Neighbours

The neighbour table establishes bindings between protocol addresses and link layer addresses for hosts sharing the same physical link. More...

Neighbour States Translations
char *	rtnl_neigh_state2str (int state, char *buf, size_t len)
int	rtnl_neigh_str2state (const char *name)

Neighbour Flags Translations
char *	rtnl_neigh_flags2str (int flags, char *buf, size_t len)
int	rtnl_neigh_str2flag (const char *name)

Neighbour Object Allocation/Freeage
struct rtnl_neigh *	rtnl_neigh_alloc (void)
void	rtnl_neigh_put (struct rtnl_neigh *neigh)

Neighbour Cache Managament
struct nl_cache *	rtnl_neigh_alloc_cache (struct nl_handle *handle)
	Build a neighbour cache including all neighbours currently configured in the kernel.
struct rtnl_neigh *	rtnl_neigh_get (struct nl_cache *cache, int ifindex, struct nl_addr *dst)
	Look up a neighbour by interface index and destination address.

Neighbour Addition
struct nl_msg *	rtnl_neigh_build_add_request (struct rtnl_neigh *tmpl, int flags)
	Build netlink request message to add a new neighbour.
int	rtnl_neigh_add (struct nl_handle *handle, struct rtnl_neigh *tmpl, int flags)
	Add a new neighbour.

Neighbour Deletion
struct nl_msg *	rtnl_neigh_build_delete_request (struct rtnl_neigh *neigh, int flags)
	Build a netlink request message to delete a neighbour.
int	rtnl_neigh_delete (struct nl_handle *handle, struct rtnl_neigh *neigh, int flags)
	Delete a neighbour.

Neighbour Modification
struct nl_msg *	rtnl_neigh_build_change_request (struct rtnl_neigh *neigh, int flags)
	Build a netlink request message to change neighbour attributes.
int	rtnl_neigh_change (struct nl_handle *handle, struct rtnl_neigh *neigh, int flags)
	Change neighbour attributes.

Attributes
void	rtnl_neigh_set_state (struct rtnl_neigh *neigh, int state)
int	rtnl_neigh_get_state (struct rtnl_neigh *neigh)
void	rtnl_neigh_unset_state (struct rtnl_neigh *neigh, int state)
void	rtnl_neigh_set_flags (struct rtnl_neigh *neigh, unsigned int flags)
unsigned int	rtnl_neigh_get_flags (struct rtnl_neigh *neigh)
void	rtnl_neigh_unset_flags (struct rtnl_neigh *neigh, unsigned int flags)
void	rtnl_neigh_set_ifindex (struct rtnl_neigh *neigh, int ifindex)
int	rtnl_neigh_get_ifindex (struct rtnl_neigh *neigh)
void	rtnl_neigh_set_lladdr (struct rtnl_neigh *neigh, struct nl_addr *addr)
struct nl_addr *	rtnl_neigh_get_lladdr (struct rtnl_neigh *neigh)
int	rtnl_neigh_set_dst (struct rtnl_neigh *neigh, struct nl_addr *addr)
struct nl_addr *	rtnl_neigh_get_dst (struct rtnl_neigh *neigh)
void	rtnl_neigh_set_family (struct rtnl_neigh *neigh, int family)
void	rtnl_neigh_set_type (struct rtnl_neigh *neigh, int type)
int	rtnl_neigh_get_type (struct rtnl_neigh *neigh)

Detailed Description

This module allows you to access and manipulate the content of these tables.

Neighbour States

NUD_INCOMPLETE
NUD_REACHABLE
NUD_STALE
NUD_DELAY
NUD_PROBE
NUD_FAILED
NUD_NOARP
NUD_PERMANENT

Neighbour Flags

NTF_PROXY
NTF_ROUTER

Neighbour Identification

A neighbour is uniquely identified by the attributes listed below, whenever you refer to an existing neighbour all of the attributes must be set. Neighbours from caches automatically have all required attributes set.

