@@ -50,6 +50,16 @@ struct xdp_umem {
struct list_head xsk_list;
};
+/* Nodes are linked in the struct xdp_sock map_list field, and used to
+ * track which maps a certain socket reside in.
+ */
+struct xsk_map;
+struct xsk_map_node {
+ struct list_head node;
+ struct xsk_map *map;
+ struct xdp_sock **map_entry;
+};
+
struct xdp_sock {
/* struct sock must be the first member of struct xdp_sock */
struct sock sk;
@@ -75,6 +85,9 @@ struct xdp_sock {
/* Protects generic receive. */
spinlock_t rx_lock;
u64 rx_dropped;
+ struct list_head map_list;
+ /* Protects map_list */
+ spinlock_t map_list_lock;
};
struct xdp_buff;
@@ -96,6 +109,11 @@ struct xdp_umem_fq_reuse *xsk_reuseq_swap(struct xdp_umem *umem,
void xsk_reuseq_free(struct xdp_umem_fq_reuse *rq);
struct xdp_umem *xdp_get_umem_from_qid(struct net_device *dev, u16 queue_id);
+void xsk_map_try_sock_delete(struct xsk_map *map, struct xdp_sock *xs,
+ struct xdp_sock **map_entry);
+int xsk_map_inc(struct xsk_map *map);
+void xsk_map_put(struct xsk_map *map);
+
static inline char *xdp_umem_get_data(struct xdp_umem *umem, u64 addr)
{
return umem->pages[addr >> PAGE_SHIFT].addr + (addr & (PAGE_SIZE - 1));
@@ -13,8 +13,71 @@ struct xsk_map {
struct bpf_map map;
struct xdp_sock **xsk_map;
struct list_head __percpu *flush_list;
+ spinlock_t lock; /* Synchronize map updates */
};
+int xsk_map_inc(struct xsk_map *map)
+{
+ struct bpf_map *m = &map->map;
+
+ m = bpf_map_inc(m, false);
+ return IS_ERR(m) ? PTR_ERR(m) : 0;
+}
+
+void xsk_map_put(struct xsk_map *map)
+{
+ bpf_map_put(&map->map);
+}
+
+static struct xsk_map_node *xsk_map_node_alloc(struct xsk_map *map,
+ struct xdp_sock **map_entry)
+{
+ struct xsk_map_node *node;
+ int err;
+
+ node = kzalloc(sizeof(*node), GFP_ATOMIC | __GFP_NOWARN);
+ if (!node)
+ return NULL;
+
+ err = xsk_map_inc(map);
+ if (err) {
+ kfree(node);
+ return ERR_PTR(err);
+ }
+
+ node->map = map;
+ node->map_entry = map_entry;
+ return node;
+}
+
+static void xsk_map_node_free(struct xsk_map_node *node)
+{
+ xsk_map_put(node->map);
+ kfree(node);
+}
+
+static void xsk_map_sock_add(struct xdp_sock *xs, struct xsk_map_node *node)
+{
+ spin_lock_bh(&xs->map_list_lock);
+ list_add_tail(&node->node, &xs->map_list);
+ spin_unlock_bh(&xs->map_list_lock);
+}
+
+static void xsk_map_sock_delete(struct xdp_sock *xs,
+ struct xdp_sock **map_entry)
+{
+ struct xsk_map_node *n, *tmp;
+
+ spin_lock_bh(&xs->map_list_lock);
+ list_for_each_entry_safe(n, tmp, &xs->map_list, node) {
+ if (map_entry == n->map_entry) {
+ list_del(&n->node);
+ xsk_map_node_free(n);
+ }
+ }
+ spin_unlock_bh(&xs->map_list_lock);
+}
+
static struct bpf_map *xsk_map_alloc(union bpf_attr *attr)
{
struct xsk_map *m;
@@ -34,6 +97,7 @@ static struct bpf_map *xsk_map_alloc(union bpf_attr *attr)
return ERR_PTR(-ENOMEM);
bpf_map_init_from_attr(&m->map, attr);
+ spin_lock_init(&m->lock);
cost = (u64)m->map.max_entries * sizeof(struct xdp_sock *);
cost += sizeof(struct list_head) * num_possible_cpus();
@@ -71,21 +135,9 @@ static struct bpf_map *xsk_map_alloc(union bpf_attr *attr)
static void xsk_map_free(struct bpf_map *map)
{
struct xsk_map *m = container_of(map, struct xsk_map, map);
- int i;
bpf_clear_redirect_map(map);
synchronize_net();
-
- for (i = 0; i < map->max_entries; i++) {
- struct xdp_sock *xs;
-
- xs = m->xsk_map[i];
- if (!xs)
- continue;
-
- sock_put((struct sock *)xs);
- }
-
free_percpu(m->flush_list);
bpf_map_area_free(m->xsk_map);
kfree(m);
@@ -164,8 +216,9 @@ static int xsk_map_update_elem(struct bpf_map *map, void *key, void *value,
u64 map_flags)
{
struct xsk_map *m = container_of(map, struct xsk_map, map);
+ struct xdp_sock *xs, *old_xs, **map_entry;
u32 i = *(u32 *)key, fd = *(u32 *)value;
- struct xdp_sock *xs, *old_xs;
+ struct xsk_map_node *node;
struct socket *sock;
int err;
