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dhcp: set client id (option 61), some routers need it

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E.g. /etc/kresd/dhcp_host_domain_ng.sh on a turris omnia incorrectly deletes
DHCP hostname mappings when more than one client does not send a client id.
This commit is contained in:
Michael Stapelberg 2017-09-05 09:52:53 +02:00
parent 3ed1e381b5
commit 6127f9566e
1 changed files with 14 additions and 0 deletions
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14
cmd/dhcp/dhcp.go
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@ -32,6 +32,8 @@ func parseDHCPDuration(b []byte) time.Duration {
var ( var (
defaultDst = net.IP([]byte{0, 0, 0, 0}) defaultDst = net.IP([]byte{0, 0, 0, 0})
defaultNetmask = net.IPMask([]byte{0, 0, 0, 0}) defaultNetmask = net.IPMask([]byte{0, 0, 0, 0})
hardwareAddr net.HardwareAddr
) )
func addHostname(p *dhcp4.Packet) { func addHostname(p *dhcp4.Packet) {
@ -50,11 +52,19 @@ func addHostname(p *dhcp4.Packet) {
p.AddOption(dhcp4.OptionHostName, nnb) p.AddOption(dhcp4.OptionHostName, nnb)
} }
func addClientId(p *dhcp4.Packet) {
id := make([]byte, len(hardwareAddr)+1)
id[0] = 1 // hardware type ethernet, https://tools.ietf.org/html/rfc1700
copy(id[1:], hardwareAddr)
p.AddOption(dhcp4.OptionClientIdentifier, id)
}
// dhcpRequest is a copy of (dhcp4client/Client).Request which // dhcpRequest is a copy of (dhcp4client/Client).Request which
// includes the hostname. // includes the hostname.
func dhcpRequest(c *dhcp4client.Client) (bool, dhcp4.Packet, error) { func dhcpRequest(c *dhcp4client.Client) (bool, dhcp4.Packet, error) {
discoveryPacket := c.DiscoverPacket() discoveryPacket := c.DiscoverPacket()
addHostname(&discoveryPacket) addHostname(&discoveryPacket)
addClientId(&discoveryPacket)
discoveryPacket.PadToMinSize() discoveryPacket.PadToMinSize()
if err := c.SendPacket(discoveryPacket); err != nil { if err := c.SendPacket(discoveryPacket); err != nil {
@ -68,6 +78,7 @@ func dhcpRequest(c *dhcp4client.Client) (bool, dhcp4.Packet, error) {
requestPacket := c.RequestPacket(&offerPacket) requestPacket := c.RequestPacket(&offerPacket)
addHostname(&requestPacket) addHostname(&requestPacket)
addClientId(&requestPacket)
requestPacket.PadToMinSize() requestPacket.PadToMinSize()
if err := c.SendPacket(requestPacket); err != nil { if err := c.SendPacket(requestPacket); err != nil {
@ -91,6 +102,7 @@ func dhcpRequest(c *dhcp4client.Client) (bool, dhcp4.Packet, error) {
// includes the hostname. // includes the hostname.
func dhcpRenew(c *dhcp4client.Client, packet dhcp4.Packet) (bool, dhcp4.Packet, error) { func dhcpRenew(c *dhcp4client.Client, packet dhcp4.Packet) (bool, dhcp4.Packet, error) {
addHostname(&packet) addHostname(&packet)
addClientId(&packet)
packet.PadToMinSize() packet.PadToMinSize()
if err := c.SendPacket(packet); err != nil { if err := c.SendPacket(packet); err != nil {
@ -139,6 +151,8 @@ func main() {
time.Sleep(1 * time.Second) time.Sleep(1 * time.Second)
} }
hardwareAddr = eth0.HardwareAddr
pktsock, err := dhcp4client.NewPacketSock(eth0.Index) pktsock, err := dhcp4client.NewPacketSock(eth0.Index)
if err != nil { if err != nil {
log.Fatal(err) log.Fatal(err)