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# 6.7 MAC Policy Entry Point Reference

## 6.7.1 General-Purpose Module Entry Points

### 6.7.1.1 `mpo_init`

``void mpo_init`(struct mac_policy_conf *conf);`

Parameter | Description | Locking
--- | --- | ---
`conf` | MAC policy definition |

Policy load event. The policy list mutex is held, so sleep operations cannot be performed, and calls out to other kernel subsystems must be made with caution. If potentially sleeping memory allocations are required during policy initialization, they should be made using a separate module SYSINIT().

### 6.7.1.2 `mpo_destroy`

``void mpo_destroy`(struct mac_policy_conf *conf);`

Parameter | Description | Locking
--- | --- | ---
`conf` | MAC policy definition |

Policy load event. The policy list mutex is held, so caution should be applied.

### 6.7.1.3 `mpo_syscall`

``int mpo_syscall`(struct thread *td, int call, void *arg);`

Parameter | Description | Locking
--- | --- | ---
`td` | Calling thread |
`call` | Policy-specific syscall number |
`arg` | Pointer to syscall arguments |

This entry point provides a policy-multiplexed system call so that policies may provide additional services to user processes without registering specific system calls. The policy name provided during registration is used to demux calls from userland, and the arguments will be forwarded to this entry point. When implementing new services, security modules should be sure to invoke appropriate access control checks from the MAC framework as needed. For example, if a policy implements an augmented signal functionality, it should call the necessary signal access control checks to invoke the MAC framework and other registered policies.

> Note: Modules must currently perform the `copyin()` of the syscall data on their own.

### 6.7.1.4 `mpo_thread_userret`

``void mpo_thread_userret`(struct thread *td);`

Parameter | Description | Locking
--- | --- | ---
`td` | Returning thread |

This entry point permits policy modules to perform MAC-related events when a thread returns to user space, via a system call return, trap return, or otherwise. This is required for policies that have floating process labels, as it is not always possible to acquire the process lock at arbitrary points in the stack during system call processing; process labels might represent traditional authentication data, process history information, or other data. To employ this mechanism, intended changes to the process credential label may be stored in the `p_label` protected by a per-policy spin lock, and then set the per-thread `TDF_ASTPENDING` flag and per-process `PS_MACPENDM` flag to schedule a call to the userret entry point. From this entry point, the policy may create a replacement credential with less concern about the locking context. Policy writers are cautioned that event ordering relating to scheduling an AST and the AST being performed may be complex and interlaced in multithreaded applications.

## 6.7.2 Label Operations

### 6.7.2.1 `mpo_init_bpfdesc_label`

``void mpo_init_bpfdesc_label`(struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`label` | New label to apply |

Initialize the label on a newly instantiated bpfdesc (BPF descriptor). Sleeping is permitted.

### 6.7.2.2 `mpo_init_cred_label`

``void mpo_init_cred_label`(struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`label` | New label to initialize |

Initialize the label for a newly instantiated user credential. Sleeping is permitted.

### 6.7.2.3 `mpo_init_devfsdirent_label`

``void mpo_init_devfsdirent_label`(struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`label` | New label to apply |

Initialize the label on a newly instantiated devfs entry. Sleeping is permitted.

### 6.7.2.4 `mpo_init_ifnet_label`

``void mpo_init_ifnet_label`(struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`label` | New label to apply |

Initialize the label on a newly instantiated network interface. Sleeping is permitted.

### 6.7.2.5 `mpo_init_ipq_label`

``void mpo_init_ipq_label`(struct label *label, int flag);`

Parameter | Description | Locking
--- | --- | ---
`label` | New label to apply |
`flag` | Sleeping/non-sleeping malloc(9); see below |

Initialize the label on a newly instantiated IP fragment reassembly queue. The `flag` field may be one of `M_WAITOK` and `M_NOWAIT`, and should be employed to avoid performing a sleeping malloc(9) during this initialization call. IP fragment reassembly queue allocation frequently occurs in performance sensitive environments, and the implementation should be careful to avoid sleeping or long-lived operations. This entry point is permitted to fail resulting in the failure to allocate the IP fragment reassembly queue.

### 6.7.2.6 `mpo_init_mbuf_label`

``void mpo_init_mbuf_label`(int flag, struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`flag` | Sleeping/non-sleeping malloc(9); see below |
`label` | Policy label to initialize |

Initialize the label on a newly instantiated mbuf packet header (`mbuf`). The `flag` field may be one of `M_WAITOK` and `M_NOWAIT`, and should be employed to avoid performing a sleeping malloc(9) during this initialization call. Mbuf allocation frequently occurs in performance sensitive environments, and the implementation should be careful to avoid sleeping or long-lived operations. This entry point is permitted to fail resulting in the failure to allocate the mbuf header.

### 6.7.2.7 `mpo_init_mount_label`

``void mpo_init_mount_label`(struct label *mntlabel, struct label *fslabel);`

Parameter | Description | Locking
--- | --- | ---
`mntlabel` | Policy label to be initialized for the mount itself |
`fslabel` | Policy label to be initialized for the file system |

Initialize the labels on a newly instantiated mount point. Sleeping is permitted.

### 6.7.2.8 `mpo_init_mount_fs_label`

``void mpo_init_mount_fs_label`(struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`label` | Label to be initialized |

Initialize the label on a newly mounted file system. Sleeping is permitted

### 6.7.2.9 `mpo_init_pipe_label`

``void mpo_init_pipe_label`(struct label*label);`

Parameter | Description | Locking
--- | --- | ---
`label` | Label to be filled in |

Initialize a label for a newly instantiated pipe. Sleeping is permitted.

### 6.7.2.10 `mpo_init_socket_label`

``void mpo_init_socket_label`(struct label *label, int flag);`

Parameter | Description | Locking
--- | --- | ---
`label` | New label to initialize |
`flag` | malloc(9) flags |

Initialize a label for a newly instantiated socket. The `flag` field may be one of `M_WAITOK` and `M_NOWAIT`, and should be employed to avoid performing a sleeping malloc(9) during this initialization call.

### 6.7.2.11 `mpo_init_socket_peer_label`

``void mpo_init_socket_peer_label`(struct label *label, int flag);`

Parameter | Description | Locking
--- | --- | ---
`label` | New label to initialize |
`flag` | malloc(9) flags |

Initialize the peer label for a newly instantiated socket. The `flag` field may be one of `M_WAITOK` and `M_NOWAIT`, and should be employed to avoid performing a sleeping malloc(9) during this initialization call.

### 6.7.2.12 `mpo_init_proc_label`

``void mpo_init_proc_label`(struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`label` | New label to initialize |

Initialize the label for a newly instantiated process. Sleeping is permitted.

### 6.7.2.13 `mpo_init_vnode_label`

``void mpo_init_vnode_label`(struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`label` | New label to initialize |

Initialize the label on a newly instantiated vnode. Sleeping is permitted.

### 6.7.2.14 `mpo_destroy_bpfdesc_label`

``void mpo_destroy_bpfdesc_label`(struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`label` | bpfdesc label |

Destroy the label on a BPF descriptor. In this entry point a policy should free any internal storage associated with `label` so that it may be destroyed.

### 6.7.2.15 `mpo_destroy_cred_label`

``void mpo_destroy_cred_label`(struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`label` | Label being destroyed |

Destroy the label on a credential. In this entry point, a policy module should free any internal storage associated with `label` so that it may be destroyed.

### 6.7.2.16 `mpo_destroy_devfsdirent_label`

``void mpo_destroy_devfsdirent_label`(struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`label` | Label being destroyed |

Destroy the label on a devfs entry. In this entry point, a policy module should free any internal storage associated with `label` so that it may be destroyed.

### 6.7.2.17 `mpo_destroy_ifnet_label`

``void mpo_destroy_ifnet_label`(struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`label` | Label being destroyed |

Destroy the label on a removed interface. In this entry point, a policy module should free any internal storage associated with `label` so that it may be destroyed.

### 6.7.2.18 `mpo_destroy_ipq_label`

``void mpo_destroy_ipq_label`(struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`label` | Label being destroyed |

Destroy the label on an IP fragment queue. In this entry point, a policy module should free any internal storage associated with `label` so that it may be destroyed.

### 6.7.2.19 `mpo_destroy_mbuf_label`

``void mpo_destroy_mbuf_label`(struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`label` | Label being destroyed |

Destroy the label on an mbuf header. In this entry point, a policy module should free any internal storage associated with `label` so that it may be destroyed.

### 6.7.2.20 `mpo_destroy_mount_label`

``void mpo_destroy_mount_label`(struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`label` | Mount point label being destroyed |

Destroy the labels on a mount point. In this entry point, a policy module should free the internal storage associated with `mntlabel` so that they may be destroyed.

### 6.7.2.21 `mpo_destroy_mount_label`

``void mpo_destroy_mount_label`(struct label *mntlabel, struct label *fslabel);`

Parameter | Description | Locking
--- | --- | ---
`mntlabel` | Mount point label being destroyed |
`fslabel` | File system label being destroyed> |

Destroy the labels on a mount point. In this entry point, a policy module should free the internal storage associated with `mntlabel` and `fslabel` so that they may be destroyed.