• interface index (rtnl_neigh_set_ifindex())
• destination address (rtnl_neigh_set_dst())

Changeable Attributes

• state (rtnl_neigh_set_state())
• link layer address (rtnl_neigh_set_lladdr())

Required Caches for Dumping

In order to dump neighbour attributes you must provide the following caches via nl_cache_provide()

• link cache holding all links

TODO

• Document proxy settings
• Document states and their influence

1) Retrieving information about configured neighbours

// The first step is to retrieve a list of all available neighbour within
// the kernel and put them into a cache.
struct nl_cache *cache = rtnl_neigh_alloc_cache(handle);
 
// Neighbours can then be looked up by the interface and destination
// address:
struct rtnl_neigh *neigh = rtnl_neigh_get(cache, ifindex, dst_addr);
 
// After successful usage, the object must be given back to the cache
rtnl_neigh_put(neigh);

2) Adding new neighbours

// Allocate an empty neighbour handle to be filled out with the attributes
// of the new neighbour.
struct rtnl_neigh *neigh = rtnl_neigh_alloc();
 
// Fill out the attributes of the new neighbour
rtnl_neigh_set_ifindex(neigh, ifindex);
rtnl_neigh_set_dst(neigh, dst_addr);
rtnl_neigh_set_state(neigh, rtnl_neigh_str2state("permanent"));
 
// Build the netlink message and send it to the kernel, the operation will
// block until the operation has been completed. Alternatively the required
// netlink message can be built using rtnl_neigh_build_add_request()
// to be sent out using nl_send_auto_complete().
rtnl_neigh_add(nl_handle, neigh, NLM_F_REPLACE);
 
// Free the memory
rtnl_neigh_put(neigh);

3) Deleting an existing neighbour

// Allocate an empty neighbour object to be filled out with the attributes
// matching the neighbour to be deleted. Alternatively a fully equipped
// neighbour object out of a cache can be used instead.
struct rtnl_neigh *neigh = rtnl_neigh_alloc();
 
// Neighbours are uniquely identified by their interface index and
// destination address, you may fill out other attributes but they
// will have no influence.
rtnl_neigh_set_ifindex(neigh, ifindex);
rtnl_neigh_set_dst(neigh, dst_addr);
 
// Build the netlink message and send it to the kernel, the operation will
// block until the operation has been completed. Alternatively the required
// netlink message can be built using rtnl_neigh_build_delete_request()
// to be sent out using nl_send_auto_complete().
rtnl_neigh_delete(handle, neigh, 0);
 
// Free the memory
rtnl_neigh_put(neigh);

4) Changing neighbour attributes

// Allocate an empty neighbour object to be filled out with the attributes
// matching the neighbour to be changed and the new parameters. Alternatively
// a fully equipped modified neighbour object out of a cache can be used.
struct rtnl_neigh *neigh = rtnl_neigh_alloc();
 
// Identify the neighbour to be changed by its interface index and
// destination address
rtnl_neigh_set_ifindex(neigh, ifindex);
rtnl_neigh_set_dst(neigh, dst_addr);
 
// The link layer address may be modified, if so it is wise to change
// its state to "permanent" in order to avoid having it overwritten.
rtnl_neigh_set_lladdr(neigh, lladdr);
 
// Secondly the state can be modified allowing normal neighbours to be
// converted into permanent entries or to manually confirm a neighbour.
rtnl_neigh_set_state(neigh, state);
 
// Build the netlink message and send it to the kernel, the operation will
// block until the operation has been completed. Alternatively the required
// netlink message can be built using rtnl_neigh_build_change_request()
// to be sent out using nl_send_auto_complete().
rtnl_neigh_change(handle, neigh, 0);
 
// Free the memory
rtnl_neigh_put(neigh);

Function Documentation

rtnl_neigh_alloc()

struct rtnl_neigh * rtnl_neigh_alloc

(

void

)

Definition at line 506 of file neigh.c.

