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63 lines
1.8 KiB
63 lines
1.8 KiB
// +build linux |
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package dns |
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// See: |
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// * http://stackoverflow.com/questions/3062205/setting-the-source-ip-for-a-udp-socket and |
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// * http://blog.powerdns.com/2012/10/08/on-binding-datagram-udp-sockets-to-the-any-addresses/ |
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// |
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// Why do we need this: When listening on 0.0.0.0 with UDP so kernel decides what is the outgoing |
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// interface, this might not always be the correct one. This code will make sure the egress |
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// packet's interface matched the ingress' one. |
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import ( |
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"net" |
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"syscall" |
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) |
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// setUDPSocketOptions4 prepares the v4 socket for sessions. |
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func setUDPSocketOptions4(conn *net.UDPConn) error { |
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file, err := conn.File() |
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if err != nil { |
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return err |
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} |
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if err := syscall.SetsockoptInt(int(file.Fd()), syscall.IPPROTO_IP, syscall.IP_PKTINFO, 1); err != nil { |
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return err |
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} |
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return nil |
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} |
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// setUDPSocketOptions6 prepares the v6 socket for sessions. |
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func setUDPSocketOptions6(conn *net.UDPConn) error { |
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file, err := conn.File() |
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if err != nil { |
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return err |
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} |
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if err := syscall.SetsockoptInt(int(file.Fd()), syscall.IPPROTO_IPV6, syscall.IPV6_RECVPKTINFO, 1); err != nil { |
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return err |
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} |
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return nil |
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} |
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// getUDPSocketOption6Only return true if the socket is v6 only and false when it is v4/v6 combined |
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// (dualstack). |
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func getUDPSocketOptions6Only(conn *net.UDPConn) (bool, error) { |
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file, err := conn.File() |
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if err != nil { |
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return false, err |
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} |
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// dual stack. See http://stackoverflow.com/questions/1618240/how-to-support-both-ipv4-and-ipv6-connections |
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v6only, err := syscall.GetsockoptInt(int(file.Fd()), syscall.IPPROTO_IPV6, syscall.IPV6_V6ONLY) |
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if err != nil { |
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return false, err |
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} |
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return v6only == 1, nil |
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} |
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func getUDPSocketName(conn *net.UDPConn) (syscall.Sockaddr, error) { |
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file, err := conn.File() |
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if err != nil { |
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return nil, err |
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} |
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return syscall.Getsockname(int(file.Fd())) |
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}
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