edge: Use rlc_data_to_dl_append in create_new_bsn
Currently TBF related tasks (status changes, counter updates,
LLC dummy command insertion) as well as
RLC data block generation are done within create_new_bsn.
The data block creation part has already been copied to
the stateless Encoding::rlc_data_to_dl_append function.
This commit changes create_new_bsn to use the encoder function and
just care about the TBF related stuff.
Since the rlc_data_to_dl_append function has been validated against
the test cases being described in annex B of TS 44.060, this
commit fixes an encoder bug which leads to broken LLC frames in
a special case (see example B.2, the main header's E bit was
erroneously set to 1 in that case). When this happens, the LLC frame
will get discarded after reassembly, so that TCP will have to
retransmit the lost packet.
Sponsored-by: On-Waves ehf
diff --git a/src/tbf_dl.cpp b/src/tbf_dl.cpp
index a1f8b60..35c3ccb 100644
--- a/src/tbf_dl.cpp
+++ b/src/tbf_dl.cpp
@@ -424,13 +424,14 @@
struct msgb *gprs_rlcmac_dl_tbf::create_new_bsn(const uint32_t fn, const uint8_t ts)
{
- struct rlc_li_field *li;
- uint8_t *delimiter, *data, *e_pointer;
- uint16_t space, chunk;
+ uint8_t *data;
gprs_rlc_data *rlc_data;
const uint16_t bsn = m_window.v_s();
GprsCodingScheme cs = current_cs();
gprs_rlc_data_block_info *rdbi;
+ int num_chunks = 0;
+ int write_offset = 0;
+ Encoding::AppendResult ar;
if (m_llc.frame_length() == 0)
schedule_next_frame();
@@ -457,12 +458,11 @@
rdbi->bsn = bsn; /* Block Sequence Number */
rdbi->e = 1; /* Extension bit, maybe set later (1: no extension) */
- e_pointer = NULL; /* points to E of current chunk if it is stored in an
- extension byte */
- delimiter = data; /* where next length header would be stored */
- space = block_data_len;
- while (1) {
+ do {
+ bool is_final;
+
if (m_llc.frame_length() == 0) {
+ int space = block_data_len - write_offset;
/* A header will need to by added, so we just need
* space-1 octets */
m_llc.put_dummy_frame(space - 1);
@@ -482,119 +482,28 @@
m_llc.frame_length(), frames_since_last_drain(fn));
}
- chunk = m_llc.chunk_size();
+ is_final = llc_queue()->size() == 0 && !keep_open(fn);
- /* if chunk will exceed block limit */
- if (chunk > space) {
- LOGP(DRLCMACDL, LOGL_DEBUG, "-- Chunk with length %d "
- "larger than space (%d) left in block: copy "
- "only remaining space, and we are done\n",
- chunk, space);
- /* block is filled, so there is no extension */
- if (e_pointer)
- *e_pointer |= 0x01;
- /* fill only space */
- m_llc.consume(data, space);
- /* return data block as message */
- break;
- }
- /* if FINAL chunk would fit precisely in space left */
- if (chunk == space && llc_queue()->size() == 0 && !keep_open(fn))
- {
- LOGP(DRLCMACDL, LOGL_DEBUG, "-- Chunk with length %d "
- "would exactly fit into space (%d): because "
- "this is a final block, we don't add length "
- "header, and we are done\n", chunk, space);
- LOGP(DRLCMACDL, LOGL_INFO, "Complete DL frame for "
- "%s that fits precisely in last block: "
- "len=%d\n", tbf_name(this), m_llc.frame_length());
- gprs_rlcmac_dl_bw(this, m_llc.frame_length());
- /* block is filled, so there is no extension */
- if (e_pointer)
- *e_pointer |= 0x01;
- /* fill space */
- m_llc.consume(data, space);
- m_llc.reset();
- /* final block */
- rdbi->cv = 0; /* we indicate final block */
- request_dl_ack();
- set_state(GPRS_RLCMAC_FINISHED);
- /* return data block as message */
- break;
- }
- /* if chunk would fit exactly in space left */
- if (chunk == space) {
- LOGP(DRLCMACDL, LOGL_DEBUG, "-- Chunk with length %d "
- "would exactly fit into space (%d): add length "
- "header with LI=0, to make frame extend to "
- "next block, and we are done\n", chunk, space);
- /* make space for delimiter */
- if (delimiter != data)
- memmove(delimiter + 1, delimiter,
- data - delimiter);
- data++;
- space--;
- /* add LI with 0 length */
- li = (struct rlc_li_field *)delimiter;
- li->e = 1; /* not more extension */
- li->m = 0; /* shall be set to 0, in case of li = 0 */
- li->li = 0; /* chunk fills the complete space */
- // no need to set e_pointer nor increase delimiter
- /* fill only space, which is 1 octet less than chunk */
- m_llc.consume(data, space);
- /* return data block as message */
- break;
- }
+ ar = Encoding::rlc_data_to_dl_append(rdbi,
+ &m_llc, &write_offset, &num_chunks, data, is_final);
- LOGP(DRLCMACDL, LOGL_DEBUG, "-- Chunk with length %d is less "
- "than remaining space (%d): add length header to "
- "to delimit LLC frame\n", chunk, space);
- /* the LLC frame chunk ends in this block */
- /* make space for delimiter */
- if (delimiter != data)
- memmove(delimiter + 1, delimiter, data - delimiter);
- data++;
- space--;
- /* add LI to delimit frame */
- li = (struct rlc_li_field *)delimiter;
- li->e = 0; /* Extension bit, maybe set later */
- li->m = 0; /* will be set later, if there is more LLC data */
- li->li = chunk; /* length of chunk */
- rdbi->e = 0; /* 0: extensions present */
- e_pointer = delimiter; /* points to E of current delimiter */
- delimiter++;
- /* copy (rest of) LLC frame to space and reset later */
- m_llc.consume(data, chunk);
- data += chunk;
- space -= chunk;
+ if (ar == Encoding::AR_NEED_MORE_BLOCKS)
+ break;
+
LOGP(DRLCMACDL, LOGL_INFO, "Complete DL frame for %s"
"len=%d\n", tbf_name(this), m_llc.frame_length());
gprs_rlcmac_dl_bw(this, m_llc.frame_length());
m_llc.reset();
- /* dequeue next LLC frame, if any */
- schedule_next_frame();
- /* if we have more data and we have space left */
- if (space > 0 && (m_llc.frame_length() || keep_open(fn))) {
- li->m = 1; /* we indicate more frames to follow */
- continue;
- }
- /* if we don't have more LLC frames */
- if (!m_llc.frame_length() && !keep_open(fn)) {
- LOGP(DRLCMACDL, LOGL_DEBUG, "-- Final block, so we "
- "done.\n");
- li->e = 1; /* we cannot extend */
- rdbi->cv = 0; /* we indicate final block */
+ if (is_final) {
request_dl_ack();
set_state(GPRS_RLCMAC_FINISHED);
- break;
}
- /* we have no space left */
- LOGP(DRLCMACDL, LOGL_DEBUG, "-- No space left, so we are "
- "done.\n");
- li->e = 1; /* we cannot extend */
- break;
- }
+
+ /* dequeue next LLC frame, if any */
+ schedule_next_frame();
+ } while (ar == Encoding::AR_COMPLETED_SPACE_LEFT);
+
LOGP(DRLCMACDL, LOGL_DEBUG, "data block (BSN %d, %s): %s\n",
bsn, rlc_data->cs.name(),
osmo_hexdump(rlc_data->block, block_data_len));