[PATCH net-next v2 1/2] Add a helper function to get socket cookie in eBPF

[Chenbo Feng <chenbofeng.kernel@gmail.com>]

From: Chenbo Feng <fengc@google.com>

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.

Signed-off-by: Chenbo Feng <chenbofeng.kernel@gmail.com>
---
 include/linux/sock_diag.h |  1 +
 include/uapi/linux/bpf.h  |  9 ++++++++-
 net/core/filter.c         | 15 +++++++++++++++
 net/core/sock_diag.c      |  2 +-
 4 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/include/linux/sock_diag.h b/include/linux/sock_diag.h
index a0596ca0..a2f8109 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 e07fd5a..6923d21 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -449,6 +449,12 @@ 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),			\
@@ -496,7 +502,8 @@ 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 0b753cb..632fb91 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>
@@ -2599,6 +2600,18 @@ 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)
 {
@@ -2622,6 +2635,8 @@ bpf_base_func_proto(enum bpf_func_id func_id)
 	case BPF_FUNC_trace_printk:
 		if (capable(CAP_SYS_ADMIN))
 			return bpf_get_trace_printk_proto();
+	case BPF_FUNC_get_socket_cookie:
+		return &bpf_get_socket_cookie_proto;
 	default:
 		return NULL;
 	}
diff --git a/net/core/sock_diag.c b/net/core/sock_diag.c
index 6b10573..acd2a6c 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);
-- 
2.7.4