63 lines
1.5 KiB
Go
63 lines
1.5 KiB
Go
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package dhcpd
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import (
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"net"
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"github.com/joomcode/errorx"
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"golang.org/x/net/ipv4"
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)
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// TODO: on windows, controlmessage does not work, try to find out another way
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// https://github.com/golang/net/blob/master/ipv4/payload.go#L13
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type filterConn struct {
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iface net.Interface
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conn *ipv4.PacketConn
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// cm *ipv4.ControlMessage
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}
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func newFilterConn(iface net.Interface, address string) (*filterConn, error) {
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c, err := net.ListenPacket("udp4", address)
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if err != nil {
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return nil, errorx.Decorate(err, "Couldn't listen to %s on UDP4", address)
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}
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p := ipv4.NewPacketConn(c)
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err = p.SetControlMessage(ipv4.FlagInterface, true)
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if err != nil {
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c.Close()
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return nil, errorx.Decorate(err, "Couldn't set control message FlagInterface on connection")
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}
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return &filterConn{iface: iface, conn: p}, nil
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}
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func (f *filterConn) ReadFrom(b []byte) (int, net.Addr, error) {
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for { // read until we find a suitable packet
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n, cm, addr, err := f.conn.ReadFrom(b)
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if err != nil {
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return 0, addr, errorx.Decorate(err, "Error when reading from socket")
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}
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if cm == nil {
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// no controlmessage was passed, so pass the packet to the caller
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return n, addr, nil
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}
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if cm.IfIndex == f.iface.Index {
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return n, addr, nil
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}
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// packet doesn't match criteria, drop it
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}
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return 0, nil, nil
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}
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func (f *filterConn) WriteTo(b []byte, addr net.Addr) (int, error) {
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cm := ipv4.ControlMessage{
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IfIndex: f.iface.Index,
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}
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return f.conn.WriteTo(b, &cm, addr)
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}
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func (f *filterConn) Close() error {
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return f.conn.Close()
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}
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