Gestire la tabella ARP senza il comando "arp"
Dal momento che attualmente in openWRT non esiste il comando arp (o meglio, esiste, ma si limita a mostrare la tabella senza poterla modificare il alcun modo), occorre un metodo per modificarla.
Il metodo che ho trovato e` usare il comando ip, parte del pacchetto iproute2.
Mediante il comando ip e` possibile modificare la tabella ARP cosi` come si farebbe con il comando arp se solo ci fosse.
Per aggiungere una entry statica ad esempio si fa cosi`:
ip neigh add 192.168.1.2 lladdr 00:de:ad:be:ef:00 nud permanent dev br0
(indirizzo ip) (mac address) (entry statica) (device)Per modificarla si usa modify anziche` add. Per visualizzare la tabella si puo` usare ip neigh show.
Riporto un pezzetto del man di ip (quello di linux debian, non quello di openwrt, spero sia uguale)
ip neighbour - neighbour/arp tables management.
neighbour objects establish bindings between protocol addresses and link layer addresses for hosts sharing the
same link. Neighbour entries are organized into tables. The IPv4 neighbour table is known by another name -
the ARP table.
The corresponding commands display neighbour bindings and their properties, add new neighbour entries and
delete old ones.
ip neighbour add - add a new neighbour entry
ip neighbour change - change an existing entry
ip neighbour replace - add a new entry or change an existing one
These commands create new neighbour records or update existing ones.
to ADDRESS (default)
the protocol address of the neighbour. It is either an IPv4 or IPv6 address.
dev NAME
the interface to which this neighbour is attached.
lladdr LLADDRESS
the link layer address of the neighbour. LLADDRESS can also be null.
nud NUD_STATE
the state of the neighbour entry. nud is an abbreviation for 'Neigh bour Unreachability Detection'.
The state can take one of the following values:
permanent - the neighbour entry is valid forever and can be only be removed administratively.
noarp - the neighbour entry is valid. No attempts to validate this entry will be made but it
can be removed when its lifetime expires.
reachable - the neighbour entry is valid until the reachability timeout expires.
stale - the neighbour entry is valid but suspicious. This option to ip neigh does not change
the neighbour state if it was valid and the address is not changed by this command.
ip neighbour delete - delete a neighbour entry
This command invalidates a neighbour entry.
The arguments are the same as with ip neigh add, except that lladdr and nud are ignored.
Warning: Attempts to delete or manually change a noarp entry created by the kernel may result in unpredictable
behaviour. Particularly, the kernel may try to resolve this address even on a NOARP interface or if the
address is multicast or broadcast.
ip neighbour show - list neighbour entries
This commands displays neighbour tables.
to ADDRESS (default)
the prefix selecting the neighbours to list.
dev NAME
only list the neighbours attached to this device.
unused only list neighbours which are not currently in use.
nud NUD_STATE
only list neighbour entries in this state. NUD_STATE takes values listed below or the special value
all which means all states. This option may occur more than once. If this option is absent, ip lists
all entries except for none and noarp.
ip neighbour flush - flush neighbour entries
This command flushes neighbour tables, selecting entries to flush by some criteria.
This command has the same arguments as show. The differences are that it does not run when no arguments are
given, and that the default neighbour states to be flushed do not include permanent and noarp.
With the -statistics option, the command becomes verbose. It prints out the number of deleted neighbours and
the number of rounds made to flush the neighbour table. If the option is given twice, ip neigh flush also
dumps all the deleted neighbours.