refactor: use long lived DHCP clients

Author: zeidlitz

dhcp.go

@@ -5,8 +5,8 @@ import (
 	"net"
 	"time"
 
-	dhcp "github.com/insomniacslk/dhcp/dhcpv4"
-	client "github.com/insomniacslk/dhcp/dhcpv4/client4"
+	"github.com/insomniacslk/dhcp/dhcpv4"
+	"github.com/insomniacslk/dhcp/dhcpv4/client4"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
 )
@@ -39,9 +39,8 @@ func init() {
 	prometheus.MustRegister(dhcpLeaseTime)
 }
 
-func sampleDhcp(iface string, verbose bool) (net.IP, int, error) {
+func sampleDhcp(client client4.Client, verbose bool) (net.IP, int, error) {
 	dhcpRequests.Inc()
-	client := client.NewClient()
 	start := time.Now()
 	conversation, err := client.Exchange(iface)
 	if err != nil {
@@ -57,12 +56,12 @@ func sampleDhcp(iface string, verbose bool) (net.IP, int, error) {
 			fmt.Println(packet.Summary())
 		}
 
-		if packet.MessageType() == dhcp.MessageTypeOffer {
+		if packet.MessageType() == dhcpv4.MessageTypeOffer {
 			dhcpOffers.Inc()
 		}
 
-		if packet.MessageType() == dhcp.MessageTypeAck {
-			if packet.Options.Has(dhcp.OptionIPAddressLeaseTime) {
+		if packet.MessageType() == dhcpv4.MessageTypeAck {
+			if packet.Options.Has(dhcpv4.OptionIPAddressLeaseTime) {
 				dhcpLeaseTime.Set(packet.IPAddressLeaseTime(0).Seconds())
 			}
 

dhcp6.go

@@ -5,8 +5,8 @@ import (
 	"net"
 	"time"
 
-	dhcp "github.com/insomniacslk/dhcp/dhcpv6"
-	client "github.com/insomniacslk/dhcp/dhcpv6/client6"
+	"github.com/insomniacslk/dhcp/dhcpv6"
+	"github.com/insomniacslk/dhcp/dhcpv6/client6"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
 )
@@ -39,9 +39,8 @@ func init() {
 	prometheus.MustRegister(dhcp6Lifetime)
 }
 
-func sampleDhcp6(iface string, verbose bool) (net.IP, int, error) {
+func sampleDhcp6(client client6.Client, verbose bool) (net.IP, int, error) {
 	dhcp6Requests.Inc()
-	client := client.NewClient()
 	start := time.Now()
 	conversation, err := client.Exchange(iface)
 	if err != nil {
@@ -63,7 +62,7 @@ func sampleDhcp6(iface string, verbose bool) (net.IP, int, error) {
 			return nil, 0, err
 		}
 
-		if message.MessageType == dhcp.MessageTypeReply {
+		if message.MessageType == dhcpv6.MessageTypeReply {
 			dhcp6Replies.Inc()
 
 			iaNa := message.Options.OneIANA()
@@ -73,5 +72,5 @@ func sampleDhcp6(iface string, verbose bool) (net.IP, int, error) {
 			yourIPAddr = naAddr.IPv6Addr
 		}
 	}
-	return yourIPAddr, prefixBits, err
+	return yourIPAddr, prefixBits, nil
 }

main.go

@@ -11,6 +11,8 @@ import (
 	"strings"
 	"time"
 
+	"github.com/insomniacslk/dhcp/dhcpv4/client4"
+	"github.com/insomniacslk/dhcp/dhcpv6/client6"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/vishvananda/netlink"
 )
@@ -66,19 +68,29 @@ func main() {
 	dnsTargetsList := strings.Split(dnsTargets, ",")
 	icmpTargetsList := strings.Split(icmpTargets, ",")
 
+	ipv4DhcpClient := client4.Client{
+		ReadTimeout:  interval,
+		WriteTimeout: interval,
+	}
+
+	ipv6DhcpClient := client6.Client{
+		ReadTimeout:  interval,
+		WriteTimeout: interval,
+	}
+
 	http.Handle("/metrics", promhttp.Handler())
 
 	go func() {
 		for {
 
 			if !disable4 {
-				if err := observeIPv4(link); err != nil {
+				if err := observeIPv4(link, ipv4DhcpClient); err != nil {
 					slog.Warn("issue with ipv4", "err", err)
 				}
 			}
 
 			if !disable6 {
-				if err := observeIPv6(link); err != nil {
+				if err := observeIPv6(link, ipv6DhcpClient); err != nil {
 					slog.Warn("issue with ipv6", "err", err)
 				}
 			}
@@ -104,8 +116,8 @@ func main() {
 	}
 }
 
-func observeIPv4(link netlink.Link) error {
-	ip, prefix, err := sampleDhcp(iface, verbose)
+func observeIPv4(link netlink.Link, client client4.Client) error {
+	ip, prefix, err := sampleDhcp(client, verbose)
 	if err != nil {
 		return fmt.Errorf("DHCPv4 sampling failed: %w", err)
 	}
@@ -135,8 +147,8 @@ func observeIPv4(link netlink.Link) error {
 	return nil
 }
 
-func observeIPv6(link netlink.Link) error {
-	ip6, prefix6, err := sampleDhcp6(iface, verbose)
+func observeIPv6(link netlink.Link, client client6.Client) error {
+	ip6, prefix6, err := sampleDhcp6(client, verbose)
 	if err != nil {
 		return fmt.Errorf("DHCPv6 sampling failed: %w", err)
 	}