flow_dissector: implements flow dissector BPF hook

Adds a hook for programs of type BPF_PROG_TYPE_FLOW_DISSECTOR and
attach type BPF_FLOW_DISSECTOR that is executed in the flow dissector
path. The BPF program is per-network namespace.

Signed-off-by: Petar Penkov <ppenkov@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 523481a3471b56675be927329c02ac6789902133..988a00797bcd7dfed289fdf1975d5573559cfb18 100644 (file)
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -212,6 +212,7 @@ enum bpf_reg_type {
        PTR_TO_PACKET_META,      /* skb->data - meta_len */
        PTR_TO_PACKET,           /* reg points to skb->data */
        PTR_TO_PACKET_END,       /* skb->data + headlen */
+       PTR_TO_FLOW_KEYS,        /* reg points to bpf_flow_keys */
 };
 
 /* The information passed from prog-specific *_is_valid_access

diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
index cd26c090e7c06a27171dbd0be2fcbe5bee4a92a8..22083712dd18d71a83e4922d96e74eae84678f90 100644 (file)
--- a/include/linux/bpf_types.h
+++ b/include/linux/bpf_types.h
@@ -32,6 +32,7 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_LIRC_MODE2, lirc_mode2)
 #ifdef CONFIG_INET
 BPF_PROG_TYPE(BPF_PROG_TYPE_SK_REUSEPORT, sk_reuseport)
 #endif
+BPF_PROG_TYPE(BPF_PROG_TYPE_FLOW_DISSECTOR, flow_dissector)
 
 BPF_MAP_TYPE(BPF_MAP_TYPE_ARRAY, array_map_ops)
 BPF_MAP_TYPE(BPF_MAP_TYPE_PERCPU_ARRAY, percpu_array_map_ops)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 17a13e4785fc3c15594c8aaee5132c44449a954a..ce0e863f02a2500425cfbbedd99a553942aee6af 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -243,6 +243,8 @@ struct scatterlist;
 struct pipe_inode_info;
 struct iov_iter;
 struct napi_struct;
+struct bpf_prog;
+union bpf_attr;
 
 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
 struct nf_conntrack {
@@ -1192,6 +1194,11 @@ void skb_flow_dissector_init(struct flow_dissector *flow_dissector,
                             const struct flow_dissector_key *key,
                             unsigned int key_count);
 
+int skb_flow_dissector_bpf_prog_attach(const union bpf_attr *attr,
+                                      struct bpf_prog *prog);
+
+int skb_flow_dissector_bpf_prog_detach(const union bpf_attr *attr);
+
 bool __skb_flow_dissect(const struct sk_buff *skb,
                        struct flow_dissector *flow_dissector,
                        void *target_container,

diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index 9b5fdc50519acfbc6ab9219579e742fe79193194..99d4148e0f903fe7f3a3d2f112104777591068b3 100644 (file)
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -43,6 +43,7 @@ struct ctl_table_header;
 struct net_generic;
 struct uevent_sock;
 struct netns_ipvs;
+struct bpf_prog;
 
 
 #define NETDEV_HASHBITS    8
@@ -145,6 +146,8 @@ struct net {
 #endif
        struct net_generic __rcu        *gen;
 
+       struct bpf_prog __rcu   *flow_dissector_prog;
+
        /* Note : following structs are cache line aligned */
 #ifdef CONFIG_XFRM
        struct netns_xfrm       xfrm;

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index a6d00093f35e70d9b5da920be22ae4fd1db0bb6a..1b81ba85fd2d75bb6fb5d82ebbd0fb064efec001 100644 (file)
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -19,6 +19,7 @@ struct Qdisc_ops;
 struct qdisc_walker;
 struct tcf_walker;
 struct module;
+struct bpf_flow_keys;
 
 typedef int tc_setup_cb_t(enum tc_setup_type type,
                          void *type_data, void *cb_priv);
@@ -307,9 +308,14 @@ struct tcf_proto {
 };
 
 struct qdisc_skb_cb {
-       unsigned int            pkt_len;
-       u16                     slave_dev_queue_mapping;
-       u16                     tc_classid;
+       union {
+               struct {
+                       unsigned int            pkt_len;
+                       u16                     slave_dev_queue_mapping;
+                       u16                     tc_classid;
+               };
+               struct bpf_flow_keys *flow_keys;
+       };
 #define QDISC_CB_PRIV_LEN 20
        unsigned char           data[QDISC_CB_PRIV_LEN];
 };

