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ovs: wait that links disappear during initial cleanup

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At startup, we remove from ovsdb any existing interface created by NM
and later an interface with the same name might be readded. This can
cause race conditions. Consider this series of events:

1. at startup NM removes the entry from ovsdb;
2. ovsdb reports success;
3. NM inserts an interface with the same name again;
4. ovs-vswitch monitors ovsdb changes, and gets events for removal and
   insertion. Depending on how those events are split in different
   batches, it might decide:
   4a. to delete the link and add it back, or
   4b. to keep the existing link because the delete and insertion
       cancel out each other.

When NM sees the link staying in platform, it doesn't know if it's
because of 4b or because 4a will happen eventually.

To avoid this ambiguity, after ovsdb reports the successful deletion
NM should also wait that the link disappears from platform.

Unfortunately, this means that ovsdb gets a dependency to the platform
code.

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/1386
This commit is contained in:
Beniamino Galvani 2022-09-20 14:05:42 +02:00
parent 1c76fe418b
commit 4f60fe293c
1 changed files with 134 additions and 25 deletions
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159
src/core/devices/ovs/nm-ovsdb.c
View file

@ -18,6 +18,7 @@
#include "nm-manager.h"
#include "nm-setting-ovs-external-ids.h"
#include "nm-priv-helper-call.h"
#include "libnm-platform/nm-platform.h"
/*****************************************************************************/
@ -120,6 +121,7 @@ enum {
static guint signals[LAST_SIGNAL] = {0};
typedef struct {
NMPlatform *platform;
GSocketConnection *conn;
GCancellable *conn_cancellable;
char buf[4096]; /* Input buffer */
@ -135,8 +137,14 @@ typedef struct {
GHashTable *bridges; /* bridge uuid => OpenvswitchBridge */
char *db_uuid;
guint num_failures;
guint num_pending_deletions;
bool ready : 1;
struct {
GPtrArray *interfaces; /* Interface names we are waiting to go away */
GSource *timeout_source; /* After all deletions complete, wait this
* timeout for interfaces to disappear */
gulong link_changed_id; /* Platform link-changed signal handle */
guint num_pending_del; /* Number of ovsdb deletions pending */
} cleanup;
} NMOvsdbPrivate;
struct _NMOvsdb {
@ -161,6 +169,7 @@ static void ovsdb_disconnect(NMOvsdb *self, gboolean retry, gboolean is_disposin
static void ovsdb_read(NMOvsdb *self);
static void ovsdb_write(NMOvsdb *self);
static void ovsdb_next_command(NMOvsdb *self);
static void cleanup_check_ready(NMOvsdb *self);
/*****************************************************************************/
@ -2289,21 +2298,114 @@ ovsdb_disconnect(NMOvsdb *self, gboolean retry, gboolean is_disposing)
}
static void
_check_ready(NMOvsdb *self)
cleanup_emit_ready(NMOvsdb *self, const char *reason)
{
NMOvsdbPrivate *priv = NM_OVSDB_GET_PRIVATE(self);
nm_assert(!priv->ready);
_LOGT("cleanup: ready (%s)", reason);
if (priv->num_pending_deletions == 0) {
priv->ready = TRUE;
g_signal_emit(self, signals[READY], 0);
nm_manager_unblock_failed_ovs_interfaces(nm_manager_get());
}
nm_clear_pointer(&priv->cleanup.interfaces, g_ptr_array_unref);
nm_clear_g_source_inst(&priv->cleanup.timeout_source);
nm_clear_g_signal_handler(priv->platform, &priv->cleanup.link_changed_id);
priv->ready = TRUE;
g_signal_emit(self, signals[READY], 0);
nm_manager_unblock_failed_ovs_interfaces(nm_manager_get());
}
static gboolean
cleanup_timeout(NMOvsdb *self)
{
cleanup_emit_ready(self, "timeout");
return G_SOURCE_CONTINUE;
}
static void
_del_initial_iface_cb(GError *error, gpointer user_data)
cleanup_link_cb(NMPlatform *platform,
int obj_type_i,
int ifindex,
NMPlatformLink *plink,
int change_type_i,
gpointer user_data)
{
const NMPlatformSignalChangeType change_type = change_type_i;
if (change_type != NM_PLATFORM_SIGNAL_REMOVED)
return;
cleanup_check_ready(user_data);
}
static void
cleanup_check_ready(NMOvsdb *self)
{
NMOvsdbPrivate *priv = NM_OVSDB_GET_PRIVATE(self);
guint i = 0;
nm_assert(!priv->ready);
if (priv->cleanup.num_pending_del > 0)
return;
/* After we have deleted an interface from ovsdb, the link will stay
* in platform until ovs-vswitch removes it. To avoid race conditions,
* we need to wait until the link goes away; otherwise, after adding the
* interface again, these race conditions can happen:
