cellular-infrastructure
/
osmo-pcu
mirror of https://gerrit.osmocom.org/osmo-pcu
9
0
Fork 1
Code Issues Releases Wiki Activity

Fix CSN1 decoding: CSN_LEFT_ALIGNED_VAR_BMP bounds 

Fix attempted read past vector boundaries in case of a starting bit offset !=
0, so that the last amount of bits read should be < 8. In the case of
CSN_LEFT_ALIGNED_VAR_BMP, the mod-8 calculation was flawed, and in the final
step, 8 bits were read instead of the remainder < 8. This lead to -EINVAL being
returned by bitvec_get_bit_pos() and bogus resulting data.

Instead, read 8 bits only as long as at least 8 bits remain, and read any
remaining bits < 8 in a final step. Drop unneeded nB1 variable and an obvious
comment.

Adjust the unit test assertion in testCsnLeftAlignedVarBmpBounds() in
RLCMACTest.cpp.

Based on a fix by Aravind Sirsikar <Arvind.Sirsikar@radisys.com>, but
implemented differently.

Related: OS#1805
Change-Id: I490498c8da6b531f54acb673379379f7b10907c0
This commit is contained in:
Neels Hofmeyr 2016-09-02 02:15:26 +02:00
parent 9f5f008aed
commit 0241526836
2 changed files with 6 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
src/csn1.cpp
View File

@ -1110,22 +1110,21 @@ csnStreamDecoder(csnStream_t* ar, const CSN_DESCR* pDescr, bitvec *vector, unsig
{ /* extract bits */
guint8* pui8 = pui8DATA(data, pDescr->offset);
gint16 nB1 = no_of_bits & 0x07;/* no_of_bits Mod 8 */
while (no_of_bits > 0)
while (no_of_bits >= 8)
{
*pui8 = bitvec_read_field(vector, readIndex, 8);
LOGPC(DCSN1, LOGL_NOTICE, "%s = %u | ", pDescr->sz , (unsigned)*pui8);
pui8++;
no_of_bits -= 8;
}
if (nB1 > 0)
if (no_of_bits > 0)
{
*pui8 = bitvec_read_field(vector, readIndex, nB1);
*pui8 = bitvec_read_field(vector, readIndex, no_of_bits);
LOGPC(DCSN1, LOGL_NOTICE, "%s = %u | ", pDescr->sz , (unsigned)*pui8);
pui8++;
no_of_bits -= nB1;
bit_offset += nB1; /* (nB1 is no_of_bits Mod 8) */
bit_offset += no_of_bits;
no_of_bits = 0;
}
}
}

7
tests/rlcmac/RLCMACTest.cpp
View File

@ -223,13 +223,8 @@ void testCsnLeftAlignedVarBmpBounds()
&data.u.Egprs_Packet_Downlink_Ack_Nack.EGPRS_AckNack.Desc;
decode_gsm_rlcmac_uplink(vector, &data);
/*
* TODO: URBB len is decoded as 102 bits. So 96 + 6 bits = 12 bytes + 6
* bits should be decoded. The 13th byte should end up as 0x00, but we
* see data coming from bitvec_get_bit_pos() returning -EINVAL.
*/
OSMO_ASSERT(!strcmp(osmo_hexdump(urbb->URBB, 13),
"7f ff ff ee 00 00 00 00 00 00 00 00 ea "));
"7f ff ff ee 00 00 00 00 00 00 00 00 00 "));
}
int main(int argc, char *argv[])