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 66917a4eba2716ebdef75a78e854f4e9874c88b9..aa5ccd2385ed196c817cb00fb32db55e799af234 100644 (file)
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -152,6 +152,7 @@ enum bpf_prog_type {
        BPF_PROG_TYPE_LWT_SEG6LOCAL,
        BPF_PROG_TYPE_LIRC_MODE2,
        BPF_PROG_TYPE_SK_REUSEPORT,
+       BPF_PROG_TYPE_FLOW_DISSECTOR,
 };
 
 enum bpf_attach_type {
@@ -172,6 +173,7 @@ enum bpf_attach_type {
        BPF_CGROUP_UDP4_SENDMSG,
        BPF_CGROUP_UDP6_SENDMSG,
        BPF_LIRC_MODE2,
+       BPF_FLOW_DISSECTOR,
        __MAX_BPF_ATTACH_TYPE
 };
 
@@ -2333,6 +2335,7 @@ struct __sk_buff {
        /* ... here. */
 
        __u32 data_meta;
+       struct bpf_flow_keys *flow_keys;
 };
 
 struct bpf_tunnel_key {
@@ -2778,4 +2781,27 @@ enum bpf_task_fd_type {
        BPF_FD_TYPE_URETPROBE,          /* filename + offset */
 };
 
+struct bpf_flow_keys {
+       __u16   nhoff;
+       __u16   thoff;
+       __u16   addr_proto;                     /* ETH_P_* of valid addrs */
+       __u8    is_frag;
+       __u8    is_first_frag;
+       __u8    is_encap;
+       __u8    ip_proto;
+       __be16  n_proto;
+       __be16  sport;
+       __be16  dport;
+       union {
+               struct {
+                       __be32  ipv4_src;
+                       __be32  ipv4_dst;
+               };
+               struct {
+                       __u32   ipv6_src[4];    /* in6_addr; network order */
+                       __u32   ipv6_dst[4];    /* in6_addr; network order */
+               };
+       };
+};
+
 #endif /* _UAPI__LINUX_BPF_H__ */

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 3c9636f03bb2e65411f5276c21a5d444d91d3580..b3c2d09bcf7a8e0ce162806e858cdb8fea336154 100644 (file)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1615,6 +1615,9 @@ static int bpf_prog_attach(const union bpf_attr *attr)
        case BPF_LIRC_MODE2:
                ptype = BPF_PROG_TYPE_LIRC_MODE2;
                break;
+       case BPF_FLOW_DISSECTOR:
+               ptype = BPF_PROG_TYPE_FLOW_DISSECTOR;
+               break;
        default:
                return -EINVAL;
        }
@@ -1636,6 +1639,9 @@ static int bpf_prog_attach(const union bpf_attr *attr)
        case BPF_PROG_TYPE_LIRC_MODE2:
                ret = lirc_prog_attach(attr, prog);
                break;
+       case BPF_PROG_TYPE_FLOW_DISSECTOR:
+               ret = skb_flow_dissector_bpf_prog_attach(attr, prog);
+               break;
        default:
                ret = cgroup_bpf_prog_attach(attr, ptype, prog);
        }
@@ -1688,6 +1694,8 @@ static int bpf_prog_detach(const union bpf_attr *attr)
                return sockmap_get_from_fd(attr, BPF_PROG_TYPE_SK_SKB, NULL);
        case BPF_LIRC_MODE2:
                return lirc_prog_detach(attr);
+       case BPF_FLOW_DISSECTOR:
+               return skb_flow_dissector_bpf_prog_detach(attr);
        default:
                return -EINVAL;
        }

