lib, pimd: add a bunch of address helpers

Just simple helpers to get a scope value, never-forward, and is-SSM for
a given address.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>

1 files changed, 65 insertions, 0 deletions

diff --git a/lib/prefix.h b/lib/prefix.h
index 816a1517e..5e03a7b4f 100644
--- a/lib/prefix.h
+++ b/lib/prefix.h
@@ -585,6 +585,71 @@ static inline int is_default_host_route(const struct prefix *p)
 	return 0;
 }
 
+/* IPv6 scope values, usable for IPv4 too (cf. below) */
+/* clang-format off */
+enum {
+	/* 0: reserved */
+	MCAST_SCOPE_IFACE  = 0x1,
+	MCAST_SCOPE_LINK   = 0x2,
+	MCAST_SCOPE_REALM  = 0x3,
+	MCAST_SCOPE_ADMIN  = 0x4,
+	MCAST_SCOPE_SITE   = 0x5,
+	/* 6-7: unassigned */
+	MCAST_SCOPE_ORG    = 0x8,
+	/* 9-d: unassigned */
+	MCAST_SCOPE_GLOBAL = 0xe,
+	/* f: reserved */
+};
+/* clang-format on */
+
+static inline uint8_t ipv6_mcast_scope(const struct in6_addr *addr)
+{
+	return addr->s6_addr[1] & 0xf;
+}
+
+static inline bool ipv6_mcast_nofwd(const struct in6_addr *addr)
+{
+	return (addr->s6_addr[1] & 0xf) <= MCAST_SCOPE_LINK;
+}
+
+static inline bool ipv6_mcast_ssm(const struct in6_addr *addr)
+{
+	uint32_t bits = ntohl(addr->s6_addr32[0]);
+
+	/* ff3x:0000::/32 */
+	return (bits & 0xfff0ffff) == 0xff300000;
+}
+
+static inline uint8_t ipv4_mcast_scope(const struct in_addr *addr)
+{
+	uint32_t bits = ntohl(addr->s_addr);
+
+	/* 224.0.0.0/24 - link scope */
+	if ((bits & 0xffffff00) == 0xe0000000)
+		return MCAST_SCOPE_LINK;
+	/* 239.0.0.0/8 - org scope */
+	if ((bits & 0xff000000) == 0xef000000)
+		return MCAST_SCOPE_ORG;
+
+	return MCAST_SCOPE_GLOBAL;
+}
+
+static inline bool ipv4_mcast_nofwd(const struct in_addr *addr)
+{
+	uint32_t bits = ntohl(addr->s_addr);
+
+	/* 224.0.0.0/24 */
+	return (bits & 0xffffff00) == 0xe0000000;
+}
+
+static inline bool ipv4_mcast_ssm(const struct in_addr *addr)
+{
+	uint32_t bits = ntohl(addr->s_addr);
+
+	/* 232.0.0.0/8 */
+	return (bits & 0xff000000) == 0xe8000000;
+}
+
 #ifdef _FRR_ATTRIBUTE_PRINTFRR
 #pragma FRR printfrr_ext "%pEA"  (struct ethaddr *)