Queueing Disciplines
[Traffic Control]

Detailed Description

Qdisc Handles

In general, qdiscs are identified by the major part of a traffic control handle (the upper 16 bits). A few special values exist though:

TC_H_ROOT: root qdisc (directly attached to the device)
TC_H_INGRESS: ingress qdisc (directly attached to the device)
TC_H_UNSPEC: unspecified qdisc (no reference)

1) Adding a Qdisc

 // Allocate a new empty qdisc to be filled out
 struct rtnl_qdisc *qdisc = rtnl_qdisc_alloc();

 // ... specify the kind of the Qdisc
 rtnl_qdisc_set_kind(qdisc, "pfifo");

 // Specify the device the qdisc should be attached to
 rtnl_qdisc_set_ifindex(qdisc, ifindex);

 // ... specify the parent qdisc
 rtnl_qdisc_set_parent(qdisc, TC_H_ROOT);

 // Specifying the handle is not required but makes reidentifying easier
 // and may help to avoid adding a qdisc twice.
 rtnl_qdisc_set_handle(qdisc, 0x000A0000);

 // Now on to specify the qdisc specific options, see the relevant qdisc
 // modules for documentation, in this example we set the upper limit of
 // the packet fifo qdisc to 64
 rtnl_qdisc_fifo_set_limit(qdisc, 64);

 rtnl_qdisc_add(handle, qdisc, NLM_R_REPLACE);

 // Free up the memory
 rtnl_qdisc_put(qdisc);

2) Deleting a Qdisc

 // Allocate a new empty qdisc to be filled out with the parameters
 // specifying the qdisc to be deleted. Alternatively a fully equiped
 // Qdisc object from a cache can be used.
 struct rtnl_qdisc *qdisc = rtnl_qdisc_alloc();

 // The interface index of the device the qdisc is on and the parent handle
 // are the least required fields to be filled out.
 // Note: Specify TC_H_ROOT or TC_H_INGRESS as parent handle to delete the
 //       root respectively root ingress qdisc.
 rtnl_qdisc_set_ifindex(qdisc, ifindex);
 rtnl_qdisc_set_parent(qdisc, parent_handle);

 // If required for identification, the handle can be specified as well.
 rtnl_qdisc_set_handle(qdisc, qdisc_handle);

 // Not required but maybe helpful as sanity check, the kind of the qdisc
 // can be specified to avoid mistakes.
 rtnl_qdisc_set_kind(qdisc, "pfifo");

 // Finally delete the qdisc with rtnl_qdisc_delete(), alternatively
 // rtnl_qdisc_build_delete_request() can be invoked to generate an
 // appropritate netlink message to send out.
 rtnl_qdisc_delete(handle, qdisc);

 // Free up the memory
 rtnl_qdisc_put(qdisc);

Modules

Queueing Discipline Modules

Queueing Discipline Object

Data Structures

struct rtnl_qdisc_ops

Qdisc Operations. More...

QDisc Addition

struct nl_msg * rtnl_qdisc_build_add_request (struct rtnl_qdisc *qdisc, int flags)

Build a netlink message to add a new qdisc.

int rtnl_qdisc_add (struct nl_handle *handle, struct rtnl_qdisc *qdisc, int flags)

Add a new qdisc.

QDisc Modification

struct nl_msg * rtnl_qdisc_build_change_request (struct rtnl_qdisc *qdisc, struct rtnl_qdisc *new)

Build a netlink message to change attributes of a existing qdisc.

int rtnl_qdisc_change (struct nl_handle *handle, struct rtnl_qdisc *qdisc, struct rtnl_qdisc *new)

Change attributes of a qdisc.

QDisc Deletion

struct nl_msg * rtnl_qdisc_build_delete_request (struct rtnl_qdisc *qdisc)

Build a netlink request message to delete a qdisc.

int rtnl_qdisc_delete (struct nl_handle *handle, struct rtnl_qdisc *qdisc)

Delete a qdisc.