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 6ff1bac1795df3b132076f99b4b4db44d6974198..8ccbff4fff93915d84f97d5a7b97eb375ae94e19 100644 (file)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -261,6 +261,7 @@ static const char * const reg_type_str[] = {
        [PTR_TO_PACKET]         = "pkt",
        [PTR_TO_PACKET_META]    = "pkt_meta",
        [PTR_TO_PACKET_END]     = "pkt_end",
+       [PTR_TO_FLOW_KEYS]      = "flow_keys",
 };
 
 static char slot_type_char[] = {
@@ -965,6 +966,7 @@ static bool is_spillable_regtype(enum bpf_reg_type type)
        case PTR_TO_PACKET:
        case PTR_TO_PACKET_META:
        case PTR_TO_PACKET_END:
+       case PTR_TO_FLOW_KEYS:
        case CONST_PTR_TO_MAP:
                return true;
        default:
@@ -1238,6 +1240,7 @@ static bool may_access_direct_pkt_data(struct bpf_verifier_env *env,
        case BPF_PROG_TYPE_LWT_XMIT:
        case BPF_PROG_TYPE_SK_SKB:
        case BPF_PROG_TYPE_SK_MSG:
+       case BPF_PROG_TYPE_FLOW_DISSECTOR:
                if (meta)
                        return meta->pkt_access;
 
@@ -1321,6 +1324,18 @@ static int check_ctx_access(struct bpf_verifier_env *env, int insn_idx, int off,
        return -EACCES;
 }
 
+static int check_flow_keys_access(struct bpf_verifier_env *env, int off,
+                                 int size)
+{
+       if (size < 0 || off < 0 ||
+           (u64)off + size > sizeof(struct bpf_flow_keys)) {
+               verbose(env, "invalid access to flow keys off=%d size=%d\n",
+                       off, size);
+               return -EACCES;
+       }
+       return 0;
+}
+
 static bool __is_pointer_value(bool allow_ptr_leaks,
                               const struct bpf_reg_state *reg)
 {
@@ -1422,6 +1437,9 @@ static int check_ptr_alignment(struct bpf_verifier_env *env,
                 * right in front, treat it the very same way.
                 */
                return check_pkt_ptr_alignment(env, reg, off, size, strict);
+       case PTR_TO_FLOW_KEYS:
+               pointer_desc = "flow keys ";
+               break;
        case PTR_TO_MAP_VALUE:
                pointer_desc = "value ";
                break;
@@ -1692,6 +1710,17 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
                err = check_packet_access(env, regno, off, size, false);
                if (!err && t == BPF_READ && value_regno >= 0)
                        mark_reg_unknown(env, regs, value_regno);
+       } else if (reg->type == PTR_TO_FLOW_KEYS) {
+               if (t == BPF_WRITE && value_regno >= 0 &&
+                   is_pointer_value(env, value_regno)) {
+                       verbose(env, "R%d leaks addr into flow keys\n",
+                               value_regno);
+                       return -EACCES;
+               }
+
+               err = check_flow_keys_access(env, off, size);
+               if (!err && t == BPF_READ && value_regno >= 0)
+                       mark_reg_unknown(env, regs, value_regno);
        } else {
                verbose(env, "R%d invalid mem access '%s'\n", regno,
                        reg_type_str[reg->type]);
@@ -1839,6 +1868,8 @@ static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
        case PTR_TO_PACKET_META:
                return check_packet_access(env, regno, reg->off, access_size,
                                           zero_size_allowed);
+       case PTR_TO_FLOW_KEYS:
+               return check_flow_keys_access(env, reg->off, access_size);
        case PTR_TO_MAP_VALUE:
                return check_map_access(env, regno, reg->off, access_size,
                                        zero_size_allowed);
@@ -4366,6 +4397,7 @@ static bool regsafe(struct bpf_reg_state *rold, struct bpf_reg_state *rcur,
        case PTR_TO_CTX:
        case CONST_PTR_TO_MAP:
        case PTR_TO_PACKET_END:
+       case PTR_TO_FLOW_KEYS:
                /* Only valid matches are exact, which memcmp() above
                 * would have accepted
                 */

diff --git a/net/core/filter.c b/net/core/filter.c
index bf5b6efd369a59ef4938fa6eb8cab2c0a1836929..9cc76f134ddbed4eb5db78ca2c863abd48e88aef 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5123,6 +5123,17 @@ sk_skb_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
        }
 }
 
