From 69e41f87ef603d05e0c98675f29d409d19900f5a Mon Sep 17 00:00:00 2001
From: Harshavardhana <harsha@minio.io>
Date: Wed, 19 Jun 2024 07:34:00 -0700
Subject: [PATCH] compute localIPs only once per server startup() (#19951)

repeatedly calling this function is not necessary,
on systems with lots of interfaces, including virtual
ones can make this reasonably delayed.
---
 cmd/net.go         | 39 ++++++++++++++++++++++++++++-----------
 cmd/server-main.go |  6 ++----
 2 files changed, 30 insertions(+), 15 deletions(-)

diff --git a/cmd/net.go b/cmd/net.go
index 2181cbaeb..082f2fb42 100644
--- a/cmd/net.go
+++ b/cmd/net.go
@@ -19,7 +19,6 @@ package cmd
 
 import (
 	"errors"
-	"fmt"
 	"net"
 	"net/url"
 	"runtime"
@@ -32,8 +31,16 @@ import (
 	xnet "github.com/minio/pkg/v3/net"
 )
 
-// IPv4 addresses of local host.
-var localIP4 = mustGetLocalIP4()
+var (
+	// IPv4 addresses of localhost.
+	localIP4 = mustGetLocalIP4()
+
+	// IPv6 addresses of localhost.
+	localIP6 = mustGetLocalIP6()
+
+	// List of all local loopback addresses.
+	localLoopbacks = mustGetLocalLoopbacks()
+)
 
 // mustSplitHostPort is a wrapper to net.SplitHostPort() where error is assumed to be a fatal.
 func mustSplitHostPort(hostPort string) (host, port string) {
@@ -74,6 +81,16 @@ func mustGetLocalIPs() (ipList []net.IP) {
 	return ipList
 }
 
+func mustGetLocalLoopbacks() (ipList set.StringSet) {
+	ipList = set.NewStringSet()
+	for _, ip := range mustGetLocalIPs() {
+		if ip != nil && ip.IsLoopback() {
+			ipList.Add(ip.String())
+		}
+	}
+	return
+}
+
 // mustGetLocalIP4 returns IPv4 addresses of localhost.  It panics on error.
 func mustGetLocalIP4() (ipList set.StringSet) {
 	ipList = set.NewStringSet()
@@ -160,15 +177,15 @@ func getConsoleEndpoints() (consoleEndpoints []string) {
 	}
 	var ipList []string
 	if globalMinioConsoleHost == "" {
-		ipList = sortIPs(mustGetLocalIP4().ToSlice())
-		ipList = append(ipList, mustGetLocalIP6().ToSlice()...)
+		ipList = sortIPs(localIP4.ToSlice())
+		ipList = append(ipList, localIP6.ToSlice()...)
 	} else {
 		ipList = []string{globalMinioConsoleHost}
 	}
 
+	consoleEndpoints = make([]string, 0, len(ipList))
 	for _, ip := range ipList {
-		endpoint := fmt.Sprintf("%s://%s", getURLScheme(globalIsTLS), net.JoinHostPort(ip, globalMinioConsolePort))
-		consoleEndpoints = append(consoleEndpoints, endpoint)
+		consoleEndpoints = append(consoleEndpoints, getURLScheme(globalIsTLS)+"://"+net.JoinHostPort(ip, globalMinioConsolePort))
 	}
 
 	return consoleEndpoints
@@ -180,15 +197,15 @@ func getAPIEndpoints() (apiEndpoints []string) {
 	}
 	var ipList []string
 	if globalMinioHost == "" {
-		ipList = sortIPs(mustGetLocalIP4().ToSlice())
-		ipList = append(ipList, mustGetLocalIP6().ToSlice()...)
+		ipList = sortIPs(localIP4.ToSlice())
+		ipList = append(ipList, localIP6.ToSlice()...)
 	} else {
 		ipList = []string{globalMinioHost}
 	}
 
+	apiEndpoints = make([]string, 0, len(ipList))
 	for _, ip := range ipList {
-		endpoint := fmt.Sprintf("%s://%s", getURLScheme(globalIsTLS), net.JoinHostPort(ip, globalMinioPort))
-		apiEndpoints = append(apiEndpoints, endpoint)
+		apiEndpoints = append(apiEndpoints, getURLScheme(globalIsTLS)+"://"+net.JoinHostPort(ip, globalMinioPort))
 	}
 
 	return apiEndpoints
diff --git a/cmd/server-main.go b/cmd/server-main.go
index b8c5808f7..075c9c482 100644
--- a/cmd/server-main.go
+++ b/cmd/server-main.go
@@ -680,10 +680,8 @@ func getServerListenAddrs() []string {
 	// Use a string set to avoid duplication
 	addrs := set.NewStringSet()
 	// Listen on local interface to receive requests from Console
-	for _, ip := range mustGetLocalIPs() {
-		if ip != nil && ip.IsLoopback() {
-			addrs.Add(net.JoinHostPort(ip.String(), globalMinioPort))
-		}
+	for _, ip := range localLoopbacks.ToSlice() {
+		addrs.Add(net.JoinHostPort(ip, globalMinioPort))
 	}
 	host, _ := mustSplitHostPort(globalMinioAddr)
 	if host != "" {