Qdisc Cache Management

struct nl_cache * rtnl_qdisc_alloc_cache (struct nl_handle *handle)

Build a qdisc cache including all qdiscs currently configured in the kernel.

struct rtnl_qdisc * rtnl_qdisc_get_by_parent (struct nl_cache *cache, int ifindex, uint32_t parent)

Look up qdisc by its parent in the provided cache.

struct rtnl_qdisc * rtnl_qdisc_get (struct nl_cache *cache, int ifindex, uint32_t handle)

Look up qdisc by its handle in the provided cache.

Function Documentation

struct nl_msg* rtnl_qdisc_build_add_request	(	struct rtnl_qdisc *	qdisc,
		int	flags
	)			`[read]`

Parameters:

	qdisc	qdisc to add
	flags	additional netlink message flags

Builds a new netlink message requesting an addition of a qdisc. The netlink message header isn't fully equipped with all relevant fields and must be sent out via nl_send_auto_complete() or supplemented as needed.

Common message flags used:

NLM_F_REPLACE - replace a potential existing qdisc

Returns:: New netlink message

Definition at line 197 of file qdisc.c.

References NLM_F_CREATE.

Referenced by rtnl_qdisc_add().

int rtnl_qdisc_add	(	struct nl_handle *	handle,
		struct rtnl_qdisc *	qdisc,
		int	flags
	)

Parameters:

	handle	netlink handle
	qdisc	qdisc to delete
	flags	additional netlink message flags

Builds a netlink message by calling rtnl_qdisc_build_add_request(), sends the request to the kernel and waits for the ACK to be received and thus blocks until the request has been processed.

Common message flags used:

NLM_F_REPLACE - replace a potential existing qdisc

Returns:: 0 on success or a negative error code

Definition at line 224 of file qdisc.c.

References nl_send_auto_complete(), nl_wait_for_ack(), nlmsg_free(), and rtnl_qdisc_build_add_request().

struct nl_msg* rtnl_qdisc_build_change_request	(	struct rtnl_qdisc *	qdisc,
		struct rtnl_qdisc *	new
	)			`[read]`

Parameters:

	qdisc	qdisc to change
	new	new qdisc attributes

Builds a new netlink message requesting an change of qdisc attributes. The netlink message header isn't fully equipped with all relevant fields and must be sent out via nl_send_auto_complete() or supplemented as needed.

Returns:: New netlink message

Definition at line 261 of file qdisc.c.

References NLM_F_REPLACE.

Referenced by rtnl_qdisc_change().

int rtnl_qdisc_change	(	struct nl_handle *	handle,
		struct rtnl_qdisc *	qdisc,
		struct rtnl_qdisc *	new
	)

Parameters:

	handle	netlink handle
	qdisc	qdisc to change
	new	new qdisc attributes

Builds a netlink message by calling rtnl_qdisc_build_change_request(), sends the request to the kernel and waits for the ACK to be received and thus blocks until the request has been processed.

Returns:: 0 on success or a negative error code

Definition at line 279 of file qdisc.c.

References nl_send_auto_complete(), nl_wait_for_ack(), nlmsg_free(), and rtnl_qdisc_build_change_request().

struct nl_msg* rtnl_qdisc_build_delete_request ( struct rtnl_qdisc * qdisc ) [read]

Parameters:

qdisc

qdisc to delete

Builds a new netlink message requesting a deletion of a qdisc. The netlink message header isn't fully equipped with all relevant fields and must thus be sent out via nl_send_auto_complete() or supplemented as needed.

Returns:: New netlink message

Definition at line 315 of file qdisc.c.

References nlmsg_alloc_simple(), and nlmsg_append().

