Add two sets (source or target) of three functions each for passt in
vhost-user mode, triggered by activity on the file descriptor passed
via VHOST_USER_PROTOCOL_F_DEVICE_STATE:
- migrate_source_pre() and migrate_target_pre() are called to prepare
for migration, before data is transferred
- migrate_source() sends, and migrate_target() receives migration data
- migrate_source_post() and migrate_target_post() are responsible for
any post-migration task
Callbacks are added to these functions with arrays of function
pointers in migrate.c. Migration handlers are versioned.
Versioned descriptions of data sections will be added to the
data_versions array, which points to versioned iovec arrays. Version
1 is currently empty and will be filled in in subsequent patches.
The source announces the data version to be used and informs the peer
about endianness, and the size of void *, time_t, flow entries and
flow hash table entries.
The target checks if the version of the source is still supported. If
it's not, it aborts the migration.
Signed-off-by: Stefano Brivio <sbrivio(a)redhat.com>
---
Makefile | 12 +--
migrate.c | 270 ++++++++++++++++++++++++++++++++++++++++++++++++++++
migrate.h | 88 +++++++++++++++++
passt.c | 2 +-
vu_common.c | 120 +++++++++++++++--------
vu_common.h | 2 +-
6 files changed, 448 insertions(+), 46 deletions(-)
create mode 100644 migrate.c
create mode 100644 migrate.h
diff --git a/Makefile b/Makefile
index 464eef1..1383875 100644
--- a/Makefile
+++ b/Makefile
@@ -38,8 +38,8 @@ FLAGS += -DDUAL_STACK_SOCKETS=$(DUAL_STACK_SOCKETS)
PASST_SRCS = arch.c arp.c checksum.c conf.c dhcp.c dhcpv6.c flow.c fwd.c \
icmp.c igmp.c inany.c iov.c ip.c isolation.c lineread.c log.c mld.c \
- ndp.c netlink.c packet.c passt.c pasta.c pcap.c pif.c tap.c tcp.c \
- tcp_buf.c tcp_splice.c tcp_vu.c udp.c udp_flow.c udp_vu.c util.c \
+ ndp.c netlink.c migrate.c packet.c passt.c pasta.c pcap.c pif.c tap.c \
+ tcp.c tcp_buf.c tcp_splice.c tcp_vu.c udp.c udp_flow.c udp_vu.c util.c \
vhost_user.c virtio.c vu_common.c
QRAP_SRCS = qrap.c
SRCS = $(PASST_SRCS) $(QRAP_SRCS)
@@ -48,10 +48,10 @@ MANPAGES = passt.1 pasta.1 qrap.1
PASST_HEADERS = arch.h arp.h checksum.h conf.h dhcp.h dhcpv6.h flow.h fwd.h \
flow_table.h icmp.h icmp_flow.h inany.h iov.h ip.h isolation.h \
- lineread.h log.h ndp.h netlink.h packet.h passt.h pasta.h pcap.h pif.h \
- siphash.h tap.h tcp.h tcp_buf.h tcp_conn.h tcp_internal.h tcp_splice.h \
- tcp_vu.h udp.h udp_flow.h udp_internal.h udp_vu.h util.h vhost_user.h \
- virtio.h vu_common.h
+ lineread.h log.h migrate.h ndp.h netlink.h packet.h passt.h pasta.h \
+ pcap.h pif.h siphash.h tap.h tcp.h tcp_buf.h tcp_conn.h tcp_internal.h \
+ tcp_splice.h tcp_vu.h udp.h udp_flow.h udp_internal.h udp_vu.h util.h \
+ vhost_user.h virtio.h vu_common.h
HEADERS = $(PASST_HEADERS) seccomp.h
C := \#include <sys/random.h>\nint main(){int a=getrandom(0, 0, 0);}
diff --git a/migrate.c b/migrate.c
new file mode 100644
index 0000000..9ddac8f
--- /dev/null
+++ b/migrate.c
@@ -0,0 +1,270 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+/* PASST - Plug A Simple Socket Transport
+ * for qemu/UNIX domain socket mode
+ *
+ * PASTA - Pack A Subtle Tap Abstraction
+ * for network namespace/tap device mode
+ *
+ * migrate.c - Migration sections, layout, and routines
+ *
+ * Copyright (c) 2025 Red Hat GmbH
+ * Author: Stefano Brivio <sbrivio(a)redhat.com>
+ */
+
+#include <errno.h>
+#include <sys/uio.h>
+
+#include "util.h"
+#include "ip.h"
+#include "passt.h"
+#include "inany.h"
+#include "flow.h"
+#include "flow_table.h"
+
+#include "migrate.h"
+
+/* Current version of migration data */
+#define MIGRATE_VERSION 1
+
+/* Magic as we see it and as seen with reverse endianness */
+#define MIGRATE_MAGIC 0xB1BB1D1B0BB1D1B0
+#define MIGRATE_MAGIC_SWAPPED 0xB0D1B1B01B1DBBB1
+
+/* Migration header to send from source */
+static union migrate_header header = {
+ /* Immutable part of header structure: keep these two sections at the
+ * beginning, because they are enough to identify a version regardless
+ * of metadata.