### 6.7.2.22 `mpo_destroy_socket_label`

``void mpo_destroy_socket_label`(struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`label` | Socket label being destroyed |

Destroy the label on a socket. In this entry point, a policy module should free any internal storage associated with `label` so that it may be destroyed.

### 6.7.2.23 `mpo_destroy_socket_peer_label`

``void mpo_destroy_socket_peer_label`(struct label *peerlabel);`

Parameter | Description | Locking
--- | --- | ---
`peerlabel` | Socket peer label being destroyed |

Destroy the peer label on a socket. In this entry point, a policy module should free any internal storage associated with `label` so that it may be destroyed.

### 6.7.2.24 `mpo_destroy_pipe_label`

``void mpo_destroy_pipe_label`(struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`label` | Pipe label |

Destroy the label on a pipe. In this entry point, a policy module should free any internal storage associated with `label` so that it may be destroyed.

### 6.7.2.25 `mpo_destroy_proc_label`

``void mpo_destroy_proc_label`(struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`label` | Process label |

Destroy the label on a process. In this entry point, a policy module should free any internal storage associated with `label` so that it may be destroyed.

### 6.7.2.26 `mpo_destroy_vnode_label`

``void mpo_destroy_vnode_label`(struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`label` | Process label |

Destroy the label on a vnode. In this entry point, a policy module should free any internal storage associated with `label` so that it may be destroyed.

### 6.7.2.27 `mpo_copy_mbuf_label`

``void mpo_copy_mbuf_label`(struct label *src, struct label *dest);`

Parameter | Description | Locking
--- | --- | ---
`src` | Source label |
`dest` | Destination label |

Copy the label information in `src` into `dest`.

### 6.7.2.28 `mpo_copy_pipe_label`

``void mpo_copy_pipe_label`(struct label *src, struct label *dest);`

Parameter | Description | Locking
--- | --- | ---
`src` | Source label |
`dest` | Destination label |

Copy the label information in `src` into `dest`.

### 6.7.2.29 `mpo_copy_vnode_label`

``void mpo_copy_vnode_label`(struct label *src, struct label *dest);`

Parameter | Description | Locking
--- | --- | ---
`src` | Source label |
`dest` | Destination label |

Copy the label information in `src` into `dest`.

### 6.7.2.30 `mpo_externalize_cred_label`

``int mpo_externalize_cred_label`(struct label *label, char *element_name, struct sbuf *sb, int *claimed);`

Parameter | Description | Locking
--- | --- | ---
`label` | Label to be externalized |
`element_name` | Name of the policy whose label should be externalized |
`sb` | String buffer to be filled with a text representation of label |
`claimed` | Should be incremented when `element_data` can be filled in. |

Produce an externalized label based on the label structure passed. An externalized label consists of a text representation of the label contents that can be used with userland applications and read by the user. Currently, all policies' `externalize` entry points will be called, so the implementation should check the contents of `element_name` before attempting to fill in `sb`. If `element_name` does not match the name of your policy, simply return 0. Only return nonzero if an error occurs while externalizing the label data. Once the policy fills in `element_data`, `*claimed` should be incremented.

### 6.7.2.31 `mpo_externalize_ifnet_label`

``int mpo_externalize_ifnet_label`(struct label *label, char *element_name, struct sbuf *sb, int *claimed);`

Parameter | Description | Locking
--- | --- | ---
`label` | Label to be externalized |
`element_name` | Name of the policy whose label should be externalized |
`sb` | String buffer to be filled with a text representation of label |
`claimed` | Should be incremented when `element_data` can be filled in. |

Produce an externalized label based on the label structure passed. An externalized label consists of a text representation of the label contents that can be used with userland applications and read by the user. Currently, all policies' `externalize` entry points will be called, so the implementation should check the contents of `element_name` before attempting to fill in `sb`. If `element_name` does not match the name of your policy, simply return 0. Only return nonzero if an error occurs while externalizing the label data. Once the policy fills in `element_data`, `*claimed` should be incremented.

### 6.7.2.32 `mpo_externalize_pipe_label`

``int mpo_externalize_pipe_label`(struct label *label, char *element_name, struct sbuf *sb, int *claimed);`

Parameter | Description | Locking
--- | --- | ---
`label` | Label to be externalized |
`element_name` | Name of the policy whose label should be externalized |
`sb` | String buffer to be filled with a text representation of label |
`claimed` | Should be incremented when `element_data` can be filled in. |

Produce an externalized label based on the label structure passed. An externalized label consists of a text representation of the label contents that can be used with userland applications and read by the user. Currently, all policies' `externalize` entry points will be called, so the implementation should check the contents of `element_name` before attempting to fill in `sb`. If `element_name` does not match the name of your policy, simply return 0. Only return nonzero if an error occurs while externalizing the label data. Once the policy fills in `element_data`, `*claimed` should be incremented.

### 6.7.2.33 `mpo_externalize_socket_label`

``int mpo_externalize_socket_label`(struct label *label, char *element_name, struct sbuf *sb, int *claimed);`

Parameter | Description | Locking
--- | --- | ---
`label` | Label to be externalized |
`element_name` | Name of the policy whose label should be externalized |
`sb` | String buffer to be filled with a text representation of label |
`claimed` | Should be incremented when `element_data` can be filled in. |

Produce an externalized label based on the label structure passed. An externalized label consists of a text representation of the label contents that can be used with userland applications and read by the user. Currently, all policies' `externalize` entry points will be called, so the implementation should check the contents of `element_name` before attempting to fill in `sb`. If `element_name` does not match the name of your policy, simply return 0. Only return nonzero if an error occurs while externalizing the label data. Once the policy fills in `element_data`, `*claimed` should be incremented.

### 6.7.2.34 `mpo_externalize_socket_peer_label`

``int mpo_externalize_socket_peer_label`(struct label *label, char *element_name, struct sbuf *sb, int *claimed);`

Parameter | Description | Locking
--- | --- | ---
`label` | Label to be externalized |
`element_name` | Name of the policy whose label should be externalized |
`sb` | String buffer to be filled with a text representation of label |
`claimed` | Should be incremented when `element_data` can be filled in. |

Produce an externalized label based on the label structure passed. An externalized label consists of a text representation of the label contents that can be used with userland applications and read by the user. Currently, all policies' `externalize` entry points will be called, so the implementation should check the contents of `element_name` before attempting to fill in `sb`. If `element_name` does not match the name of your policy, simply return 0. Only return nonzero if an error occurs while externalizing the label data. Once the policy fills in `element_data`, `*claimed` should be incremented.

### 6.7.2.35 `mpo_externalize_vnode_label`

``int mpo_externalize_vnode_label`(struct label *label, char *element_name, struct sbuf *sb, int *claimed);`

Parameter | Description | Locking
--- | --- | ---
`label` | Label to be externalized |
`element_name` | Name of the policy whose label should be externalized |
`sb` | String buffer to be filled with a text representation of label |
`claimed` | Should be incremented when `element_data` can be filled in. |

Produce an externalized label based on the label structure passed. An externalized label consists of a text representation of the label contents that can be used with userland applications and read by the user. Currently, all policies' `externalize` entry points will be called, so the implementation should check the contents of `element_name` before attempting to fill in `sb`. If `element_name` does not match the name of your policy, simply return 0. Only return nonzero if an error occurs while externalizing the label data. Once the policy fills in `element_data`, `*claimed` should be incremented.

### 6.7.2.36 `mpo_internalize_cred_label`

``int mpo_internalize_cred_label`(struct label *label, char *element_name, char *element_data, int *claimed);`

Parameter | Description | Locking
--- | --- | ---
`label` | Label to be filled in |
`element_name` | Name of the policy whose label should be internalized |
`element_data` | Text data to be internalized |
`claimed` | Should be incremented when data can be successfully internalized. |

Produce an internal label structure based on externalized label data in text format. Currently, all policies' `internalize` entry points are called when internalization is requested, so the implementation should compare the contents of `element_name` to its own name in order to be sure it should be internalizing the data in `element_data`. Just as in the `externalize` entry points, the entry point should return 0 if `element_name` does not match its own name, or when data can successfully be internalized, in which case `*claimed` should be incremented.

### 6.7.2.37 `mpo_internalize_ifnet_label`

``int mpo_internalize_ifnet_label`(struct label *label, char *element_name, char *element_data, int *claimed);`

Parameter | Description | Locking
--- | --- | ---
`label` | Label to be filled in |
`element_name` | Name of the policy whose label should be internalized |
`element_data` | Text data to be internalized |
`claimed` | Should be incremented when data can be successfully internalized. |

Produce an internal label structure based on externalized label data in text format. Currently, all policies' `internalize` entry points are called when internalization is requested, so the implementation should compare the contents of `element_name` to its own name in order to be sure it should be internalizing the data in `element_data`. Just as in the `externalize` entry points, the entry point should return 0 if `element_name` does not match its own name, or when data can successfully be internalized, in which case `*claimed` should be incremented.

