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dhcp4d: respect broadcast bit

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Mac’s Internet Recovery DHCP client requires broadcast responses and will ignore
unicast responses outright.
This commit is contained in:
Michael Stapelberg 2018-10-07 17:36:00 +02:00
parent f7638dfeaa
commit f606e70250
1 changed files with 9 additions and 3 deletions
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12
internal/dhcp4d/dhcp4d.go
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@ -163,8 +163,14 @@ func (h *Handler) ServeDHCP(p dhcp4.Packet, msgType dhcp4.MessageType, options d
ComputeChecksums: true, ComputeChecksums: true,
FixLengths: true, FixLengths: true,
} }
destMAC := p.CHAddr()
destIP := reply.YIAddr()
if p.Broadcast() {
destMAC = []byte{0xff, 0xff, 0xff, 0xff, 0xff, 0xff}
destIP = net.IPv4bcast
}
ethernet := &layers.Ethernet{ ethernet := &layers.Ethernet{
DstMAC: p.CHAddr(), DstMAC: destMAC,
SrcMAC: h.iface.HardwareAddr, SrcMAC: h.iface.HardwareAddr,
EthernetType: layers.EthernetTypeIPv4, EthernetType: layers.EthernetTypeIPv4,
} }
@ -173,7 +179,7 @@ func (h *Handler) ServeDHCP(p dhcp4.Packet, msgType dhcp4.MessageType, options d
Version: 4, Version: 4,
TTL: 255, TTL: 255,
SrcIP: h.serverIP, SrcIP: h.serverIP,
DstIP: reply.YIAddr(), DstIP: destIP,
Protocol: layers.IPProtocolUDP, Protocol: layers.IPProtocolUDP,
Flags: layers.IPv4DontFragment, Flags: layers.IPv4DontFragment,
} }
@ -188,7 +194,7 @@ func (h *Handler) ServeDHCP(p dhcp4.Packet, msgType dhcp4.MessageType, options d
udp, udp,
gopacket.Payload(reply)) gopacket.Payload(reply))
if _, err := h.rawConn.WriteTo(buf.Bytes(), &raw.Addr{p.CHAddr()}); err != nil { if _, err := h.rawConn.WriteTo(buf.Bytes(), &raw.Addr{destMAC}); err != nil {
log.Printf("WriteTo: %v", err) log.Printf("WriteTo: %v", err)
} }