[RFC PATCH 07/16] bpf/crib: Add struct sock related CRIB kfuncs

[Juntong Deng]

This patch adds struct sock related CRIB kfuncs.

bpf_sock_from_socket() is used to get struct sock from struct socket
and bpf_sock_from_task_fd() is used to get the struct sock corresponding
to the task file descriptor. Both kfuncs will acquires a reference to
struct sock.

bpf_sock_acquire()/bpf_sock_release() are used to acquire/release
reference on struct sock.

Signed-off-by: Juntong Deng <juntong.deng@xxxxxxxxxxx>
---
 kernel/bpf/crib/bpf_crib.c | 82 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)

diff --git a/kernel/bpf/crib/bpf_crib.c b/kernel/bpf/crib/bpf_crib.c
index b901d7d60290..d83e5f0e8bfc 100644
--- a/kernel/bpf/crib/bpf_crib.c
+++ b/kernel/bpf/crib/bpf_crib.c
@@ -9,6 +9,7 @@
 #include <linux/bpf_crib.h>
 #include <linux/init.h>
 #include <linux/fdtable.h>
+#include <net/sock.h>
 
 __bpf_kfunc_start_defs();
 
@@ -45,6 +46,82 @@ __bpf_kfunc void bpf_file_release(struct file *file)
 	fput(file);
 }
 
+/**
+ * bpf_sock_acquire() - Acquire a reference to struct sock
+ *
+ * @sk: struct sock that needs to acquire a reference
+ *
+ * @returns struct sock that has acquired the reference
+ */
+__bpf_kfunc struct sock *bpf_sock_acquire(struct sock *sk)
+{
+	sock_hold(sk);
+	return sk;
+}
+
+/**
+ * bpf_sock_release() - Release the reference acquired on struct sock.
+ *
+ * @sk: struct sock that has acquired the reference
+ */
+__bpf_kfunc void bpf_sock_release(struct sock *sk)
+{
+	sock_put(sk);
+}
+
+/**
+ * bpf_sock_from_socket() - Get struct sock from struct socket, and acquire
+ * a reference to struct sock.
+ *
+ * Note that this function acquires a reference to struct sock.
+ *
+ * @sock: specified struct socket
+ *
+ * @returns a pointer to the struct sock
+ */
+__bpf_kfunc struct sock *bpf_sock_from_socket(struct socket *sock)
+{
+	struct sock *sk = sock->sk;
+
+	bpf_sock_acquire(sk);
+	return sk;
+}
+
+/**
+ * bpf_sock_from_task_fd() - Get a pointer to the struct sock
+ * corresponding to the task file descriptor.
+ *
+ * Note that this function acquires a reference to struct sock.
+ *
+ * @task: specified struct task_struct
+ * @fd: file descriptor
+ *
+ * @returns the corresponding struct sock pointer if found,
+ * otherwise returns NULL.
+ */
+__bpf_kfunc struct sock *bpf_sock_from_task_fd(struct task_struct *task, int fd)
+{
+	struct file *file;
+	struct socket *sock;
+	struct sock *sk;
+
+	file = bpf_file_from_task_fd(task, fd);
+	if (!file)
+		return NULL;
+
+	sock = sock_from_file(file);
+	if (!sock) {
+		bpf_file_release(file);
+		return NULL;
+	}
+
+	sk = sock->sk;
+
+	bpf_sock_acquire(sk);
+	bpf_file_release(file);
+	return sk;
+}
+
 __bpf_kfunc_end_defs();
 
 BTF_KFUNCS_START(bpf_crib_kfuncs)
@@ -57,6 +134,11 @@ BTF_ID_FLAGS(func, bpf_iter_task_file_next, KF_ITER_NEXT | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_iter_task_file_get_fd, KF_ITER_GETTER)
 BTF_ID_FLAGS(func, bpf_iter_task_file_destroy, KF_ITER_DESTROY)
 
+BTF_ID_FLAGS(func, bpf_sock_acquire, KF_ACQUIRE | KF_TRUSTED_ARGS)
+BTF_ID_FLAGS(func, bpf_sock_release, KF_RELEASE)
+BTF_ID_FLAGS(func, bpf_sock_from_socket, KF_ACQUIRE | KF_TRUSTED_ARGS)
+BTF_ID_FLAGS(func, bpf_sock_from_task_fd, KF_ACQUIRE | KF_TRUSTED_ARGS | KF_RET_NULL)
+
 BTF_KFUNCS_END(bpf_crib_kfuncs)
 
 static int bpf_prog_run_crib(struct bpf_prog *prog,
-- 
2.39.2