### 6.7.2.38 `mpo_internalize_pipe_label`

``int mpo_internalize_pipe_label`(struct label *label, char *element_name, char *element_data, int *claimed);`

Parameter | Description | Locking
--- | --- | ---
`label` | Label to be filled in |
`element_name` | Name of the policy whose label should be internalized |
`element_data` | Text data to be internalized |
`claimed` | Should be incremented when data can be successfully internalized. |

Produce an internal label structure based on externalized label data in text format. Currently, all policies' `internalize` entry points are called when internalization is requested, so the implementation should compare the contents of `element_name` to its own name in order to be sure it should be internalizing the data in `element_data`. Just as in the `externalize` entry points, the entry point should return 0 if `element_name` does not match its own name, or when data can successfully be internalized, in which case `*claimed` should be incremented.

### 6.7.2.39 `mpo_internalize_socket_label`

``int mpo_internalize_socket_label`(struct label *label, char *element_name, char *element_data, int *claimed);`

Parameter | Description | Locking
--- | --- | ---
`label` | Label to be filled in |
`element_name` | Name of the policy whose label should be internalized |
`element_data` | Text data to be internalized |
`claimed` | Should be incremented when data can be successfully internalized. |

Produce an internal label structure based on externalized label data in text format. Currently, all policies' `internalize` entry points are called when internalization is requested, so the implementation should compare the contents of `element_name` to its own name in order to be sure it should be internalizing the data in `element_data`. Just as in the `externalize` entry points, the entry point should return 0 if `element_name` does not match its own name, or when data can successfully be internalized, in which case `*claimed` should be incremented.

### 6.7.2.40 `mpo_internalize_vnode_label`

``int mpo_internalize_vnode_label`(struct label *label, char *element_name, char *element_data, int *claimed);`

Parameter | Description | Locking
--- | --- | ---
`label` | Label to be filled in |
`element_name` | Name of the policy whose label should be internalized |
`element_data` | Text data to be internalized |
`claimed` | Should be incremented when data can be successfully internalized. |

Produce an internal label structure based on externalized label data in text format. Currently, all policies' `internalize` entry points are called when internalization is requested, so the implementation should compare the contents of `element_name` to its own name in order to be sure it should be internalizing the data in `element_data`. Just as in the `externalize` entry points, the entry point should return 0 if `element_name` does not match its own name, or when data can successfully be internalized, in which case `*claimed` should be incremented.

## 6.7.3 Label Events

This class of entry points is used by the MAC framework to permit policies to maintain label information on kernel objects. For each labeled kernel object of interest to a MAC policy, entry points may be registered for relevant life cycle events. All objects implement initialization, creation, and destruction hooks. Some objects will also implement relabeling, allowing user processes to change the labels on objects. Some objects will also implement object-specific events, such as label events associated with IP reassembly. A typical labeled object will have the following life cycle of entry points:

    Label initialization          o
    (object-specific wait)         \
    Label creation                  o
                                     \
    Relabel events,                   o--<--.
    Various object-specific,          |     |
    Access control events             ~-->--o
                                             \
    Label destruction                         o

Label initialization permits policies to allocate memory and set initial values for labels without context for the use of the object. The label slot allocated to a policy will be zeroed by default, so some policies may not need to perform initialization.

Label creation occurs when the kernel structure is associated with an actual kernel object. For example, Mbufs may be allocated and remain unused in a pool until they are required. mbuf allocation causes label initialization on the mbuf to take place, but mbuf creation occurs when the mbuf is associated with a datagram. Typically, context will be provided for a creation event, including the circumstances of the creation, and labels of other relevant objects in the creation process. For example, when an mbuf is created from a socket, the socket and its label will be presented to registered policies in addition to the new mbuf and its label. Memory allocation in creation events is discouraged, as it may occur in performance sensitive ports of the kernel; in addition, creation calls are not permitted to fail so a failure to allocate memory cannot be reported.

Object specific events do not generally fall into the other broad classes of label events, but will generally provide an opportunity to modify or update the label on an object based on additional context. For example, the label on an IP fragment reassembly queue may be updated during the `MAC_UPDATE_IPQ` entry point as a result of the acceptance of an additional mbuf to that queue.

Access control events are discussed in detail in the following section.

Label destruction permits policies to release storage or state associated with a label during its association with an object so that the kernel data structures supporting the object may be reused or released.

In addition to labels associated with specific kernel objects, an additional class of labels exists: temporary labels. These labels are used to store update information submitted by user processes. These labels are initialized and destroyed as with other label types, but the creation event is `MAC_INTERNALIZE`, which accepts a user label to be converted to an in-kernel representation.

### 6.7.3.1 File System Object Labeling Event Operations

#### 6.7.3.1.1 `mpo_associate_vnode_devfs`

``void mpo_associate_vnode_devfs`(struct mount *mp, struct label *fslabel, struct devfs_dirent *de, struct label *delabel, struct vnode *vp, struct label *vlabel);`

Parameter | Description | Locking
--- | --- | ---
`mp` | Devfs mount point |
`fslabel` | Devfs file system label (`mp->mnt_fslabel`) |
`de` | Devfs directory entry |
`delabel` | Policy label associated with `de` |
`vp` | vnode associated with `de` |
`vlabel` | Policy label associated with `vp` |

Fill in the label (`vlabel`) for a newly created devfs vnode based on the devfs directory entry passed in `de` and its label.

#### 6.7.3.1.2 `mpo_associate_vnode_extattr`

``int mpo_associate_vnode_extattr`(struct mount *mp, struct label *fslabel, struct vnode *vp, struct label *vlabel);`

Parameter | Description | Locking
--- | --- | ---
`mp` | File system mount point |
`fslabel` | File system label |
`vp` | Vnode to label |
`vlabel` | Policy label associated with `vp` |

Attempt to retrieve the label for `vp` from the file system extended attributes. Upon success, the value `0` is returned. Should extended attribute retrieval not be supported, an accepted fallback is to copy `fslabel` into `vlabel`. In the event of an error, an appropriate value for `errno` should be returned.

#### 6.7.3.1.3 `mpo_associate_vnode_singlelabel`

``void mpo_associate_vnode_singlelabel`(struct mount *mp, struct label *fslabel, struct vnode *vp, struct label *vlabel);`

Parameter | Description | Locking
--- | --- | ---
`mp` | File system mount point |
`fslabel` | File system label |
`vp` | Vnode to label |
`vlabel` | Policy label associated with `vp` |

On non-multilabel file systems, this entry point is called to set the policy label for `vp` based on the file system label, `fslabel`.

#### 6.7.3.1.4 `mpo_create_devfs_device`

``void mpo_create_devfs_device`(dev_t dev, struct devfs_dirent *devfs_dirent, struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`dev` | Device corresponding with `devfs_dirent` |
`devfs_dirent` | Devfs directory entry to be labeled. |
`label` | Label for `devfs_dirent` to be filled in. |

Fill out the label on a devfs_dirent being created for the passed device. This call will be made when the device file system is mounted, regenerated, or a new device is made available.

#### 6.7.3.1.5 `mpo_create_devfs_directory`

``void mpo_create_devfs_directory`(char *dirname, int dirnamelen, struct devfs_dirent *devfs_dirent, struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`dirname` | Name of directory being created |
`namelen` | Length of string `dirname` |
`devfs_dirent` | Devfs directory entry for directory being created. |

Fill out the label on a devfs_dirent being created for the passed directory. This call will be made when the device file system is mounted, regenerated, or a new device requiring a specific directory hierarchy is made available.

#### 6.7.3.1.6 `mpo_create_devfs_symlink`

``void mpo_create_devfs_symlink`(struct ucred *cred, struct mount *mp, struct devfs_dirent *dd, struct label *ddlabel, struct devfs_dirent *de, struct label *delabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`mp` | Devfs mount point |
`dd` | Link destination |
`ddlabel` | Label associated with `dd` |
`de` | Symlink entry |
`delabel` | Label associated with `de` |

Fill in the label (`delabel`) for a newly created devfs(5) symbolic link entry.

#### 6.7.3.1.7 `mpo_create_vnode_extattr`

``int mpo_create_vnode_extattr`(struct ucred *cred, struct mount *mp, struct label *fslabel, struct vnode *dvp, struct label *dlabel, struct vnode *vp, struct label *vlabel, struct componentname *cnp);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`mount` | File system mount point |
`label` | File system label |
`dvp` | Parent directory vnode |
`dlabel` | Label associated with `dvp` |
`vp` | Newly created vnode |
`vlabel` | Policy label associated with `vp` |
`cnp` | Component name for `vp` |

Write out the label for `vp` to the appropriate extended attribute. If the write succeeds, fill in `vlabel` with the label, and return 0. Otherwise, return an appropriate error.

#### 6.7.3.1.8 `mpo_create_mount`

``void mpo_create_mount`(struct ucred *cred, struct mount *mp, struct label *mnt, struct label *fslabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`mp` | Object; file system being mounted |
`mntlabel` | Policy label to be filled in for `mp` |
`fslabel` | Policy label for the file system `mp` mounts. |

Fill out the labels on the mount point being created by the passed subject credential. This call will be made when a new file system is mounted.

