Ah, I did not read well enough - sorry for that.
You'd have to sort this out in Docker indeed.
I see no reason why you should not try using host mode for a start.
And it wouldn't require swarm. (click for more)
I think I recall the sentence in Docker's documentaton that may have convinced you to think otherwise:
hostis only available for swarm services on Docker 17.06 and higher
would be be less misleading if rephrased
hostfor swarm services is only available on Docker 17.06 and higher
It becomes clearer if you actually follow the link in that same paragraph:
See use the host network.
I've only recently replied to a similar topic that may apply to your setup as well.
Please have a look at Source address in docker shows as bridge gateway from other subnets.