{
        return (struct rtnl_neigh *) nl_object_alloc(&neigh_obj_ops);
}

rtnl_neigh_put()

void rtnl_neigh_put

(

struct rtnl_neigh *

neigh

)

Definition at line 511 of file neigh.c.

{
        nl_object_put((struct nl_object *) neigh);
}

rtnl_neigh_alloc_cache()

struct nl_cache * rtnl_neigh_alloc_cache

(

struct nl_handle *

handle

)

Parameters

handle

netlink handle

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

Note

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

Returns

The new cache or NULL if an error occured.

Definition at line 534 of file neigh.c.

{
        struct nl_cache *cache;
 
        cache = nl_cache_alloc(&rtnl_neigh_ops);
        if (cache == NULL)
                return NULL;
 
        if (handle && nl_cache_refill(handle, cache) < 0) {
                nl_cache_free(cache);
                return NULL;
        }
 
        NL_DBG(2, "Returning new cache %p\n", cache);
 
        return cache;
}

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

rtnl_neigh_get()

struct rtnl_neigh * rtnl_neigh_get	(	struct nl_cache *	cache,
		int	ifindex,
		struct nl_addr *	dst
	)

Parameters

cache	neighbour cache
ifindex	interface index the neighbour is on
dst	destination address of the neighbour

Returns

neighbour handle or NULL if no match was found.

Definition at line 559 of file neigh.c.

{
        struct rtnl_neigh *neigh;
 
        nl_list_for_each_entry(neigh, &cache->c_items, ce_list) {
                if (neigh->n_ifindex == ifindex &&
                    !nl_addr_cmp(neigh->n_dst, dst)) {
                        nl_object_get((struct nl_object *) neigh);
                        return neigh;
                }
        }
 
        return NULL;
}

References nl_addr_cmp(), and nl_object_get().

rtnl_neigh_build_add_request()

struct nl_msg * rtnl_neigh_build_add_request	(	struct rtnl_neigh *	tmpl,
		int	flags
	)

Parameters

tmpl	template with data of new neighbour
flags	additional netlink message flags

Builds a new netlink message requesting a addition of a new neighbour. 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. tmpl must contain the attributes of the new neighbour set via rtnl_neigh_set_* functions.

The following attributes must be set in the template:

• Interface index (rtnl_neigh_set_ifindex())
• State (rtnl_neigh_set_state())
• Destination address (rtnl_neigh_set_dst())
• Link layer address (rtnl_neigh_set_lladdr())

Returns

The netlink message

Definition at line 633 of file neigh.c.

{
        return build_neigh_msg(tmpl, RTM_NEWNEIGH, NLM_F_CREATE | flags);
}

References NLM_F_CREATE.

Referenced by rtnl_neigh_add().

rtnl_neigh_add()

int rtnl_neigh_add	(	struct nl_handle *	handle,
		struct rtnl_neigh *	tmpl,
		int	flags
	)

Parameters

handle	netlink handle
tmpl	template with requested changes
flags	additional netlink message flags

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

The following attributes must be set in the template:

• Interface index (rtnl_neigh_set_ifindex())
• State (rtnl_neigh_set_state())
• Destination address (rtnl_neigh_set_dst())
• Link layer address (rtnl_neigh_set_lladdr())

Returns

0 on sucess or a negative error if an error occured.

Definition at line 656 of file neigh.c.

{
        int err;
        struct nl_msg *msg;
        
        msg = rtnl_neigh_build_add_request(tmpl, 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_neigh_build_add_request().

rtnl_neigh_build_delete_request()

struct nl_msg * rtnl_neigh_build_delete_request	(	struct rtnl_neigh *	neigh,
		int	flags
	)

Parameters

neigh	neighbour to delete
flags	additional netlink message flags

Builds a new netlink message requesting a deletion of a neighbour. 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. neigh must point to an existing neighbour.

Returns

The netlink message

Definition at line 693 of file neigh.c.

