[PATCH v7 10/13] migrate: Update protocol to v3 for multi-address support

[Jon Maloy <jmaloy@redhat.com>]

We update the migration protocol to version 3 to support distributing
multiple addresses from the unified address array. The new protocol
migrates all address entries in the array, along with their prefix
lengths and flags, and leaves it to the receiver to filter which
ones he wants to apply.

Signed-off-by: Jon Maloy <jmaloy@redhat.com>

---
v4: - Broke out as separate commit
    - Made number of transferable addresses variable

v6: - Separated internal and wire transfer format

v7: - Using uint32_t instead of uint8_t for fields in migration format
    - Replaced term "wire format" with "migration format"
    - Some other minor changes after feedback from Stefano.
---
 migrate.c | 179 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 179 insertions(+)

diff --git a/migrate.c b/migrate.c
index 2dc4dd9..93f67ae 100644
--- a/migrate.c
+++ b/migrate.c
@@ -44,6 +44,71 @@ struct migrate_seen_addrs_v2 {
 	unsigned char mac[ETH_ALEN];
 } __attribute__((packed));
 
+/**
+ * Migration format flags for address migration (v3)
+ * These are stable values - do not change existing assignments
+ */
+#define MIGRATE_ADDR_USER	BIT(0)
+#define MIGRATE_ADDR_HOST	BIT(1)
+#define MIGRATE_ADDR_LINKLOCAL	BIT(2)
+#define MIGRATE_ADDR_OBSERVED	BIT(3)
+
+/**
+ * struct migrate_addr_v3 - Migration format for a single address entry
+ * @addr:	IPv6 or IPv4-mapped address (16 bytes)
+ * @prefix_len:	Prefix length
+ * @flags:	MIGRATE_ADDR_* flags (migration format)
+ */
+struct migrate_addr_v3 {
+	struct in6_addr addr;
+	uint32_t prefix_len;
+	uint32_t flags;
+} __attribute__((__packed__));
+
+/**
+ * flags_to_migration() - Convert internal flags to stable migration format
+ * @flags:	Internal CONF_ADDR_* flags
+ *
+ * Return: Migration format MIGRATE_ADDR_* flags
+ */
+static uint8_t flags_to_migration(uint8_t flags)
+{
+	uint8_t migration = 0;
+
+	if (flags & CONF_ADDR_USER)
+		migration |= MIGRATE_ADDR_USER;
+	if (flags & CONF_ADDR_HOST)
+		migration |= MIGRATE_ADDR_HOST;
+	if (flags & CONF_ADDR_LINKLOCAL)
+		migration |= MIGRATE_ADDR_LINKLOCAL;
+	if (flags & CONF_ADDR_OBSERVED)
+		migration |= MIGRATE_ADDR_OBSERVED;
+
+	return migration;
+}
+
+/**
+ * flags_from_migration() - Convert migration format flags to internal format
+ * @migration:	Migration format MIGRATE_ADDR_* flags
+ *
+ * Return: Internal CONF_ADDR_* flags
+ */
+static uint8_t flags_from_migration(uint8_t migration)
+{
+	uint8_t flags = 0;
+
+	if (migration & MIGRATE_ADDR_USER)
+		flags |= CONF_ADDR_USER;
+	if (migration & MIGRATE_ADDR_HOST)
+		flags |= CONF_ADDR_HOST;
+	if (migration & MIGRATE_ADDR_LINKLOCAL)
+		flags |= CONF_ADDR_LINKLOCAL;
+	if (migration & MIGRATE_ADDR_OBSERVED)
+		flags |= CONF_ADDR_OBSERVED;
+
+	return flags;
+}
+
 /**
  * seen_addrs_source_v2() - Copy and send guest observed addresses from source
  * @c:		Execution context
@@ -126,6 +191,99 @@ static int seen_addrs_target_v2(struct ctx *c,
 	return 0;
 }
 
