[PATCH v4 12/12] 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 transferrable addresses variable
---
 migrate.c | 123 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 123 insertions(+)

diff --git a/migrate.c b/migrate.c
index f937793..13a5d6f 100644
--- a/migrate.c
+++ b/migrate.c
@@ -124,6 +124,108 @@ 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 with their flags. The receiver can filter
+ * based on flags as needed. This provides forward compatibility if
+ * future versions need different address types.
+ *
+ * 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;
+
+	(void)stage;
+
+	/* Send count, then all addresses with flags, then MAC */
+	if (write_all_buf(fd, &addr_count, sizeof(addr_count)))
+		return errno;
+
+	if (addr_count && write_all_buf(fd, c->addrs,
+					addr_count * sizeof(c->addrs[0])))
+		return errno;
+
+	if (write_all_buf(fd, c->guest_mac, ETH_ALEN))
+		return errno;
+
+	return 0;
+}
+
+/**
+ * migrate_merge_addr() - Merge migrated address into local array
+ * @c:		Execution context
+ * @addr:	Address entry from migration source
+ *
+ * If the address already exists locally, merge the flags (preserving
+ * local flags and adding migrated ones). Otherwise add as new entry.
+ */
+static void migrate_merge_addr(struct ctx *c,
+			       const struct inany_addr_entry *addr)
+{
+	struct inany_addr_entry *e;
+
+	if (inany_is_unspecified(&addr->addr))
+		return;
+
+	/* Check if address already exists, merge flags */
+	for_each_addr(e, c, 0) {
+		if (inany_equals(&e->addr, &addr->addr)) {
+			e->flags |= addr->flags;
+			return;
+		}
+	}
+
+	/* Add new entry if there's room */
+	if (c->addr_count < INANY_MAX_ADDRS)
+		c->addrs[c->addr_count++] = *addr;
+}
+
+/**
+ * addrs_target_v3() - Receive addresses on target
+ * @c:		Execution context
+ * @stage:	Migration stage, unused
+ * @fd:		File descriptor for state transfer
+ *
+ * Receive all address entries and merge only observed addresses into local
+ * array. Source sends all addresses for forward compatibility, but target
+ * only applies those marked as observed by guest traffic.
+ *
+ * Return: 0 on success, positive error code on failure
+ */
+static int addrs_target_v3(struct ctx *c,
+			   const struct migrate_stage *stage, int fd)
+{
+	struct inany_addr_entry addrs[INANY_MAX_ADDRS];
+	uint8_t addr_count, i;
+
+	(void)stage;
+
+	if (read_all_buf(fd, &addr_count, sizeof(addr_count)))
+		return errno;
+
+	if (addr_count > INANY_MAX_ADDRS)
+		addr_count = INANY_MAX_ADDRS;
+
+	if (addr_count && read_all_buf(fd, addrs, addr_count * sizeof(addrs[0])))
+		return errno;
+
+	if (read_all_buf(fd, c->guest_mac, ETH_ALEN))
+		return errno;
+
+	for (i = 0; i < addr_count; i++)
+		if (addrs[i].flags & CONF_ADDR_OBSERVED)
+			migrate_merge_addr(c, &addrs[i]);
+
+	return 0;
+}
+
 /* Stages for version 2 */
 static const struct migrate_stage stages_v2[] = {
 	{
@@ -144,8 +246,29 @@ static const struct migrate_stage stages_v2[] = {
 	{ 0 },
 };
 
+/* Stages for version 3 (multiple observed IPv4 addresses) */
+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