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DHCP lease maintenance should terminate when interface no longer exists. #1143

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DHCP lease maintenance should terminate when interface no longer exists. #1143

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53 changes: 51 additions & 2 deletions plugins/ipam/dhcp/lease.go
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@ package main

import (
"context"
"errors"
"fmt"
"log"
"math/rand"
Expand Down Expand Up @@ -55,6 +56,13 @@ const (
leaseStateRebinding
)

// Timing for retrying link existence check
const (
linkCheckDelay0 = 1 * time.Second
linkCheckRetryMax = 10 * time.Second
linkCheckTotalTimeout = 30 * time.Second
)

// This implementation uses 1 OS thread per lease. This is because
// all the network operations have to be done in network namespace
// of the interface. This can be improved by switching to the proper
Expand All @@ -65,6 +73,7 @@ type DHCPLease struct {
clientID string
latestLease *nclient4.Lease
link netlink.Link
linkName string
renewalTime time.Time
rebindingTime time.Time
expireTime time.Time
Expand Down Expand Up @@ -190,6 +199,7 @@ func AcquireLease(
}

l.link = link
l.linkName = link.Attrs().Name

if err = l.acquire(); err != nil {
return err
Expand Down Expand Up @@ -243,7 +253,7 @@ func withAllOptions(l *DHCPLease) dhcp4.Modifier {

func (l *DHCPLease) acquire() error {
if (l.link.Attrs().Flags & net.FlagUp) != net.FlagUp {
log.Printf("Link %q down. Attempting to set up", l.link.Attrs().Name)
log.Printf("Link %q down. Attempting to set up", l.linkName)
if err := netlink.LinkSetUp(l.link); err != nil {
return err
}
Expand Down Expand Up @@ -292,6 +302,14 @@ func (l *DHCPLease) maintain() {
for {
var sleepDur time.Duration

linkCheckCtx, cancel := context.WithTimeoutCause(l.ctx, l.resendTimeout, errNoMoreTries)
defer cancel()
linkExists, _ := checkLinkExistsWithBackoff(linkCheckCtx, l.linkName)
if !linkExists {
log.Printf("%v: interface %s no longer exists or link check failed, terminating lease maintenance", l.clientID, l.linkName)
return
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}

switch state {
case leaseStateBound:
sleepDur = time.Until(l.renewalTime)
Expand Down Expand Up @@ -344,9 +362,40 @@ func (l *DHCPLease) maintain() {
}
}

func checkLinkExistsWithBackoff(ctx context.Context, linkName string) (bool, error) {
baseDelay := linkCheckDelay0
for {
exists, err := checkLinkByName(linkName)
if err == nil {
return exists, nil
}

select {
case <-ctx.Done():
return false, ctx.Err() // Context's done, return with its error
case <-time.After(baseDelay):
if baseDelay < linkCheckRetryMax {
baseDelay *= 2
}
}
}
}

func checkLinkByName(linkName string) (bool, error) {
_, err := netlink.LinkByName(linkName)
if err != nil {
var linkNotFoundErr *netlink.LinkNotFoundError = &netlink.LinkNotFoundError{}
if errors.As(err, linkNotFoundErr) {
return false, nil
}
return false, err
}
return true, nil
}

func (l *DHCPLease) downIface() {
if err := netlink.LinkSetDown(l.link); err != nil {
log.Printf("%v: failed to bring %v interface DOWN: %v", l.clientID, l.link.Attrs().Name, err)
log.Printf("%v: failed to bring %v interface DOWN: %v", l.clientID, l.linkName, err)
}
}

Expand Down
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