bssap: paging: page entire BSS for unimplemented cell id list
3GPP TS ยง 08.08 defines various types of Cell Identifier List IEs, but we only
implement "entire BSS" and "one LAC". If the MSC sends a Cell Identifier List
that we don't implement, it is best for interoperability to page the entire BSS
and post a log message instead of rejecting the paging altogether. Apart from
resource management, it is not harmful to page more than the MSC requested; if
use of resources becomes an issue, the log message will guide towards the
solution of providing an actually implemented Cell Identifier List IE.
Upon IE length that is other than we expect, log the error, but also fall back
to paging the entire BSS. Overall message length correctness has been checked
earlier.
The particular case observed is that a Huwaei MSC sends a LAI for Cell
Identifier List (MCC+MNC in bcd, followed by a LAC), parsing of which we may
want to add later.
Improve logging: identify the subscriber that is being paged.
Coding style: use a switch() statement to clarify flow and provide a place to
add more implementations later.
Add regression test bssap_test.c: fabricates BSSAP Paging messages with the two
implemented Cell Identifier List IEs as well as the unimplemented LAI
identifier, verify the resulting paging LAC in wrapped function and stderr.
Change-Id: Ie934c5d229140a89763bf2efff86d6a3766cd351
8 files changed