#### 6.7.3.1.9 `mpo_create_root_mount`

``void mpo_create_root_mount`(struct ucred *cred, struct mount *mp, struct label *mntlabel, struct label *fslabel);`

Parameter | Description | Locking
--- | --- | ---
See Section 6.7.3.1.8.

Fill out the labels on the mount point being created by the passed subject credential. This call will be made when the root file system is mounted, after mpo_create_mount;.

#### 6.7.3.1.10 `mpo_relabel_vnode`

``void mpo_relabel_vnode`(struct ucred *cred, struct vnode *vp, struct label *vnodelabel, struct label *newlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`vp` | vnode to relabel |
`vnodelabel` | Existing policy label for `vp` |
`newlabel` | New, possibly partial label to replace `vnodelabel` |

Update the label on the passed vnode given the passed update vnode label and the passed subject credential.

#### 6.7.3.1.11 `mpo_setlabel_vnode_extattr`

``int mpo_setlabel_vnode_extattr`(struct ucred *cred, struct vnode *vp, struct label *vlabel, struct label *intlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`vp` | Vnode for which the label is being written |
`vlabel` | Policy label associated with `vp` |
`intlabel` | Label to write out |

Write out the policy from `intlabel` to an extended attribute. This is called from `vop_stdcreatevnode_ea`.

#### 6.7.3.1.12 `mpo_update_devfsdirent`

``void mpo_update_devfsdirent`(struct devfs_dirent *devfs_dirent, struct label *direntlabel, struct vnode *vp, struct label *vnodelabel);`

Parameter | Description | Locking
--- | --- | ---
`devfs_dirent` | Object; devfs directory entry |
`direntlabel` | Policy label for `devfs_dirent` to be updated. |
`vp` | Parent vnode | Locked
`vnodelabel` | Policy label for `vp` |

Update the `devfs_dirent` label from the passed devfs vnode label. This call will be made when a devfs vnode has been successfully relabeled to commit the label change such that it lasts even if the vnode is recycled. It will also be made when a symlink is created in devfs, following a call to `mac_vnode_create_from_vnode` to initialize the vnode label.

### 6.7.3.2 IPC Object Labeling Event Operations

#### 6.7.3.2.1 `mpo_create_mbuf_from_socket`

``void mpo_create_mbuf_from_socket`(struct socket *so, struct label *socketlabel, struct mbuf *m, struct label *mbuflabel);`

Parameter | Description | Locking
--- | --- | ---
`socket` | Socket | Socket locking WIP
`socketlabel` | Policy label for `socket` |
`m` | Object; mbuf |
`mbuflabel` | Policy label to fill in for `m` |

Set the label on a newly created mbuf header from the passed socket label. This call is made when a new datagram or message is generated by the socket and stored in the passed mbuf.

#### 6.7.3.2.2 `mpo_create_pipe`

``void mpo_create_pipe`(struct ucred *cred, struct pipe *pipe, struct label *pipelabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`pipe` | Pipe |
`pipelabel` | Policy label associated with `pipe` |

Set the label on a newly created pipe from the passed subject credential. This call is made when a new pipe is created.

#### 6.7.3.2.3 `mpo_create_socket`

``void mpo_create_socket`(struct ucred *cred, struct socket *so, struct label *socketlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential | Immutable
`so` | Object; socket to label |
`socketlabel` | Label to fill in for `so` |

Set the label on a newly created socket from the passed subject credential. This call is made when a socket is created.

#### 6.7.3.2.4 `mpo_create_socket_from_socket`

``void mpo_create_socket_from_socket`(struct socket *oldsocket, struct label *oldsocketlabel, struct socket *newsocket, struct label *newsocketlabel);`

Parameter | Description | Locking
--- | --- | ---
`oldsocket` | Listening socket |
`oldsocketlabel` | Policy label associated with `oldsocket` |
`newsocket` | New socket |
`newsocketlabel` | Policy label associated with `newsocketlabel` |

Label a socket, `newsocket`, newly accept(2)ed, based on the listen(2) socket, `oldsocket`.

#### 6.7.3.2.5 `mpo_relabel_pipe`

``void mpo_relabel_pipe`(struct ucred *cred, struct pipe *pipe, struct label *oldlabel, struct label *newlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`pipe` | Pipe |
`oldlabel` | Current policy label associated with `pipe` |
`newlabel` | Policy label update to apply to `pipe` |

Apply a new label, `newlabel`, to `pipe`.

#### 6.7.3.2.6 `mpo_relabel_socket`

``void mpo_relabel_socket`(struct ucred *cred, struct socket *so, struct label *oldlabel, struct label *newlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential | Immutable
`so` | Object; socket |
`oldlabel` | Current label for `so` |
`newlabel` | Label update for `so` |

Update the label on a socket from the passed socket label update.

#### 6.7.3.2.7 `mpo_set_socket_peer_from_mbuf`

``void mpo_set_socket_peer_from_mbuf`(struct mbuf *mbuf, struct label *mbuflabel, struct label *oldlabel, struct label *newlabel);`

Parameter | Description | Locking
--- | --- | ---
`mbuf` | First datagram received over socket |
`mbuflabel` | Label for `mbuf` |
`oldlabel` | Current label for the socket |
`newlabel` | Policy label to be filled out for the socket |

Set the peer label on a stream socket from the passed mbuf label. This call will be made when the first datagram is received by the stream socket, with the exception of Unix domain sockets.

#### 6.7.3.2.8 `mpo_set_socket_peer_from_socket`

``void mpo_set_socket_peer_from_socket`(struct socket *oldsocket, struct label *oldsocketlabel, struct socket *newsocket, struct label *newsocketpeerlabel);`

Parameter | Description | Locking
--- | --- | ---
`oldsocket` | Local socket |
`oldsocketlabel` | Policy label for `oldsocket` |
`newsocket` | Peer socket |
`newsocketpeerlabel` | Policy label to fill in for `newsocket` |

Set the peer label on a stream UNIX domain socket from the passed remote socket endpoint. This call will be made when the socket pair is connected, and will be made for both endpoints.

### 6.7.3.3 Network Object Labeling Event Operations

#### 6.7.3.3.1 `mpo_create_bpfdesc`

``void mpo_create_bpfdesc`(struct ucred *cred, struct bpf_d *bpf_d, struct label *bpflabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential | Immutable
`bpf_d` | Object; bpf descriptor |
`bpf` | Policy label to be filled in for `bpf_d` |

Set the label on a newly created BPF descriptor from the passed subject credential. This call will be made when a BPF device node is opened by a process with the passed subject credential.

#### 6.7.3.3.2 `mpo_create_ifnet`

``void mpo_create_ifnet`(struct ifnet *ifnet, struct label *ifnetlabel);`

Parameter | Description | Locking
--- | --- | ---
`ifnet` | Network interface |
`ifnetlabel` | Policy label to fill in for `ifnet` |

Set the label on a newly created interface. This call may be made when a new physical interface becomes available to the system, or when a pseudo-interface is instantiated during the boot or as a result of a user action.

#### 6.7.3.3.3 `mpo_create_ipq`

``void mpo_create_ipq`(struct mbuf *fragment, struct label *fragmentlabel, struct ipq *ipq, struct label *ipqlabel);`

Parameter | Description | Locking
--- | --- | ---
`fragment` | First received IP fragment |
`fragmentlabel` | Policy label for `fragment` |
`ipq` | IP reassembly queue to be labeled |
`ipqlabel` | Policy label to be filled in for `ipq` |

Set the label on a newly created IP fragment reassembly queue from the mbuf header of the first received fragment.

#### 6.7.3.3.4 `mpo_create_datagram_from_ipq`

``void mpo_create_create_datagram_from_ipq`(struct ipq *ipq, struct label *ipqlabel, struct mbuf *datagram, struct label *datagramlabel);`

Parameter | Description | Locking
--- | --- | ---
`ipq` | IP reassembly queue |
`ipqlabel` | Policy label for `ipq` |
`datagram` | Datagram to be labeled |
`datagramlabel` | Policy label to be filled in for `datagramlabel` |

Set the label on a newly reassembled IP datagram from the IP fragment reassembly queue from which it was generated.

#### 6.7.3.3.5 `mpo_create_fragment`

``void mpo_create_fragment`(struct mbuf *datagram, struct label *datagramlabel, struct mbuf *fragment, struct label *fragmentlabel);`

Parameter | Description | Locking
--- | --- | ---
`datagram` | Datagram |
`datagramlabel` | Policy label for `datagram` |
`fragment` | Fragment to be labeled |
`fragmentlabel` | Policy label to be filled in for `datagram` |

Set the label on the mbuf header of a newly created IP fragment from the label on the mbuf header of the datagram it was generate from.

