ipv6: Annotate ipv6_addr_is_* bitwise pointer casts

The sparse commit 6002ded74587 ("add a flag to warn on casts to/from
bitwise pointers") introduced a check for non-direct casts from/to
restricted datatypes (when -Wbitwise-pointer is enabled).

This triggered a warning in the 64 bit optimized ipv6_addr_is_*() functions
because sparse doesn't know that the buffer already points to some data in
the correct bitwise integer format. But these were correct and can
therefore be marked with __force to signalize sparse an intended cast to a
specific bitwise type.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/addrconf.h

@@ -437,7 +437,7 @@ static inline void addrconf_addr_solict_mult(const struct in6_addr *addr,
 static inline bool ipv6_addr_is_ll_all_nodes(const struct in6_addr *addr)
 {
 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
-	__be64 *p = (__be64 *)addr;
+	__be64 *p = (__force __be64 *)addr;
 	return ((p[0] ^ cpu_to_be64(0xff02000000000000UL)) | (p[1] ^ cpu_to_be64(1))) == 0UL;
 #else
 	return ((addr->s6_addr32[0] ^ htonl(0xff020000)) |
@@ -449,7 +449,7 @@ static inline bool ipv6_addr_is_ll_all_nodes(const struct in6_addr *addr)
 static inline bool ipv6_addr_is_ll_all_routers(const struct in6_addr *addr)
 {
 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
-	__be64 *p = (__be64 *)addr;
+	__be64 *p = (__force __be64 *)addr;
 	return ((p[0] ^ cpu_to_be64(0xff02000000000000UL)) | (p[1] ^ cpu_to_be64(2))) == 0UL;
 #else
 	return ((addr->s6_addr32[0] ^ htonl(0xff020000)) |
@@ -466,7 +466,7 @@ static inline bool ipv6_addr_is_isatap(const struct in6_addr *addr)
 static inline bool ipv6_addr_is_solict_mult(const struct in6_addr *addr)
 {
 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
-	__be64 *p = (__be64 *)addr;
+	__be64 *p = (__force __be64 *)addr;
 	return ((p[0] ^ cpu_to_be64(0xff02000000000000UL)) |
 		((p[1] ^ cpu_to_be64(0x00000001ff000000UL)) &
 		 cpu_to_be64(0xffffffffff000000UL))) == 0UL;
@@ -481,7 +481,7 @@ static inline bool ipv6_addr_is_solict_mult(const struct in6_addr *addr)
 static inline bool ipv6_addr_is_all_snoopers(const struct in6_addr *addr)
 {
 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
-	__be64 *p = (__be64 *)addr;
+	__be64 *p = (__force __be64 *)addr;
 
 	return ((p[0] ^ cpu_to_be64(0xff02000000000000UL)) |
 		(p[1] ^ cpu_to_be64(0x6a))) == 0UL;