diff options
Diffstat (limited to 'vendor/github.com/rsc/letsencrypt/vendor/github.com/miekg/dns/udp_linux.go')
-rw-r--r-- | vendor/github.com/rsc/letsencrypt/vendor/github.com/miekg/dns/udp_linux.go | 105 |
1 files changed, 105 insertions, 0 deletions
diff --git a/vendor/github.com/rsc/letsencrypt/vendor/github.com/miekg/dns/udp_linux.go b/vendor/github.com/rsc/letsencrypt/vendor/github.com/miekg/dns/udp_linux.go new file mode 100644 index 000000000..033df4239 --- /dev/null +++ b/vendor/github.com/rsc/letsencrypt/vendor/github.com/miekg/dns/udp_linux.go @@ -0,0 +1,105 @@ +// +build linux,!appengine + +package dns + +// See: +// * http://stackoverflow.com/questions/3062205/setting-the-source-ip-for-a-udp-socket and +// * http://blog.powerdns.com/2012/10/08/on-binding-datagram-udp-sockets-to-the-any-addresses/ +// +// Why do we need this: When listening on 0.0.0.0 with UDP so kernel decides what is the outgoing +// interface, this might not always be the correct one. This code will make sure the egress +// packet's interface matched the ingress' one. + +import ( + "net" + "syscall" +) + +// setUDPSocketOptions sets the UDP socket options. +// This function is implemented on a per platform basis. See udp_*.go for more details +func setUDPSocketOptions(conn *net.UDPConn) error { + sa, err := getUDPSocketName(conn) + if err != nil { + return err + } + switch sa.(type) { + case *syscall.SockaddrInet6: + v6only, err := getUDPSocketOptions6Only(conn) + if err != nil { + return err + } + setUDPSocketOptions6(conn) + if !v6only { + setUDPSocketOptions4(conn) + } + case *syscall.SockaddrInet4: + setUDPSocketOptions4(conn) + } + return nil +} + +// setUDPSocketOptions4 prepares the v4 socket for sessions. +func setUDPSocketOptions4(conn *net.UDPConn) error { + file, err := conn.File() + if err != nil { + return err + } + if err := syscall.SetsockoptInt(int(file.Fd()), syscall.IPPROTO_IP, syscall.IP_PKTINFO, 1); err != nil { + file.Close() + return err + } + // Calling File() above results in the connection becoming blocking, we must fix that. + // See https://github.com/miekg/dns/issues/279 + err = syscall.SetNonblock(int(file.Fd()), true) + if err != nil { + file.Close() + return err + } + file.Close() + return nil +} + +// setUDPSocketOptions6 prepares the v6 socket for sessions. +func setUDPSocketOptions6(conn *net.UDPConn) error { + file, err := conn.File() + if err != nil { + return err + } + if err := syscall.SetsockoptInt(int(file.Fd()), syscall.IPPROTO_IPV6, syscall.IPV6_RECVPKTINFO, 1); err != nil { + file.Close() + return err + } + err = syscall.SetNonblock(int(file.Fd()), true) + if err != nil { + file.Close() + return err + } + file.Close() + return nil +} + +// getUDPSocketOption6Only return true if the socket is v6 only and false when it is v4/v6 combined +// (dualstack). +func getUDPSocketOptions6Only(conn *net.UDPConn) (bool, error) { + file, err := conn.File() + if err != nil { + return false, err + } + // dual stack. See http://stackoverflow.com/questions/1618240/how-to-support-both-ipv4-and-ipv6-connections + v6only, err := syscall.GetsockoptInt(int(file.Fd()), syscall.IPPROTO_IPV6, syscall.IPV6_V6ONLY) + if err != nil { + file.Close() + return false, err + } + file.Close() + return v6only == 1, nil +} + +func getUDPSocketName(conn *net.UDPConn) (syscall.Sockaddr, error) { + file, err := conn.File() + if err != nil { + return nil, err + } + defer file.Close() + return syscall.Getsockname(int(file.Fd())) +} |