@@ -192,32 +245,64 @@ static int xsk_map_update_elem(struct bpf_map *map, void *key, void *value,
return -EOPNOTSUPP;
}
- sock_hold(sock->sk);
+ map_entry = &m->xsk_map[i];
+ node = xsk_map_node_alloc(m, map_entry);
+ if (IS_ERR(node)) {
+ sockfd_put(sock);
+ return PTR_ERR(node);
+ }
- old_xs = xchg(&m->xsk_map[i], xs);
+ spin_lock_bh(&m->lock);
+ old_xs = READ_ONCE(*map_entry);
+ if (old_xs == xs) {
+ err = 0;
+ goto out;
+ }
+ xsk_map_sock_add(xs, node);
+ WRITE_ONCE(*map_entry, xs);
if (old_xs)
- sock_put((struct sock *)old_xs);
-
+ xsk_map_sock_delete(old_xs, map_entry);
+ spin_unlock_bh(&m->lock);
sockfd_put(sock);
return 0;
+
+out:
+ spin_unlock_bh(&m->lock);
+ sockfd_put(sock);
+ xsk_map_node_free(node);
+ return err;
}
static int xsk_map_delete_elem(struct bpf_map *map, void *key)
{
struct xsk_map *m = container_of(map, struct xsk_map, map);
- struct xdp_sock *old_xs;
+ struct xdp_sock *old_xs, **map_entry;
int k = *(u32 *)key;
if (k >= map->max_entries)
return -EINVAL;
- old_xs = xchg(&m->xsk_map[k], NULL);
+ spin_lock_bh(&m->lock);
+ map_entry = &m->xsk_map[k];
+ old_xs = xchg(map_entry, NULL);
if (old_xs)
- sock_put((struct sock *)old_xs);
+ xsk_map_sock_delete(old_xs, map_entry);
+ spin_unlock_bh(&m->lock);
return 0;
}
+void xsk_map_try_sock_delete(struct xsk_map *map, struct xdp_sock *xs,
+ struct xdp_sock **map_entry)
+{
+ spin_lock_bh(&map->lock);
+ if (READ_ONCE(*map_entry) == xs) {
+ WRITE_ONCE(*map_entry, NULL);
+ xsk_map_sock_delete(xs, map_entry);
+ }
+ spin_unlock_bh(&map->lock);
+}
+
const struct bpf_map_ops xsk_map_ops = {
.map_alloc = xsk_map_alloc,
.map_free = xsk_map_free,
@@ -362,6 +362,52 @@ static void xsk_unbind_dev(struct xdp_sock *xs)
dev_put(dev);
}
+static struct xsk_map *xsk_get_map_list_entry(struct xdp_sock *xs,
+ struct xdp_sock ***map_entry)
+{
+ struct xsk_map *map = NULL;
+ struct xsk_map_node *node;
+
+ *map_entry = NULL;
+
+ spin_lock_bh(&xs->map_list_lock);
+ node = list_first_entry_or_null(&xs->map_list, struct xsk_map_node,
+ node);
+ if (node) {
+ WARN_ON(xsk_map_inc(node->map));
+ map = node->map;
+ *map_entry = node->map_entry;
+ }
+ spin_unlock_bh(&xs->map_list_lock);
+ return map;
+}
+
+static void xsk_delete_from_maps(struct xdp_sock *xs)
+{
+ /* This function removes the current XDP socket from all the
+ * maps it resides in. We need to take extra care here, due to
+ * the two locks involved. Each map has a lock synchronizing
+ * updates to the entries, and each socket has a lock that
+ * synchronizes access to the list of maps (map_list). For
+ * deadlock avoidance the locks need to be taken in the order
+ * "map lock"->"socket map list lock". We start off by
+ * accessing the socket map list, and take a reference to the
+ * map to guarantee existence between the
+ * xsk_get_map_list_entry() and xsk_map_try_sock_delete()
+ * calls. Then we ask the map to remove the socket, which
+ * tries to remove the socket from the map. Note that there
+ * might be updates to the map between
+ * xsk_get_map_list_entry() and xsk_map_try_sock_delete().
+ */
+ struct xdp_sock **map_entry = NULL;
+ struct xsk_map *map;
+
+ while ((map = xsk_get_map_list_entry(xs, &map_entry))) {
+ xsk_map_try_sock_delete(map, xs, map_entry);
+ xsk_map_put(map);
+ }
+}
+
static int xsk_release(struct socket *sock)
{
struct sock *sk = sock->sk;
@@ -381,6 +427,7 @@ static int xsk_release(struct socket *sock)
sock_prot_inuse_add(net, sk->sk_prot, -1);
local_bh_enable();
+ xsk_delete_from_maps(xs);
xsk_unbind_dev(xs);
xskq_destroy(xs->rx);
@@ -855,6 +902,9 @@ static int xsk_create(struct net *net, struct socket *sock, int protocol,
spin_lock_init(&xs->rx_lock);
spin_lock_init(&xs->tx_completion_lock);
+ INIT_LIST_HEAD(&xs->map_list);
+ spin_lock_init(&xs->map_list_lock);
+
mutex_lock(&net->xdp.lock);
sk_add_node_rcu(sk, &net->xdp.list);
mutex_unlock(&net->xdp.lock);