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IFNET(9) FreeBSD Kernel Developer's Manual IFNET(9)
NAME
ifnet, ifaddr, ifqueue, if_data - kernel interfaces for manipulating
network interfaces
SYNOPSIS
#include <sys/param.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <net/if.h>
#include <net/if_var.h>
#include <net/if_types.h>
Interface Manipulation Functions
struct ifnet *
if_alloc(u_char type);
struct ifnet *
if_alloc_dev(u_char type, device_t dev);
struct ifnet *
if_alloc_domain(u_char type, int numa_domain);
void
if_attach(struct ifnet *ifp);
void
if_detach(struct ifnet *ifp);
void
if_free(struct ifnet *ifp);
void
if_free_type(struct ifnet *ifp, u_char type);
void
if_down(struct ifnet *ifp);
int
ifioctl(struct socket *so, u_long cmd, caddr_t data, struct thread *td);
int
ifpromisc(struct ifnet *ifp, int pswitch);
int
if_allmulti(struct ifnet *ifp, int amswitch);
struct ifnet *
ifunit(const char *name);
struct ifnet *
ifunit_ref(const char *name);
void
if_up(struct ifnet *ifp);
Interface Address Functions
struct ifaddr *
struct ifaddr *
ifa_ifwithnet(struct sockaddr *addr, int ignore_ptp, int fib);
struct ifaddr *
ifaof_ifpforaddr(struct sockaddr *addr, struct ifnet *ifp);
void
ifa_ref(struct ifaddr *ifa);
void
ifa_free(struct ifaddr *ifa);
Interface Multicast Address Functions
int
if_addmulti(struct ifnet *ifp, struct sockaddr *sa,
struct ifmultiaddr **ifmap);
int
if_delmulti(struct ifnet *ifp, struct sockaddr *sa);
struct ifmultiaddr *
if_findmulti(struct ifnet *ifp, struct sockaddr *sa);
Output queue macros
IF_DEQUEUE(struct ifqueue *ifq, struct mbuf *m);
struct ifnet Member Functions
void
(*if_input)(struct ifnet *ifp, struct mbuf *m);
int
(*if_output)(struct ifnet *ifp, struct mbuf *m,
const struct sockaddr *dst, struct route *ro);
void
(*if_start)(struct ifnet *ifp);
int
(*if_transmit)(struct ifnet *ifp, struct mbuf *m);
void
(*if_qflush)(struct ifnet *ifp);
int
(*if_ioctl)(struct ifnet *ifp, u_long cmd, caddr_t data);
void
(*if_init)(void *if_softc);
int
(*if_resolvemulti)(struct ifnet *ifp, struct sockaddr **retsa,
struct sockaddr *addr);
struct ifaddr member function
void
(*ifa_rtrequest)(int cmd, struct rtentry *rt, struct rt_addrinfo *info);
Global Variables
<net/if_var.h> and the functions named above and defined in
/sys/net/if.c. Those interfaces which are intended to be used by user
programs are defined in <net/if.h>; these include the interface flags,
the if_data structure, and the structures defining the appearance of
interface-related messages on the route(4) routing socket and in
sysctl(3). The header file <net/if_var.h> defines the kernel-internal
interfaces, including the ifnet, ifaddr, and ifmultiaddr structures and
the functions which manipulate them. (A few user programs will need
<net/if_var.h> because it is the prerequisite of some other header file
like <netinet/if_ether.h>. Most references to those two files in
particular can be replaced by <net/ethernet.h>.)
The system keeps a linked list of interfaces using the TAILQ macros
defined in queue(3); this list is headed by a struct ifnethead called
ifnet. The elements of this list are of type struct ifnet, and most
kernel routines which manipulate interface as such accept or return
pointers to these structures. Each interface structure contains an
if_data structure used for statistics and information. Each interface
also has a TAILQ of interface addresses, described by ifaddr structures.
An AF_LINK address (see link_addr(3)) describing the link layer
implemented by the interface (if any) is accessed by the ifaddr_byindex()
function or if_addr structure. (Some trivial interfaces do not provide
any link layer addresses; this structure, while still present, serves
only to identify the interface name and index.)
