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Bug #4035

LAPDm implementation truncates L3 messages at 200 bytes

Added by laforge about 2 months ago. Updated about 2 months ago.

Status:
Resolved
Priority:
Normal
Assignee:
Category:
-
Target version:
-
Start date:
06/01/2019
Due date:
% Done:

100%

Spec Reference:

Description

While writing BTS_Tests_LAPDm.TC_segm_concat, I discovered that sending segmented LAPDm messages with a total length exceeding 200 bytes will be truncated. Interestingly, the incoming I-frames are acknowledged to the sender, but the recipient gets a truncated message.

The log output looks like this:

DLLAPD <0011> lapd_core.c:1503 I received in state LAPD_STATE_MF_EST on SAPI(0) (dl=0x7fcb04210da8)
DLLAPD <0011> lapd_core.c:1591 incrementing V(R) to 4 (dl=0x7fcb04210da8)
DLLAPD <0011> lapd_core.c:1618 Received frame overflow! (dl=0x7fcb04210da8)
DLLAPD <0011> lapd_core.c:1633 message in multiple I frames (next message) (dl=0x7fcb04210da8)
DLLAPD <0011> lapd_core.c:1837 lapd_send_i() called from line 1661 (dl=0x7fcb04210da8)
DLLAPD <0011> lapd_core.c:1671 we are not busy and have no pending data, send RR (dl=0x7fcb04210da8)

Attached pcap file shows the issue.

lapdm_truncation.pcap lapdm_truncation.pcap 2.96 KB laforge, 06/01/2019 09:44 AM

Related issues

Related to OsmoBTS - Feature #3750: Extension of BTS_Tests.ttcn test coverageIn Progress01/08/2019

History

#1 Updated by laforge about 2 months ago

  • Related to Feature #3750: Extension of BTS_Tests.ttcn test coverage added

#2 Updated by laforge about 2 months ago

  • Status changed from New to In Progress
  • % Done changed from 0 to 90

patch in https://gerrit.osmocom.org/c/libosmocore/+/14317 confirmed by f_TC_segm_concat test.

#3 Updated by laforge about 2 months ago

  • Status changed from In Progress to Resolved
  • % Done changed from 90 to 100

patch merged.

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