Add a helper function to get socket cookie in eBPF

Retrieve the socket cookie generated by sock_gen_cookie() from a sk_buff
with a known socket. Generates a new cookie if one was not yet set.If
the socket pointer inside sk_buff is NULL, 0 is returned. The helper
function coud be useful in monitoring per socket networking traffic
statistics and provide a unique socket identifier per namespace.

Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Chenbo Feng <fengc@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

5 files changed, 29 insertions, 3 deletions

diff --git a/include/linux/sock_diag.h b/include/linux/sock_diag.h
index a0596ca0e80a..a2f8109bb215 100644
--- a/include/linux/sock_diag.h
+++ b/include/linux/sock_diag.h
@@ -24,6 +24,7 @@ void sock_diag_unregister(const struct sock_diag_handler *h);
 void sock_diag_register_inet_compat(int (*fn)(struct sk_buff *skb, struct nlmsghdr *nlh));
 void sock_diag_unregister_inet_compat(int (*fn)(struct sk_buff *skb, struct nlmsghdr *nlh));
 
+u64 sock_gen_cookie(struct sock *sk);
 int sock_diag_check_cookie(struct sock *sk, const __u32 *cookie);
 void sock_diag_save_cookie(struct sock *sk, __u32 *cookie);
 
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index ce6f029ac368..cdfc5595fbc1 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -459,6 +459,12 @@ union bpf_attr {
  *     Return:
  *       > 0 length of the string including the trailing NUL on success
  *       < 0 error
+ *
+ * u64 bpf_bpf_get_socket_cookie(skb)
+ *     Get the cookie for the socket stored inside sk_buff.
+ *     @skb: pointer to skb
+ *     Return: 8 Bytes non-decreasing number on success or 0 if the socket
+ *     field is missing inside sk_buff
  */
 #define __BPF_FUNC_MAPPER(FN)           \
         FN(unspec),                     \
@@ -506,7 +512,8 @@ union bpf_attr {
         FN(get_numa_node_id),           \
         FN(skb_change_head),            \
         FN(xdp_adjust_head),            \
-        FN(probe_read_str),
+        FN(probe_read_str),             \
+        FN(get_socket_cookie),
 
 /* 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 c7f0ccd1c0d3..35b0f97c3fdf 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -26,6 +26,7 @@
 #include <linux/mm.h>
 #include <linux/fcntl.h>
 #include <linux/socket.h>
+#include <linux/sock_diag.h>
 #include <linux/in.h>
 #include <linux/inet.h>
 #include <linux/netdevice.h>
@@ -2606,6 +2607,18 @@ static const struct bpf_func_proto bpf_xdp_event_output_proto = {
         .arg5_type      = ARG_CONST_SIZE,
 };
 
+BPF_CALL_1(bpf_get_socket_cookie, struct sk_buff *, skb)
+{
+        return skb->sk ? sock_gen_cookie(skb->sk) : 0;
+}
+
+static const struct bpf_func_proto bpf_get_socket_cookie_proto = {
+        .func           = bpf_get_socket_cookie,
+        .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)
 {
@@ -2640,6 +2653,8 @@ sk_filter_func_proto(enum bpf_func_id func_id)
         switch (func_id) {
         case BPF_FUNC_skb_load_bytes:
                 return &bpf_skb_load_bytes_proto;
+        case BPF_FUNC_get_socket_cookie:
+                return &bpf_get_socket_cookie_proto;
         default:
                 return bpf_base_func_proto(func_id);
         }
@@ -2699,6 +2714,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id)
                 return &bpf_get_smp_processor_id_proto;
         case BPF_FUNC_skb_under_cgroup:
                 return &bpf_skb_under_cgroup_proto;
+        case BPF_FUNC_get_socket_cookie:
+                return &bpf_get_socket_cookie_proto;
         default:
                 return bpf_base_func_proto(func_id);
         }
diff --git a/net/core/sock_diag.c b/net/core/sock_diag.c
index 8d11ee75a100..fb9d0e2fd148 100644
--- a/net/core/sock_diag.c
+++ b/net/core/sock_diag.c
@@ -19,7 +19,7 @@ static int (*inet_rcv_compat)(struct sk_buff *skb, struct nlmsghdr *nlh);
 static DEFINE_MUTEX(sock_diag_table_mutex);
 static struct workqueue_struct *broadcast_wq;
 
-static u64 sock_gen_cookie(struct sock *sk)
+u64 sock_gen_cookie(struct sock *sk)
 {
         while (1) {
                 u64 res = atomic64_read(&sk->sk_cookie);
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index ce6f029ac368..a3851859e5f3 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -506,7 +506,8 @@ union bpf_attr {
         FN(get_numa_node_id),           \
         FN(skb_change_head),            \
         FN(xdp_adjust_head),            \
-        FN(probe_read_str),
+        FN(probe_read_str),             \
+        FN(get_socket_cookie),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call