Queueing Disciplines

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.

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);

Function Documentation

rtnl_qdisc_build_add_request()

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

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.

{
        struct nl_msg *msg;
 
        msg = qdisc_build(qdisc, RTM_NEWQDISC, NLM_F_CREATE | flags);
        if (!msg)
                nl_errno(ENOMEM);
 
        return msg;
}

References NLM_F_CREATE.

Referenced by rtnl_qdisc_add().

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.

{
        struct nl_msg *msg;
        int err;
 
        msg = rtnl_qdisc_build_add_request(qdisc, flags);
        if (!msg)
                return nl_errno(ENOMEM);
 
        err = nl_send_auto_complete(handle, msg);
        nlmsg_free(msg);
        if (err < 0)
                return err;
 
        return nl_wait_for_ack(handle);
}

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

rtnl_qdisc_build_change_request()

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

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.

{
        return qdisc_build(qdisc, RTM_NEWQDISC, NLM_F_REPLACE);
}

References NLM_F_REPLACE.

Referenced by rtnl_qdisc_change().

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.

{
        struct nl_msg *msg;
        int err;
 
        msg = rtnl_qdisc_build_change_request(qdisc, new);
        if (!msg)
                return nl_errno(ENOMEM);
 
        err = nl_send_auto_complete(handle, msg);
        nlmsg_free(msg);
        if (err < 0)
                return err;
 
        return nl_wait_for_ack(handle);
}

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

rtnl_qdisc_build_delete_request()

struct nl_msg * rtnl_qdisc_build_delete_request

(

struct rtnl_qdisc *

qdisc

)

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.

{
        struct nl_msg *msg;
        struct tcmsg tchdr;
        int required = TCA_ATTR_IFINDEX | TCA_ATTR_PARENT;
 
        if ((qdisc->ce_mask & required) != required)
                BUG();
 
        msg = nlmsg_alloc_simple(RTM_DELQDISC, 0);
        if (!msg)
                return NULL;
 
        tchdr.tcm_family = AF_UNSPEC,
        tchdr.tcm_handle = qdisc->q_handle,
        tchdr.tcm_parent = qdisc->q_parent,
        tchdr.tcm_ifindex = qdisc->q_ifindex,
        nlmsg_append(msg, &tchdr, sizeof(tchdr), NLMSG_ALIGNTO);
 
        return msg;
}

References nlmsg_alloc_simple(), and nlmsg_append().

Referenced by rtnl_qdisc_delete().

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.

{
        struct nl_msg *msg;
        int err;
 
        msg = rtnl_qdisc_build_delete_request(qdisc);
        if (!msg)
                return nl_errno(ENOMEM);
 
        err = nl_send_auto_complete(handle, msg);
        nlmsg_free(msg);
        if (err < 0)
                return err;
 
        return nl_wait_for_ack(handle);
}

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

rtnl_qdisc_alloc_cache()

struct nl_cache * rtnl_qdisc_alloc_cache

(

struct nl_handle *

handle

)

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.

{
        struct nl_cache * cache;
        
        cache = nl_cache_alloc(&rtnl_qdisc_ops);
        if (cache == NULL)
                return NULL;
 
        if (handle && nl_cache_refill(handle, cache) < 0) {
                nl_cache_free(cache);
                return NULL;
        }
 
        return cache;
}

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

rtnl_qdisc_get_by_parent()

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

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.

{
        struct rtnl_qdisc *q;
 
        if (cache->c_ops != &rtnl_qdisc_ops)
                return NULL;
 
        nl_list_for_each_entry(q, &cache->c_items, ce_list) {
                if (q->q_parent == parent && q->q_ifindex == ifindex) {
                        nl_object_get((struct nl_object *) q);
                        return q;
                }
        }
 
        return NULL;
}

References nl_object_get().

Referenced by rtnl_class_leaf_qdisc().

rtnl_qdisc_get()

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

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.

{
        struct rtnl_qdisc *q;
 
        if (cache->c_ops != &rtnl_qdisc_ops)
                return NULL;
 
        nl_list_for_each_entry(q, &cache->c_items, ce_list) {
                if (q->q_handle == handle && q->q_ifindex == ifindex) {
                        nl_object_get((struct nl_object *) q);
                        return q;
                }
        }
 
        return NULL;
}

References nl_object_get().