#### 6.7.3.3.6 `mpo_create_mbuf_from_mbuf`

``void mpo_create_mbuf_from_mbuf`(struct mbuf *oldmbuf, struct label *oldmbuflabel, struct mbuf *newmbuf, struct label *newmbuflabel);`

Parameter | Description | Locking
--- | --- | ---
`oldmbuf` | Existing (source) mbuf |
`oldmbuflabel` | Policy label for `oldmbuf` |
`newmbuf` | New mbuf to be labeled |
`newmbuflabel` | Policy label to be filled in for `newmbuf` |

Set the label on the mbuf header of a newly created datagram from the mbuf header of an existing datagram. This call may be made in a number of situations, including when an mbuf is re-allocated for alignment purposes.

#### 6.7.3.3.7 `mpo_create_mbuf_linklayer`

``void mpo_create_mbuf_linklayer`(struct ifnet *ifnet, struct label *ifnetlabel, struct mbuf *mbuf, struct label *mbuflabel);`

Parameter | Description | Locking
--- | --- | ---
`ifnet` | Network interface |
`ifnetlabel` | Policy label for `ifnet` |
`mbuf` | mbuf header for new datagram |
`mbuflabel` | Policy label to be filled in for `mbuf` |

Set the label on the mbuf header of a newly created datagram generated for the purposes of a link layer response for the passed interface. This call may be made in a number of situations, including for ARP or ND6 responses in the IPv4 and IPv6 stacks.

#### 6.7.3.3.8 `mpo_create_mbuf_from_bpfdesc`

``void mpo_create_mbuf_from_bpfdesc`(struct bpf_d *bpf_d, struct label *bpflabel, struct mbuf *mbuf, struct label *mbuflabel);`

Parameter | Description | Locking
--- | --- | ---
`bpf_d` | BPF descriptor |
`bpflabel` | Policy label for `bpflabel` |
`mbuf` | New mbuf to be labeled |
`mbuflabel` | Policy label to fill in for `mbuf` |

Set the label on the mbuf header of a newly created datagram generated using the passed BPF descriptor. This call is made when a write is performed to the BPF device associated with the passed BPF descriptor.

#### 6.7.3.3.9 `mpo_create_mbuf_from_ifnet`

``void mpo_create_mbuf_from_ifnet`(struct ifnet *ifnet, struct label *ifnetlabel, struct mbuf *mbuf, struct label *mbuflabel);`

Parameter | Description | Locking
--- | --- | ---
`ifnet` | Network interface |
`ifnetlabel` | Policy label for `ifnetlabel` |
`mbuf` | mbuf header for new datagram |
`mbuflabel` | Policy label to be filled in for `mbuf` |

Set the label on the mbuf header of a newly created datagram generated from the passed network interface.

#### 6.7.3.3.10 `mpo_create_mbuf_multicast_encap`

``void mpo_create_mbuf_multicast_encap`(struct mbuf *oldmbuf, struct label *oldmbuflabel, struct ifnet *ifnet, struct label *ifnetlabel, struct mbuf *newmbuf, struct label *newmbuflabel);`

Parameter | Description | Locking
--- | --- | ---
`oldmbuf` | mbuf header for existing datagram |
`oldmbuflabel` | Policy label for `oldmbuf` |
`ifnet` | Network interface |
`ifnetlabel` | Policy label for `ifnet` |
`newmbuf` | mbuf header to be labeled for new datagram |
`newmbuflabel` | Policy label to be filled in for `newmbuf` |

Set the label on the mbuf header of a newly created datagram generated from the existing passed datagram when it is processed by the passed multicast encapsulation interface. This call is made when an mbuf is to be delivered using the virtual interface.

#### 6.7.3.3.11 `mpo_create_mbuf_netlayer`

``void mpo_create_mbuf_netlayer`(struct mbuf *oldmbuf, struct label *oldmbuflabel, struct mbuf *newmbuf, struct label *newmbuflabel);`

Parameter | Description | Locking
--- | --- | ---
`oldmbuf` | Received datagram |
`oldmbuflabel` | Policy label for `oldmbuf` |
`newmbuf` | Newly created datagram |
`newmbuflabel` | Policy label for `newmbuf` |

Set the label on the mbuf header of a newly created datagram generated by the IP stack in response to an existing received datagram (`oldmbuf`). This call may be made in a number of situations, including when responding to ICMP request datagrams.

#### 6.7.3.3.12 `mpo_fragment_match`

``int mpo_fragment_match`(struct mbuf *fragment, struct label *fragmentlabel, struct ipq *ipq, struct label *ipqlabel);`

Parameter | Description | Locking
--- | --- | ---
`fragment` | IP datagram fragment |
`fragmentlabel` | Policy label for `fragment` |
`ipq` | IP fragment reassembly queue |
`ipqlabel` | Policy label for `ipq` |

Determine whether an mbuf header containing an IP datagram (`fragment`) fragment matches the label of the passed IP fragment reassembly queue (`ipq`). Return (1) for a successful match, or (0) for no match. This call is made when the IP stack attempts to find an existing fragment reassembly queue for a newly received fragment; if this fails, a new fragment reassembly queue may be instantiated for the fragment. Policies may use this entry point to prevent the reassembly of otherwise matching IP fragments if policy does not permit them to be reassembled based on the label or other information.

#### 6.7.3.3.13 `mpo_relabel_ifnet`

``void mpo_relabel_ifnet`(struct ucred *cred, struct ifnet *ifnet, struct label *ifnetlabel, struct label *newlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`ifnet` | Object; Network interface |
`ifnetlabel` | Policy label for `ifnet` |
`newlabel` | Label update to apply to `ifnet` |

Update the label of network interface, `ifnet`, based on the passed update label, `newlabel`, and the passed subject credential, `cred`.

#### 6.7.3.3.14 `mpo_update_ipq`

``void mpo_update_ipq`(struct mbuf *fragment, struct label *fragmentlabel, struct ipq *ipq, struct label *ipqlabel);`

Parameter | Description | Locking
--- | --- | ---
`mbuf` | IP fragment |
`mbuflabel` | Policy label for `mbuf` |
`ipq` | IP fragment reassembly queue |
`ipqlabel` | Policy label to be updated for `ipq` |

Update the label on an IP fragment reassembly queue (`ipq`) based on the acceptance of the passed IP fragment mbuf header (`mbuf`).

### 6.7.3.4 Process Labeling Event Operations

#### 6.7.3.4.1 `mpo_create_cred`

``void mpo_create_cred`(struct ucred *parent_cred, struct ucred *child_cred);`

Parameter | Description | Locking
--- | --- | ---
`parent_cred` | Parent subject credential |
`child_cred` | Child subject credential |

Set the label of a newly created subject credential from the passed subject credential. This call will be made when crcopy(9) is invoked on a newly created struct ucred. This call should not be confused with a process forking or creation event.

#### 6.7.3.4.2 `mpo_execve_transition`

``void mpo_execve_transition`(struct ucred *old, struct ucred *new, struct vnode *vp, struct label *vnodelabel);`

Parameter | Description | Locking
--- | --- | ---
`old` | Existing subject credential | Immutable
`new` | New subject credential to be labeled |
`vp` | File to execute | Locked
`vnodelabel` | Policy label for `vp` |

Update the label of a newly created subject credential (`new`) from the passed existing subject credential (`old`) based on a label transition caused by executing the passed vnode (`vp`). This call occurs when a process executes the passed vnode and one of the policies returns a success from the `mpo_execve_will_transition` entry point. Policies may choose to implement this call simply by invoking `mpo_create_cred` and passing the two subject credentials so as not to implement a transitioning event. Policies should not leave this entry point unimplemented if they implement `mpo_create_cred`, even if they do not implement `mpo_execve_will_transition`.

#### 6.7.3.4.3 `mpo_execve_will_transition`

``int mpo_execve_will_transition`(struct ucred *old, struct vnode *vp, struct label *vnodelabel);`

Parameter | Description | Locking
--- | --- | ---
`old` | Subject credential prior to execve(2) | Immutable
`vp` | File to execute |
`vnodelabel` | Policy label for `vp` |

Determine whether the policy will want to perform a transition event as a result of the execution of the passed vnode by the passed subject credential. Return 1 if a transition is required, 0 if not. Even if a policy returns 0, it should behave correctly in the presence of an unexpected invocation of `mpo_execve_transition`, as that call may happen as a result of another policy requesting a transition.

#### 6.7.3.4.4 `mpo_create_proc0`

``void mpo_create_proc0`(struct ucred *cred);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential to be filled in |

Create the subject credential of process 0, the parent of all kernel processes.

#### 6.7.3.4.5 `mpo_create_proc1`

``void mpo_create_proc1`(struct ucred *cred);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential to be filled in |

Create the subject credential of process 1, the parent of all user processes.

#### 6.7.3.4.6 `mpo_relabel_cred`

``void mpo_relabel_cred`(struct ucred *cred, struct label *newlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`newlabel` | Label update to apply to `cred` |

Update the label on a subject credential from the passed update label.