+ */
+ .magic = MIGRATE_MAGIC,
+ .version = htonl_constant(MIGRATE_VERSION),
+ /* End of immutable part of header structure */
+
+ .time_t_size = htonl_constant(sizeof(time_t)),
+ .flow_size = htonl_constant(sizeof(union flow)),
+ .flow_sidx_size = htonl_constant(sizeof(struct flow_sidx)),
+ .voidp_size = htonl_constant(sizeof(void *)),
+};
+
+/* Data sections for version 1 */
+static struct iovec sections_v1[] = {
+ { &header, sizeof(header) },
+};
+
+/* Set of data versions */
+static struct migrate_data data_versions[] = {
+ {
+ 1, sections_v1,
+ },
+ { 0 },
+};
+
+/* Handlers to call in source before sending data */
+struct migrate_handler handlers_source_pre[] = {
+ { 0 },
+};
+
+/* Handlers to call in source after sending data */
+struct migrate_handler handlers_source_post[] = {
+ { 0 },
+};
+
+/* Handlers to call in target before receiving data with version 1 */
+struct migrate_handler handlers_target_pre_v1[] = {
+ { 0 },
+};
+
+/* Handlers to call in target after receiving data with version 1 */
+struct migrate_handler handlers_target_post_v1[] = {
+ { 0 },
+};
+
+/* Versioned sets of migration handlers */
+struct migrate_target_handlers target_handlers[] = {
+ {
+ 1,
+ handlers_target_pre_v1,
+ handlers_target_post_v1,
+ },
+ { 0 },
+};
+
+/**
+ * migrate_source_pre() - Pre-migration tasks as source
+ * @c: Execution context
+ * @m: Migration metadata
+ *
+ * Return: 0 on success, error code on failure
+ */
+int migrate_source_pre(struct ctx *c, struct migrate_meta *m)
+{
+ struct migrate_handler *h;
+
+ for (h = handlers_source_pre; h->fn; h++) {
+ int rc;
+
+ if ((rc = h->fn(c, m)))
+ return rc;
+ }
+
+ return 0;
+}
+
+/**
+ * migrate_source() - Perform migration as source: send state to hypervisor
+ * @fd: Descriptor for state transfer
+ * @m: Migration metadata
+ *
+ * Return: 0 on success, error code on failure
+ */
+int migrate_source(int fd, const struct migrate_meta *m)
+{
+ static struct migrate_data *d;
+ int count, rc;
+
+ (void)m;
+
+ for (d = data_versions; d->v != MIGRATE_VERSION; d++);
+
+ for (count = 0; d->sections[count].iov_len; count++);
+
+ debug("Writing %u migration sections", count - 1 /* minus header */);
+ rc = write_remainder(fd, d->sections, count, 0);
+ if (rc < 0)
+ return errno;
+
+ return 0;
+}
+
+/**
+ * migrate_source_post() - Post-migration tasks as source
+ * @c: Execution context
+ * @m: Migration metadata
+ *
+ * Return: 0 on success, error code on failure
+ */
+void migrate_source_post(struct ctx *c, struct migrate_meta *m)
+{
+ struct migrate_handler *h;
+
+ for (h = handlers_source_post; h->fn; h++)
+ h->fn(c, m);
+}
+
+/**
+ * migrate_target_read_header() - Set metadata in target from source header
+ * @fd: Descriptor for state transfer
+ * @m: Migration metadata, filled on return
+ *
+ * Return: 0 on success, error code on failure
+ */
+int migrate_target_read_header(int fd, struct migrate_meta *m)
+{
+ static struct migrate_data *d;
+ union migrate_header h;
+
+ if (read_all_buf(fd, &h, sizeof(h)))
+ return errno;
+
+ debug("Source magic: 0x%016" PRIx64 ", sizeof(void *): %u, version:
%u",
+ h.magic, ntohl(h.voidp_size), ntohl(h.version));
+
