Re: [Int-area] I-D Action: draft-ietf-intarea-frag-fragile-06.txt

[Ole Troan <[e-mail]>]

Tom,

> It does seem that Cisco configuration manuals and marketing materials
> are the best source of information on virtual reassembly.
> 
> https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipaddr_frre/configuration/xe-3s/frre-xe-3s-book/virt-frag-reassembly.html
> is a little more interesting in that it provides a few more details.
> In particular the requirement that all fragments must traverse the
> same intermediate device is mentioned:
> 
> "The reassembly process requires all fragments within an IP datagram.
> If fragments within an IP datagram are sent to different devices due
> to load balancing VFR may fail and fragments may be dropped.”

I can’t tell if you are actually interested in how it works, or if you are trying to make a point.
Assuming the former, here is an implementation:
https://github.com/FDio/vpp/blob/master/src/plugins/map/ip4_map.c#L517

if first fragment in chain
  found = lookup 4 tuple in reassenbly cache
  if found
     forward buffered packets
  else
    create session state entry in reassembly cache
    forward packet
else
  found = lookup 4 tuple in reassembly cache
  if found
    forward packet
  else
    buffer packet

Ole