{
        return build_neigh_msg(neigh, RTM_DELNEIGH, flags);
}

Referenced by rtnl_neigh_delete().

rtnl_neigh_delete()

int rtnl_neigh_delete	(	struct nl_handle *	handle,
		struct rtnl_neigh *	neigh,
		int	flags
	)

Parameters

handle	netlink handle
neigh	neighbour to delete
flags	additional netlink message flags

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

Returns

0 on sucess or a negative error if an error occured.

Definition at line 711 of file neigh.c.

{
        int err;
        struct nl_msg *msg;
        
        msg = rtnl_neigh_build_delete_request(neigh, 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_neigh_build_delete_request().

rtnl_neigh_build_change_request()

struct nl_msg * rtnl_neigh_build_change_request	(	struct rtnl_neigh *	neigh,
		int	flags
	)

Parameters

neigh	the neighbour to change
flags	additional netlink message flags

Builds a new netlink message requesting a change of a neigh attributes. 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

The netlink message

Note

Not all attributes can be changed, see Changeable Attributes for a list.

Definition at line 750 of file neigh.c.

{
        return build_neigh_msg(neigh, RTM_NEWNEIGH, NLM_F_REPLACE | flags);
}

References NLM_F_REPLACE.

Referenced by rtnl_neigh_change().

rtnl_neigh_change()

int rtnl_neigh_change	(	struct nl_handle *	handle,
		struct rtnl_neigh *	neigh,
		int	flags
	)

Parameters

handle	netlink handle
neigh	neighbour to be changed
flags	additional netlink message flags

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

Returns

0 on sucess or a negative error if an error occured.

Note

Not all attributes can be changed, see Changeable Attributes for a list.

Definition at line 770 of file neigh.c.

{
        int err;
        struct nl_msg *msg;
        
        msg = rtnl_neigh_build_change_request(neigh, 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_neigh_build_change_request().

rtnl_neigh_state2str()

char * rtnl_neigh_state2str	(	int	state,
		char *	buf,
		size_t	len
	)

Definition at line 806 of file neigh.c.

{
        return __flags2str(state, buf, len, neigh_states,
            ARRAY_SIZE(neigh_states));
}

rtnl_neigh_str2state()

int rtnl_neigh_str2state

(

const char *

name

)

Definition at line 812 of file neigh.c.

{
        return __str2type(name, neigh_states, ARRAY_SIZE(neigh_states));
}

rtnl_neigh_flags2str()

char * rtnl_neigh_flags2str	(	int	flags,
		char *	buf,
		size_t	len
	)

Definition at line 829 of file neigh.c.

{
        return __flags2str(flags, buf, len, neigh_flags,
            ARRAY_SIZE(neigh_flags));
}

rtnl_neigh_str2flag()

int rtnl_neigh_str2flag

(

const char *

name

)

Definition at line 835 of file neigh.c.

{
        return __str2type(name, neigh_flags, ARRAY_SIZE(neigh_flags));
}

rtnl_neigh_set_state()

void rtnl_neigh_set_state	(	struct rtnl_neigh *	neigh,
		int	state
	)

Definition at line 847 of file neigh.c.

{
        neigh->n_state_mask |= state;
        neigh->n_state |= state;
        neigh->ce_mask |= NEIGH_ATTR_STATE;
}

rtnl_neigh_get_state()

int rtnl_neigh_get_state

(

struct rtnl_neigh *

neigh

)

Definition at line 854 of file neigh.c.

{
        if (neigh->ce_mask & NEIGH_ATTR_STATE)
                return neigh->n_state;
        else
                return -1;
}

rtnl_neigh_unset_state()

void rtnl_neigh_unset_state	(	struct rtnl_neigh *	neigh,
		int	state
	)

Definition at line 862 of file neigh.c.

