Merge branch 'master' into fix_label

3 files changed, 49 insertions, 1 deletions

diff --git a/dhcpv4/nclient4/client.go b/dhcpv4/nclient4/client.go
index 02bd1f6..d40e1a9 100644
--- a/dhcpv4/nclient4/client.go
+++ b/dhcpv4/nclient4/client.go
@@ -493,6 +493,7 @@ func (e *ErrNak) Error() string {
 }
 
 // RequestFromOffer sends a Request message and waits for an response.
+// It assumes the SELECTING state by default, see Section 4.3.2 in RFC 2131 for more details.
 func (c *Client) RequestFromOffer(ctx context.Context, offer *dhcpv4.DHCPv4, modifiers ...dhcpv4.Modifier) (*Lease, error) {
 	// TODO(chrisko): should this be unicast to the server?
 	request, err := dhcpv4.NewRequestFromOffer(offer, dhcpv4.PrependModifiers(modifiers,
diff --git a/dhcpv4/nclient4/lease.go b/dhcpv4/nclient4/lease.go
index 184fae2..1895dd0 100644
--- a/dhcpv4/nclient4/lease.go
+++ b/dhcpv4/nclient4/lease.go
@@ -3,6 +3,7 @@
 package nclient4
 
 import (
+	"context"
 	"fmt"
 	"net"
 	"time"
@@ -36,3 +37,41 @@ func (c *Client) Release(lease *Lease, modifiers ...dhcpv4.Modifier) error {
 	}
 	return err
 }
+
+// Renew sends a DHCPv4 request to the server to renew the given lease. The renewal information is
+// sourced from the initial offer in the lease, and the ACK of the lease is updated to the ACK of
+// the latest renewal. This avoids issues with DHCP servers that omit information needed to build a
+// completely new lease from their renewal ACK (such as the Windows DHCP Server).
+func (c *Client) Renew(ctx context.Context, lease *Lease, modifiers ...dhcpv4.Modifier) error {
+	if lease == nil {
+		return fmt.Errorf("lease is nil")
+	}
+
+	request, err := dhcpv4.NewRenewFromOffer(lease.Offer, dhcpv4.PrependModifiers(modifiers,
+		dhcpv4.WithOption(dhcpv4.OptMaxMessageSize(MaxMessageSize)))...)
+	if err != nil {
+		return fmt.Errorf("unable to create a request: %w", err)
+	}
+
+	// Servers are supposed to only respond to Requests containing their server identifier,
+	// but sometimes non-compliant servers respond anyway.
+	// Clients are not required to validate this field, but servers are required to
+	// include the server identifier in their Offer per RFC 2131 Section 4.3.1 Table 3.
+	response, err := c.SendAndRead(ctx, c.serverAddr, request, IsAll(
+		IsCorrectServer(lease.Offer.ServerIdentifier()),
+		IsMessageType(dhcpv4.MessageTypeAck, dhcpv4.MessageTypeNak)))
+	if err != nil {
+		return fmt.Errorf("got an error while processing the request: %w", err)
+	}
+	if response.MessageType() == dhcpv4.MessageTypeNak {
+		return &ErrNak{
+			Offer: lease.Offer,
+			Nak:   response,
+		}
+	}
+
+	// Update the ACK of the lease with the ACK of the latest renewal
+	lease.ACK = response
+
+	return nil
+}
diff --git a/dhcpv4/nclient4/lease_test.go b/dhcpv4/nclient4/lease_test.go
index 361847f..d27eeca 100644
--- a/dhcpv4/nclient4/lease_test.go
+++ b/dhcpv4/nclient4/lease_test.go
@@ -1,4 +1,4 @@
-// this tests nclient4 with lease and release
+// this tests nclient4 with lease, renew and release
 
 package nclient4
 
@@ -236,6 +236,14 @@ func (sll *testServerLeaseList) runTest(t *testing.T) {
 		sll.lastTestSvrErrLock.RLock()
 		keepgoing := chkerr(err, sll.lastTestSvrErr, l.ShouldFail, t)
 		sll.lastTestSvrErrLock.RUnlock()
+
+		if keepgoing {
+			err = clnt.Renew(context.Background(), lease)
+			sll.lastTestSvrErrLock.RLock()
+			keepgoing = chkerr(err, sll.lastTestSvrErr, l.ShouldFail, t)
+			sll.lastTestSvrErrLock.RUnlock()
+		}
+
 		if keepgoing {
 			err = clnt.Release(lease)
 			//this sleep is to make sure release is handled by server