[RFC PATCHv2 bpf-next 1/2] xdp: add a new helper for dev map multicast support

Hangbin Liu
2020-04-24T08:56:31Z

This is a prototype for xdp multicast support. In this implemention we
add a new helper to accept two maps, forward map and exclude map.
We will redirect the packet to all the interfaces in *forward map*, but
exclude the interfaces that in *exclude map*.

To achive this I add a new ex_map for struct bpf_redirect_info.
in the helper I set tgt_value to NULL to make a difference with
bpf_xdp_redirect_map()

We also add a flag *BPF_F_EXCLUDE_INGRESS* incase you don't want to
create a exclude map for each interface and just want to exclude the
ingress interface.

The general data path is kept in net/core/filter.c. The native data
path is in kernel/bpf/devmap.c so we can use direct calls to
get better performace.

v2: add new syscall bpf_xdp_redirect_map_multi() which could accept
include/exclude maps directly.

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
---
include/linux/bpf.h | 20 ++++++
include/linux/filter.h | 1 +
include/net/xdp.h | 1 +
include/uapi/linux/bpf.h | 23 ++++++-
kernel/bpf/devmap.c | 114 +++++++++++++++++++++++++++++++++
kernel/bpf/verifier.c | 6 ++
net/core/filter.c | 98 ++++++++++++++++++++++++++--
net/core/xdp.c | 26 ++++++++
tools/include/uapi/linux/bpf.h | 23 ++++++-
9 files changed, 305 insertions(+), 7 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index fd2b2322412d..3fd2903def3f 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1161,6 +1161,11 @@ int dev_xdp_enqueue(struct net_device *dev, struct xdp_buff *xdp,
struct net_device *dev_rx);
int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
struct net_device *dev_rx);
+bool dev_in_exclude_map(struct bpf_dtab_netdev *obj, struct bpf_map *map,
+ int exclude_ifindex);
+int dev_map_enqueue_multi(struct xdp_buff *xdp, struct net_device *dev_rx,
+ struct bpf_map *map, struct bpf_map *ex_map,
+ bool exclude_ingress);
int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb,
struct bpf_prog *xdp_prog);

@@ -1297,6 +1302,21 @@ int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
return 0;
}

+static inline
+bool dev_in_exclude_map(struct bpf_dtab_netdev *obj, struct bpf_map *map,
+ int exclude_ifindex)
+{
+ return false;
+}
+
+static inline
+int dev_map_enqueue_multi(struct xdp_buff *xdp, struct net_device *dev_rx,
+ struct bpf_map *map, struct bpf_map *ex_map,
+ bool exclude_ingress)
+{
+ return 0;
+}
+
struct sk_buff;

static inline int dev_map_generic_redirect(struct bpf_dtab_netdev *dst,
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 9b5aa5c483cc..5b4e1ccd2d37 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -614,6 +614,7 @@ struct bpf_redirect_info {
u32 tgt_index;
void *tgt_value;
struct bpf_map *map;
+ struct bpf_map *ex_map;
u32 kern_flags;
};

diff --git a/include/net/xdp.h b/include/net/xdp.h
index 40c6d3398458..a214dce8579c 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -92,6 +92,7 @@ static inline void xdp_scrub_frame(struct xdp_frame *frame)
}

struct xdp_frame *xdp_convert_zc_to_xdp_frame(struct xdp_buff *xdp);
+struct xdp_frame *xdpf_clone(struct xdp_frame *xdpf);

/* Convert xdp_buff to xdp_frame */
static inline
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 2e29a671d67e..1dbe42290223 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3025,6 +3025,21 @@ union bpf_attr {
* * **-EOPNOTSUPP** Unsupported operation, for example a
* call from outside of TC ingress.
* * **-ESOCKTNOSUPPORT** Socket type not supported (reuseport).
+ *
+ * int bpf_redirect_map_multi(struct bpf_map *map, struct bpf_map *ex_map, u64 flags)
+ * Description
+ * Redirect the packet to all the interfaces in *map*, and
+ * exclude the interfaces that in *ex_map*. The *ex_map* could
+ * be NULL.
+ *
+ * Currently the *flags* only supports *BPF_F_EXCLUDE_INGRESS*,
+ * which could exlcude redirect to the ingress device.
+ *
+ * See also bpf_redirect_map(), which supports redirecting
+ * packet to a specific ifindex in the map.
+ * Return
+ * **XDP_REDIRECT** on success, or **XDP_ABORTED** on error.
+ *
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3151,7 +3166,8 @@ union bpf_attr {
FN(xdp_output), \
FN(get_netns_cookie), \
FN(get_current_ancestor_cgroup_id), \
- FN(sk_assign),
+ FN(sk_assign), \
+ FN(redirect_map_multi),

