BACKPORT: UPSTREAM: Add a helper function to get socket cookie in eBPF

Cherrypick from commit: 91b8270f2a4d1d9b268de90451cdca63a70052d6

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>
Bug: 30950746
Change-Id: I95918dcc3ceffb3061495a859d28aee88e3cde3c

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);
 

include/uapi/linux/bpf.h

@@ -486,6 +486,15 @@ enum bpf_func_id {
 	 */
 	BPF_FUNC_probe_read_str,
 
+	/**
+	 * 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
+	 */
+	BPF_FUNC_get_socket_cookie,
+
 	__BPF_FUNC_MAX_ID,
 };
 

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>
@@ -2534,6 +2535,18 @@ static const struct bpf_func_proto bpf_xdp_event_output_proto = {
 	.arg5_type	= ARG_CONST_STACK_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 *
 sk_filter_func_proto(enum bpf_func_id func_id)
 {
@@ -2555,6 +2568,8 @@ sk_filter_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;
 	}

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);

tools/include/uapi/linux/bpf.h

@@ -456,6 +456,16 @@ enum bpf_func_id {
 	 */
 	BPF_FUNC_probe_read_str,
 
+	/**
+	 * u64 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
+	 */
+	BPF_FUNC_get_socket_cookie,
+
 	__BPF_FUNC_MAX_ID,
 };