[PATCH v10 04/10] migrate: Migrate guest observed addresses

[David Gibson <david@gibson.dropbear.id.au>]

Most of the information in struct ctx doesn't need to be migrated.
Either it's strictly back end information which is allowed to differ
between the two ends, or it must already be configured identically on
the two ends.

There are a few exceptions though.  In particular passt learns several
addresses of the guest by observing what it sends out.  If we lose
this information across migration we might get away with it, but if
there are active flows we might misdirect some packets before
re-learning the guest address.

Avoid this by migrating the guest's observed addresses.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 migrate.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/migrate.c b/migrate.c
index b5d87547..ba8332df 100644
--- a/migrate.c
+++ b/migrate.c
@@ -27,8 +27,58 @@
 /* Magic identifier for migration data */
 #define MIGRATE_MAGIC		0xB1BB1D1B0BB1D1B0
 
+/**
+ * struct migrate_seen_addrs_v1 - Migratable guest addresses for v1 state stream
+ * @addr6:	Observed guest IPv6 address
+ * @addr6_ll:	Observed guest IPv6 link-local address
+ * @addr4:	Observed guest IPv4 address
+ * @mac:	Observed guest MAC address
+ */
+struct migrate_seen_addrs_v1 {
+	struct in6_addr addr6;
+	struct in6_addr addr6_ll;
+	struct in_addr addr4;
+	unsigned char mac[ETH_ALEN];
+} __attribute__((packed));
+
+static int seen_addrs_source_v1(struct ctx *c,
+				const struct migrate_stage *stage, int fd)
+{
+	struct migrate_seen_addrs_v1 addrs = {
+		.addr6 = c->ip6.addr_seen,
+		.addr6_ll = c->ip6.addr_ll_seen,
+		.addr4 = c->ip4.addr_seen,
+	};
+
+	(void)stage;
+	memcpy(addrs.mac, c->guest_mac, sizeof(addrs.mac));
+	return write_all_buf(fd, &addrs, sizeof(addrs));
+}
+
+static int seen_addrs_target_v1(struct ctx *c,
+				const struct migrate_stage *stage, int fd)
+{
+	struct migrate_seen_addrs_v1 addrs;
+
+	(void)stage;
+
+	if (read_all_buf(fd, &addrs, sizeof(addrs)))
+		return errno;
+
+	c->ip6.addr_seen = addrs.addr6;
+	c->ip6.addr_ll_seen = addrs.addr6_ll;
+	c->ip4.addr_seen = addrs.addr4;
+	memcpy(c->guest_mac, addrs.mac, sizeof(c->guest_mac));
+	return 0;
+}
+
 /* Stages for version 1 */
 static const struct migrate_stage stages_v1[] = {
+	{
+		.name = "seen addresses",
+		.source = seen_addrs_source_v1,
+		.target = seen_addrs_target_v1,
+	},
 	{ 0 },
 };
 
-- 
@@ -27,8 +27,58 @@
 /* Magic identifier for migration data */
 #define MIGRATE_MAGIC		0xB1BB1D1B0BB1D1B0
 
+/**
+ * struct migrate_seen_addrs_v1 - Migratable guest addresses for v1 state stream
+ * @addr6:	Observed guest IPv6 address
+ * @addr6_ll:	Observed guest IPv6 link-local address
+ * @addr4:	Observed guest IPv4 address
+ * @mac:	Observed guest MAC address
+ */
+struct migrate_seen_addrs_v1 {
+	struct in6_addr addr6;
+	struct in6_addr addr6_ll;
+	struct in_addr addr4;
+	unsigned char mac[ETH_ALEN];
+} __attribute__((packed));
+
+static int seen_addrs_source_v1(struct ctx *c,
+				const struct migrate_stage *stage, int fd)
+{
+	struct migrate_seen_addrs_v1 addrs = {
+		.addr6 = c->ip6.addr_seen,
+		.addr6_ll = c->ip6.addr_ll_seen,
+		.addr4 = c->ip4.addr_seen,
+	};
+
+	(void)stage;
+	memcpy(addrs.mac, c->guest_mac, sizeof(addrs.mac));
+	return write_all_buf(fd, &addrs, sizeof(addrs));
+}
+
+static int seen_addrs_target_v1(struct ctx *c,
+				const struct migrate_stage *stage, int fd)
+{
+	struct migrate_seen_addrs_v1 addrs;
+
+	(void)stage;
+
+	if (read_all_buf(fd, &addrs, sizeof(addrs)))
+		return errno;
+
+	c->ip6.addr_seen = addrs.addr6;
+	c->ip6.addr_ll_seen = addrs.addr6_ll;
+	c->ip4.addr_seen = addrs.addr4;
+	memcpy(c->guest_mac, addrs.mac, sizeof(c->guest_mac));
+	return 0;
+}
+
 /* Stages for version 1 */
 static const struct migrate_stage stages_v1[] = {
+	{
+		.name = "seen addresses",
+		.source = seen_addrs_source_v1,
+		.target = seen_addrs_target_v1,
+	},
 	{ 0 },
 };
 
-- 
2.48.1