## 6.7.4 Access Control Checks

Access control entry points permit policy modules to influence access control decisions made by the kernel. Generally, although not always, arguments to an access control entry point will include one or more authorizing credentials, information (possibly including a label) for any other objects involved in the operation. An access control entry point may return 0 to permit the operation, or an errno(2) error value. The results of invoking the entry point across various registered policy modules will be composed as follows: if all modules permit the operation to succeed, success will be returned. If one or modules returns a failure, a failure will be returned. If more than one module returns a failure, the errno value to return to the user will be selected using the following precedence, implemented by the `error_select()` function in `kern_mac.c`:

Most precedence | EDEADLK
| EINVAL
| ESRCH
| EACCES
Least precedence | EPERM

If none of the error values returned by all modules are listed in the precedence chart then an arbitrarily selected value from the set will be returned. In general, the rules provide precedence to errors in the following order: kernel failures, invalid arguments, object not present, access not permitted, other.

### 6.7.4.1 `mpo_check_bpfdesc_receive`

``int mpo_check_bpfdesc_receive`(struct bpf_d *bpf_d, struct label *bpflabel, struct ifnet *ifnet, struct label *ifnetlabel);`

Parameter | Description | Locking
--- | --- | ---
`bpf_d` | Subject; BPF descriptor |
`bpflabel` | Policy label for `bpf_d` |
`ifnet` | Object; network interface |
`ifnetlabel` | Policy label for `ifnet` |

Determine whether the MAC framework should permit datagrams from the passed interface to be delivered to the buffers of the passed BPF descriptor. Return (0) for success, or an `errno` value for failure Suggested failure: EACCES for label mismatches, EPERM for lack of privilege.

### 6.7.4.2 `mpo_check_kenv_dump`

``int mpo_check_kenv_dump`(struct ucred *cred);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |

Determine whether the subject should be allowed to retrieve the kernel environment (see kenv(2)).

### 6.7.4.3 `mpo_check_kenv_get`

``int mpo_check_kenv_get`(struct ucred *cred, char *name);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`name` | Kernel environment variable name |

Determine whether the subject should be allowed to retrieve the value of the specified kernel environment variable.

### 6.7.4.4 `mpo_check_kenv_set`

``int mpo_check_kenv_set`(struct ucred *cred, char *name);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`name` | Kernel environment variable name |

Determine whether the subject should be allowed to set the specified kernel environment variable.

### 6.7.4.5 `mpo_check_kenv_unset`

``int mpo_check_kenv_unset`(struct ucred *cred, char *name);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`name` | Kernel environment variable name |

Determine whether the subject should be allowed to unset the specified kernel environment variable.

### 6.7.4.6 `mpo_check_kld_load`

``int mpo_check_kld_load`(struct ucred *cred, struct vnode *vp, struct label *vlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`vp` | Kernel module vnode |
`vlabel` | Label associated with `vp` |

Determine whether the subject should be allowed to load the specified module file.

### 6.7.4.7 `mpo_check_kld_stat`

``int mpo_check_kld_stat`(struct ucred *cred);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |

Determine whether the subject should be allowed to retrieve a list of loaded kernel module files and associated statistics.

### 6.7.4.8 `mpo_check_kld_unload`

``int mpo_check_kld_unload`(struct ucred *cred);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |

Determine whether the subject should be allowed to unload a kernel module.

### 6.7.4.9 `mpo_check_pipe_ioctl`

``int mpo_check_pipe_ioctl`(struct ucred *cred, struct pipe *pipe, struct label *pipelabel, unsigned long cmd, void *data);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`pipe` | Pipe |
`pipelabel` | Policy label associated with `pipe` |
`cmd` | ioctl(2) command |
`data` | ioctl(2) data |

Determine whether the subject should be allowed to make the specified ioctl(2) call.

### 6.7.4.10 `mpo_check_pipe_poll`

``int mpo_check_pipe_poll`(struct ucred *cred, struct pipe *pipe, struct label *pipelabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`pipe` | Pipe |
`pipelabel` | Policy label associated with `pipe` |

Determine whether the subject should be allowed to poll `pipe`.

### 6.7.4.11 `mpo_check_pipe_read`

``int mpo_check_pipe_read`(struct ucred *cred, struct pipe *pipe, struct label *pipelabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`pipe` | Pipe |
`pipelabel` | Policy label associated with `pipe` |

Determine whether the subject should be allowed read access to `pipe`.

### 6.7.4.12 `mpo_check_pipe_relabel`

``int mpo_check_pipe_relabel`(struct ucred *cred, struct pipe *pipe, struct label *pipelabel, struct label *newlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`pipe` | Pipe |
`pipelabel` | Current policy label associated with `pipe` |
`newlabel` | Label update to `pipelabel` |

Determine whether the subject should be allowed to relabel `pipe`.

### 6.7.4.13 `mpo_check_pipe_stat`

``int mpo_check_pipe_stat`(struct ucred *cred, struct pipe *pipe, struct label *pipelabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`pipe` | Pipe |
`pipelabel` | Policy label associated with `pipe` |

Determine whether the subject should be allowed to retrieve statistics related to `pipe`.

### 6.7.4.14 `mpo_check_pipe_write`

``int mpo_check_pipe_write`(struct ucred *cred, struct pipe *pipe, struct label *pipelabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`pipe` | Pipe |
`pipelabel` | Policy label associated with `pipe` |

Determine whether the subject should be allowed to write to `pipe`.

### 6.7.4.15 `mpo_check_socket_bind`

``int mpo_check_socket_bind`(struct ucred *cred, struct socket *socket, struct label *socketlabel, struct sockaddr *sockaddr);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`socket` | Socket to be bound |
`socketlabel` | Policy label for `socket` |
`sockaddr` | Address of `socket` |

### 6.7.4.16 `mpo_check_socket_connect`

``int mpo_check_socket_connect`(struct ucred *cred, struct socket *socket, struct label *socketlabel, struct sockaddr *sockaddr);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`socket` | Socket to be connected |
`socketlabel` | Policy label for `socket` |
`sockaddr` | Address of `socket` |

Determine whether the subject credential (`cred`) can connect the passed socket (`socket`) to the passed socket address (`sockaddr`). Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatches, EPERM for lack of privilege.

### 6.7.4.17 `mpo_check_socket_receive`

``int mpo_check_socket_receive`(struct ucred *cred, struct socket *so, struct label *socketlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`so` | Socket |
`socketlabel` | Policy label associated with `so` |

Determine whether the subject should be allowed to receive information from the socket `so`.

### 6.7.4.18 `mpo_check_socket_send`

``int mpo_check_socket_send`(struct ucred *cred, struct socket *so, struct label *socketlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`so` | Socket |
`socketlabel` | Policy label associated with `so` |

Determine whether the subject should be allowed to send information across the socket `so`.

### 6.7.4.19 `mpo_check_cred_visible`

``int mpo_check_cred_visible`(struct ucred *u1, struct ucred *u2);`

Parameter | Description | Locking
--- | --- | ---
`u1` | Subject credential |
`u2` | Object credential |

Determine whether the subject credential `u1` can see other subjects with the passed subject credential `u2`. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatches, EPERM for lack of privilege, or ESRCH to hide visibility. This call may be made in a number of situations, including inter-process status sysctl's used by `ps`, and in procfs lookups.

### 6.7.4.20 `mpo_check_socket_visible`

``int mpo_check_socket_visible`(struct ucred *cred, struct socket *socket, struct label *socketlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`socket` | Object; socket |
`socketlabel` | Policy label for `socket` |

### 6.7.4.21 `mpo_check_ifnet_relabel`

``int mpo_check_ifnet_relabel`(struct ucred *cred, struct ifnet *ifnet, struct label *ifnetlabel, struct label *newlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`ifnet` | Object; network interface |
`ifnetlabel` | Existing policy label for `ifnet` |
`newlabel` | Policy label update to later be applied to `ifnet` |

Determine whether the subject credential can relabel the passed network interface to the passed label update.

### 6.7.4.22 `mpo_check_socket_relabel`

``int mpo_check_socket_relabel`(struct ucred *cred, struct socket *socket, struct label *socketlabel, struct label *newlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`socket` | Object; socket |
`socketlabel` | Existing policy label for `socket` |
`newlabel` | Label update to later be applied to `socketlabel` |

Determine whether the subject credential can relabel the passed socket to the passed label update.

### 6.7.4.23 `mpo_check_cred_relabel`

``int mpo_check_cred_relabel`(struct ucred *cred, struct label *newlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`newlabel` | Label update to later be applied to `cred` |

Determine whether the subject credential can relabel itself to the passed label update.

### 6.7.4.24 `mpo_check_vnode_relabel`

``int mpo_check_vnode_relabel`(struct ucred *cred, struct vnode *vp, struct label *vnodelabel, struct label *newlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential | Immutable
`vp` | Object; vnode | Locked
`vnodelabel` | Existing policy label for `vp` |
`newlabel` | Policy label update to later be applied to `vp` |

Determine whether the subject credential can relabel the passed vnode to the passed label update.

### 6.7.4.25 `mpo_check_mount_stat`

``int mpo_check_mount_stat`(struct ucred *cred, struct mount *mp, struct label *mountlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`mp` | Object; file system mount |
`mountlabel` | Policy label for `mp` |

Determine whether the subject credential can see the results of a statfs performed on the file system. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatches or EPERM for lack of privilege. This call may be made in a number of situations, including during invocations of statfs(2) and related calls, as well as to determine what file systems to exclude from listings of file systems, such as when getfsstat(2) is invoked.

