ctx = talloc_named_const(NULL, 0, "osmo_gtphub");
test_nr_map_basic();
+ test_nr_map_wrap();
test_expiry();
test_echo();
test_create_pdp_ctx();
--
2.1.4
25 Nov
25 Nov
9:05 p.m.
New subject: [PATCH 3/3] gtphub: nr_map: add min,max and wrap.
On 17 Nov 2015, at 14:38, Neels Hofmeyr
<nhofmeyr(a)sysmocom.de> wrote:
+ /* The TEI numbers will simply wrap and be reused, which will work out
+ * in practice. Problems would arise if one given peer maintained the
+ * same TEI for a time long enough for the TEI nr map to wrap an entire
+ * uint32_t; if a new TEI were mapped every second, this would take
+ * more than 100 years (in which a single given TEI must not time out)
+ * to cause a problem. */
Unless performance matters I am not for probalistic correct, specially not in the
beginning of a new piece of software. "Modern" smartphones will open a PDP
context very early and they live for a potentially long time (until you reboot your
phone or such).
So I would prefer to check if a TEI is used (at least the number should be random)
before using it. So even if the assignment is not random right now I would still
prefer the check if it is assigned or not.
E.g. a unit test that exhausts the entire number space should be feasible.
holger
26 Nov
26 Nov
5:51 p.m.
New subject: [PATCH 3/3] gtphub: nr_map: add min,max and wrap.
On Wed, Nov 25, 2015 at 09:05:40PM +0100, Holger Freyther wrote:
The TEI space will exhaust even slower, then :)
The more *new* PDP contexts are created, the faster the pool will wrap.
+ /* The TEI
numbers will simply wrap and be reused, which will work out
+ * in practice. Problems would arise if one given peer maintained the
+ * same TEI for a time long enough for the TEI nr map to wrap an entire
+ * uint32_t; if a new TEI were mapped every second, this would take
+ * more than 100 years (in which a single given TEI must not time out)
+ * to cause a problem. */
Unless performance matters I am not for probalistic correct, specially not in the
beginning of a new piece of software. "Modern" smartphones will open a PDP
context very early and they live for a potentially long time (until you reboot your
phone or such). So I would prefer to check if a TEI is used (at least
the number should be random)
before using it. So even if the assignment is not random right now I would still
prefer the check if it is assigned or not.
So I should iterate all tunnels to ensure a new TEI is unused.
I'm anyway iterating all tunnels to detect a peer reusing a TEI it had sent
before, also checking against the mapped TEI is easy to add.
E.g. a unit test that exhausts the entire number space
should be feasible.
Really? 4.294.967.295 TEI mappings?? Thats 4*sizeof(mapping) gigabytes and
might need special memory model options to work, and the testing
machine needs that many gigs of ram and will take quite a while: O(n²)...
Probably easier to manually assign a given TEI and make the pool return
that TEI next.
Is your suggestion to shrink the TEI space?
And next, what about sequence numbers? The space is much smaller (65.536
values), and expires after 30 seconds. To me, it is much more realistic
that we receive 66.000 messages with distinct sequence numbers within the
space of 30 seconds, than that a given TEI will remain in use for more
than 100 years in a place where a new subscriber shows up every single
second. So, verifying that a *sequence number* is unused seems to be way
more critical than the TEI check.
Which touches the optimization topic. Currently gtphub will have to
iterate everything all the time. To optimize, one way would be to list
tunnels at the peers they associate with, but if gtphub is used as proxy
for a single peer, that has exactly zero effect. So some way of hash map
might be more useful. But gtphub wants several different views, i.e.
sometimes it wants to find an original TEI, sometimes a mapped TEI,
sometimes from SGSN and sometimes from GGSN side, and sometimes it wants
to find all tunnels for a given peer. So, to optimize we'd want a couple
of separate hash maps hashing one and the same list from different angles.
I'd be glad for any ideas, or hints at existing Osmocom API. But, unless
told otherwise, I simply won't bother about optimization for now...
~Neels
--
- Neels Hofmeyr <nhofmeyr(a)sysmocom.de> http://www.sysmocom.de/
=======================================================================
* sysmocom - systems for mobile communications GmbH
* Alt-Moabit 93
* 10559 Berlin, Germany
* Sitz / Registered office: Berlin, HRB 134158 B
* Geschäftsführer / Managing Directors: Holger Freyther, Harald Welte
11:46 p.m.
New subject: [PATCH 3/3] gtphub: nr_map: add min,max and wrap.
On Thu, Nov 26, 2015 at 05:51:52PM +0100, Neels Hofmeyr wrote:
Which touches the optimization topic. Currently gtphub
will have to
[...]
of separate hash maps hashing one and the same list
from different angles.
I'm thinking, if we want persistence as well as several optimized querying
angles: sqlite might do both at the same time.
