diff options
| -rw-r--r-- | dhcpv6/server6/conn.go | 62 | ||||
| -rw-r--r-- | dhcpv6/server6/server.go | 32 | ||||
| -rw-r--r-- | dhcpv6/server6/server_test.go | 2 |
3 files changed, 85 insertions, 11 deletions
diff --git a/dhcpv6/server6/conn.go b/dhcpv6/server6/conn.go new file mode 100644 index 0000000..08c54e8 --- /dev/null +++ b/dhcpv6/server6/conn.go @@ -0,0 +1,62 @@ +package server6 + +import ( + "errors" + "fmt" + "net" + "os" + + "github.com/insomniacslk/dhcp/interfaces" + "golang.org/x/sys/unix" +) + +// NewIPv6UDPConn returns a UDPv6-only connection bound to both the interface and port +// given based on a IPv6 DGRAM socket. +// As a bonus, you can actually listen on a multicast address instead of being punted to the wildcard +// +// The interface must already be configured. +func NewIPv6UDPConn(iface string, addr *net.UDPAddr) (net.PacketConn, error) { + fd, err := unix.Socket(unix.AF_INET6, 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.IPPROTO_IPV6, unix.IPV6_V6ONLY, 1); err != nil { + if errno, ok := err.(unix.Errno); !ok { + return nil, fmt.Errorf("unexpected socket error: %v", err) + } else if errno != unix.ENOPROTOOPT { // Unsupported on some OSes (but in that case v6only is default), so we ignore ENOPROTOOPT + return nil, fmt.Errorf("cannot bind socket v6only %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 := interfaces.BindToInterface(fd, iface); err != nil { + if errno, ok := err.(unix.Errno); ok && errno == unix.EACCES { + // Return a more helpful error message in this (fairly common) case + return nil, errors.New("Cannot bind to interface without CAP_NET_RAW or root permissions. " + + "Restart with elevated privilege, or run without specifying an interface to bind to all available interfaces.") + } + return nil, fmt.Errorf("cannot bind to interface %s: %v", iface, err) + } + } + + if addr == nil { + return nil, errors.New("An address to listen on needs to be specified") + } + // Bind to the port. + saddr := unix.SockaddrInet6{Port: addr.Port} + copy(saddr.Addr[:], addr.IP) + if err := unix.Bind(fd, &saddr); err != nil { + return nil, fmt.Errorf("cannot bind to address %v: %v", addr, err) + } + + return net.FilePacketConn(f) +} diff --git a/dhcpv6/server6/server.go b/dhcpv6/server6/server.go index 4506195..ac25076 100644 --- a/dhcpv6/server6/server.go +++ b/dhcpv6/server6/server.go @@ -112,9 +112,14 @@ func WithConn(conn net.PacketConn) ServerOpt { } } -// NewServer initializes and returns a new Server object, listening on `addr`, -// and joining the multicast group ff02::1:2 . If `addr` is nil, IPv6 unspec is -// used. If `WithConn` is used with a non-nil address, `addr` and `ifname` have +// NewServer initializes and returns a new Server object, listening on `addr`. +// * If `addr` is a multicast group, the group will be additionally joined +// * If `addr` is the wildcard address on the DHCPv6 server port (`[::]:547), the +// multicast groups All_DHCP_Relay_Agents_and_Servers(`[ff02::1:2]`) and +// All_DHCP_Servers(`[ff05::1:3]:547`) will be joined. +// * If `addr` is nil, IPv6 unspec on the DHCP server port is used and the above +// behaviour applies +// If `WithConn` is used with a non-nil address, `addr` and `ifname` have // no effect. In such case, joining the multicast group is the caller's // responsibility. func NewServer(ifname string, addr *net.UDPAddr, handler Handler, opt ...ServerOpt) (*Server, error) { @@ -125,19 +130,21 @@ func NewServer(ifname string, addr *net.UDPAddr, handler Handler, opt ...ServerO for _, o := range opt { o(s) } - if s.conn != nil { return s, nil } - var err error - // no connection provided by the user, create a new one - s.conn, err = net.ListenUDP("udp6", addr) - if err != nil { - return nil, err + if addr == nil { + addr = &net.UDPAddr{ + IP: net.IPv6unspecified, + Port: dhcpv6.DefaultServerPort, + } } - var iface *net.Interface + var ( + err error + iface *net.Interface + ) if ifname == "" { iface = nil } else { @@ -146,6 +153,11 @@ func NewServer(ifname string, addr *net.UDPAddr, handler Handler, opt ...ServerO return nil, err } } + // no connection provided by the user, create a new one + s.conn, err = NewIPv6UDPConn(ifname, addr) + if err != nil { + return nil, err + } p := ipv6.NewPacketConn(s.conn) if addr.IP.IsMulticast() { diff --git a/dhcpv6/server6/server_test.go b/dhcpv6/server6/server_test.go index cf5fbea..09cde4c 100644 --- a/dhcpv6/server6/server_test.go +++ b/dhcpv6/server6/server_test.go @@ -33,7 +33,7 @@ func setUpClientAndServer(handler Handler) (*nclient6.Client, *Server) { IP: net.ParseIP("::1"), Port: 0, } - s, err := NewServer("lo", laddr, handler) + s, err := NewServer("", laddr, handler) if err != nil { panic(err) } |