### 6.7.4.26 `mpo_check_proc_debug`

``int mpo_check_proc_debug`(struct ucred *cred, struct proc *proc);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential | Immutable
`proc` | Object; process |

Determine whether the subject credential can debug the passed process. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, EPERM for lack of privilege, or ESRCH to hide visibility of the target. This call may be made in a number of situations, including use of the ptrace(2) and ktrace(2) APIs, as well as for some types of procfs operations.

### 6.7.4.27 `mpo_check_vnode_access`

``int mpo_check_vnode_access`(struct ucred *cred, struct vnode *vp, struct label *label, int flags);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`vp` | Object; vnode |
`label` | Policy label for `vp` |
`flags` | access(2) flags |

Determine how invocations of access(2) and related calls by the subject credential should return when performed on the passed vnode using the passed access flags. This should generally be implemented using the same semantics used in `mpo_check_vnode_open`. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatches or EPERM for lack of privilege.

### 6.7.4.28 `mpo_check_vnode_chdir`

``int mpo_check_vnode_chdir`(struct ucred *cred, struct vnode *dvp, struct label *dlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`dvp` | Object; vnode to chdir(2) into |
`dlabel` | Policy label for `dvp` |

Determine whether the subject credential can change the process working directory to the passed vnode. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

### 6.7.4.29 `mpo_check_vnode_chroot`

``int mpo_check_vnode_chroot`(struct ucred *cred, struct vnode *dvp, struct label *dlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`dvp` | Directory vnode |
`dlabel` | Policy label associated with `dvp` |

Determine whether the subject should be allowed to chroot(2) into the specified directory (`dvp`).

### 6.7.4.30 `mpo_check_vnode_create`

``int mpo_check_vnode_create`(struct ucred *cred, struct vnode *dvp, struct label *dlabel, struct componentname *cnp, struct vattr *vap);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`dvp` | Object; vnode |
`dlabel` | Policy label for `dvp` |
`cnp` | Component name for `dvp` |
`vap` | vnode attributes for `vap` |

Determine whether the subject credential can create a vnode with the passed parent directory, passed name information, and passed attribute information. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. This call may be made in a number of situations, including as a result of calls to open(2) with `O_CREAT`, mknod(2), mkfifo(2), and others.

### 6.7.4.31 `mpo_check_vnode_delete`

``int mpo_check_vnode_delete`(struct ucred *cred, struct vnode *dvp, struct label *dlabel, struct vnode *vp, void *label, struct componentname *cnp);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`dvp` | Parent directory vnode |
`dlabel` | Policy label for `dvp` |
`vp` | Object; vnode to delete |
`label` | Policy label for `vp` |
`cnp` | Component name for `vp` |

Determine whether the subject credential can delete a vnode from the passed parent directory and passed name information. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. This call may be made in a number of situations, including as a result of calls to unlink(2) and rmdir(2). Policies implementing this entry point should also implement `mpo_check_rename_to` to authorize deletion of objects as a result of being the target of a rename.

### 6.7.4.32 `mpo_check_vnode_deleteacl`

``int mpo_check_vnode_deleteacl`(struct ucred *cred, struct vnode *vp, struct label *label, acl_type_t type);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential | Immutable
`vp` | Object; vnode | Locked
`label` | Policy label for `vp` |
`type` | ACL type |

Determine whether the subject credential can delete the ACL of passed type from the passed vnode. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

### 6.7.4.33 `mpo_check_vnode_exec`

``int mpo_check_vnode_exec`(struct ucred *cred, struct vnode *vp, struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`vp` | Object; vnode to execute |
`label` | Policy label for `vp` |

Determine whether the subject credential can execute the passed vnode. Determination of execute privilege is made separately from decisions about any transitioning event. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

### 6.7.4.34 `mpo_check_vnode_getacl`

``int mpo_check_vnode_getacl`(struct ucred *cred, struct vnode *vp, struct label *label, acl_type_t type);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`vp` | Object; vnode |
`label` | Policy label for `vp` |
`type` | ACL type |

Determine whether the subject credential can retrieve the ACL of passed type from the passed vnode. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

### 6.7.4.35 `mpo_check_vnode_getextattr`

``int mpo_check_vnode_getextattr`(struct ucred *cred, struct vnode *vp, struct label *label, int attrnamespace, const char *name, struct uio *uio);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`vp` | Object; vnode |
`label` | Policy label for `vp` |
`attrnamespace` | Extended attribute namespace |
`name` | Extended attribute name |
`uio` | I/O structure pointer; see uio(9) |

Determine whether the subject credential can retrieve the extended attribute with the passed namespace and name from the passed vnode. Policies implementing labeling using extended attributes may be interested in special handling of operations on those extended attributes. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

### 6.7.4.36 `mpo_check_vnode_link`

``int mpo_check_vnode_link`(struct ucred *cred, struct vnode *dvp, struct label *dlabel, struct vnode *vp, struct label *label, struct componentname *cnp);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`dvp` | Directory vnode |
`dlabel` | Policy label associated with `dvp` |
`vp` | Link destination vnode |
`label` | Policy label associated with `vp` |
`cnp` | Component name for the link being created |

Determine whether the subject should be allowed to create a link to the vnode `vp` with the name specified by `cnp`.

### 6.7.4.37 `mpo_check_vnode_mmap`

``int mpo_check_vnode_mmap`(struct ucred *cred, struct vnode *vp, struct label *label, int prot);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`vp` | Vnode to map |
`label` | Policy label associated with `vp` |
`prot` | Mmap protections (see mmap(2)) |

Determine whether the subject should be allowed to map the vnode `vp` with the protections specified in `prot`.

### 6.7.4.38 `mpo_check_vnode_mmap_downgrade`

``void mpo_check_vnode_mmap_downgrade`(struct ucred *cred, struct vnode *vp, struct label *label, int *prot);`

Parameter | Description | Locking
--- | --- | ---
`cred` | See Section 6.7.4.37. |
`vp` |
`label` |
`prot` | Mmap protections to be downgraded |

Downgrade the mmap protections based on the subject and object labels.

### 6.7.4.39 `mpo_check_vnode_mprotect`

``int mpo_check_vnode_mprotect`(struct ucred *cred, struct vnode *vp, struct label *label, int prot);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`vp` | Mapped vnode |
`prot` | Memory protections |

Determine whether the subject should be allowed to set the specified memory protections on memory mapped from the vnode `vp`.

### 6.7.4.40 `mpo_check_vnode_poll`

``int mpo_check_vnode_poll`(struct ucred *active_cred, struct ucred *file_cred, struct vnode *vp, struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`active_cred` | Subject credential |
`file_cred` | Credential associated with the struct file |
`vp` | Polled vnode |
`label` | Policy label associated with `vp` |

Determine whether the subject should be allowed to poll the vnode `vp`.

### 6.7.4.41 `mpo_check_vnode_rename_from`

``int mpo_vnode_rename_from`(struct ucred *cred, struct vnode *dvp, struct label *dlabel, struct vnode *vp, struct label *label, struct componentname *cnp);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`dvp` | Directory vnode |
`dlabel` | Policy label associated with `dvp` |
`vp` | Vnode to be renamed |
`label` | Policy label associated with `vp` |
`cnp` | Component name for `vp` |

Determine whether the subject should be allowed to rename the vnode `vp` to something else.

### 6.7.4.42 `mpo_check_vnode_rename_to`

``int mpo_check_vnode_rename_to`(struct ucred *cred, struct vnode *dvp, struct label *dlabel, struct vnode *vp, struct label *label, int samedir, struct componentname *cnp);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`dvp` | Directory vnode |
`dlabel` | Policy label associated with `dvp` |
`vp` | Overwritten vnode |
`label` | Policy label associated with `vp` |
`samedir` | Boolean; `1` if the source and destination directories are the same |
`cnp` | Destination component name |

Determine whether the subject should be allowed to rename to the vnode `vp`, into the directory `dvp`, or to the name represented by `cnp`. If there is no existing file to overwrite, `vp` and `label` will be NULL.

### 6.7.4.43 `mpo_check_socket_listen`

``int mpo_check_socket_listen`(struct ucred *cred, struct socket *socket, struct label *socketlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`socket` | Object; socket |
`socketlabel` | Policy label for `socket` |

Determine whether the subject credential can listen on the passed socket. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

### 6.7.4.44 `mpo_check_vnode_lookup`

``int mpo_check_vnode_lookup`(struct ucred *cred, struct vnode *dvp, struct label *dlabel, struct componentname *cnp);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`dvp` | Object; vnode |
`dlabel` | Policy label for `dvp` |
`cnp` | Component name being looked up |

Determine whether the subject credential can perform a lookup in the passed directory vnode for the passed name. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

### 6.7.4.45 `mpo_check_vnode_open`

``int mpo_check_vnode_open`(struct ucred *cred, struct vnode *vp, struct label *label, int acc_mode);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`vp` | Object; vnode |
`label` | Policy label for `vp` |
`acc_mode` | open(2) access mode |

Determine whether the subject credential can perform an open operation on the passed vnode with the passed access mode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

### 6.7.4.46 `mpo_check_vnode_readdir`

``int mpo_check_vnode_readdir`(struct ucred *cred, struct vnode *dvp, struct label *dlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`dvp` | Object; directory vnode |
`dlabel` | Policy label for `dvp` |

Determine whether the subject credential can perform a `readdir` operation on the passed directory vnode. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

### 6.7.4.47 `mpo_check_vnode_readlink`

``int mpo_check_vnode_readlink`(struct ucred *cred, struct vnode *vp, struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`vp` | Object; vnode |
`label` | Policy label for `vp` |

Determine whether the subject credential can perform a `readlink` operation on the passed symlink vnode. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. This call may be made in a number of situations, including an explicit `readlink` call by the user process, or as a result of an implicit `readlink` during a name lookup by the process.

