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Cherry-pick: Avoid integer overflow in dhcp renewal (#8154) #8178

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Merged
hickeng merged 1 commit into from
Aug 6, 2018
Merged

Cherry-pick: Avoid integer overflow in dhcp renewal (#8154) #8178

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9 changes: 6 additions & 3 deletions lib/tether/ops_linux.go
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Original file line number Diff line number Diff line change
Expand Up @@ -756,8 +756,11 @@ func ApplyEndpoint(nl Netlink, t *BaseOperations, endpoint *NetworkEndpoint) err
}

func (t *BaseOperations) dhcpLoop(stop chan struct{}, e *NetworkEndpoint, dc client.Client) {
divisor := time.Duration(2)
// wait half of the remaining lease time before trying again if we fail to renew
exp := time.After(dc.LastAck().LeaseTime() / 2)
// the divisor starts set to 4 so that we can update it AFTER the duration is calculated. This allows combining the check for integer overflow with
// the minimum wait time.
divisor := time.Duration(4)
for {
select {
case <-stop:
Expand All @@ -772,13 +775,13 @@ func (t *BaseOperations) dhcpLoop(stop chan struct{}, e *NetworkEndpoint, dc cli
if err != nil {
log.Errorf("failed to renew ip address for network %s: %s", e.Name, err)

// wait half of the remaining lease time before trying again
divisor *= 2
duration := dc.LastAck().LeaseTime() / divisor

// for now go with a minimum retry of 1min
if duration < time.Minute {
duration = time.Minute
} else if divisor*2 > divisor {
divisor *= 2
}

exp = time.After(duration)
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