pim6d: add fresh MLD implementation

Fresh ground-up MLD implementation with subscriber-tracking for MLDv2.
Intended to be adapted for IPv4 and replace the IGMP implementation at a
later point.

Tested in ANVL, currently at 94/116.  Some issues/TODOs are left in the
code as CPP_NOTICE markers, but the code is very much good enough to
proceed since otherwise we're blocked on overall PIM v6 progress.

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

1 files changed, 125 insertions, 0 deletions

diff --git a/pimd/pim6_mld_protocol.h b/pimd/pim6_mld_protocol.h
new file mode 100644
index 0000000000..8e602d3396
--- /dev/null
+++ b/pimd/pim6_mld_protocol.h
@@ -0,0 +1,125 @@
+/*
+ * MLD protocol definitions
+ * Copyright (C) 2022  David Lamparter for NetDEF, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; see the file COPYING; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef _PIM6_MLD_PROTOCOL_H
+#define _PIM6_MLD_PROTOCOL_H
+
+#include <stdalign.h>
+#include <stdint.h>
+
+/* There is a struct icmp6_hdr provided by OS, but it includes 4 bytes of data.
+ * Not helpful for us if we want to put the MLD struct after it.
+ */
+
+struct icmp6_plain_hdr {
+	uint8_t icmp6_type;
+	uint8_t icmp6_code;
+	uint16_t icmp6_cksum;
+};
+static_assert(sizeof(struct icmp6_plain_hdr) == 4, "struct mismatch");
+static_assert(alignof(struct icmp6_plain_hdr) <= 4, "struct mismatch");
+
+/* for MLDv1 query, report and leave all use the same packet format */
+struct mld_v1_pkt {
+	uint16_t max_resp_code;
+	uint16_t rsvd0;
+	struct in6_addr grp;
+};
+static_assert(sizeof(struct mld_v1_pkt) == 20, "struct mismatch");
+static_assert(alignof(struct mld_v1_pkt) <= 4, "struct mismatch");
+
+
+struct mld_v2_query_hdr {
+	uint16_t max_resp_code;
+	uint16_t rsvd0;
+	struct in6_addr grp;
+	uint8_t flags;
+	uint8_t qqic;
+	uint16_t n_src;
+	struct in6_addr srcs[0];
+};
+static_assert(sizeof(struct mld_v2_query_hdr) == 24, "struct mismatch");
+static_assert(alignof(struct mld_v2_query_hdr) <= 4, "struct mismatch");
+
+
+struct mld_v2_report_hdr {
+	uint16_t rsvd;
+	uint16_t n_records;
+};
+static_assert(sizeof(struct mld_v2_report_hdr) == 4, "struct mismatch");
+static_assert(alignof(struct mld_v2_report_hdr) <= 4, "struct mismatch");
+
+
+struct mld_v2_rec_hdr {
+	uint8_t type;
+	uint8_t aux_len;
+	uint16_t n_src;
+	struct in6_addr grp;
+	struct in6_addr srcs[0];
+};
+static_assert(sizeof(struct mld_v2_rec_hdr) == 20, "struct mismatch");
+static_assert(alignof(struct mld_v2_rec_hdr) <= 4, "struct mismatch");
+
+/* clang-format off */
+enum icmp6_mld_type {
+	ICMP6_MLD_QUERY			= 130,
+	ICMP6_MLD_V1_REPORT		= 131,
+	ICMP6_MLD_V1_DONE		= 132,
+	ICMP6_MLD_V2_REPORT		= 143,
+};
+
+enum mld_v2_rec_type {
+	MLD_RECTYPE_IS_INCLUDE		= 1,
+	MLD_RECTYPE_IS_EXCLUDE		= 2,
+	MLD_RECTYPE_CHANGE_TO_INCLUDE	= 3,
+	MLD_RECTYPE_CHANGE_TO_EXCLUDE	= 4,
+	MLD_RECTYPE_ALLOW_NEW_SOURCES	= 5,
+	MLD_RECTYPE_BLOCK_OLD_SOURCES	= 6,
+};
+/* clang-format on */
+
+/* helper functions */
+
+static inline unsigned int mld_max_resp_decode(uint16_t wire)
+{
+	uint16_t code = ntohs(wire);
+	uint8_t exp;
+
+	if (code < 0x8000)
+		return code;
+	exp = (code >> 12) & 0x7;
+	return ((code & 0xfff) | 0x1000) << (exp + 3);
+}
+
+static inline uint16_t mld_max_resp_encode(uint32_t value)
+{
+	uint16_t code;
+	uint8_t exp;
+
+	if (value < 0x8000)
+		code = value;
+	else {
+		exp = 16 - __builtin_clz(value);
+		code = (value >> (exp + 3)) & 0xfff;
+		code |= 0x8000 | (exp << 12);
+	}
+	return htons(code);
+}
+
+#endif /* _PIM6_MLD_PROTOCOL_H */