From 4b6985718a1f7afeb622a842872f80097c3f2972 Mon Sep 17 00:00:00 2001
From: Owen <owen@txv.io>
Date: Thu, 27 Mar 2025 22:13:39 -0400
Subject: [PATCH] Fix ip picking from subnet in exclusion

---
 server/lib/ip.test.ts | 15 ++++++++++++++-
 server/lib/ip.ts      | 32 +++++++++++++++++++-------------
 2 files changed, 33 insertions(+), 14 deletions(-)

diff --git a/server/lib/ip.test.ts b/server/lib/ip.test.ts
index 2c2dd057..67a2faaa 100644
--- a/server/lib/ip.test.ts
+++ b/server/lib/ip.test.ts
@@ -4,7 +4,14 @@ import { assertEquals } from "@test/assert";
 // Test cases
 function testFindNextAvailableCidr() {
     console.log("Running findNextAvailableCidr tests...");
-    
+  
+    // Test 0: Basic IPv4 allocation with a subnet in the wrong range
+    {
+        const existing = ["100.90.130.1/30", "100.90.128.4/30"];
+        const result = findNextAvailableCidr(existing, 30, "100.90.130.1/24");
+        assertEquals(result, "100.90.130.4/30", "Basic IPv4 allocation failed");
+    }
+
     // Test 1: Basic IPv4 allocation
     {
         const existing = ["10.0.0.0/16", "10.1.0.0/16"];
@@ -26,6 +33,12 @@ function testFindNextAvailableCidr() {
         assertEquals(result, null, "No available space test failed");
     }
 
+    // Test 4: Empty existing 
+    {
+        const existing: string[] = [];
+        const result = findNextAvailableCidr(existing, 30, "10.0.0.0/8");
+        assertEquals(result, "10.0.0.0/30", "Empty existing test failed");
+    }
     // // Test 4: IPv6 allocation
     // {
     //     const existing = ["2001:db8::/32", "2001:db8:1::/32"];
diff --git a/server/lib/ip.ts b/server/lib/ip.ts
index 86fe1169..a4f05126 100644
--- a/server/lib/ip.ts
+++ b/server/lib/ip.ts
@@ -132,7 +132,6 @@ export function findNextAvailableCidr(
     blockSize: number,
     startCidr?: string
 ): string | null {
-
     if (!startCidr && existingCidrs.length === 0) {
         return null;
     }
@@ -150,40 +149,47 @@ export function findNextAvailableCidr(
         existingCidrs.some(cidr => detectIpVersion(cidr.split('/')[0]) !== version)) {
         throw new Error('All CIDRs must be of the same IP version');
     }
-
+    
+    // Extract the network part from startCidr to ensure we stay in the right subnet
+    const startCidrRange = cidrToRange(startCidr);
+    
     // Convert existing CIDRs to ranges and sort them
     const existingRanges = existingCidrs
         .map(cidr => cidrToRange(cidr))
         .sort((a, b) => (a.start < b.start ? -1 : 1));
-
+    
     // Calculate block size
     const maxPrefix = version === 4 ? 32 : 128;
     const blockSizeBigInt = BigInt(1) << BigInt(maxPrefix - blockSize);
-
+    
     // Start from the beginning of the given CIDR
-    let current = cidrToRange(startCidr).start;
-    const maxIp = cidrToRange(startCidr).end;
-
+    let current = startCidrRange.start;
+    const maxIp = startCidrRange.end;
+    
     // Iterate through existing ranges
     for (let i = 0; i <= existingRanges.length; i++) {
         const nextRange = existingRanges[i];
+        
         // Align current to block size
         const alignedCurrent = current + ((blockSizeBigInt - (current % blockSizeBigInt)) % blockSizeBigInt);
-
+        
         // Check if we've gone beyond the maximum allowed IP
         if (alignedCurrent + blockSizeBigInt - BigInt(1) > maxIp) {
             return null;
         }
-
+        
         // If we're at the end of existing ranges or found a gap
         if (!nextRange || alignedCurrent + blockSizeBigInt - BigInt(1) < nextRange.start) {
             return `${bigIntToIp(alignedCurrent, version)}/${blockSize}`;
         }
-
-        // Move current pointer to after the current range
-        current = nextRange.end + BigInt(1);
+        
+        // If next range overlaps with our search space, move past it
+        if (nextRange.end >= startCidrRange.start && nextRange.start <= maxIp) {
+            // Move current pointer to after the current range
+            current = nextRange.end + BigInt(1);
+        }
     }
-
+    
     return null;
 }