Merge pull request #3 from get9/bsdp

Add BSDP client support to DHCPv4

1 files changed, 117 insertions, 0 deletions

diff --git a/dhcpv4/bsdp/client.go b/dhcpv4/bsdp/client.go
new file mode 100644
index 0000000..c2e8ae0
--- /dev/null
+++ b/dhcpv4/bsdp/client.go
@@ -0,0 +1,117 @@
+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
+}