+static const struct bpf_func_proto *
+flow_dissector_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
+{
+       switch (func_id) {
+       case BPF_FUNC_skb_load_bytes:
+               return &bpf_skb_load_bytes_proto;
+       default:
+               return bpf_base_func_proto(func_id);
+       }
+}
+
 static const struct bpf_func_proto *
 lwt_out_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
@@ -5241,6 +5252,10 @@ static bool bpf_skb_is_valid_access(int off, int size, enum bpf_access_type type
                if (size != size_default)
                        return false;
                break;
+       case bpf_ctx_range(struct __sk_buff, flow_keys):
+               if (size != sizeof(struct bpf_flow_keys *))
+                       return false;
+               break;
        default:
                /* Only narrow read access allowed for now. */
                if (type == BPF_WRITE) {
@@ -5266,6 +5281,7 @@ static bool sk_filter_is_valid_access(int off, int size,
        case bpf_ctx_range(struct __sk_buff, data):
        case bpf_ctx_range(struct __sk_buff, data_meta):
        case bpf_ctx_range(struct __sk_buff, data_end):
+       case bpf_ctx_range(struct __sk_buff, flow_keys):
        case bpf_ctx_range_till(struct __sk_buff, family, local_port):
                return false;
        }
@@ -5291,6 +5307,7 @@ static bool lwt_is_valid_access(int off, int size,
        case bpf_ctx_range(struct __sk_buff, tc_classid):
        case bpf_ctx_range_till(struct __sk_buff, family, local_port):
        case bpf_ctx_range(struct __sk_buff, data_meta):
+       case bpf_ctx_range(struct __sk_buff, flow_keys):
                return false;
        }
 
@@ -5501,6 +5518,7 @@ static bool tc_cls_act_is_valid_access(int off, int size,
        case bpf_ctx_range(struct __sk_buff, data_end):
                info->reg_type = PTR_TO_PACKET_END;
                break;
+       case bpf_ctx_range(struct __sk_buff, flow_keys):
        case bpf_ctx_range_till(struct __sk_buff, family, local_port):
                return false;
        }
@@ -5702,6 +5720,7 @@ static bool sk_skb_is_valid_access(int off, int size,
        switch (off) {
        case bpf_ctx_range(struct __sk_buff, tc_classid):
        case bpf_ctx_range(struct __sk_buff, data_meta):
+       case bpf_ctx_range(struct __sk_buff, flow_keys):
                return false;
        }
 
@@ -5761,6 +5780,39 @@ static bool sk_msg_is_valid_access(int off, int size,
        return true;
 }
 
+static bool flow_dissector_is_valid_access(int off, int size,
+                                          enum bpf_access_type type,
+                                          const struct bpf_prog *prog,
+                                          struct bpf_insn_access_aux *info)
+{
+       if (type == BPF_WRITE) {
+               switch (off) {
+               case bpf_ctx_range_till(struct __sk_buff, cb[0], cb[4]):
+                       break;
+               default:
+                       return false;
+               }
+       }
+
+       switch (off) {
+       case bpf_ctx_range(struct __sk_buff, data):
+               info->reg_type = PTR_TO_PACKET;
+               break;
+       case bpf_ctx_range(struct __sk_buff, data_end):
+               info->reg_type = PTR_TO_PACKET_END;
+               break;
+       case bpf_ctx_range(struct __sk_buff, flow_keys):
+               info->reg_type = PTR_TO_FLOW_KEYS;
+               break;
+       case bpf_ctx_range(struct __sk_buff, tc_classid):
+       case bpf_ctx_range(struct __sk_buff, data_meta):
+       case bpf_ctx_range_till(struct __sk_buff, family, local_port):
+               return false;
+       }
+
+       return bpf_skb_is_valid_access(off, size, type, prog, info);
+}
+
 static u32 bpf_convert_ctx_access(enum bpf_access_type type,
                                  const struct bpf_insn *si,
                                  struct bpf_insn *insn_buf,
@@ -6055,6 +6107,15 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type,
                                      bpf_target_off(struct sock_common,
                                                     skc_num, 2, target_size));
                break;
+
+       case offsetof(struct __sk_buff, flow_keys):
+               off  = si->off;
+               off -= offsetof(struct __sk_buff, flow_keys);
+               off += offsetof(struct sk_buff, cb);
+               off += offsetof(struct qdisc_skb_cb, flow_keys);
+               *insn++ = BPF_LDX_MEM(BPF_SIZEOF(void *), si->dst_reg,
+                                     si->src_reg, off);
+               break;
        }
 
        return insn - insn_buf;
@@ -7018,6 +7079,15 @@ const struct bpf_verifier_ops sk_msg_verifier_ops = {
 const struct bpf_prog_ops sk_msg_prog_ops = {
 };
 
