bsc: Let the VTY verify that the timeout is a number

Before the old code allowed to specify "timeout-ping bla" which
would be parsed as '0' which would trigger a flood of pings. Use
the VTY code to parse it as a number.
nitb: Add subscriber delete command
gbproxy/test: Test IMSI acquisition for RA UDP REQ

When a MS is state GMM_REGISTERED enters a new RA, it sends a RA
Update Request which is then handled by a gbproxy that possibly
doesn't have a matching tlli_info. In this case, depending on the
configuration an identification procedure to acquire the IMSI must be
started.

This adds tests to test_gbproxy_imsi_acquisition():
 - IMSI acquisition triggered by a RA Update Request message
 - Reaction to repeated RA Update Request messages, like it could be
   caused by packet loss between PCU and gbproxy.

Sponsored-by: On-Waves ehf
gbproxy: Restart IMSI acquisition on RA UDP REQ

Currently the IMSI acquisition is not restarted when a RA Update
Request is received. This leads to repeated N(U) in the generated
Ident Request message, which in turn causes the MS to drop the
second of these message. This is bad, when the first Ident Response
has been lost between MS and gbproxy.

This patch changes gbproxy_imsi_acquisition() to handle RA Update
Request messages like Attach Requests.

Sponsored-by: On-Waves ehf
gbproxy/sgsn: Enforce termination when creating a P-TMSI/TLLI

Currently the number of iterations when creating a P-TMSI/TLLI is not
limited. It is nevertheless very unlikely that the loop will not
terminate. On the other hand, the number of iterations of every loop
should have an upper bound (loop variant) which wouldn't be the case
here if an arbitrary random generator was used.

This patch limits the number of iterations to 23 and logs an error if
the creation of the indentifier was aborted due to this limit.

Sponsored-by: On-Waves ehf
gbproxy: Rename identifiers related to IMSI matching

This patch renames gbproxy_check_tlli() to
gbproxy_imsi_matches() and struct tlli_info's
enable_patching to imsi_matches.

It's meant to be more obvious and consistent this way.

Sponsored-by: On-Waves ehf
gbproxy: Remove sgsn_nsei parameter

The function gbproxy_imsi_acquisition() has a parameter sgsn_nsei
that is alyways equal to tlli_info->sgsn_nsei (if tlli_info is not
NULL).

This patch removes this parameter from gbproxy_imsi_acquisition() and
gbproxy_flush_stored_messages() and accesses tlli_info->sgsn_nsei
instead within these functions.

Sponsored-by: On-Waves ehf
gbproxy: Rename functions related to tlli_info

This patch replaces 'tlli' by 'tlli_info' within the following
function identifiers:
  - gbproxy_delete_tlli
  - gbproxy_delete_tllis
  - gbproxy_remove_stale_tllis
  - gbproxy_touch_tlli
  - gbproxy_unregister_tlli
  - gbproxy_remove_matching_tllis
  - gbproxy_find_tlli -> gbproxy_tlli_info_by_tlli
  - gbproxy_find_tlli_by_* -> gbproxy_tlli_info_by_*

These functions refer to the whole logical link info rather than to a
certain TLLI. So they are renamed to be named consistently with
gbproxy_attach_tlli_info and others.

Sponsored-by: On-Waves ehf
gbproxy: Use the term 'link' instead of 'tlli'

Currently in many places where 'tlli' (Temporary Logical Link
Identifier) within identifiers is used, the logical link itself is
meant instead. For instance, the tlli_info contain information about
an LLC logical link including up to four individual TLLI.

To avoid confusion between these concepts, this patch replaces all
'tlli_info' by 'link_info' and a few 'tlli' by 'link'.

Sponsored-by: On-Waves ehf
gbproxy: Rename the field 'enabled_tllis' to 'logical_links'

This field in struct gbproxy_patch_state has involved and holds a
list of all tracked logical links now. Thus the name is modified
accordingly.

Sponsored-by: On-Waves ehf
gbproxy: Replace 'tlli' by 'link' in VTY commands

Since the (former) TLLI list has developed into a logical link list,
related commands are renamed accordingly.

 - tlli-list * -> link-list *
 - delete-gbproxy-tlli * -> delete-gbproxy-link *
 - show gbproxy tllis -> show gbproxy links

Sponsored-by: On-Waves ehf
gbproxy: Only search by valid identifiers

Don't return a link_info if TLLI is 0 resp. P-TMSI is 0xffff. These
values are used for uninitialised or cleared fields and can possibly
match several entries.

Sponsored-by: On-Waves ehf
gbproxy: Use monotonic system time instead of time-of-day

Currently time() is used for age calculations. This time source
may jump either forwards or backwards in time (NTP update, leap
seconds).

This patch replaces the use of time() by using
clock_gettime(CLOCK_MONOTONIC) instead.

Sponsored-by: On-Waves ehf
gbproxy/test: Fix time calculation in test_gbproxy_tlli_expire()

A single test case still uses time() to obtain the reference time.

This commit fixes this by using the 'now' variable instead, that
contains a fixed time value and does therefore not depend on when the
test is executed.

Sponsored-by: On-Waves ehf
gbproxy/test: Fix IMSI length check (Coverity)

This fixes the IMSI length assertion, which currently uses a
greater-or-equal than zero comparison which always yields true. It is
replaced by a greater than zero check.

Fixes: Coverity CID 1239442

Sponsored-by: On-Waves ehf
gbproxy/test: Add invalidation tests to test_gbproxy_keep_info()

The TLLI should also be invalidated:
 - when an Attach Reject info is received from the SGSN
 - when an Attach Req is immediately followed by a Detach Req
 - when an Attach Req is immediately followed by an MT detach
   procedure

To verify that, this patch adds corresponding message sequences to
the test.

Sponsored-by: On-Waves ehf
gbproxy: Parse Attach Reject messages

That message is currently ignored but should invalidate the TLLI and
de-register the logical link instead.

This patch extends the parser to recognize such messages and to set
the invalidate_tlli flag.

Sponsored-by: On-Waves ehf
gbproxy: Reset IMSI acquisition within gbproxy_unregister_link_info

Currently then link_info is not cleanup up completely, when
gbproxy_unregister_link_info is called.

This patch adds a function gbproxy_reset_link that must be defined
externally. This is done in gb_proxy.c, where it resets the IMSI
acquisition.

Sponsored-by: On-Waves ehf
gbproxy: Refactor local message generation

This patch adds und uses the function gbproxy_gsm48_to_peer() which
takes a GSM 04.08 message, encapsulates it in BSSGP and LLC, and
sends it to the BSS peer. This function increments vu_gen_tx_bss
which is now used instead of imsi_acq_retries to set the N(U) of the
outgoing message.

Since imsi_acq_retries isn't currently incremented before a Detach
Accept is generated, this patch also fixes the N(U) of such messages.

Sponsored-by: On-Waves ehf
gprs: Fix gprs_msgb_copy pointer computation

Currently the pointer are computed by adding an offset to the new
message's _data pointer even when the original pointer is NULL.
This leads to invalid pointers in the copied msgb.

This patch adds a NULL check to each computation such that NULL
pointers are not adjusted.

Sponsored-by: On-Waves ehf