/* integer value in 'imm' field of BPF_CALL instruction selects which helper
* function eBPF program intends to call
@@ -3280,6 +3296,11 @@ enum bpf_lwt_encap_mode {
BPF_LWT_ENCAP_IP,
};

+/* BPF_FUNC_redirect_map_multi flags. */
+enum {
+ BPF_F_EXCLUDE_INGRESS = (1ULL << 0),
+};
+
#define __bpf_md_ptr(type, name) \
union { \
type name; \
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 58bdca5d978a..34b171f7826c 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -456,6 +456,120 @@ int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
return __xdp_enqueue(dev, xdp, dev_rx);
}

+/* Use direct call in fast path instead of map->ops->map_get_next_key() */
+static int devmap_get_next_key(struct bpf_map *map, void *key, void *next_key)
+{
+
+ switch (map->map_type) {
+ case BPF_MAP_TYPE_DEVMAP:
+ return dev_map_get_next_key(map, key, next_key);
+ case BPF_MAP_TYPE_DEVMAP_HASH:
+ return dev_map_hash_get_next_key(map, key, next_key);
+ default:
+ break;
+ }
+
+ return -ENOENT;
+}
+
+bool dev_in_exclude_map(struct bpf_dtab_netdev *obj, struct bpf_map *map,
+ int exclude_ifindex)
+{
+ struct bpf_dtab_netdev *in_obj = NULL;
+ u32 key, next_key;
+ int err;
+
+ if (!map)
+ return false;
+
+ if (obj->dev->ifindex == exclude_ifindex)
+ return true;
+
+ devmap_get_next_key(map, NULL, &key);
+
+ for (;;) {
+ switch (map->map_type) {
+ case BPF_MAP_TYPE_DEVMAP:
+ in_obj = __dev_map_lookup_elem(map, key);
+ break;
+ case BPF_MAP_TYPE_DEVMAP_HASH:
+ in_obj = __dev_map_hash_lookup_elem(map, key);
+ break;
+ default:
+ break;
+ }
+
+ if (in_obj && in_obj->dev->ifindex == obj->dev->ifindex)
+ return true;
+
+ err = devmap_get_next_key(map, &key, &next_key);
+
+ if (err)
+ break;
+
+ key = next_key;
+ }
+
+ return false;
+}
+
+int dev_map_enqueue_multi(struct xdp_buff *xdp, struct net_device *dev_rx,
+ struct bpf_map *map, struct bpf_map *ex_map,
+ bool exclude_ingress)
+{
+ struct bpf_dtab_netdev *obj = NULL;
+ struct xdp_frame *xdpf, *nxdpf;
+ struct net_device *dev;
+ u32 key, next_key;
+ int err;
+
+ devmap_get_next_key(map, NULL, &key);
+
+ xdpf = convert_to_xdp_frame(xdp);
+ if (unlikely(!xdpf))
+ return -EOVERFLOW;
+
+ for (;;) {
+ switch (map->map_type) {
+ case BPF_MAP_TYPE_DEVMAP:
+ obj = __dev_map_lookup_elem(map, key);
+ break;
+ case BPF_MAP_TYPE_DEVMAP_HASH:
+ obj = __dev_map_hash_lookup_elem(map, key);
+ break;
+ default:
+ break;
+ }
+
+ if (!obj || dev_in_exclude_map(obj, ex_map,
+ exclude_ingress ? dev_rx->ifindex : 0))
+ goto find_next;
+
+ dev = obj->dev;
+
+ if (!dev->netdev_ops->ndo_xdp_xmit)
+ return -EOPNOTSUPP;
+
+ err = xdp_ok_fwd_dev(dev, xdp->data_end - xdp->data);
+ if (unlikely(err))
+ return err;
+
+ nxdpf = xdpf_clone(xdpf);
+ if (unlikely(!nxdpf))
+ return -ENOMEM;
+
+ bq_enqueue(dev, nxdpf, dev_rx);
+
+find_next:
+ err = devmap_get_next_key(map, &key, &next_key);
+ if (err)
+ break;
+ key = next_key;
+ }
+
+ return 0;
+}
+
int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb,
struct bpf_prog *xdp_prog)
{
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 38cfcf701eeb..f77213a0e354 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3880,6 +3880,7 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
case BPF_MAP_TYPE_DEVMAP:
case BPF_MAP_TYPE_DEVMAP_HASH:
if (func_id != BPF_FUNC_redirect_map &&
+ func_id != BPF_FUNC_redirect_map_multi &&
func_id != BPF_FUNC_map_lookup_elem)
goto error;
break;
@@ -3970,6 +3971,11 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
map->map_type != BPF_MAP_TYPE_XSKMAP)
goto error;
break;
+ case BPF_FUNC_redirect_map_multi:
+ if (map->map_type != BPF_MAP_TYPE_DEVMAP &&
+ map->map_type != BPF_MAP_TYPE_DEVMAP_HASH)
+ goto error;
+ break;
case BPF_FUNC_sk_redirect_map:
case BPF_FUNC_msg_redirect_map:
case BPF_FUNC_sock_map_update:
diff --git a/net/core/filter.c b/net/core/filter.c
index 7d6ceaa54d21..94d1530e5ac6 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3473,12 +3473,17 @@ static const struct bpf_func_proto bpf_xdp_adjust_meta_proto = {
};

