bpf, sockmap: convert to generic sk_msg interface

Add a generic sk_msg layer, and convert current sockmap and later
kTLS over to make use of it. While sk_buff handles network packet
representation from netdevice up to socket, sk_msg handles data
representation from application to socket layer.

This means that sk_msg framework spans across ULP users in the
kernel, and enables features such as introspection or filtering
of data with the help of BPF programs that operate on this data
structure.

Latter becomes in particular useful for kTLS where data encryption
is deferred into the kernel, and as such enabling the kernel to
perform L7 introspection and policy based on BPF for TLS connections
where the record is being encrypted after BPF has run and came to
a verdict. In order to get there, first step is to transform open
coding of scatter-gather list handling into a common core framework
that subsystems can use.

The code itself has been split and refactored into three bigger
pieces: i) the generic sk_msg API which deals with managing the
scatter gather ring, providing helpers for walking and mangling,
transferring application data from user space into it, and preparing
it for BPF pre/post-processing, ii) the plain sock map itself
where sockets can be attached to or detached from; these bits
are independent of i) which can now be used also without sock
map, and iii) the integration with plain TCP as one protocol
to be used for processing L7 application data (later this could
e.g. also be extended to other protocols like UDP). The semantics
are the same with the old sock map code and therefore no change
of user facing behavior or APIs. While pursuing this work it
also helped finding a number of bugs in the old sockmap code
that we've fixed already in earlier commits. The test_sockmap
kselftest suite passes through fine as well.

Joint work with John.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

include/linux/bpf.h

@@ -737,33 +737,18 @@ static inline void bpf_map_offload_map_free(struct bpf_map *map)
 }
 #endif /* CONFIG_NET && CONFIG_BPF_SYSCALL */
 
-#if defined(CONFIG_STREAM_PARSER) && defined(CONFIG_BPF_SYSCALL) && defined(CONFIG_INET)
-struct sock  *__sock_map_lookup_elem(struct bpf_map *map, u32 key);
-struct sock  *__sock_hash_lookup_elem(struct bpf_map *map, void *key);
-int sock_map_prog(struct bpf_map *map, struct bpf_prog *prog, u32 type);
-int sockmap_get_from_fd(const union bpf_attr *attr, int type,
-			struct bpf_prog *prog);
+#if defined(CONFIG_BPF_STREAM_PARSER)
+int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog, u32 which);
+int sock_map_get_from_fd(const union bpf_attr *attr, struct bpf_prog *prog);
 #else
-static inline struct sock  *__sock_map_lookup_elem(struct bpf_map *map, u32 key)
-{
-	return NULL;
-}
-
-static inline struct sock  *__sock_hash_lookup_elem(struct bpf_map *map,
-						    void *key)
-{
-	return NULL;
-}
-
-static inline int sock_map_prog(struct bpf_map *map,
-				struct bpf_prog *prog,
-				u32 type)
+static inline int sock_map_prog_update(struct bpf_map *map,
+				       struct bpf_prog *prog, u32 which)
 {
 	return -EOPNOTSUPP;
 }
 
-static inline int sockmap_get_from_fd(const union bpf_attr *attr, int type,
-				      struct bpf_prog *prog)
+static inline int sock_map_get_from_fd(const union bpf_attr *attr,
+				       struct bpf_prog *prog)
 {
 	return -EINVAL;
 }
@@ -839,6 +824,10 @@ extern const struct bpf_func_proto bpf_get_stack_proto;
 extern const struct bpf_func_proto bpf_sock_map_update_proto;
 extern const struct bpf_func_proto bpf_sock_hash_update_proto;
 extern const struct bpf_func_proto bpf_get_current_cgroup_id_proto;
+extern const struct bpf_func_proto bpf_msg_redirect_hash_proto;
+extern const struct bpf_func_proto bpf_msg_redirect_map_proto;
+extern const struct bpf_func_proto bpf_sk_redirect_hash_proto;
+extern const struct bpf_func_proto bpf_sk_redirect_map_proto;
 
 extern const struct bpf_func_proto bpf_get_local_storage_proto;
 

include/linux/bpf_types.h

@@ -57,7 +57,7 @@ BPF_MAP_TYPE(BPF_MAP_TYPE_ARRAY_OF_MAPS, array_of_maps_map_ops)
 BPF_MAP_TYPE(BPF_MAP_TYPE_HASH_OF_MAPS, htab_of_maps_map_ops)
 #ifdef CONFIG_NET
 BPF_MAP_TYPE(BPF_MAP_TYPE_DEVMAP, dev_map_ops)
-#if defined(CONFIG_STREAM_PARSER) && defined(CONFIG_INET)
+#if defined(CONFIG_BPF_STREAM_PARSER)
 BPF_MAP_TYPE(BPF_MAP_TYPE_SOCKMAP, sock_map_ops)
 BPF_MAP_TYPE(BPF_MAP_TYPE_SOCKHASH, sock_hash_ops)
 #endif

include/linux/filter.h

@@ -520,24 +520,6 @@ struct bpf_skb_data_end {
 	void *data_end;
 };
 
-struct sk_msg_buff {
-	void *data;
-	void *data_end;
-	__u32 apply_bytes;
-	__u32 cork_bytes;
-	int sg_copybreak;
-	int sg_start;
-	int sg_curr;
-	int sg_end;
-	struct scatterlist sg_data[MAX_SKB_FRAGS];
-	bool sg_copy[MAX_SKB_FRAGS];
-	__u32 flags;
-	struct sock *sk_redir;
-	struct sock *sk;
-	struct sk_buff *skb;
-	struct list_head list;
-};
-
 struct bpf_redirect_info {
 	u32 ifindex;
 	u32 flags;
@@ -833,9 +815,6 @@ void xdp_do_flush_map(void);
 
 void bpf_warn_invalid_xdp_action(u32 act);
 
-struct sock *do_sk_redirect_map(struct sk_buff *skb);
-struct sock *do_msg_redirect_map(struct sk_msg_buff *md);
-
 #ifdef CONFIG_INET
 struct sock *bpf_run_sk_reuseport(struct sock_reuseport *reuse, struct sock *sk,
 				  struct bpf_prog *prog, struct sk_buff *skb,