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dhcp: set hostname for renewal packets as well

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Otherwise, router restarts might result in the hostname getting
lost (observed using dnsmasq on OpenWrt).
This commit is contained in:
Michael Stapelberg 2017-07-01 11:29:10 +02:00
parent 3999a60a05
commit 13173460da
1 changed files with 33 additions and 6 deletions
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39
cmd/dhcp/dhcp.go
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@ -34,9 +34,7 @@ var (
defaultNetmask = net.IPMask([]byte{0, 0, 0, 0})
)
// dhcpRequest is a copy of (dhcp4client/Client).Request which
// includes the hostname.
func dhcpRequest(c *dhcp4client.Client) (bool, dhcp4.Packet, error) {
func addHostname(p *dhcp4.Packet) {
var utsname unix.Utsname
if err := unix.Uname(&utsname); err != nil {
log.Fatal(err)
@ -49,8 +47,14 @@ func dhcpRequest(c *dhcp4client.Client) (bool, dhcp4.Packet, error) {
nnb = append(nnb, byte(i))
}
p.AddOption(dhcp4.OptionHostName, nnb)
}
// dhcpRequest is a copy of (dhcp4client/Client).Request which
// includes the hostname.
func dhcpRequest(c *dhcp4client.Client) (bool, dhcp4.Packet, error) {
discoveryPacket := c.DiscoverPacket()
discoveryPacket.AddOption(dhcp4.OptionHostName, nnb)
addHostname(&discoveryPacket)
discoveryPacket.PadToMinSize()
if err := c.SendPacket(discoveryPacket); err != nil {
@ -63,7 +67,7 @@ func dhcpRequest(c *dhcp4client.Client) (bool, dhcp4.Packet, error) {
}
requestPacket := c.RequestPacket(&offerPacket)
requestPacket.AddOption(dhcp4.OptionHostName, nnb)
addHostname(&requestPacket)
requestPacket.PadToMinSize()
if err := c.SendPacket(requestPacket); err != nil {
@ -83,6 +87,29 @@ func dhcpRequest(c *dhcp4client.Client) (bool, dhcp4.Packet, error) {
return true, acknowledgement, nil
}
// dhcpRenew is a copy of (dhcp4client/Client).Renew which
// includes the hostname.
func dhcpRenew(c *dhcp4client.Client, packet dhcp4.Packet) (bool, dhcp4.Packet, error) {
addHostname(&packet)
packet.PadToMinSize()
if err := c.SendPacket(packet); err != nil {
return false, packet, err
}
acknowledgement, err := c.GetAcknowledgement(&packet)
if err != nil {
return false, acknowledgement, err
}
acknowledgementOptions := acknowledgement.ParseOptions()
if dhcp4.MessageType(acknowledgementOptions[dhcp4.OptionDHCPMessageType][0]) != dhcp4.ACK {
return false, acknowledgement, nil
}
return true, acknowledgement, nil
}
func main() {
log.SetFlags(log.LstdFlags | log.Lshortfile)
@ -228,6 +255,6 @@ func main() {
}
time.Sleep(renewalTime)
ok, ack, err = dhcp.Renew(ack)
ok, ack, err = dhcpRenew(dhcp, dhcp.RenewalRequestPacket(&ack))
}
}