Finally, those interfaces supporting reception of multicast datagrams
have a TAILQ of multicast group memberships, described by ifmultiaddr
structures. These memberships are reference-counted.
Interfaces are also associated with an output queue, defined as a struct
ifqueue; this structure is used to hold packets while the interface is in
the process of sending another.
The ifnet Structure
The fields of struct ifnet are as follows:
if_softc (void *) A pointer to the driver's private state
block. (Initialized by driver.)
if_l2com (void *) A pointer to the common data for the
interface's layer 2 protocol. (Initialized by
if_alloc().)
if_vnet (struct vnet *) A pointer to the virtual network
stack instance. (Initialized by if_attach().)
if_home_vnet (struct vnet *) A pointer to the parent virtual
network stack, where this struct ifnet originates
from. (Initialized by if_attach().)
if_link (TAILQ_ENTRY(ifnet)) queue(3) macro glue.
if_xname (char *) The name of the interface, (e.g., "fxp0"
or "lo0"). (Initialized by driver (usually via
if_initname()).)
if_dname (const char *) The name of the driver.
(Initialized by driver (usually via
if_initname()).)
if_refcount (u_int) The reference count. (Initialized by
if_alloc().)
if_addrhead (struct ifaddrhead) The head of the queue(3) TAILQ
containing the list of addresses assigned to this
interface.
if_pcount (int) A count of promiscuous listeners on this
interface, used to reference-count the IFF_PROMISC
flag.
if_carp (struct carp_if *) A pointer to the CARP interface
structure, carp(4). (Initialized by the driver-
specific if_ioctl() routine.)
if_bpf (struct bpf_if *) Opaque per-interface data for
the packet filter, bpf(4). (Initialized by
bpf_attach().)
if_index (u_short) A unique number assigned to each
interface in sequence as it is attached. This
number can be used in a struct sockaddr_dl to
refer to a particular interface by index (see
link_addr(3)). (Initialized by if_alloc().)
if_vlantrunk (struct ifvlantrunk *) A pointer to 802.1Q trunk
structure, vlan(4). (Initialized by the driver-
specific if_ioctl() routine.)
if_flags (int) Flags describing operational parameters of
this interface (see below). (Manipulated by
generic code.)
if_drv_flags (int) Flags describing operational status of this
interface (see below). (Manipulated by driver.)
if_capabilities (int) Flags describing the capabilities the
interface supports (see below).
if_capenable (int) Flags describing the enabled capabilities of
the interface (see below).
if_linkmib (void *) A pointer to an interface-specific MIB
structure exported by ifmib(4). (Initialized by
driver.)
if_linkmiblen (size_t) The size of said structure. (Initialized
by driver.)
if_data (struct if_data) More statistics and information;
see The if_data structure, below. (Initialized by
driver, manipulated by both driver and generic
code.)
if_multiaddrs (struct ifmultihead) The head of the queue(3)
TAILQ containing the list of multicast addresses
assigned to this interface.
if_snd (struct ifaltq) The output queue. (Manipulated by
driver.)
if_broadcastaddr
(const u_int8_t *) A link-level broadcast
bytestring for protocols with variable address
length.
if_bridge (void *) A pointer to the bridge interface
structure, if_bridge(4). (Initialized by the
driver-specific if_ioctl() routine.)
if_label (struct label *) A pointer to the MAC Framework
label structure, mac(4). (Initialized by
if_alloc().)
if_afdata (void *) An address family dependent data region.
if_afdata_initialized
(int) Used to track the current state of address
family initialization.
if_afdata_lock (struct rwlock) An rwlock(9) lock used to protect
if_afdata internals.
if_linktask (struct task) A taskqueue(9) task scheduled for
link state change events of the interface.
if_addr_lock (struct rwlock) An rwlock(9) lock used to protect
interface-related address lists.
if_clones (LIST_ENTRY(ifnet)) queue(3) macro glue for the
list of clonable network interfaces.
