1 files changed, 135 insertions, 0 deletions
diff --git a/src/check_prefix_boundary.c b/src/check_prefix_boundary.c
new file mode 100644
index 00000000..1c9ee30a
--- /dev/null
+++ b/src/check_prefix_boundary.c
@@ -0,0 +1,135 @@
+/*
+ * Check format of network prefix
+ */
+#include <stdio.h>
+#include <stdarg.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+
+typedef struct
+{
+	uint8_t family;
+	uint8_t bytelen;
+	unsigned int plen;
+	uint32_t data[4];
+} inet_prefix;
+
+static void err(const char *fmt, ...)
+{
+	va_list ap;
+	
+	va_start(ap, fmt);
+	vfprintf(stderr, fmt, ap);
+	va_end(ap);
+
+	exit(1);
+}
+
+static void usage(void)
+{
+	fprintf(stderr, "Usage: check-prefix-boundary [-4|-6] address/prefix\n");
+	exit(1);
+}
+
+static void get_addr_1(inet_prefix *addr, const char *name, int family)
+{
+	memset(addr, 0, sizeof(*addr));
+
+	if (strchr(name, ':')) {
+		addr->family = AF_INET6;
+		addr->bytelen = 16;
+		if (family != AF_UNSPEC && family != AF_INET6)
+			err("IPV6 address not allowed\n");
+
+		if (inet_pton(AF_INET6, name, addr->data) <= 0)
+			err("Invalid IPV6 address: %s\n", name);
+
+		return;
+	}
+
+	addr->family = AF_INET;
+	addr->bytelen = 4;
+	if (family != AF_UNSPEC && family != AF_INET)
+		err("IPV4 address not allowed\n");
+
+	if (inet_pton(AF_INET, name, addr->data) <= 0)
+		err("Invalid IPV4 address: %s\n", name);
+	return;
+}
+
+static void get_prefix_1(inet_prefix *dst, char *arg, int family)
+{
+	char *slash, *endp;
+
+	memset(dst, 0, sizeof(*dst));
+
+	slash = strchr(arg, '/');
+	if (!slash || slash[1] == '\0')
+		err("Missing prefix length\n");
+	*slash = 0;
+
+	get_addr_1(dst, arg, family);
+
+	dst->plen = strtoul(slash+1, &endp, 0);
+	if (*endp != '\0')
+		err("Invalid character in prefix length\n");
+
+	if (dst->plen > 8 * dst->bytelen)
+		err("Prefix length is too large\n");
+
+	*slash = '/';
+}
+
+static void get_netmask(inet_prefix *msk, const inet_prefix *dst)
+{
+	int i, plen = dst->plen;
+
+	memset(msk, 0, sizeof(*msk));
+	msk->family = dst->family;
+	msk->bytelen = dst->bytelen;
+
+	for (i = 0; plen > 0 && i < dst->bytelen / sizeof(uint32_t); i++) {
+		uint32_t m = (plen > 32) ? ~0 : htonl(~0 << (32 - plen));
+		
+		msk->data[i] = dst->data[i] & m;
+		plen -= 32;
+	}
+}
+
+int main(int argc, char **argv)
+{
+	int family = AF_UNSPEC;
+
+	while (--argc) {
+		char *arg = *++argv;
+		inet_prefix dst, msk;
+
+		if (arg[0] == '-') 
+			switch(arg[1]) {
+			case '4':
+				family = AF_INET;
+				break;
+			case '6':
+				family = AF_INET6;
+				break;
+			default:
+				usage();
+			}
+
+		get_prefix_1(&dst, arg, family);
+		get_netmask(&msk, &dst);
+		
+		if (memcmp(msk.data, dst.data, dst.bytelen) != 0) {
+			char buf[INET_ADDRSTRLEN];
+			err("Prefix not on a natural network boundary."
+			    "Did you mean %s?\n", 
+			    inet_ntop(msk.family, msk.data, buf, sizeof buf));
+		}
+	}
+
+	return 0;
+}