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package bsdp
import (
"fmt"
"net"
"syscall"
"github.com/insomniacslk/dhcp/dhcpv4"
)
// Client is a BSDP-specific client suitable for performing BSDP exchanges.
type Client dhcpv4.Client
// Exchange runs a full BSDP exchange (Inform[list], Ack, Inform[select],
// Ack). Returns a list of DHCPv4 structures representing the exchange.
func (c *Client) Exchange(ifname string, informList *dhcpv4.DHCPv4) ([]dhcpv4.DHCPv4, error) {
conversation := make([]dhcpv4.DHCPv4, 1)
var err error
// INFORM[LIST]
if informList == nil {
informList, err = NewInformListForInterface(ifname, dhcpv4.ClientPort)
if err != nil {
return conversation, err
}
}
conversation[0] = *informList
// TODO: deduplicate with code in dhcpv4/client.go
fd, err := syscall.Socket(syscall.AF_INET, syscall.SOCK_RAW, syscall.IPPROTO_RAW)
if err != nil {
return conversation, err
}
err = syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1)
if err != nil {
return conversation, err
}
err = syscall.SetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_HDRINCL, 1)
if err != nil {
return conversation, err
}
err = syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_BROADCAST, 1)
if err != nil {
return conversation, err
}
err = dhcpv4.BindToInterface(fd, ifname)
if err != nil {
return conversation, err
}
bcast := [4]byte{}
copy(bcast[:], net.IPv4bcast)
daddr := syscall.SockaddrInet4{Port: dhcpv4.ClientPort, Addr: bcast}
packet, err := dhcpv4.MakeRawBroadcastPacket(informList.ToBytes())
if err != nil {
return conversation, err
}
err = syscall.Sendto(fd, packet, 0, &daddr)
if err != nil {
return conversation, err
}
// ACK 1
conn, err := net.ListenUDP("udp4", &net.UDPAddr{IP: net.IPv4zero, Port: dhcpv4.ClientPort})
if err != nil {
return conversation, err
}
defer conn.Close()
buf := make([]byte, dhcpv4.MaxUDPReceivedPacketSize)
oobdata := []byte{} // ignoring oob data
n, _, _, _, err := conn.ReadMsgUDP(buf, oobdata)
ack1, err := dhcpv4.FromBytes(buf[:n])
if err != nil {
return conversation, err
}
// TODO match the packet content
// TODO check that the peer address matches the declared server IP and port
conversation = append(conversation, *ack1)
// Parse boot images sent back by server
bootImages, err := ParseBootImageListFromAck(*ack1)
if err != nil {
return conversation, err
}
if len(bootImages) == 0 {
return conversation, fmt.Errorf("Got no BootImages from server")
}
// INFORM[SELECT]
informSelect, err := InformSelectForAck(*ack1, dhcpv4.ClientPort, bootImages[0])
if err != nil {
return conversation, err
}
conversation = append(conversation, *informSelect)
packet, err = dhcpv4.MakeRawBroadcastPacket(informSelect.ToBytes())
if err != nil {
return conversation, err
}
err = syscall.Sendto(fd, packet, 0, &daddr)
if err != nil {
return conversation, err
}
// ACK 2
buf = make([]byte, dhcpv4.MaxUDPReceivedPacketSize)
n, _, _, _, err = conn.ReadMsgUDP(buf, oobdata)
ack2, err := dhcpv4.FromBytes(buf[:n])
if err != nil {
return conversation, err
}
// TODO match the packet content
// TODO check that the peer address matches the declared server IP and port
conversation = append(conversation, *ack2)
return conversation, nil
}
|
