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Vadim Yanitskiy d02927b036 layer23/l1ctl.c: fix: verify msg length using l1h, not l2h 
The actual L1CTL header is pointed by 'msg->l1h', not 'l2h'!
Since msg->l2h is NULL (because nobody set it), the result of
msgb_l2len() would always be bigger than size of L1CTL header,
as it is calculated in the following way:

  return msgb->tail - (uint8_t *)msgb_l2(msgb);

So, in case if 'msg->l2h' is NULL, it turns into:

  return msgb->tail - 0;

Change-Id: I7fe2e00bb45ba07c9bb7438445eededfa09c96f3
 		2018-10-03 19:21:58 +07:00
..
include lua: Expose API to trigger a network reselection 2018-09-16 13:51:29 +00:00
src layer23/l1ctl.c: fix: verify msg length using l1h, not l2h 2018-10-03 19:21:58 +07:00
.gitignore misc: Ignore two misc application binaries 2011-01-23 11:36:30 +01:00
COPYING Rename 'layer2' program to 'layer23' program 2010-03-03 14:25:21 +01:00
Makefile.am Rename 'layer2' program to 'layer23' program 2010-03-03 14:25:21 +01:00
README add some notes about layer23 architecture 2010-03-03 14:37:21 +01:00
configure.ac layer23: Add --enable-sanitize and --enable-werror configure flags 2018-08-11 12:59:30 +00:00

README 

= OsmocomBB layer23 architecture =

layer23 is an (incomplete) MS-side implementation of the L2 and L3 GSM
protocols as described in GSM TS 04.06, 04.08 and others.

== Interfaces ==

L1 (on the phone) uses the L1CTL protocol to talk with layer23 (on the PC).

L2 (inside layer23) uses the RSLms protocol to talk with the L3 (inside layer23)


=== RSLms ===

RSLms is modeled after the GSM TS 08.58 Radio Subsystem Link protocol.  Despite
being designed for the network side, RSL seems a good match for the L2/L3
interface inside a MS, too.

At least the RLL (Radio Link Layer) part of RSL is 100% as applicable to the MS
side as it is for the ntwork side.

==== Lower interface (L2 to RSLms) ====

Layer2 calls rslms_sendmsg() with a msgb that has the msgb->l2h pointing to a
RSL header (struct abis_rsl_common_hdr).

==== Upper interface (L3 to RSLms) ====

Layer3 calls rslms_recvmsg() with a msgb that has the msgb->l2h pointing to a
RSL header (struct abis_rsl_common_hdr).

There are utility functions like rslms_tx_rll_req() and rslms_tx_rsll_req_l3()
for creating msgb's with the apropriate RSL/RLL headers.


=== LAPDm ===

LAPDm is the GSM TS 04.06 protocol

The lower interface (to L1) is using L1CTL

The upper interface (to L3) is using RSLms