[PATCH v11 25/27] tools/xenstore: add read watch state for live update

[Juergen Gross <jgross@xxxxxxxx>]

Add reading the watch state records for live update.

This requires factoring out some of the add watch functionality into a
dedicated function.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Paul Durrant <paul@xxxxxxx>
---
V4:
- add comment (Julien Grall)

V6:
- correct check_watch_path() (setting errno)
---
 tools/xenstore/xenstored_control.c |   2 +
 tools/xenstore/xenstored_watch.c   | 114 +++++++++++++++++++++--------
 tools/xenstore/xenstored_watch.h   |   2 +
 3 files changed, 88 insertions(+), 30 deletions(-)

diff --git a/tools/xenstore/xenstored_control.c 
b/tools/xenstore/xenstored_control.c
index d73e1dca7e..ba48358c31 100644
--- a/tools/xenstore/xenstored_control.c
+++ b/tools/xenstore/xenstored_control.c
@@ -35,6 +35,7 @@ Interactive commands for Xen Store Daemon.
 #include "xenstored_core.h"
 #include "xenstored_control.h"
 #include "xenstored_domain.h"
+#include "xenstored_watch.h"
 
 /* Mini-OS only knows about MAP_ANON. */
 #ifndef MAP_ANONYMOUS
@@ -542,6 +543,7 @@ void lu_read_state(void)
                        read_state_connection(ctx, head + 1);
                        break;
                case XS_STATE_TYPE_WATCH:
+                       read_state_watch(ctx, head + 1);
                        break;
                case XS_STATE_TYPE_TA:
                        xprintf("live-update: ignore transaction record\n");
diff --git a/tools/xenstore/xenstored_watch.c b/tools/xenstore/xenstored_watch.c
index 9248f08bd9..db89e0141f 100644
--- a/tools/xenstore/xenstored_watch.c
+++ b/tools/xenstore/xenstored_watch.c
@@ -205,6 +205,62 @@ static int destroy_watch(void *_watch)
        return 0;
 }
 
+static int check_watch_path(struct connection *conn, const void *ctx,
+                           char **path, bool *relative)
+{
+       /* Check if valid event. */
+       if (strstarts(*path, "@")) {
+               *relative = false;
+               if (strlen(*path) > XENSTORE_REL_PATH_MAX)
+                       goto inval;
+       } else {
+               *relative = !strstarts(*path, "/");
+               *path = canonicalize(conn, ctx, *path);
+               if (!*path)
+                       return errno;
+               if (!is_valid_nodename(*path))
+                       goto inval;
+       }
+
+       return 0;
+
+ inval:
+       errno = EINVAL;
+       return errno;
+}
+
+static struct watch *add_watch(struct connection *conn, char *path, char 
*token,
+                              bool relative)
+{
+       struct watch *watch;
+
+       watch = talloc(conn, struct watch);
+       if (!watch)
+               goto nomem;
+       watch->node = talloc_strdup(watch, path);
+       watch->token = talloc_strdup(watch, token);
+       if (!watch->node || !watch->token)
+               goto nomem;
+
+       if (relative)
+               watch->relative_path = get_implicit_path(conn);
+       else
+               watch->relative_path = NULL;
+
+       INIT_LIST_HEAD(&watch->events);
+
+       domain_watch_inc(conn);
+       list_add_tail(&watch->list, &conn->watches);
+       talloc_set_destructor(watch, destroy_watch);
+
+       return watch;
+
+ nomem:
+       talloc_free(watch);
+       errno = ENOMEM;
+       return NULL;
+}
+
 int do_watch(struct connection *conn, struct buffered_data *in)
 {
        struct watch *watch;
@@ -214,19 +270,9 @@ int do_watch(struct connection *conn, struct buffered_data 
*in)
        if (get_strings(in, vec, ARRAY_SIZE(vec)) != ARRAY_SIZE(vec))
                return EINVAL;
 
-       if (strstarts(vec[0], "@")) {
-               relative = false;
-               if (strlen(vec[0]) > XENSTORE_REL_PATH_MAX)
-                       return EINVAL;
-               /* check if valid event */
-       } else {
-               relative = !strstarts(vec[0], "/");
-               vec[0] = canonicalize(conn, in, vec[0]);
-               if (!vec[0])
-                       return ENOMEM;
-               if (!is_valid_nodename(vec[0]))
-                       return EINVAL;
-       }
+       errno = check_watch_path(conn, in, &(vec[0]), &relative);
+       if (errno)
+               return errno;
 
        /* Check for duplicates. */
        list_for_each_entry(watch, &conn->watches, list) {
@@ -238,26 +284,11 @@ int do_watch(struct connection *conn, struct 
buffered_data *in)
        if (domain_watch(conn) > quota_nb_watch_per_domain)
                return E2BIG;
 
-       watch = talloc(conn, struct watch);
+       watch = add_watch(conn, vec[0], vec[1], relative);
        if (!watch)
-               return ENOMEM;
-       watch->node = talloc_strdup(watch, vec[0]);
-       watch->token = talloc_strdup(watch, vec[1]);
-       if (!watch->node || !watch->token) {
-               talloc_free(watch);
-               return ENOMEM;
-       }
-       if (relative)
-               watch->relative_path = get_implicit_path(conn);
-       else
-               watch->relative_path = NULL;
+               return errno;
 
-       INIT_LIST_HEAD(&watch->events);
-
-       domain_watch_inc(conn);
-       list_add_tail(&watch->list, &conn->watches);
        trace_create(watch, "watch");
-       talloc_set_destructor(watch, destroy_watch);
        send_ack(conn, XS_WATCH);
 
        /* We fire once up front: simplifies clients and restart. */
@@ -338,6 +369,29 @@ const char *dump_state_watches(FILE *fp, struct connection 
*conn,
        return ret;
 }
 
+void read_state_watch(const void *ctx, const void *state)
+{
+       const struct xs_state_watch *sw = state;
+       struct connection *conn;
+       char *path, *token;
+       bool relative;
+
+       conn = get_connection_by_id(sw->conn_id);
+       if (!conn)
+               barf("connection not found for read watch");
+
+       path = (char *)sw->data;
+       token = path + sw->path_length;
+
+       /* Don't check success, we want the relative information only. */
+       check_watch_path(conn, ctx, &path, &relative);
+       if (!path)
+               barf("allocation error for read watch");
+
+       if (!add_watch(conn, path, token, relative))
+               barf("error adding watch");
+}
+
 /*
  * Local variables:
  *  mode: C
diff --git a/tools/xenstore/xenstored_watch.h b/tools/xenstore/xenstored_watch.h
index 3d81645f45..0e693f0839 100644
--- a/tools/xenstore/xenstored_watch.h
+++ b/tools/xenstore/xenstored_watch.h
@@ -33,4 +33,6 @@ void conn_delete_all_watches(struct connection *conn);
 const char *dump_state_watches(FILE *fp, struct connection *conn,
                               unsigned int conn_id);
 
+void read_state_watch(const void *ctx, const void *state);
+
 #endif /* _XENSTORED_WATCH_H */
-- 
2.26.2