bpf: Support socket lookup in CGROUP_SOCK_ADDR progs

Make bpf_sk_lookup_tcp, bpf_sk_lookup_udp and bpf_sk_release helpers
available in programs of type BPF_PROG_TYPE_CGROUP_SOCK_ADDR.

Such programs operate on sockets and have access to socket and struct
sockaddr passed by user to system calls such as sys_bind, sys_connect,
sys_sendmsg.

It's useful to be able to lookup other sockets from these programs.
E.g. sys_connect may lookup IP:port endpoint and if there is a server
socket bound to that endpoint ("server" can be defined by saddr & sport
being zero), redirect client connection to it by rewriting IP:port in
sockaddr passed to sys_connect.
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

net/core/filter.c

@@ -5042,6 +5042,43 @@ static const struct bpf_func_proto bpf_xdp_sk_lookup_tcp_proto = {
 	.arg4_type      = ARG_ANYTHING,
 	.arg5_type      = ARG_ANYTHING,
 };
+
+BPF_CALL_5(bpf_sock_addr_sk_lookup_tcp, struct bpf_sock_addr_kern *, ctx,
+	   struct bpf_sock_tuple *, tuple, u32, len, u64, netns_id, u64, flags)
+{
+	return __bpf_sk_lookup(NULL, tuple, len, sock_net(ctx->sk), 0,
+			       IPPROTO_TCP, netns_id, flags);
+}
+
+static const struct bpf_func_proto bpf_sock_addr_sk_lookup_tcp_proto = {
+	.func		= bpf_sock_addr_sk_lookup_tcp,
+	.gpl_only	= false,
+	.ret_type	= RET_PTR_TO_SOCKET_OR_NULL,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_PTR_TO_MEM,
+	.arg3_type	= ARG_CONST_SIZE,
+	.arg4_type	= ARG_ANYTHING,
+	.arg5_type	= ARG_ANYTHING,
+};
+
+BPF_CALL_5(bpf_sock_addr_sk_lookup_udp, struct bpf_sock_addr_kern *, ctx,
+	   struct bpf_sock_tuple *, tuple, u32, len, u64, netns_id, u64, flags)
+{
+	return __bpf_sk_lookup(NULL, tuple, len, sock_net(ctx->sk), 0,
+			       IPPROTO_UDP, netns_id, flags);
+}
+
+static const struct bpf_func_proto bpf_sock_addr_sk_lookup_udp_proto = {
+	.func		= bpf_sock_addr_sk_lookup_udp,
+	.gpl_only	= false,
+	.ret_type	= RET_PTR_TO_SOCKET_OR_NULL,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_PTR_TO_MEM,
+	.arg3_type	= ARG_CONST_SIZE,
+	.arg4_type	= ARG_ANYTHING,
+	.arg5_type	= ARG_ANYTHING,
+};
+
 #endif /* CONFIG_INET */
 
 bool bpf_helper_changes_pkt_data(void *func)
@@ -5148,6 +5185,14 @@ sock_addr_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_get_socket_cookie_sock_addr_proto;
 	case BPF_FUNC_get_local_storage:
 		return &bpf_get_local_storage_proto;
+#ifdef CONFIG_INET
+	case BPF_FUNC_sk_lookup_tcp:
+		return &bpf_sock_addr_sk_lookup_tcp_proto;
+	case BPF_FUNC_sk_lookup_udp:
+		return &bpf_sock_addr_sk_lookup_udp_proto;
+	case BPF_FUNC_sk_release:
+		return &bpf_sk_release_proto;
+#endif /* CONFIG_INET */
 	default:
 		return bpf_base_func_proto(func_id);
 	}