Add a eBPF helper function to retrieve socket uid

Returns the owner uid of the socket inside a sk_buff. This is useful to
perform per-UID accounting of network traffic or per-UID packet
filtering. The socket need to be a fullsock otherwise overflowuid is
returned.

Signed-off-by: Chenbo Feng <fengc@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index cdfc5595fbc1ba962eb8bf0474c1a0266ca68f8d..28317a04c34de769d5cf69842aa930559627d6c7 100644 (file)
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -465,6 +465,12 @@ union bpf_attr {
  *     @skb: pointer to skb
  *     Return: 8 Bytes non-decreasing number on success or 0 if the socket
  *     field is missing inside sk_buff
+ *
+ * u32 bpf_get_socket_uid(skb)
+ *     Get the owner uid of the socket stored inside sk_buff.
+ *     @skb: pointer to skb
+ *     Return: uid of the socket owner on success or 0 if the socket pointer
+ *     inside sk_buff is NULL
  */
 #define __BPF_FUNC_MAPPER(FN)          \
        FN(unspec),                     \
@@ -513,7 +519,8 @@ union bpf_attr {
        FN(skb_change_head),            \
        FN(xdp_adjust_head),            \
        FN(probe_read_str),             \
-       FN(get_socket_cookie),
+       FN(get_socket_cookie),          \
+       FN(get_socket_uid),
 
 /* 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 35b0f97c3fdf92197eed8622121f0fbcff60fcaf..dfb9f61a2fd53a4ca7f53133600dc5913268b1a9 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2619,6 +2619,24 @@ static const struct bpf_func_proto bpf_get_socket_cookie_proto = {
        .arg1_type      = ARG_PTR_TO_CTX,
 };
 
+BPF_CALL_1(bpf_get_socket_uid, struct sk_buff *, skb)
+{
+       struct sock *sk = sk_to_full_sk(skb->sk);
+       kuid_t kuid;
+
+       if (!sk || !sk_fullsock(sk))
+               return overflowuid;
+       kuid = sock_net_uid(sock_net(sk), sk);
+       return from_kuid_munged(sock_net(sk)->user_ns, kuid);
+}
+
+static const struct bpf_func_proto bpf_get_socket_uid_proto = {
+       .func           = bpf_get_socket_uid,
+       .gpl_only       = false,
+       .ret_type       = RET_INTEGER,
+       .arg1_type      = ARG_PTR_TO_CTX,
+};
+
 static const struct bpf_func_proto *
 bpf_base_func_proto(enum bpf_func_id func_id)
 {
@@ -2655,6 +2673,8 @@ sk_filter_func_proto(enum bpf_func_id func_id)
                return &bpf_skb_load_bytes_proto;
        case BPF_FUNC_get_socket_cookie:
                return &bpf_get_socket_cookie_proto;
+       case BPF_FUNC_get_socket_uid:
+               return &bpf_get_socket_uid_proto;
        default:
                return bpf_base_func_proto(func_id);
        }
@@ -2716,6 +2736,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id)
                return &bpf_skb_under_cgroup_proto;
        case BPF_FUNC_get_socket_cookie:
                return &bpf_get_socket_cookie_proto;
+       case BPF_FUNC_get_socket_uid:
+               return &bpf_get_socket_uid_proto;
        default:
                return bpf_base_func_proto(func_id);
        }

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index a3851859e5f3bd40a8e6d7178b59711430b21b69..1ea08ce355678c0cd3f20d67ebb7b82dbe7f4a93 100644 (file)
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -507,7 +507,8 @@ union bpf_attr {
        FN(skb_change_head),            \
        FN(xdp_adjust_head),            \
        FN(probe_read_str),             \
-       FN(get_socket_cookie),
+       FN(get_socket_cookie),          \
+       FN(get_socket_uid),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call