+const struct bpf_verifier_ops flow_dissector_verifier_ops = {
+       .get_func_proto         = flow_dissector_func_proto,
+       .is_valid_access        = flow_dissector_is_valid_access,
+       .convert_ctx_access     = bpf_convert_ctx_access,
+};
+
+const struct bpf_prog_ops flow_dissector_prog_ops = {
+};
+
 int sk_detach_filter(struct sock *sk)
 {
        int ret = -ENOENT;

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index ce9eeeb7c024c8ab98ca77a03317105c73b8e108..5c5dd74b5b3b03d730f7b859eafb564009f6feb2 100644 (file)
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -25,6 +25,9 @@
 #include <net/flow_dissector.h>
 #include <scsi/fc/fc_fcoe.h>
 #include <uapi/linux/batadv_packet.h>
+#include <linux/bpf.h>
+
+static DEFINE_MUTEX(flow_dissector_mutex);
 
 static void dissector_set_key(struct flow_dissector *flow_dissector,
                              enum flow_dissector_key_id key_id)
@@ -62,6 +65,44 @@ void skb_flow_dissector_init(struct flow_dissector *flow_dissector,
 }
 EXPORT_SYMBOL(skb_flow_dissector_init);
 
+int skb_flow_dissector_bpf_prog_attach(const union bpf_attr *attr,
+                                      struct bpf_prog *prog)
+{
+       struct bpf_prog *attached;
+       struct net *net;
+
+       net = current->nsproxy->net_ns;
+       mutex_lock(&flow_dissector_mutex);
+       attached = rcu_dereference_protected(net->flow_dissector_prog,
+                                            lockdep_is_held(&flow_dissector_mutex));
+       if (attached) {
+               /* Only one BPF program can be attached at a time */
+               mutex_unlock(&flow_dissector_mutex);
+               return -EEXIST;
+       }
+       rcu_assign_pointer(net->flow_dissector_prog, prog);
+       mutex_unlock(&flow_dissector_mutex);
+       return 0;
+}
+
+int skb_flow_dissector_bpf_prog_detach(const union bpf_attr *attr)
+{
+       struct bpf_prog *attached;
+       struct net *net;
+
+       net = current->nsproxy->net_ns;
+       mutex_lock(&flow_dissector_mutex);
+       attached = rcu_dereference_protected(net->flow_dissector_prog,
+                                            lockdep_is_held(&flow_dissector_mutex));
+       if (!attached) {
+               mutex_unlock(&flow_dissector_mutex);
+               return -ENOENT;
+       }
+       bpf_prog_put(attached);
+       RCU_INIT_POINTER(net->flow_dissector_prog, NULL);
+       mutex_unlock(&flow_dissector_mutex);
+       return 0;
+}
 /**
  * skb_flow_get_be16 - extract be16 entity
  * @skb: sk_buff to extract from
@@ -588,6 +629,60 @@ static bool skb_flow_dissect_allowed(int *num_hdrs)
        return (*num_hdrs <= MAX_FLOW_DISSECT_HDRS);
 }
 