static int __bpf_tx_xdp_map(struct net_device *dev_rx, void *fwd,
- struct bpf_map *map, struct xdp_buff *xdp)
+ struct bpf_map *map, struct xdp_buff *xdp,
+ struct bpf_map *ex_map, bool exclude_ingress)
{
switch (map->map_type) {
case BPF_MAP_TYPE_DEVMAP:
case BPF_MAP_TYPE_DEVMAP_HASH:
- return dev_map_enqueue(fwd, xdp, dev_rx);
+ if (fwd)
+ return dev_map_enqueue(fwd, xdp, dev_rx);
+ else
+ return dev_map_enqueue_multi(xdp, dev_rx, map, ex_map,
+ exclude_ingress);
case BPF_MAP_TYPE_CPUMAP:
return cpu_map_enqueue(fwd, xdp, dev_rx);
case BPF_MAP_TYPE_XSKMAP:
@@ -3534,6 +3539,8 @@ int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp,
struct bpf_prog *xdp_prog)
{
struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+ bool exclude_ingress = !!(ri->flags & BPF_F_EXCLUDE_INGRESS);
+ struct bpf_map *ex_map = READ_ONCE(ri->ex_map);
struct bpf_map *map = READ_ONCE(ri->map);
u32 index = ri->tgt_index;
void *fwd = ri->tgt_value;
@@ -3552,7 +3559,7 @@ int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp,

err = dev_xdp_enqueue(fwd, xdp, dev);
} else {
- err = __bpf_tx_xdp_map(dev, fwd, map, xdp);
+ err = __bpf_tx_xdp_map(dev, fwd, map, xdp, ex_map, exclude_ingress);
}

if (unlikely(err))
@@ -3566,6 +3573,49 @@ int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp,
}
EXPORT_SYMBOL_GPL(xdp_do_redirect);

+static int dev_map_redirect_multi(struct net_device *dev, struct sk_buff *skb,
+ struct bpf_prog *xdp_prog,
+ struct bpf_map *map, struct bpf_map *ex_map,
+ bool exclude_ingress)
+
+{
+ struct bpf_dtab_netdev *dst;
+ struct sk_buff *nskb;
+ u32 key, next_key;
+ int err;
+ void *fwd;
+
+ /* Get first key from forward map */
+ map->ops->map_get_next_key(map, NULL, &key);
+
+ for (;;) {
+ fwd = __xdp_map_lookup_elem(map, key);
+ if (fwd) {
+ dst = (struct bpf_dtab_netdev *)fwd;
+ if (dev_in_exclude_map(dst, ex_map,
+ exclude_ingress ? dev->ifindex : 0))
+ goto find_next;
+
+ nskb = skb_clone(skb, GFP_ATOMIC);
+ if (!nskb)
+ return -EOVERFLOW;
+
+ err = dev_map_generic_redirect(dst, nskb, xdp_prog);
+ if (unlikely(err))
+ return err;
+ }
+
+find_next:
+ err = map->ops->map_get_next_key(map, &key, &next_key);
+ if (err)
+ break;
+
+ key = next_key;
+ }
+
+ return 0;
+}
+
static int xdp_do_generic_redirect_map(struct net_device *dev,
struct sk_buff *skb,
struct xdp_buff *xdp,
@@ -3573,6 +3623,8 @@ static int xdp_do_generic_redirect_map(struct net_device *dev,
struct bpf_map *map)
{
struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+ bool exclude_ingress = !!(ri->flags & BPF_F_EXCLUDE_INGRESS);
+ struct bpf_map *ex_map = READ_ONCE(ri->ex_map);
u32 index = ri->tgt_index;
void *fwd = ri->tgt_value;
int err = 0;
@@ -3583,9 +3635,16 @@ static int xdp_do_generic_redirect_map(struct net_device *dev,

if (map->map_type == BPF_MAP_TYPE_DEVMAP ||
map->map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
- struct bpf_dtab_netdev *dst = fwd;
+ if (fwd) {
+ struct bpf_dtab_netdev *dst = fwd;
+
+ err = dev_map_generic_redirect(dst, skb, xdp_prog);
+ } else {
+ /* Deal with multicast maps */
+ err = dev_map_redirect_multi(dev, skb, xdp_prog, map,
+ ex_map, exclude_ingress);
+ }

