Compression/decompression failure with large IPv6 extension

The ROHC library fails to correctly compress and decompress an IPv6 packet with a large IPv6 extension (2048 bytes). The library does not report any error either during compression or during decompression. However, the generated ROHC packet is 4150-byte long and the generated IP packet is 4144-byte long while the original IPv6 packet is only 2096-byte long.

The problem may be reproduced with the non-regression tool and the attached PCAP capture. The output of the command below is attached to the bug too.
   $ ./test/test smallcid ipv6_with_large_extension.pcap

The PCAP capture was generated with Scapy (http://www.secdev.org/projects/scapy/) with the following Python commands:
  >>> pad = ''
  >>> for i in range(0, 255):
  ... pad += '\x00'
  ...
  >>> packet = Ether() / IPv6() / \
  ... IPv6ExtHdrHopByHop(options = [ \
  ... PadN(otype='PadN', optlen=255, optdata=pad), \
  ... PadN(otype='PadN', optlen=255, optdata=pad), \
  ... PadN(otype='PadN', optlen=255, optdata=pad), \
  ... PadN(otype='PadN', optlen=255, optdata=pad), \
  ... PadN(otype='PadN', optlen=255, optdata=pad), \
  ... PadN(otype='PadN', optlen=255, optdata=pad), \
  ... PadN(otype='PadN', optlen=255, optdata=pad), \
  ... PadN(otype='PadN', optlen=245, optdata=pad[0:245]) \
  ... ] ) / \
  ... ICMPv6EchoRequest()
  >>> wrpcap("ipv6_with_large_extension.pcap", packet)