+static void __skb_flow_bpf_to_target(const struct bpf_flow_keys *flow_keys,
+                                    struct flow_dissector *flow_dissector,
+                                    void *target_container)
+{
+       struct flow_dissector_key_control *key_control;
+       struct flow_dissector_key_basic *key_basic;
+       struct flow_dissector_key_addrs *key_addrs;
+       struct flow_dissector_key_ports *key_ports;
+
+       key_control = skb_flow_dissector_target(flow_dissector,
+                                               FLOW_DISSECTOR_KEY_CONTROL,
+                                               target_container);
+       key_control->thoff = flow_keys->thoff;
+       if (flow_keys->is_frag)
+               key_control->flags |= FLOW_DIS_IS_FRAGMENT;
+       if (flow_keys->is_first_frag)
+               key_control->flags |= FLOW_DIS_FIRST_FRAG;
+       if (flow_keys->is_encap)
+               key_control->flags |= FLOW_DIS_ENCAPSULATION;
+
+       key_basic = skb_flow_dissector_target(flow_dissector,
+                                             FLOW_DISSECTOR_KEY_BASIC,
+                                             target_container);
+       key_basic->n_proto = flow_keys->n_proto;
+       key_basic->ip_proto = flow_keys->ip_proto;
+
+       if (flow_keys->addr_proto == ETH_P_IP &&
+           dissector_uses_key(flow_dissector, FLOW_DISSECTOR_KEY_IPV4_ADDRS)) {
+               key_addrs = skb_flow_dissector_target(flow_dissector,
+                                                     FLOW_DISSECTOR_KEY_IPV4_ADDRS,
+                                                     target_container);
+               key_addrs->v4addrs.src = flow_keys->ipv4_src;
+               key_addrs->v4addrs.dst = flow_keys->ipv4_dst;
+               key_control->addr_type = FLOW_DISSECTOR_KEY_IPV4_ADDRS;
+       } else if (flow_keys->addr_proto == ETH_P_IPV6 &&
+                  dissector_uses_key(flow_dissector,
+                                     FLOW_DISSECTOR_KEY_IPV6_ADDRS)) {
+               key_addrs = skb_flow_dissector_target(flow_dissector,
+                                                     FLOW_DISSECTOR_KEY_IPV6_ADDRS,
+                                                     target_container);
+               memcpy(&key_addrs->v6addrs, &flow_keys->ipv6_src,
+                      sizeof(key_addrs->v6addrs));
+               key_control->addr_type = FLOW_DISSECTOR_KEY_IPV6_ADDRS;
+       }
+
+       if (dissector_uses_key(flow_dissector, FLOW_DISSECTOR_KEY_PORTS)) {
+               key_ports = skb_flow_dissector_target(flow_dissector,
+                                                     FLOW_DISSECTOR_KEY_PORTS,
+                                                     target_container);
+               key_ports->src = flow_keys->sport;
+               key_ports->dst = flow_keys->dport;
+       }
+}
+
 /**
  * __skb_flow_dissect - extract the flow_keys struct and return it
  * @skb: sk_buff to extract the flow from, can be NULL if the rest are specified
@@ -619,6 +714,7 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
        struct flow_dissector_key_vlan *key_vlan;
        enum flow_dissect_ret fdret;
        enum flow_dissector_key_id dissector_vlan = FLOW_DISSECTOR_KEY_MAX;
+       struct bpf_prog *attached;
        int num_hdrs = 0;
        u8 ip_proto = 0;
        bool ret;
@@ -658,6 +754,44 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
                                              FLOW_DISSECTOR_KEY_BASIC,
                                              target_container);
 
+       rcu_read_lock();
+       attached = skb ? rcu_dereference(dev_net(skb->dev)->flow_dissector_prog)
+                      : NULL;
+       if (attached) {
+               /* Note that even though the const qualifier is discarded
+                * throughout the execution of the BPF program, all changes(the
+                * control block) are reverted after the BPF program returns.
+                * Therefore, __skb_flow_dissect does not alter the skb.
+                */
+               struct bpf_flow_keys flow_keys = {};
+               struct bpf_skb_data_end cb_saved;
+               struct bpf_skb_data_end *cb;
+               u32 result;
+
+               cb = (struct bpf_skb_data_end *)skb->cb;
+
+               /* Save Control Block */
+               memcpy(&cb_saved, cb, sizeof(cb_saved));
+               memset(cb, 0, sizeof(cb_saved));
+
+               /* Pass parameters to the BPF program */
+               cb->qdisc_cb.flow_keys = &flow_keys;
+               flow_keys.nhoff = nhoff;
+
+               bpf_compute_data_pointers((struct sk_buff *)skb);
+               result = BPF_PROG_RUN(attached, skb);
+
+               /* Restore state */
+               memcpy(cb, &cb_saved, sizeof(cb_saved));
+
+               __skb_flow_bpf_to_target(&flow_keys, flow_dissector,
+                                        target_container);
+               key_control->thoff = min_t(u16, key_control->thoff, skb->len);
+               rcu_read_unlock();
+               return result == BPF_OK;
+       }
+       rcu_read_unlock();
+
        if (dissector_uses_key(flow_dissector,
                               FLOW_DISSECTOR_KEY_ETH_ADDRS)) {
                struct ethhdr *eth = eth_hdr(skb);