if_groups (TAILQ_HEAD(, ifg_list)) The head of the queue(3)
TAILQ containing the list of groups per interface.
if_pf_kif (void *) A pointer to the structure used for
interface abstraction by pf(4).
if_lagg (void *) A pointer to the lagg(4) interface
structure.
if_alloctype (u_char) The type of the interface as it was at
the time of its allocation. It is used to cache
the type passed to if_alloc(), but unlike if_type,
it would not be changed by drivers.
if_numa_domain (uint8_t) The NUMA domain of the hardware device
associated with the interface. This is filled in
with a wildcard value unless the kernel is NUMA
aware, the system is a NUMA system, and the ifnet
is allocated using if_alloc_dev() or
if_alloc_domain().
References to ifnet structures are gained by calling the if_ref()
function and released by calling the if_rele() function. They are used
to allow kernel code walking global interface lists to release the ifnet
lock yet keep the ifnet structure stable.
an interrupt handler or used to emulate reception of a packet on
this interface. A single function implementing if_input() can be
shared among multiple drivers utilizing the same link-layer
framing, e.g., Ethernet.
if_output()
Output a packet on interface ifp, or queue it on the output queue
if the interface is already active.
if_transmit()
Transmit a packet on an interface or queue it if the interface is
in use. This function will return ENOBUFS if the devices software
and hardware queues are both full. This function must be installed
after if_attach() to override the default implementation. This
function is exposed in order to allow drivers to manage their own
queues and to reduce the latency caused by a frequently gratuitous
enqueue / dequeue pair to ifq. The suggested internal software
queuing mechanism is buf_ring.
if_qflush()
Free mbufs in internally managed queues when the interface is
marked down. This function must be installed after if_attach() to
override the default implementation. This function is exposed in
order to allow drivers to manage their own queues and to reduce the
latency caused by a frequently gratuitous enqueue / dequeue pair to
ifq. The suggested internal software queuing mechanism is
buf_ring.
if_start()
Start queued output on an interface. This function is exposed in
order to provide for some interface classes to share a if_output()
among all drivers. if_start() may only be called when the
IFF_DRV_OACTIVE flag is not set. (Thus, IFF_DRV_OACTIVE does not
literally mean that output is active, but rather that the device's
internal output queue is full.) Please note that this function will
soon be deprecated.
if_ioctl()
Process interface-related ioctl(2) requests (defined in
<sys/sockio.h>). Preliminary processing is done by the generic
routine ifioctl() to check for appropriate privileges, locate the
interface being manipulated, and perform certain generic operations
like twiddling flags and flushing queues. See the description of
ifioctl() below for more information.
if_init()
Initialize and bring up the hardware, e.g., reset the chip and
enable the receiver unit. Should mark the interface running, but
not active (IFF_DRV_RUNNING, ~IIF_DRV_OACTIVE).
if_resolvemulti()
Check the requested multicast group membership, addr, for validity,
and if necessary compute a link-layer group which corresponds to
that address which is returned in *retsa. Returns zero on success,
or an error code on failure.
Interface Flags
Interface flags are used for a number of different purposes. Some flags
simply indicate information about the type of interface and its
by an asterisk (`*') in the following listing.
IFF_UP <D> The interface has been configured up by the
user-level code.
IFF_BROADCAST <S*> The interface supports broadcast.
IFF_DEBUG <D> Used to enable/disable driver debugging code.
IFF_LOOPBACK <S> The interface is a loopback device.
IFF_POINTOPOINT <S*> The interface is point-to-point; "broadcast"
address is actually the address of the other end.
IFF_DRV_RUNNING <D*> The interface has been configured and dynamic
resources were successfully allocated. Probably
only useful internal to the interface.
IFF_NOARP <D> Disable network address resolution on this
interface.
IFF_PROMISC <D*> This interface is in promiscuous mode.
IFF_PPROMISC <D> This interface is in the permanently
promiscuous mode (implies IFF_PROMISC).
IFF_ALLMULTI <D*> This interface is in all-multicasts mode
(used by multicast routers).
IFF_DRV_OACTIVE <D*> The interface's hardware output queue (if
any) is full; output packets are to be queued.
