Behavioral differences

If io-pkt has problems loading a device, it doesn't print failure messages to the console by default; they're automatically sent to slogger . You can use the -v option to io-pkt to force the output to the console for debugging purposes.

The way in which the SIOCGIFCONF ioctl() command was used in our io-net code was incorrect but it worked. We've changed the implementation, but applications that use the old method will no longer work. Here's some code that illustrates the old and new methods:

/*
 * Example demonstrating a common pitfall with SIOCGIFCONF handling.
 */


#include <sys/sockio.h>
#include <net/if.h>
#include <malloc.h>
#include <stdlib.h>
#include <err.h>
#include <ifaddrs.h>

void gifconf(int);
void gifaddrs(int);


int
main(void)
{
	int             s;

	if ((s = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
		err(EXIT_FAILURE, "socket");

	gifconf(s);     /* Old code often used SIOCGIFCONF ioctl        */
	gifaddrs(s);    /* New code should use getifaddrs()             */

	close(s);

	return 0;
}

void
gifconf(int s)
{
	struct ifconf   ifc;
	struct ifreq    *inext, *iend, *icur;
	size_t		size;


	size = 4096;
	ifc.ifc_len = size;
	if ((ifc.ifc_buf = malloc(ifc.ifc_len)) == NULL)
		err(EXIT_FAILURE, "malloc");
	if (ioctl(s, SIOCGIFCONF, &ifc) == -1)
		err(EXIT_FAILURE, "SIOCGIFCONF");

	if (ifc.ifc_len >= size) {
		/* realloc and try again */
		errx(EXIT_FAILURE, "SIOCGIFCONF: buf too small");
	}

	inext = ifc.ifc_req;
	iend = (struct ifreq *)(ifc.ifc_buf + ifc.ifc_len);
	for (;;) {
		icur = inext;
#if 0
		/*
		 * Broken code.  This would happen to work for most cases
		 * because previously:
		 *
		 * sizeof(struct sockaddr) + IFNAMSIZ == sizeof(struct ifreq)
		 *
		 * Under this scenario  the two 'if' cases in the working
		 * case below work out to the same thing.
		 */
		inext = (struct ifreq *)
		    ((char *)inext + inext->ifr_addr.sa_len + IFNAMSIZ);
#else
		/* This will work against old / new libsocket */
		if (inext->ifr_addr.sa_len + IFNAMSIZ > sizeof(struct ifreq))
			inext = (struct ifreq *)
			    ((char *)inext + inext->ifr_addr.sa_len + IFNAMSIZ);
		else
			inext++;
#endif
		if (inext > iend)
			break;

		/* process icur */
	}

	free(ifc.ifc_buf);
}

void
gifaddrs(int s)
{
	struct ifaddrs	*ifaddrs, *ifap;

	if (getifaddrs(&ifaddrs) == -1)
		err(EXIT_FAILURE, "getifaddrs");

	for (ifap = ifaddrs; ifap != NULL; ifap = ifap->ifa_next) {
		continue;
	}

	freeifaddrs(ifaddrs);
}

If you compile the test case against the old headers, the SIOCGIFCONF ioctl() will produce the expected results in all environments: old / new stack, old / new libc. If you compile it against the io-pkt headers, the SIOCGIFCONF command will work only with the io-pkt stack and the 6.4 libc. In either case, there's no dependency on any version of libsocket.

The getifaddrs() call will work everywhere and is recommended for new code.