ROHC library fails to handle a specific ICMP stream

[Didier Barvaux]

During testing, a specific ICMP stream was not handled correctly by the ROHC library. I'm going to attach a PCAP capture of the ICMP stream to this bug report and the traces output by the non-regression tool.

[Didier Barvaux (didier-barvaux)]

Branch 1.2.x is affected by the bug.

[Didier Barvaux (didier-barvaux)]

Branch 1.3.x is affected by the bug.

[Didier Barvaux (didier-barvaux)]

Main branch is affected by the bug.

[Didier Barvaux (didier-barvaux)]

The problem comes from the way the ROHC library decodes the Offset IP-ID encoding. The shift parameter (variable p) for W-LSB encoding should be p = 0 for Offset IP-ID encoding not 2.

RFC 3095 states in section 4.5.5 "Offset IP-ID encoding" that:
   The remainder of section 4.5.5 describes how to compress/decompress
   the sequence of offsets using W-LSB encoding/decoding, with p = 0
   (see section 4.5.1). All IP-ID arithmetic is done using unsigned
   16-bit quantities, i.e., modulo 2^16.

Offset IP-ID decoding uses p = 2 at line 43 of src/common/ip_id.c. See http://bazaar.launchpad.net/~didier-barvaux/rohc/1.2.x/annotate/head:/src/common/ip_id.c#L43. Changing p = 2 into p = 0 solves the problem.

[Didier Barvaux (didier-barvaux)]

Fix committed to branch 1.2.x. Attached traffic capture added as new non-regression test. See http://bazaar.launchpad.net/~didier-barvaux/rohc/1.2.x/revision/118.

[Didier Barvaux (didier-barvaux)]

Fix committed to branch 1.3.x. Attached traffic capture added as new non-regression test. See http://bazaar.launchpad.net/~didier-barvaux/rohc/1.3.x/revision/146.

[Didier Barvaux (didier-barvaux)]

Fix committed to main branch. Attached traffic capture added as new non-regression test. See http://bazaar.launchpad.net/~didier-barvaux/rohc/main/revision/169.

[Didier Barvaux (didier-barvaux)]

Fix released in version 1.3.1.

[Didier Barvaux (didier-barvaux)]

Fix released in version 1.2.2.