Use VPS as source of truth for VPN IP allocation

src/main/java/com/litoralregas/vpnprovisioner/ipam/dto/VpnIpAllocationResponse.java

@@ -1,12 +1,14 @@
 package com.litoralregas.vpnprovisioner.ipam.dto;
 
+import com.litoralregas.vpnprovisioner.ipam.entity.VpnIpAllocationStatus;
+
 import java.time.Instant;
 import java.util.UUID;
 
 public record VpnIpAllocationResponse(
         UUID id,
         String ipAddress,
-        boolean allocated,
+        VpnIpAllocationStatus status,
         UUID routerId,
         Instant allocatedAt,
         Instant releasedAt

src/main/java/com/litoralregas/vpnprovisioner/ipam/entity/VpnIpAllocation.java

@@ -15,8 +15,9 @@ public class VpnIpAllocation {
     @Column(nullable = false, unique = true)
     private String ipAddress;
 
+    @Enumerated(EnumType.STRING)
     @Column(nullable = false)
-    private boolean allocated;
+    private VpnIpAllocationStatus status;
 
     private UUID routerId;
 
@@ -30,18 +31,32 @@ public class VpnIpAllocation {
     public VpnIpAllocation(String ipAddress) {
         this.id = UUID.randomUUID();
         this.ipAddress = ipAddress;
-        this.allocated = false;
+        this.status = VpnIpAllocationStatus.ALLOCATED_EXTERNAL;
+        this.allocatedAt = Instant.now();
+    }
+
+    public static VpnIpAllocation backendAllocated(String ipAddress, UUID routerId) {
+        VpnIpAllocation allocation = new VpnIpAllocation(ipAddress);
+        allocation.allocateTo(routerId);
+        return allocation;
     }
 
     public void allocateTo(UUID routerId) {
-        this.allocated = true;
+        this.status = VpnIpAllocationStatus.ALLOCATED;
         this.routerId = routerId;
         this.allocatedAt = Instant.now();
         this.releasedAt = null;
     }
 
+    public void markExternal() {
+        if (this.status != VpnIpAllocationStatus.ALLOCATED) {
+            this.status = VpnIpAllocationStatus.ALLOCATED_EXTERNAL;
+            this.allocatedAt = this.allocatedAt == null ? Instant.now() : this.allocatedAt;
+        }
+    }
+
     public void release() {
-        this.allocated = false;
+        this.status = VpnIpAllocationStatus.RELEASED;
         this.routerId = null;
         this.releasedAt = Instant.now();
     }
@@ -54,8 +69,8 @@ public class VpnIpAllocation {
         return ipAddress;
     }
 
-    public boolean isAllocated() {
+    public VpnIpAllocationStatus getStatus() {
-        return allocated;
+        return status;
     }
 
     public UUID getRouterId() {

src/main/java/com/litoralregas/vpnprovisioner/ipam/entity/VpnIpAllocationStatus.java

@@ -0,0 +1,8 @@
+package com.litoralregas.vpnprovisioner.ipam.entity;
+
+public enum VpnIpAllocationStatus {
+    ALLOCATED,
+    ALLOCATED_EXTERNAL,
+    RELEASED,
+    RETIRED
+}

src/main/java/com/litoralregas/vpnprovisioner/ipam/repository/VpnIpAllocationRepository.java

@@ -4,7 +4,6 @@ import com.litoralregas.vpnprovisioner.ipam.entity.VpnIpAllocation;
 import org.springframework.data.jpa.repository.*;
 import org.springframework.data.repository.query.Param;
 
-import java.util.List;
 import java.util.Optional;
 import java.util.UUID;
 
@@ -12,40 +11,15 @@ public interface VpnIpAllocationRepository extends JpaRepository<VpnIpAllocation
 
     Optional<VpnIpAllocation> findByRouterId(UUID routerId);
 
-    @Query(
+    Optional<VpnIpAllocation> findByIpAddress(String ipAddress);
-            value = """
-                    SELECT *
-                    FROM vpn_ip_allocations
-                    WHERE allocated = false
-                    ORDER BY ip_address
-                    LIMIT 1
-                    FOR UPDATE SKIP LOCKED
-                    """,
-            nativeQuery = true
-    )
-    Optional<VpnIpAllocation> findNextFreeForUpdate();
 
     @Modifying
     @Query("""
             UPDATE VpnIpAllocation ip
-            SET ip.allocated = false,
+            SET ip.status = 'RELEASED',
                 ip.routerId = null,
                 ip.releasedAt = CURRENT_TIMESTAMP
             WHERE ip.routerId = :routerId
             """)
     void releaseByRouterId(@Param("routerId") UUID routerId);
-
-    @Query(
-            value = """
-        SELECT *
-        FROM vpn_ip_allocations
-        WHERE allocated = false
-        ORDER BY ip_address
-        FOR UPDATE SKIP LOCKED
-        """,
-            nativeQuery = true
-    )
-    List<VpnIpAllocation> findFreeCandidatesForUpdate();
-
-    Optional<VpnIpAllocation> findByIpAddress(String ipAddress);
 }

src/main/java/com/litoralregas/vpnprovisioner/ipam/service/VpnIpAllocationService.java

@@ -10,13 +10,18 @@ import com.litoralregas.vpnprovisioner.vps.WireGuardVpsService;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
-import java.util.List;
 import java.util.Set;
 import java.util.UUID;
+import java.util.stream.Collectors;
 