IFF_SIMPLEX <S*> The interface cannot hear its own
transmissions.
IFF_LINK0
IFF_LINK1
IFF_LINK2 <D> Control flags for the link layer. (Currently
abused to select among multiple physical layers on
some devices.)
IFF_MULTICAST <S*> This interface supports multicast.
IFF_CANTCONFIG <S*> The interface is not configurable in a
meaningful way. Primarily useful for IFT_USB
interfaces registered at the interface list.
IFF_MONITOR <D> This interface blocks transmission of packets
and discards incoming packets after BPF
processing. Used to monitor network traffic but
not interact with the network in question.
IFF_STATICARP <D> Used to enable/disable ARP requests on this
interface.
IFF_DYING <D*> Set when the ifnet structure of this
interface is being released and still has
if_refcount references.
IFF_RENAMING <D> Set when this interface is being renamed.
Interface Capabilities Flags
Interface capabilities are specialized features an interface may or may
not support. These capabilities are very hardware-specific and allow,
when enabled, to offload specific network processing to the interface or
to offer a particular feature for use by other kernel parts.
It should be stressed that a capability can be completely uncontrolled
(i.e., stay always enabled with no way to disable it) or allow limited
control over itself (e.g., depend on another capability's state.) Such
peculiarities are determined solely by the hardware and driver of a
particular interface. Only the driver possesses the knowledge on whether
and how the interface capabilities can be controlled. Consequently,
capabilities flags in if_capenable should never be modified directly by
kernel code other than the interface driver. The command SIOCSIFCAP to
ifioctl() is the dedicated means to attempt altering if_capenable on an
interface. Userland code shall use ioctl(2).
driver for the interface might disable
hardware checksum validation if the MTU is
set above the hardcoded limit.
IFCAP_TXCSUM This interface can do checksum calculation on
transmitting data.
IFCAP_HWCSUM A shorthand for (IFCAP_RXCSUM |
IFCAP_TXCSUM).
IFCAP_NETCONS This interface can be a network console.
IFCAP_VLAN_MTU The vlan(4) driver can operate over this
interface in software tagging mode without
having to decrease MTU on vlan(4) interfaces
below 1500 bytes. This implies the ability
of this interface to cope with frames
somewhat longer than permitted by the
Ethernet specification.
IFCAP_VLAN_HWTAGGING This interface can do VLAN tagging on output
and demultiplex frames by their VLAN tag on
input.
IFCAP_JUMBO_MTU This Ethernet interface can transmit and
receive frames up to 9000 bytes long.
IFCAP_POLLING This interface supports polling(4). See
below for details.
IFCAP_VLAN_HWCSUM This interface can do checksum calculation on
both transmitting and receiving data on
vlan(4) interfaces (implies IFCAP_HWCSUM).
IFCAP_TSO4 This Ethernet interface supports TCP4
Segmentation offloading.
IFCAP_TSO6 This Ethernet interface supports TCP6
Segmentation offloading.
IFCAP_TSO A shorthand for (IFCAP_TSO4 | IFCAP_TSO6).
IFCAP_TOE4 This Ethernet interface supports TCP4 Offload
Engine.
IFCAP_TOE6 This Ethernet interface supports TCP6 Offload
Engine.
IFCAP_TOE A shorthand for (IFCAP_TOE4 | IFCAP_TOE6).
IFCAP_WOL_UCAST This Ethernet interface supports waking up on
any Unicast packet.
IFCAP_WOL_MCAST This Ethernet interface supports waking up on
any Multicast packet.
IFCAP_WOL_MAGIC This Ethernet interface supports waking up on
any Magic packet such as those sent by
wake(8).
IFCAP_VLAN_HWTSO This interface supports TCP Segmentation
offloading on vlan(4) interfaces (implies
IFCAP_TSO).
IFCAP_LINKSTATE This Ethernet interface supports dynamic link
state changes.
IFCAP_NETMAP This Ethernet interface supports netmap(4).
