net: fix IPv6 link local compliance with RFC 4291

As specified in RFC 4291 section 2.5.1, link local addresses must be
generated based on a modified EUI-64 interface identifier:

> Modified EUI-64 format interface identifiers are formed by inverting
> the "u" bit (universal/local bit in IEEE EUI-64 terminology) when
> forming the interface identifier from IEEE EUI-64 identifiers.

This translates to 'mac->addr_bytes[0] ^= 0x02'.

Fixes: 3d6d85f ("net: add utilities for well known IPv6 address types")
Cc: [email protected]

Signed-off-by: Christophe Fontaine <[email protected]>
Signed-off-by: Robin Jarry <[email protected]>

Author: christophefontaine

app/test/test_net_ip6.c

@@ -160,7 +160,7 @@ test_ipv6_llocal_from_ethernet(void)
 {
 	const struct rte_ether_addr local_mac = {{0x04, 0x7b, 0xcb, 0x5c, 0x08, 0x44}};
 	const struct rte_ipv6_addr local_ip =
-		RTE_IPV6(0xfe80, 0, 0, 0, 0x047b, 0xcbff, 0xfe5c, 0x0844);
+		RTE_IPV6(0xfe80, 0, 0, 0, 0x067b, 0xcbff, 0xfe5c, 0x0844);
 	struct rte_ipv6_addr ip;
 
 	rte_ipv6_llocal_from_ethernet(&ip, &local_mac);

lib/net/rte_ip6.h

@@ -393,7 +393,7 @@ rte_ipv6_mc_scope(const struct rte_ipv6_addr *ip)
 
 /*
  * Generate a link-local IPv6 address from an Ethernet address as specified in
- * RFC 2464, section 5.
+ * RFC 4291, section 2.5.1.
  *
  * @param[out] ip
  *   The link-local IPv6 address to generate.
@@ -406,7 +406,12 @@ rte_ipv6_llocal_from_ethernet(struct rte_ipv6_addr *ip, const struct rte_ether_a
 	ip->a[0] = 0xfe;
 	ip->a[1] = 0x80;
 	memset(&ip->a[2], 0, 6);
-	ip->a[8] = mac->addr_bytes[0];
+	/*
+	 * The "u" bit (universal/local bit in IEEE EUI-64 terminology)
+	 * must be inverted for IPv6 link local address.
+	 * 0 means local scope, 1 means universal scope.
+	 */
+	ip->a[8] = mac->addr_bytes[0] ^ RTE_ETHER_LOCAL_ADMIN_ADDR;
 	ip->a[9] = mac->addr_bytes[1];
 	ip->a[10] = mac->addr_bytes[2];
 	ip->a[11] = 0xff;