András Korn's questions

I have a Devuan system with an inconveniently large number of physical network interfaces. I occasionally have to disconnect the cables and it's a pain to make sure they get reconnected to the same interface.

I also use expressive interface names; instead of ethX I have names like intra or mgmt or someprovider, based on the purpose of the interface. These names are referenced in firewall rules etc.

I wrote a script that runs at boot and figures out which interface is plugged into what, then renames them accordingly. I'm not satisifed with this solution because it involves a lot of custom scripting; I'd like something more mainstream, if possible.

The script currently identifies networks in the following ways:

• It can temporarily configure the interface with an address and see if it can ping or arping a specific destination (this works for uplinks -- I ping the upstream router).
• It can listen on the interface using tcpdump to see if there is traffic from any of a number of specific MAC addresses, at least one of which will likely send something within a few seconds. I know this isn't foolproof, but it's good enough for me. (I use something like timeout ... tcpdump -c 1 -i interfacename "(ether host foo) or (ether host bar) or ...".) This works well for internal networks where I don't have anything specific to ping but where I can expect almost constant traffic.
• It can configure a temporary IP on the interface and run nmap -sn -oG against an IP range to see how many hosts are present and reachable from that range. This is a useful heuristic for some internal networks that will contain many hosts but where I don't know for sure which ones.

I'm looking for a way to preferably integrate this with ifupdown. I've looked at mappings, but it seems to me that with a map script I can only choose a logical configuration to apply to a physical interface, not rename the interface. interfaces(5) says that Lines beginning with "rename" are used to rename interfaces. It takes one or more arguments in the form of "CUR=NEW", where CUR is the name of an existing interface, and NEW is the new name. This becomes very powerful when combined with pattern matching for the CUR interface.; however, pattern matching also doesn't help me.

If it were possible to use the result of a mapping in a rename statement somehow, that might work.

I've also looked at the whereami package, but it didn't look promising.

What I would most like is a way to have ifupdown rename a network interface based on something an if-pre-up script or a mapping script outputs.

I'm in a situation where I have to provide a transparent reverse proxy in front of a set of thousands of backend https webservers, with the list changing (relatively) frequently.

I know I can tell haproxy to select a backend to connect to based on the SNI string the client sends along with the Client Hello (see e.g. Can a Reverse Proxy use SNI with SSL pass through?), but it seems I would need to enumerate all backends and refer to them individually in the configuration; i.e. "if SNI is so-and-so, talk to backend this-and-that".

I'd instead like to just take the SNI string from the Client Hello, look it up in DNS, connect to the IP DNS provides (on tcp port 443), relay the client hello to the server, and then keep relaying between the client and the server.

I don't want to inspect the traffic and don't want to install a new certificate on the clients.

Can haproxy do this? If not, what other program can?