+ for (d = data_versions; d->v != ntohl(h.version) && d->v; d++);
+ if (!d->v)
+ return ENOTSUP;
+ m->v = d->v;
+
+ if (h.magic == MIGRATE_MAGIC)
+ m->bswap = false;
+ else if (h.magic == MIGRATE_MAGIC_SWAPPED)
+ m->bswap = true;
+ else
+ return ENOTSUP;
+
+ if (ntohl(h.voidp_size) == 4)
+ m->source_64b = false;
+ else if (ntohl(h.voidp_size) == 8)
+ m->source_64b = true;
+ else
+ return ENOTSUP;
+
+ if (ntohl(h.time_t_size) == 4)
+ m->time_64b = false;
+ else if (ntohl(h.time_t_size) == 8)
+ m->time_64b = true;
+ else
+ return ENOTSUP;
+
+ m->flow_size = ntohl(h.flow_size);
+ m->flow_sidx_size = ntohl(h.flow_sidx_size);
+
+ return 0;
+}
+
+/**
+ * migrate_target_pre() - Pre-migration tasks as target
+ * @c: Execution context
+ * @m: Migration metadata
+ *
+ * Return: 0 on success, error code on failure
+ */
+int migrate_target_pre(struct ctx *c, struct migrate_meta *m)
+{
+ struct migrate_target_handlers *th;
+ struct migrate_handler *h;
+
+ for (th = target_handlers; th->v != m->v && th->v; th++);
+
+ for (h = th->pre; h->fn; h++) {
+ int rc;
+
+ if ((rc = h->fn(c, m)))
+ return rc;
+ }
+
+ return 0;
+}
+
+/**
+ * migrate_target() - Perform migration as target: receive state from hypervisor
+ * @fd: Descriptor for state transfer
+ * @m: Migration metadata
+ *
+ * Return: 0 on success, error code on failure
+ *
+ * #syscalls:vu readv
+ */
+int migrate_target(int fd, const struct migrate_meta *m)
+{
+ static struct migrate_data *d;
+ unsigned cnt;
+ int rc;
+
+ for (d = data_versions; d->v != m->v && d->v; d++);
+
+ for (cnt = 0; d->sections[cnt + 1 /* skip header */].iov_len; cnt++);
+
+ debug("Reading %u migration sections", cnt);
+ rc = read_remainder(fd, d->sections + 1, cnt, 0);
+ if (rc < 0)
+ return errno;
+
+ return 0;
+}
+
+/**
+ * migrate_target_post() - Post-migration tasks as target
+ * @c: Execution context
+ * @m: Migration metadata
+ */
+void migrate_target_post(struct ctx *c, struct migrate_meta *m)
+{
+ struct migrate_target_handlers *th;
+ struct migrate_handler *h;
+
+ for (th = target_handlers; th->v != m->v && th->v; th++);
+
+ for (h = th->post; h->fn; h++)
+ h->fn(c, m);
+}
diff --git a/migrate.h b/migrate.h
new file mode 100644
index 0000000..9a68f17
--- /dev/null
+++ b/migrate.h
@@ -0,0 +1,88 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright (c) 2025 Red Hat GmbH
+ * Author: Stefano Brivio <sbrivio(a)redhat.com>
+ */
+
+#ifndef MIGRATE_H
+#define MIGRATE_H
+
+/**
+ * struct migrate_meta - Migration metadata
+ * @v: Chosen migration data version, host order
+ * @bswap: Source has opposite endianness
+ * @peer_64b: Source uses 64-bit void *
+ * @time_64b: Source uses 64-bit time_t
+ * @flow_size: Size of union flow in source
+ * @flow_sidx_size: Size of struct flow_sidx in source
+ */
+struct migrate_meta {
+ uint32_t v;
+ bool bswap;
+ bool source_64b;
+ bool time_64b;
+ size_t flow_size;
+ size_t flow_sidx_size;
+};
+
+/**
+ * union migrate_header - Migration header from source
+ * @magic: 0xB1BB1D1B0BB1D1B0, host order
+ * @version: Source sends highest known, target aborts if unsupported
+ * @voidp_size: sizeof(void *), network order
+ * @time_t_size: sizeof(time_t), network order
