diff options
| author | Jonathan Santos <jrsantos@jonathanrsantos.com> | 2011-06-23 17:53:27 -0400 |
|---|---|---|
| committer | Holger Hans Peter Freyther <zecke@selfish.org> | 2011-10-16 17:59:51 +0200 |
| commit | 0b21bd9b92f1267dfb2a274189069e7fa6b9bd8c (patch) | |
| tree | c736f9dbe8a93352db86a944dd5fe459b6adf8db | |
| parent | 16073cf54640f1a71361ab80410fe937970006c6 (diff) | |
gprs: Fix LLC UI window
According to TS 44.064 section 8.4.2, the LLC layer should only
drop UI frames if V(UR)-32 <= N(U) < V(UR). The code was dropping
frames whenever N(U) < V(UR). Consequently, large amounts of
packets could be dropped if, e.g., V(UR)==511 and the frame with
N(U)==511 was lost. All frames would be dropped until the next
time a frame with N(U)==511 is received.
| -rw-r--r-- | openbsc/src/gprs/gprs_llc.c | 26 |
1 files changed, 15 insertions, 11 deletions
diff --git a/openbsc/src/gprs/gprs_llc.c b/openbsc/src/gprs/gprs_llc.c index d29694fe4..7d5c63f7a 100644 --- a/openbsc/src/gprs/gprs_llc.c +++ b/openbsc/src/gprs/gprs_llc.c @@ -483,17 +483,21 @@ static int gprs_llc_hdr_rx(struct gprs_llc_hdr_parsed *gph, } break; case GPRS_LLC_UI: - if (gph->seq_tx < lle->vu_recv) { - LOGP(DLLC, LOGL_NOTICE, "TLLI=%08x dropping UI, vurecv %u <= %u\n", - lle->llme ? lle->llme->tlli : -1, - gph->seq_tx, lle->vu_recv); - return -EIO; - } - /* Increment the sequence number that we expect in the next frame */ - lle->vu_recv = (gph->seq_tx + 1) % 512; - /* Increment Overflow Counter */ - if ((gph->seq_tx + 1) / 512) - lle->oc_ui_recv += 512; + { + int delta = (lle->vu_recv - gph->seq_tx) & 0x1ff; + if (0 < delta && delta < 32) { + LOGP(DLLC, LOGL_NOTICE, "TLLI=%08x dropping UI, vurecv %u <= %u\n", + lle->llme ? lle->llme->tlli : -1, + gph->seq_tx, lle->vu_recv); + return -EIO; + } + /* Increment the sequence number that we expect in the next frame */ + lle->vu_recv = (gph->seq_tx + 1) & 0x1ff; + /* Increment Overflow Counter */ + if (lle->vu_recv == 0) { + lle->oc_ui_recv += 512; + } + } break; } |