bpf: Adding helper function bpf_getsockops

Adding support for helper function bpf_getsockops to socket_ops BPF
programs. This patch only supports TCP_CONGESTION.

Signed-off-by: Vlad Vysotsky <vlad@cs.ucla.edu>
Acked-by: Lawrence Brakmo <brakmo@fb.com>
Acked-by: Alexei Starovoitov <ast@fb.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 63 insertions, 5 deletions

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 1aca744c220f..f650346aaa1a 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -613,12 +613,22 @@ union bpf_attr {
  * int bpf_setsockopt(bpf_socket, level, optname, optval, optlen)
  *     Calls setsockopt. Not all opts are available, only those with
  *     integer optvals plus TCP_CONGESTION.
- *     Supported levels: SOL_SOCKET and IPROTO_TCP
+ *     Supported levels: SOL_SOCKET and IPPROTO_TCP
  *     @bpf_socket: pointer to bpf_socket
- *     @level: SOL_SOCKET or IPROTO_TCP
+ *     @level: SOL_SOCKET or IPPROTO_TCP
  *     @optname: option name
  *     @optval: pointer to option value
- *     @optlen: length of optval in byes
+ *     @optlen: length of optval in bytes
+ *     Return: 0 or negative error
+ *
+ * int bpf_getsockopt(bpf_socket, level, optname, optval, optlen)
+ *     Calls getsockopt. Not all opts are available.
+ *     Supported levels: IPPROTO_TCP
+ *     @bpf_socket: pointer to bpf_socket
+ *     @level: IPPROTO_TCP
+ *     @optname: option name
+ *     @optval: pointer to option value
+ *     @optlen: length of optval in bytes
  *     Return: 0 or negative error
  *
  * int bpf_skb_adjust_room(skb, len_diff, mode, flags)
@@ -721,7 +731,8 @@ union bpf_attr {
         FN(sock_map_update),            \
         FN(xdp_adjust_meta),            \
         FN(perf_event_read_value),      \
-        FN(perf_prog_read_value),
+        FN(perf_prog_read_value),       \
+        FN(getsockopt),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call
diff --git a/net/core/filter.c b/net/core/filter.c
index 09e011f20291..ccf62f44140a 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3273,7 +3273,7 @@ BPF_CALL_5(bpf_setsockopt, struct bpf_sock_ops_kern *, bpf_sock,
 
 static const struct bpf_func_proto bpf_setsockopt_proto = {
         .func           = bpf_setsockopt,
-        .gpl_only       = true,
+        .gpl_only       = false,
         .ret_type       = RET_INTEGER,
         .arg1_type      = ARG_PTR_TO_CTX,
         .arg2_type      = ARG_ANYTHING,
@@ -3282,6 +3282,48 @@ static const struct bpf_func_proto bpf_setsockopt_proto = {
         .arg5_type      = ARG_CONST_SIZE,
 };
 
+BPF_CALL_5(bpf_getsockopt, struct bpf_sock_ops_kern *, bpf_sock,
+           int, level, int, optname, char *, optval, int, optlen)
+{
+        struct sock *sk = bpf_sock->sk;
+        int ret = 0;
+
+        if (!sk_fullsock(sk))
+                goto err_clear;
+
+#ifdef CONFIG_INET
+        if (level == SOL_TCP && sk->sk_prot->getsockopt == tcp_getsockopt) {
+                if (optname == TCP_CONGESTION) {
+                        struct inet_connection_sock *icsk = inet_csk(sk);
+
+                        if (!icsk->icsk_ca_ops || optlen <= 1)
+                                goto err_clear;
+                        strncpy(optval, icsk->icsk_ca_ops->name, optlen);
+                        optval[optlen - 1] = 0;
+                } else {
+                        goto err_clear;
+                }
+        } else {
+                goto err_clear;
+        }
+        return ret;
+#endif
+err_clear:
+        memset(optval, 0, optlen);
+        return -EINVAL;
+}
+
+static const struct bpf_func_proto bpf_getsockopt_proto = {
+        .func           = bpf_getsockopt,
+        .gpl_only       = false,
+        .ret_type       = RET_INTEGER,
+        .arg1_type      = ARG_PTR_TO_CTX,
+        .arg2_type      = ARG_ANYTHING,
+        .arg3_type      = ARG_ANYTHING,
+        .arg4_type      = ARG_PTR_TO_UNINIT_MEM,
+        .arg5_type      = ARG_CONST_SIZE,
+};
+
 static const struct bpf_func_proto *
 bpf_base_func_proto(enum bpf_func_id func_id)
 {
@@ -3460,6 +3502,8 @@ static const struct bpf_func_proto *
         switch (func_id) {
         case BPF_FUNC_setsockopt:
                 return &bpf_setsockopt_proto;
+        case BPF_FUNC_getsockopt:
+                return &bpf_getsockopt_proto;
         case BPF_FUNC_sock_map_update:
                 return &bpf_sock_map_update_proto;
         default:
diff --git a/tools/testing/selftests/bpf/bpf_helpers.h b/tools/testing/selftests/bpf/bpf_helpers.h
index e25dbf6038cf..609514f74482 100644
--- a/tools/testing/selftests/bpf/bpf_helpers.h
+++ b/tools/testing/selftests/bpf/bpf_helpers.h
@@ -67,6 +67,9 @@ static int (*bpf_xdp_adjust_meta)(void *ctx, int offset) =
 static int (*bpf_setsockopt)(void *ctx, int level, int optname, void *optval,
                              int optlen) =
         (void *) BPF_FUNC_setsockopt;
+static int (*bpf_getsockopt)(void *ctx, int level, int optname, void *optval,
+                             int optlen) =
+        (void *) BPF_FUNC_getsockopt;
 static int (*bpf_sk_redirect_map)(void *map, int key, int flags) =
         (void *) BPF_FUNC_sk_redirect_map;
 static int (*bpf_sock_map_update)(void *map, void *key, void *value,