* 1) we see the link in platform, and proceed with activation. But after
* that, ovs-vswitchd reads the updates from ovsdb-server and deletes/recreates
* the link.
* 2) ovs-vswitch combines the delete/insert of the interface to a no-op. NM sees
* the link staying in platform, but doesn't know whether the link is ready
* or we are again in case 1)
* In other words, it's necessary to wait that the link goes away before inserting
* the interface again.
*/
while (i < nm_g_ptr_array_len(priv->cleanup.interfaces)) {
const char *ifname;
const NMDedupMultiHeadEntry *pl_links_head_entry;
NMDedupMultiIter pliter;
const NMPlatformLink *link;
gboolean found = FALSE;
ifname = priv->cleanup.interfaces->pdata[i];
pl_links_head_entry = nm_platform_lookup_link_by_ifname(priv->platform, ifname);
nmp_cache_iter_for_each_link (&pliter, pl_links_head_entry, &link) {
if (link->type == NM_LINK_TYPE_OPENVSWITCH
&& nmp_object_is_visible(NMP_OBJECT_UP_CAST(link))) {
found = TRUE;
break;
}
}
if (!found) {
g_ptr_array_remove_index_fast(priv->cleanup.interfaces, i);
continue;
}
i++;
}
if (nm_g_ptr_array_len(priv->cleanup.interfaces) == 0) {
cleanup_emit_ready(self, "all interfaces deleted");
return;
}
_LOGT("cleanup: still waiting for %d interfaces", priv->cleanup.interfaces->len);
if (priv->cleanup.timeout_source) {
/* We already registered the timeout/change-callback */
return;
}
priv->cleanup.timeout_source =
nm_g_timeout_add_seconds_source(6, G_SOURCE_FUNC(cleanup_timeout), self);
priv->cleanup.link_changed_id = g_signal_connect(priv->platform,
NM_PLATFORM_SIGNAL_LINK_CHANGED,
G_CALLBACK(cleanup_link_cb),
self);
}
static void
cleanup_del_iface_cb(GError *error, gpointer user_data)
{
NMOvsdb *self;
gs_free char *ifname = NULL;
@ -2315,18 +2417,18 @@ _del_initial_iface_cb(GError *error, gpointer user_data)
return;
priv = NM_OVSDB_GET_PRIVATE(self);
nm_assert(priv->num_pending_deletions > 0);
priv->num_pending_deletions--;
nm_assert(priv->cleanup.num_pending_del > 0);
priv->cleanup.num_pending_del--;
_LOGD("delete initial interface '%s': %s %s%s%s, pending %u",
_LOGD("cleanup: deleted interface '%s': %s %s%s%s, pending %u",
ifname,
error ? "error" : "success",
error ? "(" : "",
error ? error->message : "",
error ? ")" : "",
priv->num_pending_deletions);
priv->cleanup.num_pending_del);
_check_ready(self);
cleanup_check_ready(self);
}
static void
@ -2337,7 +2439,7 @@ ovsdb_cleanup_initial_interfaces(NMOvsdb *self)
NMUtilsUserData *data;
GHashTableIter iter;
if (priv->ready || priv->num_pending_deletions != 0)
if (priv->ready || priv->cleanup.num_pending_del > 0 || priv->cleanup.interfaces)
return;
/* Delete OVS interfaces added by NM. Bridges and ports and
@ -2345,17 +2447,22 @@ ovsdb_cleanup_initial_interfaces(NMOvsdb *self)
* when no interface is present. */
g_hash_table_iter_init(&iter, self->_priv.interfaces);
while (g_hash_table_iter_next(&iter, NULL, (gpointer *) &interface)) {
if (interface->connection_uuid) {
priv->num_pending_deletions++;
_LOGD("deleting initial interface '%s' (pending: %u)",
interface->name,
priv->num_pending_deletions);
data = nm_utils_user_data_pack(self, g_strdup(interface->name));
nm_ovsdb_del_interface(self, interface->name, _del_initial_iface_cb, data);
if (!interface->connection_uuid) {
/* not created by NM, ignore */
continue;
}
if (!priv->cleanup.interfaces)
priv->cleanup.interfaces = g_ptr_array_new_with_free_func(g_free);
g_ptr_array_add(priv->cleanup.interfaces, g_strdup(interface->name));
_LOGD("cleanup: deleting interface '%s'", interface->name);
priv->cleanup.num_pending_del++;
data = nm_utils_user_data_pack(self, g_strdup(interface->name));
nm_ovsdb_del_interface(self, interface->name, cleanup_del_iface_cb, data);
}
_check_ready(self);
cleanup_check_ready(self);
}
static void
@ -2628,8 +2735,9 @@ nm_ovsdb_init(NMOvsdb *self)
c_list_init(&priv->calls_lst_head);
priv->input = g_string_new(NULL);
priv->output = g_string_new(NULL);
priv->platform = g_object_ref(NM_PLATFORM_GET);
priv->input = g_string_new(NULL);
priv->output = g_string_new(NULL);
priv->bridges =
g_hash_table_new_full(nm_pstr_hash, nm_pstr_equal, (GDestroyNotify) _free_bridge, NULL);
priv->ports =
@ -2659,6 +2767,7 @@ dispose(GObject *object)
priv->output = NULL;
}
g_clear_object(&priv->platform);
nm_clear_pointer(&priv->bridges, g_hash_table_destroy);
nm_clear_pointer(&priv->ports, g_hash_table_destroy);
nm_clear_pointer(&priv->interfaces, g_hash_table_destroy);