small test program that produces same symptom

weird_getsockopt.c (text/plain), 1.03 KB, created by Wormo (RETIRED) on 2006-07-19 22:48:33 UTC

#include <stdio.h>
#include <errno.h>
#include <ctype.h>
#include <iptables.h>

static int compatible_revision(const char *name, u_int8_t revision, int opt)
{
	struct ipt_get_revision rev;
	socklen_t s = sizeof(rev);
	int max_rev, sockfd;

	sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_RAW);
	if (sockfd < 0) {
		fprintf(stderr, "Could not open socket to kernel: %s\n",
			strerror(errno));
		exit(1);
	}

	strcpy(rev.name, name);
	rev.revision = revision;

	max_rev = getsockopt(sockfd, IPPROTO_IP, opt, &rev, &s);
	if (max_rev < 0) {
		/* Definitely don't support this? */
		if (errno == EPROTONOSUPPORT) {
			close(sockfd);
			return 0;
		} else if (errno == ENOPROTOOPT) {
			close(sockfd);
			/* Assume only revision 0 support (old kernel) */
			return (revision == 0);
		} else {
			fprintf(stderr, "getsockopt failed strangely: %s\n",
				strerror(errno));
			exit(1);
		}
	}
	close(sockfd);
	return 1;
}

int main(void)
{
  char *name = "multiport";
  u_int8_t revision = 0;

  compatible_revision(name, revision, IPT_SO_GET_REVISION_MATCH);
}