71 lines
2.2 KiB
Go
71 lines
2.2 KiB
Go
// Copied with modifications from https://github.com/insomniacslk/dhcp/blob/master/dhcpv4/server4/conn_unix.go (under BSD-3-Clause license)
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//go:build !windows
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package cmd
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import (
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"errors"
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"fmt"
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"net"
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"os"
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"github.com/adrianokf/go-dhcp/pkg/types"
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"golang.org/x/sys/unix"
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)
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// NewIPv4UDPConn returns a UDP connection bound to both the interface and port
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// given based on a IPv4 DGRAM socket. The UDP connection allows broadcasting.
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//
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// The interface must already be configured.
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func NewIPv4UDPConn(iface string, addr *net.UDPAddr) (*net.UDPConn, error) {
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fd, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, unix.IPPROTO_UDP)
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if err != nil {
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return nil, fmt.Errorf("cannot get a UDP socket: %v", err)
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}
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f := os.NewFile(uintptr(fd), "")
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// net.FilePacketConn dups the FD, so we have to close this in any case.
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defer f.Close()
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// Allow broadcasting.
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if err := unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_BROADCAST, 1); err != nil {
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return nil, fmt.Errorf("cannot set broadcasting on socket: %v", err)
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}
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// Allow reusing the addr to aid debugging.
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if err := unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_REUSEADDR, 1); err != nil {
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return nil, fmt.Errorf("cannot set reuseaddr on socket: %v", err)
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}
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// Allow reusing the port to aid debugging and testing.
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if err := unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_REUSEPORT, 1); err != nil {
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return nil, fmt.Errorf("cannot set reuseport on socket: %v", err)
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}
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if len(iface) != 0 {
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// Bind directly to the interface.
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if err := unix.BindToDevice(fd, iface); err != nil {
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return nil, fmt.Errorf("cannot bind to interface %s: %v", iface, err)
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}
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}
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if addr == nil {
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addr = &net.UDPAddr{Port: types.ServerPort}
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}
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// Bind to the port.
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saddr := unix.SockaddrInet4{Port: addr.Port}
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if addr.IP != nil && addr.IP.To4() == nil {
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return nil, fmt.Errorf("wrong address family (expected v4) for %s", addr.IP)
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}
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copy(saddr.Addr[:], addr.IP.To4())
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if err := unix.Bind(fd, &saddr); err != nil {
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return nil, fmt.Errorf("cannot bind to port %d: %v", addr.Port, err)
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}
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conn, err := net.FilePacketConn(f)
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if err != nil {
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return nil, err
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}
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udpconn, ok := conn.(*net.UDPConn)
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if !ok {
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return nil, errors.New("BUG: incorrect socket type, expected UDP")
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}
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return udpconn, nil
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}
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