Avoid routes using transports between visors at the same IP address

[0pcom]

When two visors share the same public IP address (e.g., on the same LAN behind NAT), transports between them should be handled specially to avoid suboptimal routing: Routes that include hops between same-IP visors create unnecessary loops

Current State

• The Address Resolver already detects same-IP visors and sets IsLocal: true in VisorData (see pkg/address-resolver/api/api.go:307-309)
• The transport network client uses this flag for connection optimization
• However, the Transport Discovery (TPD) does not store or expose this information
• Local route calculation has no awareness of same-IP transports

Proposed Solution

1. TPD: Add is_local or same_ip flag to transport entries (don't modify /all-transports ; only /metrics)
   - At registration time, TPD could query AR for both edges' IPs and compare
   - Or accept the flag from the registering visor
2. Route calculation: Filter or deprioritize same-IP transports
   - Route finder should exclude these from routes to external destinations
   - Local route calculation should do the same
   - Routes including transports between visors at the same public ip address could still be used when the destination is on the same IP or at user discretion - but by default not used.

Related

• VisorData.IsLocal flag: pkg/transport/network/addrresolver/client.go:74
• Same-IP detection: pkg/address-resolver/api/api.go:307-311
• Transport Entry struct: pkg/transport/entry.go:33