+ * @flow_size: sizeof(union flow), network order
+ * @flow_sidx_size: sizeof(struct flow_sidx_t), network order
+ * @unused: Go figure
+ */
+union migrate_header {
+ struct {
+ uint64_t magic;
+ uint32_t version;
+ uint32_t voidp_size;
+ uint32_t time_t_size;
+ uint32_t flow_size;
+ uint32_t flow_sidx_size;
+ };
+ uint8_t unused[4096];
+} __attribute__((packed));
+
+/**
+ * struct migrate_data - Data sections for given source version
+ * @v: Source version this applies to, host order
+ * @sections: Array of data sections, NULL-terminated
+ */
+struct migrate_data {
+ uint32_t v;
+ struct iovec *sections;
+};
+
+/**
+ * struct migrate_handler - Function to handle a specific data section
+ * @fn: Function pointer taking pointer to context and metadata
+ */
+struct migrate_handler {
+ int (*fn)(struct ctx *c, struct migrate_meta *m);
+};
+
+/**
+ * struct migrate_target_handlers - Versioned sets of migration target handlers
+ * @v: Source version this applies to, host order
+ * @pre: Set of functions to execute in target before data copy
+ * @post: Set of functions to execute in target after data copy
+ */
+struct migrate_target_handlers {
+ uint32_t v;
+ struct migrate_handler *pre;
+ struct migrate_handler *post;
+};
+
+int migrate_source_pre(struct ctx *c, struct migrate_meta *m);
+int migrate_source(int fd, const struct migrate_meta *m);
+void migrate_source_post(struct ctx *c, struct migrate_meta *m);
+
+int migrate_target_read_header(int fd, struct migrate_meta *m);
+int migrate_target_pre(struct ctx *c, struct migrate_meta *m);
+int migrate_target(int fd, const struct migrate_meta *m);
+void migrate_target_post(struct ctx *c, struct migrate_meta *m);
+
+#endif /* MIGRATE_H */
diff --git a/passt.c b/passt.c
index b1c8ab6..184d4e5 100644
--- a/passt.c
+++ b/passt.c
@@ -358,7 +358,7 @@ loop:
vu_kick_cb(c.vdev, ref, &now);
break;
case EPOLL_TYPE_VHOST_MIGRATION:
- vu_migrate(c.vdev, eventmask);
+ vu_migrate(&c, eventmask);
break;
default:
/* Can't happen */
diff --git a/vu_common.c b/vu_common.c
index 2c12dca..6c346c8 100644
--- a/vu_common.c
+++ b/vu_common.c
@@ -5,6 +5,7 @@
* common_vu.c - vhost-user common UDP and TCP functions
*/
+#include <errno.h>
#include <unistd.h>
#include <sys/uio.h>
#include <sys/eventfd.h>
@@ -17,6 +18,7 @@
#include "vhost_user.h"
#include "pcap.h"
#include "vu_common.h"
+#include "migrate.h"
#define VU_MAX_TX_BUFFER_NB 2
@@ -305,48 +307,90 @@ err:
}
/**
- * vu_migrate() - Send/receive passt insternal state to/from QEMU
- * @vdev: vhost-user device
+ * vu_migrate_source() - Migration as source, send state to hypervisor
+ * @c: Execution context
+ * @fd: File descriptor for state transfer
+ *
+ * Return: 0 on success, positive error code on failure
+ */
+static int vu_migrate_source(struct ctx *c, int fd)
+{
+ struct migrate_meta m;
+ int rc;
+
+ if ((rc = migrate_source_pre(c, &m))) {
+ err("Source pre-migration failed: %s, abort", strerror_(rc));
+ return rc;
+ }
+
+ debug("Saving backend state");
+
+ rc = migrate_source(fd, &m);
+ if (rc)
+ err("Source migration failed: %s", strerror_(rc));
+ else
+ migrate_source_post(c, &m);
+
+ return rc;
+}
+
+/**
+ * vu_migrate_target() - Migration as target, receive state from hypervisor
