Use non APIPA when assigning IP Address (#4032)

* use APIPA as last resort

Signed-off-by: Jimmy Bonds <[email protected]>

* Update CHANGELOG.md

Signed-off-by: Jimmy Bonds <[email protected]>

* tidy up changelog

Signed-off-by: Jimmy Bonds <[email protected]>

* avoid empty value overwrites, preserving APIPA

Signed-off-by: Jimmy Bonds <[email protected]>

* remove duplicates

Signed-off-by: Jimmy Bonds <[email protected]>

Author: jbvmio

CHANGELOG.md

@@ -32,6 +32,7 @@
 * [ENHANCEMENT] Distributor: Added distributors ring status section in the admin page. #4151
 * [ENHANCEMENT] Added zone-awareness support to alertmanager for use when sharding is enabled. When zone-awareness is enabled, alerts will be replicated across availability zones. #4204
 * [ENHANCEMENT] Added `tenant_ids` tag to tracing spans #4147
+* [ENHANCEMENT] Ring, query-frontend: Avoid using automatic private IPs (APIPA) when discovering IP address from the interface during the registration of the instance in the ring, or by query-frontend when used with query-scheduler. APIPA still used as last resort with logging indicating usage. #4032
 * [BUGFIX] Purger: fix `Invalid null value in condition for column range` caused by `nil` value in range for WriteBatch query. #4128
 * [BUGFIX] Ingester: fixed infrequent panic caused by a race condition between TSDB mmap-ed head chunks truncation and queries. #4176
 * [BUGFIX] Alertmanager: fix Alertmanager status page if clustering via gossip is disabled or sharding is enabled. #4184

pkg/util/net.go

@@ -3,21 +3,22 @@ package util
 import (
 	"fmt"
 	"net"
+	"strings"
 
 	"github.com/go-kit/kit/log/level"
 
 	util_log "github.com/cortexproject/cortex/pkg/util/log"
 )
 
-// GetFirstAddressOf returns the first IPv4 address of the supplied interface names.
+// GetFirstAddressOf returns the first IPv4 address of the supplied interface names, omitting any 169.254.x.x automatic private IPs if possible.
 func GetFirstAddressOf(names []string) (string, error) {
+	var ipAddr string
 	for _, name := range names {
 		inf, err := net.InterfaceByName(name)
 		if err != nil {
 			level.Warn(util_log.Logger).Log("msg", "error getting interface", "inf", name, "err", err)
 			continue
 		}
-
 		addrs, err := inf.Addrs()
 		if err != nil {
 			level.Warn(util_log.Logger).Log("msg", "error getting addresses for interface", "inf", name, "err", err)
@@ -27,16 +28,35 @@ func GetFirstAddressOf(names []string) (string, error) {
 			level.Warn(util_log.Logger).Log("msg", "no addresses found for interface", "inf", name, "err", err)
 			continue
 		}
+		if ip := filterIPs(addrs); ip != "" {
+			ipAddr = ip
+		}
+		if strings.HasPrefix(ipAddr, `169.254.`) || ipAddr == "" {
+			continue
+		}
+		return ipAddr, nil
+	}
+	if ipAddr == "" {
+		return "", fmt.Errorf("No address found for %s", names)
+	}
+	if strings.HasPrefix(ipAddr, `169.254.`) {
+		level.Warn(util_log.Logger).Log("msg", "using automatic private ip", "address", ipAddr)
+	}
+	return ipAddr, nil
+}
 
-		for _, addr := range addrs {
-			switch v := addr.(type) {
-			case *net.IPNet:
-				if ip := v.IP.To4(); ip != nil {
-					return v.IP.String(), nil
+// filterIPs attempts to return the first non automatic private IP (APIPA / 169.254.x.x) if possible, only returning APIPA if available and no other valid IP is found.
+func filterIPs(addrs []net.Addr) string {
+	var ipAddr string
+	for _, addr := range addrs {
+		if v, ok := addr.(*net.IPNet); ok {
+			if ip := v.IP.To4(); ip != nil {
+				ipAddr = v.IP.String()
+				if !strings.HasPrefix(ipAddr, `169.254.`) {
+					return ipAddr
 				}
 			}
 		}
 	}
-
-	return "", fmt.Errorf("No address found for %s", names)
+	return ipAddr
 }