Sequentialip+predifined subnet

management/server/network.go

@@ -5,13 +5,16 @@
 	"net"
 	"sync"
 	"time"
+	"os"
+	"log"
+	"fmt"
 
 	"github.com/c-robinson/iplib"
 	"github.com/rs/xid"
 
 	nbdns "github.com/netbirdio/netbird/dns"
 	nbpeer "github.com/netbirdio/netbird/management/server/peer"
 	"github.com/netbirdio/netbird/management/server/status"
 	"github.com/netbirdio/netbird/route"
 )
 
@@ -48,19 +51,35 @@
 // NewNetwork creates a new Network initializing it with a Serial=0
 // It takes a random /16 subnet from 100.64.0.0/10 (64 different subnets)
 func NewNetwork() *Network {
-
-	n := iplib.NewNet4(net.ParseIP("100.64.0.0"), NetSize)
-	sub, _ := n.Subnet(SubnetSize)
-
-	s := rand.NewSource(time.Now().Unix())
-	r := rand.New(s)
-	intn := r.Intn(len(sub))
-
-	return &Network{
-		Identifier: xid.New().String(),
-		Net:        sub[intn].IPNet,
-		Dns:        "",
-		Serial:     0}
+    // Check if the NETBIRD_SUBNET environment variable is set
+    customSubnet := os.Getenv("NETBIRD_SUBNET")
+    if customSubnet != "" {
+        if _, subnet, err := net.ParseCIDR(customSubnet); err == nil {
+            return &Network{
+                Identifier: xid.New().String(),
+                Net:        *subnet,
+                Dns:        "",
+                Serial:     0,
+            }
+        }
+        // Handle error if parsing custom subnet fails
+        log.Println("Error parsing custom subnet from NETBIRD_SUBNET variable:", err)
+    }
+
+    // If NETBIRD_SUBNET is not set or parsing fails, choose a random subnet
+    n := iplib.NewNet4(net.ParseIP("100.64.0.0"), NetSize)
+    sub, _ := n.Subnet(SubnetSize)
+
+    s := rand.NewSource(time.Now().Unix())
+    r := rand.New(s)
+    intn := r.Intn(len(sub))
+
+    return &Network{
+        Identifier: xid.New().String(),
+        Net:        sub[intn].IPNet,
+        Dns:        "",
+        Serial:     0,
+    }
 }
 
 // IncSerial increments Serial by 1 reflecting that the network state has been changed
@@ -90,24 +109,34 @@
 // This method considers already taken IPs and reuses IPs if there are gaps in takenIps
 // E.g. if ipNet=100.30.0.0/16 and takenIps=[100.30.0.1, 100.30.0.4] then the result would be 100.30.0.2 or 100.30.0.3
 func AllocatePeerIP(ipNet net.IPNet, takenIps []net.IP) (net.IP, error) {
-	takenIPMap := make(map[string]struct{})
-	takenIPMap[ipNet.IP.String()] = struct{}{}
-	for _, ip := range takenIps {
-		takenIPMap[ip.String()] = struct{}{}
-	}
-
-	ips, _ := generateIPs(&ipNet, takenIPMap)
-
-	if len(ips) == 0 {
-		return nil, status.Errorf(status.PreconditionFailed, "failed allocating new IP for the ipNet %s - network is out of IPs", ipNet.String())
-	}
-
-	// pick a random IP
-	s := rand.NewSource(time.Now().Unix())
-	r := rand.New(s)
-	intn := r.Intn(len(ips))
-
-	return ips[intn], nil
+    // Check if NETBIRD_ALLOCATE_SEQUENTIAL_IPS is set to 1
+    allocateSequential := os.Getenv("NETBIRD_ALLOCATE_SEQUENTIAL_IPS") == "1"
+
+    takenIPMap := make(map[string]struct{})
+    takenIPMap[ipNet.IP.String()] = struct{}{}
+    for _, ip := range takenIps {
+        takenIPMap[ip.String()] = struct{}{}
+    }
+
+    ips, _ := generateIPs(&ipNet, takenIPMap)
+
+    if len(ips) == 0 {
+        return nil, fmt.Errorf("failed allocating new IP for the ipNet %s - network is out of IPs", ipNet.String())
+    }
+
+    // Pick an IP based on the allocation method
+    var selectedIP net.IP
+    if allocateSequential {
+        selectedIP = ips[0] // Allocate the smallest available IP
+    } else {
+        // Pick a random IP
+        s := rand.NewSource(time.Now().Unix())
+        r := rand.New(s)
+        intn := r.Intn(len(ips))
+        selectedIP = ips[intn]
+    }
+
+    return selectedIP, nil
 }
 
 // generateIPs generates a list of all possible IPs of the given network excluding IPs specified in the exclusion list