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b802021cc4
Building on top of the gateway PR (#6941), this PR transitions the clients to the new control protocol. Clients are **not** backwards-compatible with old gateways. As a result, a certain customer environment MUST have at least one gateway with the above PR running in order for clients to be able to establish connections. With this transition, Clients send explicit events to Gateways whenever they assign IPs to a DNS resource name. The actual assignment only happens once and the IPs then remain stable for the duration of the client session. When the Gateway receives such an event, it will perform a DNS resolution of the requested domain name and set up the NAT between the assigned proxy IPs and the IPs the domain actually resolves to. In order to support self-healing of any problems that happen during this process, the client will send an "Assigned IPs" event every time it receives a DNS query for a particular domain. This in turn will trigger another DNS resolution on the Gateway. Effectively, this means that DNS queries for DNS resources propagate to the Gateway, triggering a DNS resolution there. In case the domain resolves to the same set of IPs, no state is changed to ensure existing connections are not interrupted. With this new functionality in place, we can delete the old logic around detecting "expired" IPs. This is considered a bugfix as this logic isn't currently working as intended. It has been observed multiple times that the Gateway can loop on this behaviour and resolving the same domain over and over again. The only theoretical "incompatibility" here is that pre-1.4.0 clients won't have access to this functionality of triggering DNS refreshes on a Gateway 1.4.2+ Gateway. However, as soon as this PR merges, we expect all admins to have already upgraded to a 1.4.0+ Gateway anyway which already mandates clients to be on 1.4.0+. Resolves: #7391. Resolves: #6828.