The ability of advanced network interfaces to offload certain
computational tasks from the host CPU to the board is limited mostly to
TCP/IP. Therefore a separate field associated with an interface (see
ifnet.if_data.ifi_hwassist below) keeps a detailed description of its
enabled capabilities specific to TCP/IP processing. The TCP/IP module
consults the field to see which tasks can be done on an outgoing packet
by the interface. The flags defined for that field are a superset of
those for mbuf.m_pkthdr.csum_flags, namely:
CSUM_IP The interface will compute IP checksums.
CSUM_TCP The interface will compute TCP checksums.
CSUM_UDP The interface will compute UDP checksums.
An interface notifies the TCP/IP module about the tasks the former has
performed on an incoming packet by setting the corresponding flags in the
field mbuf.m_pkthdr.csum_flags of the mbuf chain containing the packet.
See mbuf(9) for details.
The capability of a network interface to operate in polling(4) mode
involves several flags in different global variables and per-interface
fields. The capability flag IFCAP_POLLING set in interface's
if_capabilities indicates support for polling(4) on the particular
interface. If set in if_capabilities, the same flag can be marked or
cleared in the interface's if_capenable within ifioctl(), thus initiating
switch of the interface to polling(4) mode or interrupt mode,
respectively. The actual mode change is managed by the driver-specific
if_ioctl() routine. The polling(4) handler returns the number of packets
processed.
The if_data Structure
The if_data structure contains statistics and identifying information
used by management programs, and which is exported to user programs by
way of the ifmib(4) branch of the sysctl(3) MIB. The following elements
of the if_data structure are initialized by the interface and are not
expected to change significantly over the course of normal operation:
ifi_type (u_char) The type of the interface, as defined in
<net/if_types.h> and described below in the
Interface Types section.
ifi_physical (u_char) Intended to represent a selection of
physical layers on devices which support more than
one; never implemented.
ifi_addrlen (u_char) Length of a link-layer address on this
device, or zero if there are none. Used to
initialized the address length field in sockaddr_dl
structures referring to this interface.
prepend a link-layer header without allocating an
additional mbuf.
ifi_datalen (u_char) Length of the if_data structure. Allows
some stabilization of the routing socket ABI in the
face of increases in the length of struct ifdata.
ifi_mtu (u_long) The maximum transmission unit of the
medium, exclusive of any link-layer overhead.
ifi_metric (u_long) A dimensionless metric interpreted by a
user-mode routing process.
ifi_baudrate (u_long) The line rate of the interface, in bits
per second.
ifi_hwassist (u_long) A detailed interpretation of the
capabilities to offload computational tasks for
outgoing packets. The interface driver must keep
this field in accord with the current value of
if_capenable.
ifi_epoch (time_t) The system uptime when interface was
attached or the statistics below were reset. This
is intended to be used to set the SNMP variable
ifCounterDiscontinuityTime. It may also be used to
determine if two successive queries for an
interface of the same index have returned results
for the same interface.
The structure additionally contains generic statistics applicable to a
variety of different interface types (except as noted, all members are of
type u_long):
ifi_link_state (u_char) The current link state of Ethernet
interfaces. See the Interface Link States section
for possible values.
ifi_ipackets Number of packets received.
ifi_ierrors Number of receive errors detected (e.g., FCS
errors, DMA overruns, etc.). More detailed
breakdowns can often be had by way of a link-
specific MIB.
ifi_opackets Number of packets transmitted.
ifi_oerrors Number of output errors detected (e.g., late
collisions, DMA overruns, etc.). More detailed
breakdowns can often be had by way of a link-
specific MIB.
ifi_collisions Total number of collisions detected on output for
CSMA interfaces. (This member is sometimes
[ab]used by other types of interfaces for other
output error counts.)
ifi_ibytes Total traffic received, in bytes.
ifi_iqdrops Number of packets dropped on input. Rarely
implemented.
ifi_oqdrops Number of packets dropped on output.
ifi_noproto Number of packets received for unknown network-
layer protocol.
ifi_lastchange (struct timeval) The time of the last
administrative change to the interface (as required
for SNMP).