 @Service
 public class VpnIpAllocationService {
 
+    private static final int START_THIRD_OCTET = 1;
+    private static final int END_THIRD_OCTET = 255;
+    private static final int START_FOURTH_OCTET = 1;
+    private static final int END_FOURTH_OCTET = 254;
+
     private final VpnIpAllocationRepository vpnIpAllocationRepository;
     private final RouterRepository routerRepository;
     private final WireGuardVpsService wireGuardVpsService;
@@ -24,7 +29,8 @@ public class VpnIpAllocationService {
     public VpnIpAllocationService(
             VpnIpAllocationRepository vpnIpAllocationRepository,
             RouterRepository routerRepository,
-            WireGuardVpsService wireGuardVpsService) {
+            WireGuardVpsService wireGuardVpsService
+    ) {
         this.vpnIpAllocationRepository = vpnIpAllocationRepository;
         this.routerRepository = routerRepository;
         this.wireGuardVpsService = wireGuardVpsService;
@@ -46,25 +52,57 @@ public class VpnIpAllocationService {
     }
 
     private VpnIpAllocationResponse allocateNewIp(Router router) {
+        Set<String> usedOnVps = refreshUsedIpsFromVps();
+
+        Set<String> knownInDb = vpnIpAllocationRepository.findAll()
+                .stream()
+                .map(VpnIpAllocation::getIpAddress)
+                .collect(Collectors.toSet());
+
+        String nextIp = findNextAvailableIp(usedOnVps, knownInDb);
+
+        VpnIpAllocation allocation = VpnIpAllocation.backendAllocated(nextIp, router.getId());
+
+        VpnIpAllocation saved = vpnIpAllocationRepository.save(allocation);
+
+        router.assignVpnIp(saved.getIpAddress());
+
+        return toResponse(saved);
+    }
+
+    private Set<String> refreshUsedIpsFromVps() {
         Set<String> usedIps = wireGuardVpsService.findUsedVpnIps();
 
-        VpnIpAllocation allocation = vpnIpAllocationRepository
+        for (String ip : usedIps) {
-                .findFreeCandidatesForUpdate()
+            vpnIpAllocationRepository.findByIpAddress(ip)
-                .stream()
+                    .ifPresentOrElse(
-                .filter(ip -> !usedIps.contains(ip.getIpAddress()))
+                            VpnIpAllocation::markExternal,
-                .findFirst()
+                            () -> vpnIpAllocationRepository.save(new VpnIpAllocation(ip))
-                .orElseThrow(() -> new IllegalStateException("No free VPN IP addresses available"));
+                    );
+        }
 
-        allocation.allocateTo(router.getId());
+        return usedIps;
+    }
 
-        return toResponse(allocation);
+    private String findNextAvailableIp(Set<String> usedOnVps, Set<String> knownInDb) {
+        for (int thirdOctet = START_THIRD_OCTET; thirdOctet <= END_THIRD_OCTET; thirdOctet++) {
+            for (int fourthOctet = START_FOURTH_OCTET; fourthOctet <= END_FOURTH_OCTET; fourthOctet++) {
+                String ip = "198.19." + thirdOctet + "." + fourthOctet;
+
+                if (!usedOnVps.contains(ip) && !knownInDb.contains(ip)) {
+                    return ip;
+                }
+            }
+        }
+
+        throw new IllegalStateException("No free VPN IP addresses available");
     }
 
     private VpnIpAllocationResponse toResponse(VpnIpAllocation allocation) {
         return new VpnIpAllocationResponse(
                 allocation.getId(),
                 allocation.getIpAddress(),
-                allocation.isAllocated(),
+                allocation.getStatus(),
                 allocation.getRouterId(),
                 allocation.getAllocatedAt(),
                 allocation.getReleasedAt()

src/main/java/com/litoralregas/vpnprovisioner/ipam/service/VpnIpPoolSeeder.java

@@ -1,32 +0,0 @@
-package com.litoralregas.vpnprovisioner.ipam.service;
-
-import com.litoralregas.vpnprovisioner.ipam.entity.VpnIpAllocation;
-import com.litoralregas.vpnprovisioner.ipam.repository.VpnIpAllocationRepository;
-import org.springframework.boot.CommandLineRunner;
-import org.springframework.stereotype.Component;
-
-@Component
-public class VpnIpPoolSeeder implements CommandLineRunner {
-
-    private final VpnIpAllocationRepository repository;
-
-    public VpnIpPoolSeeder(VpnIpAllocationRepository repository) {
-        this.repository = repository;
-    }
-
-    @Override
-    public void run(String... args) {
-
-        for (int thirdOctet = 1; thirdOctet <= 1; thirdOctet++) {
-
-            for (int fourthOctet = 2; fourthOctet <= 254; fourthOctet++) {
-
-                String ip = "198.19." + thirdOctet + "." + fourthOctet;
-
-                if (repository.findByIpAddress(ip).isEmpty()) {
-                    repository.save(new VpnIpAllocation(ip));
-                }
-            }
-        }
-    }
-}

src/main/java/com/litoralregas/vpnprovisioner/router/entity/Router.java

@@ -63,4 +63,8 @@ public class Router {
         this.hardwareModel = hardwareModel;
         this.firmwareVersion = firmwareVersion;
     }
+
+    public void assignVpnIp(String vpnIp) {
+        this.vpnIp = vpnIp;
+    }
 }

src/main/resources/db/migration/V3__ip_allocation_status.sql

@@ -0,0 +1,11 @@
+ALTER TABLE vpn_ip_allocations
+ADD COLUMN status VARCHAR(50);
+
+UPDATE vpn_ip_allocations
+SET status = CASE
+    WHEN allocated = true THEN 'ALLOCATED'
+    ELSE 'AVAILABLE'
+END;
+
+ALTER TABLE vpn_ip_allocations
+ALTER COLUMN status SET NOT NULL;