+ * @c: Execution context
+ * @fd: File descriptor for state transfer
+ *
+ * Return: 0 on success, positive error code on failure
+ */
+static int vu_migrate_target(struct ctx *c, int fd)
+{
+ struct migrate_meta m;
+ int rc;
+
+ rc = migrate_target_read_header(fd, &m);
+ if (rc) {
+ err("Migration header check failed: %s, abort", strerror_(rc));
+ return rc;
+ }
+
+ if ((rc = migrate_target_pre(c, &m))) {
+ err("Target pre-migration failed: %s, abort", strerror_(rc));
+ return rc;
+ }
+
+ debug("Loading backend state");
+
+ rc = migrate_target(fd, &m);
+ if (rc)
+ err("Target migration failed: %s", strerror_(rc));
+ else
+ migrate_target_post(c, &m);
+
+ return rc;
+}
+
+/**
+ * vu_migrate() - Send/receive passt internal state to/from QEMU
+ * @c: Execution context
* @events: epoll events
*/
-void vu_migrate(struct vu_dev *vdev, uint32_t events)
+void vu_migrate(struct ctx *c, uint32_t events)
{
- int ret;
+ struct vu_dev *vdev = c->vdev;
+ int rc = EIO;
- /* TODO: collect/set passt internal state
- * and use vdev->device_state_fd to send/receive it
- */
debug("vu_migrate fd %d events %x", vdev->device_state_fd, events);
- if (events & EPOLLOUT) {
- debug("Saving backend state");
-
- /* send some stuff */
- ret = write(vdev->device_state_fd, "PASST", 6);
- /* value to be returned by VHOST_USER_CHECK_DEVICE_STATE */
- vdev->device_state_result = ret == -1 ? -1 : 0;
- /* Closing the file descriptor signals the end of transfer */
- epoll_del(vdev->context, vdev->device_state_fd);
- close(vdev->device_state_fd);
- vdev->device_state_fd = -1;
- } else if (events & EPOLLIN) {
- char buf[6];
-
- debug("Loading backend state");
- /* read some stuff */
- ret = read(vdev->device_state_fd, buf, sizeof(buf));
- /* value to be returned by VHOST_USER_CHECK_DEVICE_STATE */
- if (ret != sizeof(buf)) {
- vdev->device_state_result = -1;
- } else {
- ret = strncmp(buf, "PASST", sizeof(buf));
- vdev->device_state_result = ret == 0 ? 0 : -1;
- }
- } else if (events & EPOLLHUP) {
- debug("Closing migration channel");
- /* The end of file signals the end of the transfer. */
- epoll_del(vdev->context, vdev->device_state_fd);
- close(vdev->device_state_fd);
- vdev->device_state_fd = -1;
- }
+ if (events & EPOLLOUT)
+ rc = vu_migrate_source(c, vdev->device_state_fd);
+ else if (events & EPOLLIN)
+ rc = vu_migrate_target(c, vdev->device_state_fd);
+
+ /* EPOLLHUP without EPOLLIN/EPOLLOUT, or EPOLLERR? Migration failed */
+
+ vdev->device_state_result = rc;
+
+ epoll_ctl(c->epollfd, EPOLL_CTL_DEL, vdev->device_state_fd, NULL);
+ debug("Closing migration channel");
+ close(vdev->device_state_fd);
+ vdev->device_state_fd = -1;
}
diff --git a/vu_common.h b/vu_common.h
index d56c021..69c4006 100644
--- a/vu_common.h
+++ b/vu_common.h
@@ -57,5 +57,5 @@ void vu_flush(const struct vu_dev *vdev, struct vu_virtq *vq,
void vu_kick_cb(struct vu_dev *vdev, union epoll_ref ref,
const struct timespec *now);
int vu_send_single(const struct ctx *c, const void *buf, size_t size);
-void vu_migrate(struct vu_dev *vdev, uint32_t events);
+void vu_migrate(struct ctx *c, uint32_t events);
#endif /* VU_COMMON_H */
--
2.43.0