{
        neigh->n_state_mask |= state;
        neigh->n_state &= ~state;
        neigh->ce_mask |= NEIGH_ATTR_STATE;
}

rtnl_neigh_set_flags()

void rtnl_neigh_set_flags	(	struct rtnl_neigh *	neigh,
		unsigned int	flags
	)

Definition at line 869 of file neigh.c.

{
        neigh->n_flag_mask |= flags;
        neigh->n_flags |= flags;
        neigh->ce_mask |= NEIGH_ATTR_FLAGS;
}

rtnl_neigh_get_flags()

unsigned int rtnl_neigh_get_flags

(

struct rtnl_neigh *

neigh

)

Definition at line 876 of file neigh.c.

{
        return neigh->n_flags;
}

rtnl_neigh_unset_flags()

void rtnl_neigh_unset_flags	(	struct rtnl_neigh *	neigh,
		unsigned int	flags
	)

Definition at line 881 of file neigh.c.

{
        neigh->n_flag_mask |= flags;
        neigh->n_flags &= ~flags;
        neigh->ce_mask |= NEIGH_ATTR_FLAGS;
}

rtnl_neigh_set_ifindex()

void rtnl_neigh_set_ifindex	(	struct rtnl_neigh *	neigh,
		int	ifindex
	)

Definition at line 888 of file neigh.c.

{
        neigh->n_ifindex = ifindex;
        neigh->ce_mask |= NEIGH_ATTR_IFINDEX;
}

rtnl_neigh_get_ifindex()

int rtnl_neigh_get_ifindex

(

struct rtnl_neigh *

neigh

)

Definition at line 894 of file neigh.c.

{
        if (neigh->ce_mask & NEIGH_ATTR_IFINDEX)
                return neigh->n_ifindex;
        else
                return RTNL_LINK_NOT_FOUND;
}

rtnl_neigh_set_lladdr()

void rtnl_neigh_set_lladdr	(	struct rtnl_neigh *	neigh,
		struct nl_addr *	addr
	)

Definition at line 927 of file neigh.c.

{
        __assign_addr(neigh, &neigh->n_lladdr, addr, NEIGH_ATTR_LLADDR, 1);
}

rtnl_neigh_get_lladdr()

struct nl_addr * rtnl_neigh_get_lladdr

(

struct rtnl_neigh *

neigh

)

Definition at line 932 of file neigh.c.

{
        if (neigh->ce_mask & NEIGH_ATTR_LLADDR)
                return neigh->n_lladdr;
        else
                return NULL;
}

rtnl_neigh_set_dst()

int rtnl_neigh_set_dst	(	struct rtnl_neigh *	neigh,
		struct nl_addr *	addr
	)

Definition at line 940 of file neigh.c.

{
        return __assign_addr(neigh, &neigh->n_dst, addr,
                             NEIGH_ATTR_DST, 0);
}

rtnl_neigh_get_dst()

struct nl_addr * rtnl_neigh_get_dst

(

struct rtnl_neigh *

neigh

)

Definition at line 946 of file neigh.c.

{
        if (neigh->ce_mask & NEIGH_ATTR_DST)
                return neigh->n_dst;
        else
                return NULL;
}

rtnl_neigh_set_family()

void rtnl_neigh_set_family	(	struct rtnl_neigh *	neigh,
		int	family
	)

Definition at line 954 of file neigh.c.

{
        neigh->n_family = family;
        neigh->ce_mask |= NEIGH_ATTR_FAMILY;
}

rtnl_neigh_set_type()

void rtnl_neigh_set_type	(	struct rtnl_neigh *	neigh,
		int	type
	)

Definition at line 960 of file neigh.c.

{
        neigh->n_type = type;
        neigh->ce_mask = NEIGH_ATTR_TYPE;
}

rtnl_neigh_get_type()

int rtnl_neigh_get_type

(

struct rtnl_neigh *

neigh

)

Definition at line 966 of file neigh.c.

{
        if (neigh->ce_mask & NEIGH_ATTR_TYPE)
                return neigh->n_type;
        else
                return -1;
}