On Wed, 11 Nov 2020 12:50:25 +0100 Georg Kohmann wrote:
> Packets are processed even though the first fragment don't include all
> headers through the upper layer header. This breaks TAHI IPv6 Core
> Conformance Test v6LC.1.3.6.
>
> Referring to RFC8200 SECTION 4.5: "If the first fragment does not include
> all headers through an Upper-Layer header, then that fragment should be
> discarded and an ICMP Parameter Problem, Code 3, message should be sent to
> the source of the fragment, with the Pointer field set to zero."
>
> The fragment needs to be validated the same way it is done in
> commit 2efdaaaf883a ("IPv6: reply ICMP error if the first fragment don't
> include all headers") for ipv6. Wrap the validation into a common function,
> ipv6_frag_thdr_truncated() to check for truncation in the upper layer
> header. This validation does not fullfill all aspects of RFC 8200,
> section 4.5, but is at the moment sufficient to pass mentioned TAHI test.
>
> In netfilter, utilize the fragment offset returned by find_prev_fhdr() to
> let ipv6_frag_thdr_truncated() start it's traverse from the fragment
> header.
>
> Return 0 to drop the fragment in the netfilter. This is the same behaviour
> as used on other protocol errors in this function, e.g. when
> nf_ct_frag6_queue() returns -EPROTO. The Fragment will later be picked up
> by ipv6_frag_rcv() in reassembly.c. ipv6_frag_rcv() will then send an
> appropriate ICMP Parameter Problem message back to the source.
>
> References commit 2efdaaaf883a ("IPv6: reply ICMP error if the first
> fragment don't include all headers")
>
> Signed-off-by: Georg Kohmann <geokohma@xxxxxxxxx>
LGTM, awaiting ack from Pablo.
