unix: implement AF_TIPC sockets on Linux

Adds initial constants and types to use with SockaddrTIPC. For more
information on TIPC, see: http://tipc.sourceforge.net/.

Because the C struct sockaddr_tipc makes use of a union for its addr
field, I have created a wrapping layer in SockaddrTIPC that uses
an interface to determine which variant is in use.

Tests accompany this change due to the complexity of this code. There
is currently little test coverage in the Sockaddr-related code, but
perhaps this is something that could be picked up as a relatively
straightforward task for a new contributor.

Change-Id: I5033a0685cb7128d4b1a23d18aca71c202d0c0aa
Reviewed-on: https://go-review.googlesource.com/c/sys/+/187960
Run-TryBot: Matt Layher <mdlayher@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

unix/syscall_linux.go

@@ -775,6 +775,70 @@ func (sa *SockaddrPPPoE) sockaddr() (unsafe.Pointer, _Socklen, error) {
 	return unsafe.Pointer(&sa.raw), SizeofSockaddrPPPoX, nil
 }
 
+// SockaddrTIPC implements the Sockaddr interface for AF_TIPC type sockets.
+// For more information on TIPC, see: http://tipc.sourceforge.net/.
+type SockaddrTIPC struct {
+	// Scope is the publication scopes when binding service/service range.
+	// Should be set to TIPC_CLUSTER_SCOPE or TIPC_NODE_SCOPE.
+	Scope int
+
+	// Addr is the type of address used to manipulate a socket. Addr must be
+	// one of:
+	//  - *TIPCSocketAddr: "id" variant in the C addr union
+	//  - *TIPCServiceRange: "nameseq" variant in the C addr union
+	//  - *TIPCServiceName: "name" variant in the C addr union
+	//
+	// If nil, EINVAL will be returned when the structure is used.
+	Addr TIPCAddr
+
+	raw RawSockaddrTIPC
+}
+
+// TIPCAddr is implemented by types that can be used as an address for
+// SockaddrTIPC. It is only implemented by *TIPCSocketAddr, *TIPCServiceRange,
+// and *TIPCServiceName.
+type TIPCAddr interface {
+	tipcAddrtype() uint8
+	tipcAddr() [12]byte
+}
+
+func (sa *TIPCSocketAddr) tipcAddr() [12]byte {
+	var out [12]byte
+	copy(out[:], (*(*[unsafe.Sizeof(TIPCSocketAddr{})]byte)(unsafe.Pointer(sa)))[:])
+	return out
+}
+
+func (sa *TIPCSocketAddr) tipcAddrtype() uint8 { return TIPC_SOCKET_ADDR }
+
+func (sa *TIPCServiceRange) tipcAddr() [12]byte {
+	var out [12]byte
+	copy(out[:], (*(*[unsafe.Sizeof(TIPCServiceRange{})]byte)(unsafe.Pointer(sa)))[:])
+	return out
+}
+
+func (sa *TIPCServiceRange) tipcAddrtype() uint8 { return TIPC_SERVICE_RANGE }
+
+func (sa *TIPCServiceName) tipcAddr() [12]byte {
+	var out [12]byte
+	copy(out[:], (*(*[unsafe.Sizeof(TIPCServiceName{})]byte)(unsafe.Pointer(sa)))[:])
+	return out
+}
+
+func (sa *TIPCServiceName) tipcAddrtype() uint8 { return TIPC_SERVICE_ADDR }
+
+func (sa *SockaddrTIPC) sockaddr() (unsafe.Pointer, _Socklen, error) {
+	if sa.Addr == nil {
+		return nil, 0, EINVAL
+	}
+
+	sa.raw.Family = AF_TIPC
+	sa.raw.Scope = int8(sa.Scope)
+	sa.raw.Addrtype = sa.Addr.tipcAddrtype()
+	sa.raw.Addr = sa.Addr.tipcAddr()
+
+	return unsafe.Pointer(&sa.raw), SizeofSockaddrTIPC, nil
+}
+
 func anyToSockaddr(fd int, rsa *RawSockaddrAny) (Sockaddr, error) {
 	switch rsa.Addr.Family {
 	case AF_NETLINK:
@@ -900,6 +964,27 @@ func anyToSockaddr(fd int, rsa *RawSockaddrAny) (Sockaddr, error) {
 				break
 			}
 		}
+		return sa, nil
+	case AF_TIPC:
+		pp := (*RawSockaddrTIPC)(unsafe.Pointer(rsa))
+
+		sa := &SockaddrTIPC{
+			Scope: int(pp.Scope),
+		}
+
+		// Determine which union variant is present in pp.Addr by checking
+		// pp.Addrtype.
+		switch pp.Addrtype {
+		case TIPC_SERVICE_RANGE:
+			sa.Addr = (*TIPCServiceRange)(unsafe.Pointer(&pp.Addr))
+		case TIPC_SERVICE_ADDR:
+			sa.Addr = (*TIPCServiceName)(unsafe.Pointer(&pp.Addr))
+		case TIPC_SOCKET_ADDR:
+			sa.Addr = (*TIPCSocketAddr)(unsafe.Pointer(&pp.Addr))
+		default:
+			return nil, EINVAL
+		}
+
 		return sa, nil
 	}
 	return nil, EAFNOSUPPORT