edge: Add experimental support for uplink CRBB

Currently only uncompressed bitmaps (URBB) are supported in
PACKET UPLINK ACK/NACK messages.

Extend decode_egprs_acknack_bits to decode compressed bitmaps (CRBB),
too.

Note that this code is only active, if the macro WITH_CRBB_DECODING
is defined.

Sponsored-by: On-Waves ehf

1 files changed, 43 insertions, 4 deletions

diff --git a/src/decoding.cpp b/src/decoding.cpp
index 11c565ac..72293a21 100644
--- a/src/decoding.cpp
+++ b/src/decoding.cpp
@@ -23,6 +23,9 @@
 
 extern "C" {
 #include <osmocom/core/utils.h>
+#if WITH_CRBB_DECODING
+#include <osmocom/core/bitcomp.h>
+#endif
 }
 
 #include <arpa/inet.h>
@@ -568,10 +571,45 @@ int Decoding::decode_egprs_acknack_bits(const EGPRS_AckNack_Desc_t *desc,
 
 		if (crbb_len > 0) {
 			int old_len = bits->cur_bit;
-			/*
-			decode_t4_rle(bits, desc->CRBB, desc->CRBB_LENGTH,
-					desc->CRBB_STARTING_COLOR_CODE);
-			 */
+#if WITH_CRBB_DECODING
+#warning "Experimental CRBB decoding enabled"
+			struct bitvec crbb;
+			int rc;
+
+			crbb.data = (uint8_t *)desc->CRBB;
+			crbb.data_len = sizeof(desc->CRBB);
+			crbb.cur_bit = desc->CRBB_LENGTH;
+
+			rc = osmo_t4_decode(&crbb, desc->CRBB_STARTING_COLOR_CODE,
+				bits);
+
+			if (rc < 0) {
+				LOGP(DRLCMACUL, LOGL_NOTICE,
+					"Failed to decode CRBB: "
+					"length %d, data '%s'\n",
+					desc->CRBB_LENGTH,
+					osmo_hexdump(crbb.data, crbb.data_len));
+				/* We don't know the SSN offset for the URBB,
+				 * return what we have so far and assume the
+				 * bitmap has stopped here */
+				goto aborted;
+			}
+#else
+			LOGP(DRLCMACUL, LOGL_ERROR, "ERROR: CRBB not supported, "
+				"please set window size to 64\n");
+
+			/* We don't know the SSN offset for the URBB, return
+			 * what we have so far and assume the bitmap has
+			 * stopped here */
+			goto aborted;
+#endif
+			LOGP(DRLCMACDL, LOGL_DEBUG,
+				"CRBB len: %d, decoded len: %d, cc: %d, crbb: '%s'\n",
+				desc->CRBB_LENGTH, bits->cur_bit - old_len,
+				desc->CRBB_STARTING_COLOR_CODE,
+				osmo_hexdump(
+					desc->CRBB, (desc->CRBB_LENGTH + 7)/8)
+			    );
 
 			num_blocks += (bits->cur_bit - old_len);
 		}
@@ -591,6 +629,7 @@ int Decoding::decode_egprs_acknack_bits(const EGPRS_AckNack_Desc_t *desc,
 		num_blocks += urbb_len;
 	}
 
+aborted:
 	*bsn_begin = window->v_a();
 	*bsn_end   = window->mod_sns(*bsn_begin + num_blocks);