ip.7: INADDR_* values cannot be assigned directly to s_addr

Signed-off-by Ricardo Biehl Pasquali <[email protected]>

---

According to The Open Group Base Specifications Issue 7, RATIONALE section of <http://pubs.opengroup.org/onlinepubs/9699919799/
basedefs/netinet_in.h.html> some INADDR_* values must be converted using htonl().

INADDR_ANY and INADDR_BROADCAST are byte-order-neutral so they do not require htonl(), however I only comment this fact in NOTES. On the text I recommend to use htonl(), "even if for some subset it's not necessary".

Proof code:

	#include <arpa/inet.h> /* inet_addr() htonl() */
	#include <inttypes.h> /* PRIu32 */
	#include <netinet/in.h> /* INADDR_* */
	#include <stdio.h> /* printf() */

	#define LOOPBACK_ADDRESS  "127.0.0.1"

	int
	main(void)
	{
		/* uint32_t as defined in the former
		 * specification */
		uint32_t addr;

		addr = inet_addr(LOOPBACK_ADDRESS);

		printf("inet_addr:              %" PRIu32 "\n"
		       "htonl(INADDR_LOOPBACK): %" PRIu32 "\n"
		       "INADDR_LOOPBACK:        %" PRIu32 "\n",
		       addr, htonl(INADDR_LOOPBACK),
		       INADDR_LOOPBACK);

		return 0;
	}

		Ricardo Biehl Pasquali

 man7/ip.7 | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

man7/ip.7 +11 -1

index d05d211..d7481e2 100644
@@ -193,8 +193,11 @@ contains the host interface address in network byte order.
 .I in_addr
 should be assigned one of the
 .BR INADDR_*
-values (e.g.,
+values
+(e.g.,
 .BR INADDR_ANY )
+using
+.BR htonl (3)
 or set using the
 .BR inet_aton (3),
 .BR inet_addr (3),

@@ -1267,6 +1270,13 @@ Using the
 socket options level isn't portable; BSD-based stacks use the
 .B IPPROTO_IP
 level.
+.PP
+.B INADDR_ANY
+(0.0.0.0) and
+.B INADDR_BROADCAST
+(255.255.255.255) are byte-order-neutral. That means
+.BR htonl (3)
+has no effect on them.
 .SS Compatibility
 For compatibility with Linux 2.0, the obsolete
 .BI "socket(AF_INET, SOCK_PACKET, " protocol )