>
> "Ananyev, Konstantin" <konstantin.anan...@intel.com> writes:
>
> >>
> >> The IPv4 specification says that each fragment must at least the size of
> >> an IP header plus 8 octets. When attempting to run ipfrag using a
> >> smaller size, the fragment library will return successful completion,
> >> even though it is a violation of RFC791 (and updates).
> >>
> >> Signed-off-by: Aaron Conole <acon...@redhat.com>
> >> ---
> >> lib/librte_ip_frag/rte_ipv4_fragmentation.c | 6 ++++++
> >> 1 file changed, 6 insertions(+)
> >>
> >> diff --git a/lib/librte_ip_frag/rte_ipv4_fragmentation.c
> >> b/lib/librte_ip_frag/rte_ipv4_fragmentation.c
> >> index 9e9f986cc5..4baaf6355c 100644
> >> --- a/lib/librte_ip_frag/rte_ipv4_fragmentation.c
> >> +++ b/lib/librte_ip_frag/rte_ipv4_fragmentation.c
> >> @@ -76,6 +76,12 @@ rte_ipv4_fragment_packet(struct rte_mbuf *pkt_in,
> >> uint16_t fragment_offset, flag_offset, frag_size;
> >> uint16_t frag_bytes_remaining;
> >>
> >> + /*
> >> + * Ensure the IP fragmentation size is at least iphdr length + 8 octets
> >> + */
> >> + if (unlikely(mtu_size < (sizeof(struct rte_ipv4_hdr) + 8*sizeof(char))))
> >> + return -EINVAL;
> >> +
> >
> > Same comment as for ipv6: ipv4 min MTU is 68B.
>
> I can change it. I suspected that if I went with 68 here and 1280 in
> the v6 code, I would get pushback, but I should have just submitted it
> that way to begin.
>
> > Why do we need extra checking here?
>
> These are error conditions to submit to fragmentation module. Someone
> needs to do the check - either it is done in the application or the
> library. If the library doesn't, and the application writer doesn't
> know they must write these checks (it isn't documented anywhere), then
> we get non compliant behavior. By putting it in the library, we can
> clearly signal the application writer such a case has occurred.
>
> Should we not do error checking?
It depends I think...
In many data-path functions we skip parameter checking.
These fragment() functions are data-path too.
Agree, it is not stated clearly in these functions formal comments,
as it should be.
After another thought - these functions are quite heavy-weighed anyway,
so probably formal parameter checking, something like:
if (pkt_in == NULL || pkts_out == NULL || pool_direct == NULL ||
pool_indirect == NULL || mtu < MIN_MTU)
return -EINVAL;
wouldn't introduce any real slowdown.
About more intense checking - like parsing all extension
headers, etc. - I think it would be too much overhead.
Again for that there is a special function that user can call directly:
rte_ipv6_frag_get_ipv6_fragment_header
(though its current implementation also checks only first extension header).
So, I think we just need to document that it is a user responsibility to
provide not fragmented yet packet, without any pre-fragment headers.
Konstantin
>
> >> /*
> >> * Ensure the IP payload length of all fragments is aligned to a
> >> * multiple of 8 bytes as per RFC791 section 2.3.
> >> --
> >> 2.25.1