- err = dev_map_generic_redirect(dst, skb, xdp_prog);
if (unlikely(err))
goto err;
} else if (map->map_type == BPF_MAP_TYPE_XSKMAP) {
@@ -3699,6 +3758,33 @@ static const struct bpf_func_proto bpf_xdp_redirect_map_proto = {
.arg3_type = ARG_ANYTHING,
};

+BPF_CALL_3(bpf_xdp_redirect_map_multi, struct bpf_map *, map,
+ struct bpf_map *, ex_map, u64, flags)
+{
+ struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+
+ if (unlikely(!map || flags > BPF_F_EXCLUDE_INGRESS))
+ return XDP_ABORTED;
+
+ ri->tgt_index = 0;
+ ri->tgt_value = NULL;
+ ri->flags = flags;
+
+ WRITE_ONCE(ri->map, map);
+ WRITE_ONCE(ri->ex_map, ex_map);
+
+ return XDP_REDIRECT;
+}
+
+static const struct bpf_func_proto bpf_xdp_redirect_map_multi_proto = {
+ .func = bpf_xdp_redirect_map_multi,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_CONST_MAP_PTR,
+ .arg1_type = ARG_CONST_MAP_PTR,
+ .arg3_type = ARG_ANYTHING,
+};
+
static unsigned long bpf_skb_copy(void *dst_buff, const void *skb,
unsigned long off, unsigned long len)
{
@@ -6304,6 +6390,8 @@ xdp_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_xdp_redirect_proto;
case BPF_FUNC_redirect_map:
return &bpf_xdp_redirect_map_proto;
+ case BPF_FUNC_redirect_map_multi:
+ return &bpf_xdp_redirect_map_multi_proto;
case BPF_FUNC_xdp_adjust_tail:
return &bpf_xdp_adjust_tail_proto;
case BPF_FUNC_fib_lookup:
diff --git a/net/core/xdp.c b/net/core/xdp.c
index 4c7ea85486af..70dfb4910f84 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -496,3 +496,29 @@ struct xdp_frame *xdp_convert_zc_to_xdp_frame(struct xdp_buff *xdp)
return xdpf;
}
EXPORT_SYMBOL_GPL(xdp_convert_zc_to_xdp_frame);
+
+struct xdp_frame *xdpf_clone(struct xdp_frame *xdpf)
+{
+ unsigned int headroom, totalsize;
+ struct xdp_frame *nxdpf;
+ struct page *page;
+ void *addr;
+
+ headroom = xdpf->headroom + sizeof(*xdpf);
+ totalsize = headroom + xdpf->len;
+
+ if (unlikely(totalsize > PAGE_SIZE))
+ return NULL;
+ page = dev_alloc_page();
+ if (!page)
+ return NULL;
+ addr = page_to_virt(page);
+
+ memcpy(addr, xdpf, totalsize);
+
+ nxdpf = addr;
+ nxdpf->data = addr + headroom;
+
+ return nxdpf;
+}
+EXPORT_SYMBOL_GPL(xdpf_clone);
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 2e29a671d67e..1dbe42290223 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3025,6 +3025,21 @@ union bpf_attr {
* * **-EOPNOTSUPP** Unsupported operation, for example a
* call from outside of TC ingress.
* * **-ESOCKTNOSUPPORT** Socket type not supported (reuseport).
+ *
+ * int bpf_redirect_map_multi(struct bpf_map *map, struct bpf_map *ex_map, u64 flags)
+ * Description
+ * Redirect the packet to all the interfaces in *map*, and
+ * exclude the interfaces that in *ex_map*. The *ex_map* could
+ * be NULL.
+ *
+ * Currently the *flags* only supports *BPF_F_EXCLUDE_INGRESS*,
+ * which could exlcude redirect to the ingress device.
+ *
+ * See also bpf_redirect_map(), which supports redirecting
+ * packet to a specific ifindex in the map.
+ * Return
+ * **XDP_REDIRECT** on success, or **XDP_ABORTED** on error.
+ *
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3151,7 +3166,8 @@ union bpf_attr {
FN(xdp_output), \
FN(get_netns_cookie), \
FN(get_current_ancestor_cgroup_id), \
- FN(sk_assign),
+ FN(sk_assign), \
+ FN(redirect_map_multi),

/* integer value in 'imm' field of BPF_CALL instruction selects which helper
* function eBPF program intends to call
@@ -3280,6 +3296,11 @@ enum bpf_lwt_encap_mode {
BPF_LWT_ENCAP_IP,
};

+/* BPF_FUNC_redirect_map_multi flags. */
+enum {
+ BPF_F_EXCLUDE_INGRESS = (1ULL << 0),
+};
+
#define __bpf_md_ptr(type, name) \
union { \
type name; \
--
2.19.2