Referenced by rtnl_qdisc_delete().

int rtnl_qdisc_delete	(	struct nl_handle *	handle,
		struct rtnl_qdisc *	qdisc
	)

Parameters:

	handle	netlink handle
	qdisc	qdisc to delete

Builds a netlink message by calling rtnl_qdisc_build_delete_request(), sends the request to the kernel and waits for the ACK to be received and thus blocks until the request has been processed.

Returns:: 0 on success or a negative error code

Definition at line 348 of file qdisc.c.

References nl_send_auto_complete(), nl_wait_for_ack(), nlmsg_free(), and rtnl_qdisc_build_delete_request().

struct nl_cache* rtnl_qdisc_alloc_cache ( struct nl_handle * handle ) [read]

Parameters:

handle

netlink handle

Allocates a new cache, initializes it properly and updates it to include all qdiscs currently configured in the kernel.

Note:: The caller is responsible for destroying and freeing the cache after using it.

Returns:: The cache or NULL if an error has occured.

Definition at line 384 of file qdisc.c.

References nl_cache_alloc(), nl_cache_free(), and nl_cache_refill().

struct rtnl_qdisc* rtnl_qdisc_get_by_parent	(	struct nl_cache *	cache,
		int	ifindex,
		uint32_t	parent
	)			`[read]`

Parameters:

	cache	qdisc cache
	ifindex	interface the qdisc is attached to
	parent	parent handle

Returns:: pointer to qdisc inside the cache or NULL if no match was found.

Definition at line 407 of file qdisc.c.

References nl_object_get().

Referenced by rtnl_class_leaf_qdisc().

struct rtnl_qdisc* rtnl_qdisc_get	(	struct nl_cache *	cache,
		int	ifindex,
		uint32_t	handle
	)			`[read]`

Parameters:

	cache	qdisc cache
	ifindex	interface the qdisc is attached to
	handle	qdisc handle

Returns:: pointer to qdisc inside the cache or NULL if no match was found.

Definition at line 432 of file qdisc.c.

References nl_object_get().


Modules
	Queueing Discipline Modules
	Queueing Discipline Object
Data Structures
struct	rtnl_qdisc_ops
	Qdisc Operations. More...
QDisc Addition
struct nl_msg *	rtnl_qdisc_build_add_request (struct rtnl_qdisc *qdisc, int flags)
	Build a netlink message to add a new qdisc.
int	rtnl_qdisc_add (struct nl_handle handle, struct rtnl_qdisc qdisc, int flags)
	Add a new qdisc.
QDisc Modification
struct nl_msg *	rtnl_qdisc_build_change_request (struct rtnl_qdisc qdisc, struct rtnl_qdisc new)
	Build a netlink message to change attributes of a existing qdisc.
int	rtnl_qdisc_change (struct nl_handle handle, struct rtnl_qdisc qdisc, struct rtnl_qdisc *new)
	Change attributes of a qdisc.
QDisc Deletion
struct nl_msg *	rtnl_qdisc_build_delete_request (struct rtnl_qdisc *qdisc)
	Build a netlink request message to delete a qdisc.
int	rtnl_qdisc_delete (struct nl_handle handle, struct rtnl_qdisc qdisc)
	Delete a qdisc.
Qdisc Cache Management
struct nl_cache *	rtnl_qdisc_alloc_cache (struct nl_handle *handle)
	Build a qdisc cache including all qdiscs currently configured in the kernel.
struct rtnl_qdisc *	rtnl_qdisc_get_by_parent (struct nl_cache *cache, int ifindex, uint32_t parent)
	Look up qdisc by its parent in the provided cache.
struct rtnl_qdisc *	rtnl_qdisc_get (struct nl_cache *cache, int ifindex, uint32_t handle)
	Look up qdisc by its handle in the provided cache.

Queueing Disciplines [Traffic Control]

Detailed Description

Modules

Data Structures

QDisc Addition

QDisc Modification

QDisc Deletion

Qdisc Cache Management

Function Documentation

Queueing Disciplines
[Traffic Control]