Interface Types
The header file <net/if_types.h> defines symbolic constants for a number
of different types of interfaces. The most common are:
IFT_OTHER none of the following
IFT_ETHER Ethernet
IFT_ISO88023 ISO 8802-3 CSMA/CD
IFT_ISO88024 ISO 8802-4 Token Bus
IFT_ISO88025 ISO 8802-5 Token Ring
IFT_ISO88026 ISO 8802-6 DQDB MAN
IFT_FDDI FDDI
IFT_PPP Internet Point-to-Point Protocol (ppp(8))
IFT_LOOP The loopback (lo(4)) interface
IFT_SLIP Serial Line IP
IFT_PARA Parallel-port IP ("PLIP")
IFT_ATM Asynchronous Transfer Mode
IFT_USB USB Interface
Interface Link States
The following link states are currently defined:
LINK_STATE_UNKNOWN The link is in an invalid or unknown state.
LINK_STATE_DOWN The link is down.
LINK_STATE_UP The link is up.
The ifaddr Structure
Every interface is associated with a list (or, rather, a TAILQ) of
addresses, rooted at the interface structure's if_addrhead member. The
first element in this list is always an AF_LINK address representing the
interface itself; multi-access network drivers should complete this
structure by filling in their link-layer addresses after calling
if_attach(). Other members of the structure represent network-layer
addresses which have been configured by means of the SIOCAIFADDR command
to ioctl(2), called on a socket of the appropriate protocol family. The
elements of this list consist of ifaddr structures. Most protocols will
declare their own protocol-specific interface address structures, but all
begin with a struct ifaddr which provides the most-commonly-needed
functionality across all protocols. Interface addresses are reference-
counted.
The members of struct ifaddr are as follows:
ifa_addr (struct sockaddr *) The local address of the
interface.
ifa_dstaddr (struct sockaddr *) The remote address of point-to-
point interfaces, and the broadcast address of
ifa_ifp (struct ifnet *) A link back to the interface
structure.
ifa_link (TAILQ_ENTRY(ifaddr)) queue(3) glue for list of
addresses on each interface.
ifa_rtrequest See below.
ifa_flags (u_short) Some of the flags which would be used for
a route representing this address in the route
table.
ifa_refcnt (short) The reference count.
References to ifaddr structures are gained by calling the ifa_ref()
function and released by calling the ifa_free() function.
ifa_rtrequest() is a pointer to a function which receives callouts from
the routing code (rtrequest()) to perform link-layer-specific actions
upon requests to add, or delete routes. The cmd argument indicates the
request in question: RTM_ADD, or RTM_DELETE. The rt argument is the
route in question; the info argument contains the specific destination
being manipulated.
FUNCTIONS
The functions provided by the generic interface code can be divided into
two groups: those which manipulate interfaces, and those which manipulate
interface addresses. In addition to these functions, there may also be
link-layer support routines which are used by a number of drivers
implementing a specific link layer over different hardware; see the
documentation for that link layer for more details.
The ifmultiaddr Structure
Every multicast-capable interface is associated with a list of multicast
group memberships, which indicate at a low level which link-layer
multicast addresses (if any) should be accepted, and at a high level, in
which network-layer multicast groups a user process has expressed
interest.
The elements of the structure are as follows:
ifma_link (LIST_ENTRY(ifmultiaddr)) queue(3) macro glue.
ifma_addr (struct sockaddr *) A pointer to the address which
this record represents. The memberships for various
address families are stored in arbitrary order.
ifma_lladdr (struct sockaddr *) A pointer to the link-layer
multicast address, if any, to which the network-
layer multicast address in ifma_addr is mapped, else
a null pointer. If this element is non-nil, this
membership also holds an invisible reference to
another membership for that link-layer address.
ifma_refcount (u_int) A reference count of requests for this
particular membership.
