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package server4
import (
"errors"
"fmt"
"net"
"os"
"github.com/insomniacslk/dhcp/dhcpv4"
"golang.org/x/sys/unix"
)
// NewIPv4UDPConn returns a UDP connection bound to both the interface and port
// given based on a IPv4 DGRAM socket. The UDP connection allows broadcasting.
//
// The interface must already be configured.
func NewIPv4UDPConn(iface string, addr *net.UDPAddr) (*net.UDPConn, error) {
fd, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, unix.IPPROTO_UDP)
if err != nil {
return nil, fmt.Errorf("cannot get a UDP socket: %v", err)
}
f := os.NewFile(uintptr(fd), "")
// net.FilePacketConn dups the FD, so we have to close this in any case.
defer f.Close()
// Allow broadcasting.
if err := unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_BROADCAST, 1); err != nil {
return nil, fmt.Errorf("cannot set broadcasting on socket: %v", err)
}
// Allow reusing the addr to aid debugging.
if err := unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_REUSEADDR, 1); err != nil {
return nil, fmt.Errorf("cannot set reuseaddr on socket: %v", err)
}
if len(iface) != 0 {
// Bind directly to the interface.
if err := dhcpv4.BindToInterface(fd, iface); err != nil {
return nil, fmt.Errorf("cannot bind to interface %s: %v", iface, err)
}
}
if addr == nil {
addr = &net.UDPAddr{Port: dhcpv4.ServerPort}
}
// Bind to the port.
saddr := unix.SockaddrInet4{Port: addr.Port}
copy(saddr.Addr[:], addr.IP.To4())
if err := unix.Bind(fd, &saddr); err != nil {
return nil, fmt.Errorf("cannot bind to port %d: %v", addr.Port, err)
}
conn, err := net.FilePacketConn(f)
if err != nil {
return nil, err
}
udpconn, ok := conn.(*net.UDPConn)
if !ok {
return nil, errors.New("BUG(dhcp4): incorrect socket type, expected UDP")
}
return udpconn, nil
}
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