+/**
+ * addrs_source_v3() - Send all addresses with flags from source
+ * @c:		Execution context
+ * @stage:	Migration stage, unused
+ * @fd:		File descriptor for state transfer
+ *
+ * Send all address entries using a stable migration format. Each field is
+ * serialised explicitly to avoid coupling the migration format to internal
+ * structure layout or flag bit assignments.
+ *
+ * Return: 0 on success, positive error code on failure
+ */
+/* cppcheck-suppress [constParameterCallback, unmatchedSuppression] */
+static int addrs_source_v3(struct ctx *c,
+			   const struct migrate_stage *stage, int fd)
+{
+	uint8_t addr_count = c->addr_count;
+	const struct guest_addr *a;
+
+	(void)stage;
+
+	/* Send count first */
+	if (write_all_buf(fd, &addr_count, sizeof(addr_count)))
+		return errno;
+
+	/* Send each address in stable migration format */
+	for_each_addr(a, c->addrs, c->addr_count, 0) {
+		struct migrate_addr_v3 migration = {
+			.addr = a->addr.a6,
+			.prefix_len = htonl(a->prefix_len),
+			.flags = htonl(flags_to_migration(a->flags)),
+		};
+
+		if (write_all_buf(fd, &migration, sizeof(migration)))
+			return errno;
+	}
+
+	/* Send MAC address */
+	if (write_all_buf(fd, c->guest_mac, ETH_ALEN))
+		return errno;
+
+	return 0;
+}
+
+/**
+ * addrs_target_v3() - Receive addresses on target
+ * @c:		Execution context
+ * @stage:	Migration stage, unused
+ * @fd:		File descriptor for state transfer
+ *
+ * Receive address entries from the stable migration format and merge only
+ * observed addresses into local array. Source sends all addresses for
+ * forward compatibility, but target only applies those marked as observed.
+ *
+ * Return: 0 on success, positive error code on failure
+ */
+static int addrs_target_v3(struct ctx *c,
+			   const struct migrate_stage *stage, int fd)
+{
+	uint8_t addr_count, i;
+
+	(void)stage;
+
+	if (read_all_buf(fd, &addr_count, sizeof(addr_count)))
+		return errno;
+
+	if (addr_count > MAX_GUEST_ADDRS)
+		addr_count = MAX_GUEST_ADDRS;
+
+	/* Read each address from stable migration format */
+	for (i = 0; i < addr_count; i++) {
+		struct migrate_addr_v3 migration;
+		struct guest_addr addr;
+
+		if (read_all_buf(fd, &migration, sizeof(migration)))
+			return errno;
+
+		addr.addr.a6 = migration.addr;
+		addr.prefix_len = ntohl(migration.prefix_len);
+		addr.flags = flags_from_migration(ntohl(migration.flags));
+
+		if (addr.flags & CONF_ADDR_OBSERVED) {
+			fwd_set_addr(c, &addr.addr, addr.flags,
+				     addr.prefix_len);
+		}
+	}
+
+	if (read_all_buf(fd, c->guest_mac, ETH_ALEN))
+		return errno;
+
+	return 0;
+}
+
 /* Stages for version 2 */
 static const struct migrate_stage stages_v2[] = {
 	{
@@ -146,8 +304,29 @@ static const struct migrate_stage stages_v2[] = {
 	{ 0 },
 };
 
+/* Stages for version 3 (all addresses, with flags) */
+static const struct migrate_stage stages_v3[] = {
+	{
+		.name = "addresses",
+		.source = addrs_source_v3,
+		.target = addrs_target_v3,
+	},
+	{
+		.name = "prepare flows",
+		.source = flow_migrate_source_pre,
+		.target = NULL,
+	},
+	{
+		.name = "transfer flows",
+		.source = flow_migrate_source,
+		.target = flow_migrate_target,
+	},
+	{ 0 },
+};
+
 /* Supported encoding versions, from latest (most preferred) to oldest */
 static const struct migrate_version versions[] = {
+	{ 3,	stages_v3, },
 	{ 2,	stages_v2, },
 	/* v1 was released, but not widely used.  It had bad endianness for the
 	 * MSS and omitted timestamps, which meant it usually wouldn't work.
-- 
2.52.0