libnl 1.1
Neighbours
Routing Netlink

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

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.

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)

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

struct nl_cache* rtnl_neigh_alloc_cache ( struct nl_handle *  handle) [read]
Parameters:
handlenetlink 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.

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

{
        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;
}
struct rtnl_neigh* rtnl_neigh_get ( struct nl_cache *  cache,
int  ifindex,
struct nl_addr *  dst 
) [read]
Parameters:
cacheneighbour cache
ifindexinterface index the neighbour is on
dstdestination address of the neighbour
Returns:
neighbour handle or NULL if no match was found.

Definition at line 559 of file neigh.c.

References nl_addr_cmp(), and nl_object_get().

{
        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;
}
struct nl_msg* rtnl_neigh_build_add_request ( struct rtnl_neigh *  tmpl,
int  flags 
) [read]
Parameters:
tmpltemplate with data of new neighbour
flagsadditional 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.

References NLM_F_CREATE.

Referenced by rtnl_neigh_add().

{
        return build_neigh_msg(tmpl, RTM_NEWNEIGH, NLM_F_CREATE | flags);
}
int rtnl_neigh_add ( struct nl_handle *  handle,
struct rtnl_neigh *  tmpl,
int  flags 
)
Parameters:
handlenetlink handle
tmpltemplate with requested changes
flagsadditional 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.

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

{
        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);
        if (err < 0)
                return err;

        nlmsg_free(msg);
        return nl_wait_for_ack(handle);
}
struct nl_msg* rtnl_neigh_build_delete_request ( struct rtnl_neigh *  neigh,
int  flags 
) [read]
Parameters:
neighneighbour to delete
flagsadditional 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.

Referenced by rtnl_neigh_delete().

{
        return build_neigh_msg(neigh, RTM_DELNEIGH, flags);
}
int rtnl_neigh_delete ( struct nl_handle *  handle,
struct rtnl_neigh *  neigh,
int  flags 
)
Parameters:
handlenetlink handle
neighneighbour to delete
flagsadditional 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.

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

{
        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);
        if (err < 0)
                return err;

        nlmsg_free(msg);
        return nl_wait_for_ack(handle);
}
struct nl_msg* rtnl_neigh_build_change_request ( struct rtnl_neigh *  neigh,
int  flags 
) [read]
Parameters:
neighthe neighbour to change
flagsadditional 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.

References NLM_F_REPLACE.

Referenced by rtnl_neigh_change().

{
        return build_neigh_msg(neigh, RTM_NEWNEIGH, NLM_F_REPLACE | flags);
}
int rtnl_neigh_change ( struct nl_handle *  handle,
struct rtnl_neigh *  neigh,
int  flags 
)
Parameters:
handlenetlink handle
neighneighbour to be changed
flagsadditional 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.

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

{
        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);
        if (err < 0)
                return err;

        nlmsg_free(msg);
        return nl_wait_for_ack(handle);
}