The original commit is over 10 years old now, so it's probably lost to the sands of time. I did some looking but couldn't find anything on the old netdev lists.

The original commit is over 10 years old now, so it's probably lost to the sands of time. I did some looking but couldn't find anything on the old netdev lists. Maybe the patch was sent directly to Pablo Neira Ayuso, the committer. It was part of a series so it's not like it was a one-off patch. In a strange twist of fate, the original author was Patrick McHardy who is now a persona non grata. Unless Pablo can remember or dig it from his emails, it probably won't ever be clear exactly what the use case was, at least not through basic investigation.