util: Introduce hton*_constant() in place of #ifdefs

We have several places where we have fairly ugly #ifdefs on __BYTE_ORDER
where we need network order values in a constant expression (so we can't
use htons() or htonl()).  We can do this more cleanly by using a single
__BYTE_ORDER ifdef to define htons_constant() and htonl_constant()
macros, then using those in all the other places.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

2 files changed, 24 insertions, 63 deletions

diff --git a/dhcpv6.c b/dhcpv6.c
index e763aed..d0e6c7f 100644
--- a/dhcpv6.c
+++ b/dhcpv6.c
@@ -39,37 +39,21 @@
  */
 struct opt_hdr {
 	uint16_t t;
-#if __BYTE_ORDER == __BIG_ENDIAN
-# define OPT_CLIENTID		1
-# define OPT_SERVERID		2
-# define OPT_IA_NA		3
-# define OPT_IA_TA		4
-# define OPT_IAAADR		5
-# define OPT_STATUS_CODE	13
-# define  STATUS_NOTONLINK	4
-# define OPT_DNS_SERVERS	23
-# define OPT_DNS_SEARCH		24
-#else
-# define OPT_CLIENTID		__bswap_constant_16(1)
-# define OPT_SERVERID		__bswap_constant_16(2)
-# define OPT_IA_NA		__bswap_constant_16(3)
-# define OPT_IA_TA		__bswap_constant_16(4)
-# define OPT_IAAADR		__bswap_constant_16(5)
-# define OPT_STATUS_CODE	__bswap_constant_16(13)
-# define  STATUS_NOTONLINK	__bswap_constant_16(4)
-# define OPT_DNS_SERVERS	__bswap_constant_16(23)
-# define OPT_DNS_SEARCH		__bswap_constant_16(24)
-#endif
+# define OPT_CLIENTID		htons_constant(1)
+# define OPT_SERVERID		htons_constant(2)
+# define OPT_IA_NA		htons_constant(3)
+# define OPT_IA_TA		htons_constant(4)
+# define OPT_IAAADR		htons_constant(5)
+# define OPT_STATUS_CODE	htons_constant(13)
+# define  STATUS_NOTONLINK	htons_constant(4)
+# define OPT_DNS_SERVERS	htons_constant(23)
+# define OPT_DNS_SEARCH		htons_constant(24)
 #define   STR_NOTONLINK		"Prefix not appropriate for link."
 
 	uint16_t l;
 } __attribute__((packed));
 
-#if __BYTE_ORDER == __BIG_ENDIAN
-# define OPT_SIZE_CONV(x)	(x)
-#else
-# define OPT_SIZE_CONV(x)	(__bswap_constant_16(x))
-#endif
+# define OPT_SIZE_CONV(x)	(htons_constant(x))
 #define OPT_SIZE(x)		OPT_SIZE_CONV(sizeof(struct opt_##x) -	\
 					      sizeof(struct opt_hdr))
 #define OPT_VSIZE(x)		(sizeof(struct opt_##x) - 		\
@@ -103,19 +87,11 @@ struct opt_server_id {
 	uint8_t duid_lladdr[ETH_ALEN];
 } __attribute__ ((packed));
 
-#if __BYTE_ORDER == __BIG_ENDIAN
-#define SERVER_ID {						\
+#define SERVER_ID {							\
 	{ OPT_SERVERID,	OPT_SIZE(server_id) },				\
-	  DUID_TYPE_LLT, ARPHRD_ETHER, 0, { 0 }				\
+	  htons_constant(DUID_TYPE_LLT),				\
+	  htons_constant(ARPHRD_ETHER), 0, { 0 }			\
 }
-#else
-#define SERVER_ID {						\
-	{ OPT_SERVERID,	OPT_SIZE(server_id) },				\
-	__bswap_constant_16(DUID_TYPE_LLT),				\
-	__bswap_constant_16(ARPHRD_ETHER),				\
-	0, { 0 }							\
-}
-#endif
 
 /**
  * struct opt_ia_na - Identity Association for Non-temporary Addresses Option
diff --git a/util.h b/util.h
index 3baec91..b4c139d 100644
--- a/util.h
+++ b/util.h
@@ -69,6 +69,14 @@
 #define MAC_ZERO		((uint8_t [ETH_ALEN]){ 0 })
 #define MAC_IS_ZERO(addr)	(!memcmp((addr), MAC_ZERO, ETH_ALEN))
 
+#if __BYTE_ORDER == __BIG_ENDIAN
+#define	htons_constant(x)	(x)
+#define	htonl_constant(x)	(x)
+#else
+#define	htons_constant(x)	(__bswap_constant_16(x))
+#define	htonl_constant(x)	(__bswap_constant_32(x))
+#endif
+
 #define IN4_IS_ADDR_UNSPECIFIED(a) \
 	((a)->s_addr == htonl(INADDR_ANY))
 #define IN4_IS_ADDR_BROADCAST(a) \
@@ -79,13 +87,8 @@
 	(IN_MULTICAST(ntohl((a)->s_addr)))
 #define IN4_ARE_ADDR_EQUAL(a, b) \
 	(((struct in_addr *)(a))->s_addr == ((struct in_addr *)b)->s_addr)
-#if __BYTE_ORDER == __BIG_ENDIAN
-#define IN4ADDR_LOOPBACK_INIT \
-	{ .s_addr	= INADDR_LOOPBACK }
-#else
 #define IN4ADDR_LOOPBACK_INIT \
-	{ .s_addr	= __bswap_constant_32(INADDR_LOOPBACK) }
-#endif
+	{ .s_addr	= htonl_constant(INADDR_LOOPBACK) }
 
 #define NS_FN_STACK_SIZE	(RLIMIT_STACK_VAL * 1024 / 8)
 int do_clone(int (*fn)(void *), char *stack_area, size_t stack_size, int flags,
@@ -99,37 +102,19 @@ int do_clone(int (*fn)(void *), char *stack_area, size_t stack_size, int flags,
 			 (void *)(arg));				\
 	} while (0)
 
-#if __BYTE_ORDER == __BIG_ENDIAN
-#define L2_BUF_ETH_IP4_INIT						\
-	{								\
-		.h_dest		= { 0 },				\
-		.h_source	= { 0 },				\
-		.h_proto	= ETH_P_IP,				\
-	}
-#else
 #define L2_BUF_ETH_IP4_INIT						\
 	{								\
 		.h_dest		= { 0 },				\
 		.h_source	= { 0 },				\
-		.h_proto	= __bswap_constant_16(ETH_P_IP),	\
+		.h_proto	= htons_constant(ETH_P_IP),		\
 	}
-#endif
 
-#if __BYTE_ORDER == __BIG_ENDIAN
-#define L2_BUF_ETH_IP6_INIT						\
-	{								\
-		.h_dest		= { 0 },				\
-		.h_source	= { 0 },				\
-		.h_proto	= ETH_P_IPV6,				\
-	}
-#else
 #define L2_BUF_ETH_IP6_INIT						\
 	{								\
 		.h_dest		= { 0 },				\
 		.h_source	= { 0 },				\
-		.h_proto	= __bswap_constant_16(ETH_P_IPV6),	\
+		.h_proto	= htons_constant(ETH_P_IPV6),		\
 	}
-#endif
 
 #define L2_BUF_IP4_INIT(proto)						\
 	{								\