> >> >> 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. > > I'll add documentation as another patch. > > > 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. > > Agreed. > > > 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. > > Makes sense. Then again, the v6 frag code will need to preserve many of > the headers anyway, so since we have to read them, maybe it makes > sense to do the check here anyway. WDYT?
If we want to make this function fully compliant to what rfc8200 says, then yes - extra changes is required in current implementation: 1. somehow obtain information about pre-fragment extensions length 2. use info from #1 to put fragment header at proper location. And extra testing of course. Probably safer and easier, for that patch just add formal parameter checking. And if you feel like that - have the hard part as a separate patch. > > > 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
