From ba026941a10325f4ac7fff93e4ad579b0b349e05 Mon Sep 17 00:00:00 2001
From: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Date: Wed, 18 Jan 2017 09:38:20 +0200
Subject: [PATCH] net: ipv6: Fix IPv6 prefix comparision

If the prefix length % 8 is not 0, then the remaining
bit length was calculated incorrectly and the prefixes
were claimed to match even though they might not be the
same.

Adding a test cases for testing this properly.

Coverity-CID: 157591

Change-Id: I9cb5a73d5cc211ec183176400fa5e2dfd209e2da
Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
---
 include/net/net_ip.h      | 21 +++++++++----
 tests/net/ipv6/src/main.c | 66 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 81 insertions(+), 6 deletions(-)

diff --git a/include/net/net_ip.h b/include/net/net_ip.h
index f058bc552c2..e055d71c95a 100644
--- a/include/net/net_ip.h
+++ b/include/net/net_ip.h
@@ -360,27 +360,36 @@ static inline bool net_is_my_ipv6_maddr(struct in6_addr *maddr)
  * @param addr2 Second IPv6 address.
  * @param length Prefix length (max length is 128).
  *
- * @return True if addresses are the same, False otherwise.
+ * @return True if IPv6 prefixes are the same, False otherwise.
  */
 static inline bool net_is_ipv6_prefix(const uint8_t *addr1,
 				      const uint8_t *addr2,
 				      uint8_t length)
 {
 	uint8_t bits = 128 - length;
-	uint8_t bytes = bits / 8;
+	uint8_t bytes = length / 8;
 	uint8_t remain = bits % 8;
+	uint8_t mask;
 
 	if (length > 128) {
 		return false;
 	}
 
-	if (memcmp(addr1, addr2, 16 - bytes)) {
+	if (memcmp(addr1, addr2, bytes)) {
 		return false;
 	}
 
-	return ((addr1[16 - bytes] & ((8 - remain) << 8))
-		==
-		(addr2[16 - bytes] & ((8 - remain) << 8)));
+	if (!remain) {
+		/* No remaining bits, the prefixes are the same as first
+		 * bytes are the same.
+		 */
+		return true;
+	}
+
+	/* Create a mask that has remaining most significant bits set */
+	mask = ((0xff << (8 - remain)) ^ 0xff) << remain;
+
+	return (addr1[bytes] & mask) == (addr2[bytes] & mask);
 }
 
 /**
diff --git a/tests/net/ipv6/src/main.c b/tests/net/ipv6/src/main.c
index db8f64d7fff..5fb277f44f6 100644
--- a/tests/net/ipv6/src/main.c
+++ b/tests/net/ipv6/src/main.c
@@ -273,6 +273,71 @@ static bool test_init(void)
 	return true;
 }
 
+static bool net_test_cmp_prefix(void)
+{
+	bool st;
+
+	struct in6_addr prefix1 = { { { 0x20, 0x01, 0x0d, 0xb8, 0, 0, 0, 0,
+					0, 0, 0, 0, 0, 0, 0, 0x1 } } };
+	struct in6_addr prefix2 = { { { 0x20, 0x01, 0x0d, 0xb8, 0, 0, 0, 0,
+					0, 0, 0, 0, 0, 0, 0, 0x2 } } };
+
+	st = net_is_ipv6_prefix((uint8_t *)&prefix1, (uint8_t *)&prefix2, 64);
+	if (!st) {
+		TC_ERROR("Prefix /64  compare failed\n");
+		return false;
+	}
+
+	st = net_is_ipv6_prefix((uint8_t *)&prefix1, (uint8_t *)&prefix2, 65);
+	if (!st) {
+		TC_ERROR("Prefix /65 compare failed\n");
+		return false;
+	}
+
+	/* Set one extra bit in the other prefix for testing /65 */
+	prefix1.s6_addr[8] = 0x80;
+
+	st = net_is_ipv6_prefix((uint8_t *)&prefix1, (uint8_t *)&prefix2, 65);
+	if (st) {
+		TC_ERROR("Prefix /65 compare should have failed\n");
+		return false;
+	}
+
+	/* Set two bits in prefix2, it is now /66 */
+	prefix2.s6_addr[8] = 0xc0;
+
+	st = net_is_ipv6_prefix((uint8_t *)&prefix1, (uint8_t *)&prefix2, 65);
+	if (!st) {
+		TC_ERROR("Prefix /65 compare failed\n");
+		return false;
+	}
+
+	/* Set all remaining bits in prefix2, it is now /128 */
+	memset(&prefix2.s6_addr[8], 0xff, 8);
+
+	st = net_is_ipv6_prefix((uint8_t *)&prefix1, (uint8_t *)&prefix2, 65);
+	if (!st) {
+		TC_ERROR("Prefix /65 compare failed\n");
+		return false;
+	}
+
+	/* Comparing /64 should be still ok */
+	st = net_is_ipv6_prefix((uint8_t *)&prefix1, (uint8_t *)&prefix2, 64);
+	if (!st) {
+		TC_ERROR("Prefix /64 compare failed\n");
+		return false;
+	}
+
+	/* But comparing /66 should should fail */
+	st = net_is_ipv6_prefix((uint8_t *)&prefix1, (uint8_t *)&prefix2, 66);
+	if (st) {
+		TC_ERROR("Prefix /66 compare should have failed\n");
+		return false;
+	}
+
+	return true;
+}
+
 static bool net_test_send_ns_mcast(void)
 {
 	int ret;
@@ -614,6 +679,7 @@ static const struct {
 	bool (*func)(void);
 } tests[] = {
 	{ "test init", test_init },
+	{ "IPv6 compare prefix", net_test_cmp_prefix },
 	{ "IPv6 send NS mcast", net_test_send_ns_mcast },
 	{ "IPv6 neighbor lookup fail", net_test_nbr_lookup_fail },
 	{ "IPv6 send NS", net_test_send_ns },