~Neels
--
- Neels Hofmeyr <nhofmeyr(a)sysmocom.de> http://www.sysmocom.de/
=======================================================================
* sysmocom - systems for mobile communications GmbH
* Alt-Moabit 93
* 10559 Berlin, Germany
* Sitz / Registered office: Berlin, HRB 134158 B
* Geschäftsführer / Managing Directors: Holger Freyther, Harald Welte
27 Nov
27 Nov
10 a.m.
New subject: [PATCH 3/3] gtphub: nr_map: add min,max and wrap.
On 26.11.2015 17:51, Neels Hofmeyr wrote:
On Wed, Nov 25, 2015 at 09:05:40PM +0100, Holger
Freyther wrote:
> E.g. a unit test that exhausts the entire number
space should be
feasible.
Really? 4.294.967.295 TEI mappings?? Thats 4*sizeof(mapping) gigabytes and
might need special memory model options to work, and the testing
machine needs that many gigs of ram and will take quite a while: O(n²)...
I am fond of exhausting tests, too.
But AFAI understand, it would be enough to establish one mapping at
first and then establishing and releasing them immediately (N = 1) or
after e.g. N = 2^16 steps. Thus you had a persistent initial one and a
sliding window of N mappings and each new mapping could be checked
against at least the first one. If you still ran into memory problems,
you would have found a bug that way.
Probably easier to manually assign a given TEI and
make the pool return
that TEI next.
This won't check the TEI generation, will it? If the allocation was
changed in the future (e.g. to be based on random numbers), this kind of
test wouldn't find bugs there.
Jacob
--
- Jacob Erlbeck <jerlbeck(a)sysmocom.de> http://www.sysmocom.de/
=======================================================================
* sysmocom - systems for mobile communications GmbH
* Alt-Moabit 93
* 10559 Berlin, Germany
* Sitz / Registered office: Berlin, HRB 134158 B
* Geschaeftsfuehrer / Managing Directors: Holger Freyther, Harald Welte
30 Nov
30 Nov
10:07 p.m.
New subject: [PATCH 3/3] gtphub: nr_map: add min,max and wrap.
On Fri, Nov 27, 2015 at 10:00:08AM +0100, Jacob Erlbeck wrote:
On 26.11.2015 17:51, Neels Hofmeyr wrote:
I think it would be best to artificially limit the range to 1..16 to test
exhaustion. We wouldn't have to run through 2^32 (!) mappings then.
Let me outline the two number spaces again...
There's the TEI space (32 bits of space), random per PDP context,
and the sequence number space (16 bits of space), ++ per GTP Request.
I really doubt that anyone will manage to exaust TEIs ("64 kilobytes of
RAM ought to be enough for anyone!"), but I accept the argument, and the
randomness, too. So for the TEIs, I have added code that runs through all
the tunnels and ensures that a TEI is not mapped twice. If it is, the code
tries to pick an unused TEI outside the seen min..max range of TEIs. But
it can't yet reliably find open gaps in the middle, which would require
having a sorted list. If no TEI guaranteed to be unused is found in that
way, gtphub will abort(). (It could just drop packets instead, but maybe
abort() is better until we have a test for it.)
TEIs are so far picked sequentially, but should (TM) be picked randomly.
Again, a sorted list would solve.
Sequence numbers are different because
- they time out after 30 seconds (I picked 30 seconds off the top of my
head, haven't really searched for a timeout in the specs yet.)
- they are specified to be sequential.
Exhausting 65535 sequence numbers in 30 seconds sounds possible; note,
this is a general limitation of GTP. If a packet is resent again and again
with the same sequence number (common strategy when no reply is received),
a given sequence mapping can linger for more than 30 seconds; but the
retries should in turn cease within another 30 seconds or so. So on the
one hand sequence nrs are more likely to wrap (space is only 2^16), on the
other hand less likely to stick around. I'm not checking sequence nr
collisions yet.
Sequence numbers are supposed to be sequential, so for those, gtphub could
remember the range of used sequence nrs as head..tail, and advance head as
used ones are discarded. If a discarded number is != head, store that in a
list; advance head, emptying the list as appropriate, once head is
released (because of the sequential nature, that list would usually stay
pretty short). If sequence numbers' tail catches up with head, the GTP
space of pending responses is exhausted, and gtphub should probably drop
any further requests to that peer until head has advanced (and ensure
its timeout is valid or something).
Any thoughts are welcome!
BTW, the same situations can arise in osmo-sgsn and openggsn. While
obsessing about this in gtphub, we should probably visit the others as
well...? ;)
~Neels
--
- Neels Hofmeyr <nhofmeyr(a)sysmocom.de> http://www.sysmocom.de/
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On Wed, Nov 25, 2015 at 09:05:40PM +0100, Holger
Freyther wrote:
> E.g. a unit test that exhausts the entire
number space should be
feasible.
Really? 4.294.967.295 TEI mappings?? Thats 4*sizeof(mapping) gigabytes and
might need special memory model options to work, and the testing
machine needs that many gigs of ram and will take quite a while: O(n²)...
I am fond of exhausting tests, too.
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Holger Freyther -
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Neels Hofmeyr