### 6.7.4.48 `mpo_check_vnode_revoke`

``int mpo_check_vnode_revoke`(struct ucred *cred, struct vnode *vp, struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`vp` | Object; vnode |
`label` | Policy label for `vp` |

Determine whether the subject credential can revoke access to the passed vnode. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

### 6.7.4.49 `mpo_check_vnode_setacl`

``int mpo_check_vnode_setacl`(struct ucred *cred, struct vnode *vp, struct label *label, acl_type_t type, struct acl *acl);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`vp` | Object; vnode |
`label` | Policy label for `vp` |
`type` | ACL type |
`acl` | ACL |

Determine whether the subject credential can set the passed ACL of passed type on the passed vnode. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

### 6.7.4.50 `mpo_check_vnode_setextattr`

``int mpo_check_vnode_setextattr`(struct ucred *cred, struct vnode *vp, struct label *label, int attrnamespace, const char *name, struct uio *uio);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`vp` | Object; vnode |
`label` | Policy label for `vp` |
`attrnamespace` | Extended attribute namespace |
`name` | Extended attribute name |
`uio` | I/O structure pointer; see uio(9) |

Determine whether the subject credential can set the extended attribute of passed name and passed namespace on the passed vnode. Policies implementing security labels backed into extended attributes may want to provide additional protections for those attributes. Additionally, policies should avoid making decisions based on the data referenced from `uio`, as there is a potential race condition between this check and the actual operation. The `uio` may also be `NULL` if a delete operation is being performed. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

### 6.7.4.51 `mpo_check_vnode_setflags`

``int mpo_check_vnode_setflags`(struct ucred *cred, struct vnode *vp, struct label *label, u_long flags);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`vp` | Object; vnode |
`label` | Policy label for `vp` |
`flags` | File flags; see chflags(2) |

Determine whether the subject credential can set the passed flags on the passed vnode. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

### 6.7.4.52 `mpo_check_vnode_setmode`

``int mpo_check_vnode_setmode`(struct ucred *cred, struct vnode *vp, struct label *label, mode_t mode);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`vp` | Object; vnode |
`label` | Policy label for `vp` |
`mode` | File mode; see chmod(2) |

Determine whether the subject credential can set the passed mode on the passed vnode. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

### 6.7.4.53 `mpo_check_vnode_setowner`

``int mpo_check_vnode_setowner`(struct ucred *cred, struct vnode *vp, struct label *label, uid_t uid, gid_t gid);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`vp` | Object; vnode |
`label` | Policy label for `vp` |
`uid` | User ID |
`gid` | Group ID |

Determine whether the subject credential can set the passed uid and passed gid as file uid and file gid on the passed vnode. The IDs may be set to (`-1`) to request no update. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

### 6.7.4.54 `mpo_check_vnode_setutimes`

``int mpo_check_vnode_setutimes`(struct ucred *cred, struct vnode *vp, struct label *label, struct timespec atime, struct timespec mtime);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`vp` | Object; vp |
`label` | Policy label for `vp` |
`atime` | Access time; see utimes(2) |
`mtime` | Modification time; see utimes(2) |

Determine whether the subject credential can set the passed access timestamps on the passed vnode. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

### 6.7.4.55 `mpo_check_proc_sched`

``int mpo_check_proc_sched`(struct ucred *ucred, struct proc *proc);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`proc` | Object; process |

Determine whether the subject credential can change the scheduling parameters of the passed process. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, EPERM for lack of privilege, or ESRCH to limit visibility.

See setpriority(2) for more information.

### 6.7.4.56 `mpo_check_proc_signal`

``int mpo_check_proc_signal`(struct ucred *cred, struct proc *proc, int signal);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`proc` | Object; process |
`signal` | Signal; see kill(2) |

Determine whether the subject credential can deliver the passed signal to the passed process. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, EPERM for lack of privilege, or ESRCH to limit visibility.

### 6.7.4.57 `mpo_check_vnode_stat`

``int mpo_check_vnode_stat`(struct ucred *cred, struct vnode *vp, struct label *label);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`vp` | Object; vnode |
`label` | Policy label for `vp` |

Determine whether the subject credential can `stat` the passed vnode. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

See stat(2) for more information.

### 6.7.4.58 `mpo_check_ifnet_transmit`

``int mpo_check_ifnet_transmit`(struct ucred *cred, struct ifnet *ifnet, struct label *ifnetlabel, struct mbuf *mbuf, struct label *mbuflabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`ifnet` | Network interface |
`ifnetlabel` | Policy label for `ifnet` |
`mbuf` | Object; mbuf to be sent |
`mbuflabel` | Policy label for `mbuf` |

Determine whether the network interface can transmit the passed mbuf. Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

### 6.7.4.59 `mpo_check_socket_deliver`

``int mpo_check_socket_deliver`(struct ucred *cred, struct ifnet *ifnet, struct label *ifnetlabel, struct mbuf *mbuf, struct label *mbuflabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`ifnet` | Network interface |
`ifnetlabel` | Policy label for `ifnet` |
`mbuf` | Object; mbuf to be delivered |
`mbuflabel` | Policy label for `mbuf` |

Determine whether the socket may receive the datagram stored in the passed mbuf header. Return 0 for success, or an `errno` value for failure. Suggested failures: EACCES for label mismatch, or EPERM for lack of privilege.

### 6.7.4.60 `mpo_check_socket_visible`

``int mpo_check_socket_visible`(struct ucred *cred, struct socket *so, struct label *socketlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential | Immutable
`so` | Object; socket |
`socketlabel` | Policy label for `so` |

Determine whether the subject credential cred can "see" the passed socket (`socket`) using system monitoring functions, such as those employed by netstat(8) and sockstat(1). Return 0 for success, or an `errno` value for failure. Suggested failure: EACCES for label mismatches, EPERM for lack of privilege, or ESRCH to hide visibility.

### 6.7.4.61 `mpo_check_system_acct`

``int mpo_check_system_acct`(struct ucred *ucred, struct vnode *vp, struct label *vlabel);`

Parameter | Description | Locking
--- | --- | ---
`ucred` | Subject credential |
`vp` | Accounting file; acct(5) |
`vlabel` | Label associated with `vp` |

Determine whether the subject should be allowed to enable accounting, based on its label and the label of the accounting log file.

### 6.7.4.62 `mpo_check_system_nfsd`

``int mpo_check_system_nfsd`(struct ucred *cred);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |

Determine whether the subject should be allowed to call nfssvc(2).

### 6.7.4.63 `mpo_check_system_reboot`

``int mpo_check_system_reboot`(struct ucred *cred, int howto);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`howto` | `howto` parameter from reboot(2) |

Determine whether the subject should be allowed to reboot the system in the specified manner.

### 6.7.4.64 `mpo_check_system_settime`

``int mpo_check_system_settime`(struct ucred *cred);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |

Determine whether the user should be allowed to set the system clock.

### 6.7.4.65 `mpo_check_system_swapon`

``int mpo_check_system_swapon`(struct ucred *cred, struct vnode *vp, struct label *vlabel);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`vp` | Swap device |
`vlabel` | Label associated with `vp` |

Determine whether the subject should be allowed to add `vp` as a swap device.

### 6.7.4.66 `mpo_check_system_sysctl`

``int mpo_check_system_sysctl`(struct ucred *cred, int *name, u_int *namelen, void *old, size_t *oldlenp, int inkernel, void *new, size_t newlen);`

Parameter | Description | Locking
--- | --- | ---
`cred` | Subject credential |
`name` | See sysctl(3) |
`namelen` |
`old` |
`oldlenp` |
`inkernel` | Boolean; `1` if called from kernel |
`new` | See sysctl(3) |
`newlen` |

Determine whether the subject should be allowed to make the specified sysctl(3) transaction.

## 6.7.5 Label Management Calls

Relabel events occur when a user process has requested that the label on an object be modified. A two-phase update occurs: first, an access control check will be performed to determine if the update is both valid and permitted, and then the update itself is performed via a separate entry point. Relabel entry points typically accept the object, object label reference, and an update label submitted by the process. Memory allocation during relabel is discouraged, as relabel calls are not permitted to fail (failure should be reported earlier in the relabel check).

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