llc: Add put_dummy_frame to create an LLC dummy command
The LLC dummy command is needed for RLC block stuffing, e.g. when a
TBF should be kept open if no LLC data is available. The RLC block
headers do not support stuffing, only the last block of a TBF can be
used partially. LLC dummy commands are discarded by the receiver
immediately, because the have an invalid FCS checksum.
This commit adds the function put_dummy_frame, which puts a LLC dummy
command into the frame buffer. The requested length is given as an
argument, but the real length might be adjusted according to the
specification (see GSM 44.064, 6.4.2.2).
Sponsored-by: On-Waves ehf
diff --git a/src/llc.h b/src/llc.h
index 1f0c114..f82c4ed 100644
--- a/src/llc.h
+++ b/src/llc.h
@@ -38,6 +38,7 @@
struct msgb *dequeue();
void put_frame(const uint8_t *data, size_t len);
+ void put_dummy_frame(size_t req_len);
void append_frame(const uint8_t *data, size_t len);
void consume(size_t len);