Interface Manipulation Functions
if_alloc()
domain derived from the dev argument passed by the caller.
if_alloc_domain()
Allocate and initialize struct ifnet as if_alloc() does, with the
addition that the ifnet will be tagged with the NUMA domain via the
numa_domain argument passed by the caller.
if_attach()
Link the specified interface ifp into the list of network
interfaces. Also initialize the list of addresses on that
interface, and create a link-layer ifaddr structure to be the first
element in that list. (A pointer to this address structure is
saved in the ifnet structure and is accessed by the
ifaddr_byindex() function.) The ifp must have been allocated by
if_alloc(), if_alloc_dev() or if_alloc_domain().
if_detach()
Shut down and unlink the specified ifp from the interface list.
if_free()
Free the given ifp back to the system. The interface must have
been previously detached if it was ever attached.
if_free_type()
Identical to if_free() except that the given type is used to free
if_l2com instead of the type in if_type. This is intended for use
with drivers that change their interface type.
if_down()
Mark the interface ifp as down (i.e., IFF_UP is not set), flush its
output queue, notify protocols of the transition, and generate a
message from the route(4) routing socket.
if_up()
Mark the interface ifp as up, notify protocols of the transition,
and generate a message from the route(4) routing socket.
ifpromisc()
Add or remove a promiscuous reference to ifp. If pswitch is true,
add a reference; if it is false, remove a reference. On reference
count transitions from zero to one and one to zero, set the
IFF_PROMISC flag appropriately and call if_ioctl() to set up the
interface in the desired mode.
if_allmulti()
As ifpromisc(), but for the all-multicasts (IFF_ALLMULTI) flag
instead of the promiscuous flag.
ifunit()
Return an ifnet pointer for the interface named name.
ifunit_ref()
Return a reference-counted (via ifa_ref()) ifnet pointer for the
interface named name. This is the preferred function over
ifunit(). The caller is responsible for releasing the reference
with if_rele() when it is finished with the ifnet.
ifioctl()
Process the ioctl request cmd, issued on socket so by thread td,
SIOCGIFCONF Get interface configuration. (No call-down
to driver.)
SIOCSIFNAME Set the interface name. RTM_IFANNOUNCE
departure and arrival messages are sent so
that routing code that relies on the
interface name will update its interface
list. Caller must have appropriate
privilege. (No call-down to driver.)
SIOCGIFCAP
SIOCGIFDATA
SIOCGIFFIB
SIOCGIFFLAGS
SIOCGIFMETRIC
SIOCGIFMTU
SIOCGIFPHYS Get interface capabilities, data, FIB, flags,
metric, MTU, medium selection. (No call-down
to driver.)
SIOCSIFCAP Enable or disable interface capabilities.
Caller must have appropriate privilege.
Before a call to the driver-specific
if_ioctl() routine, the requested mask for
enabled capabilities is checked against the
mask of capabilities supported by the
interface, if_capabilities. Requesting to
enable an unsupported capability is invalid.
The rest is supposed to be done by the
driver, which includes updating if_capenable
and if_data.ifi_hwassist appropriately.
SIOCGIFCAPNV NV(9) version of the SIOCGIFCAP ioctl.
Caller must provide a pointer to struct
ifreq_cap_nv as data, where the member buffer
points to some buffer containing buf_length
bytes. The serialized nvlist with
description of the device capabilities is
written to the buffer. If buffer is too
short, the structure is updated with buffer
member set to NULL, length set to the minimal
required length, and error EFBIG is returned.
Elements of the returned nvlist for simple
capabilities are boolean, identified by
names. Presence of the boolean element means
that corresponding capability is supported by
the interface. Element's value describes the
current configured state: true means that the
capability is enabled, and false that it is
disabled.
Driver indicates support for both
SIOCGIFCAPNV and SIOCSIFCAPNV requests by
setting IFCAP_NV non-modifiable capability
bit in if_capabilities.
SIOCSIFCAPNV NV(9) version of the SIOCSIFCAP ioctl.
Caller must provide the pointer to struct
ifreq_cap_nv as data, where the member buffer
capabilities listed in the nvlist are
affected by the call.
SIOCSIFFIB Sets interface FIB. Caller must have
appropriate privilege. FIB values start at 0
and values greater or equals than net.fibs
are considered invalid.
SIOCSIFFLAGS Change interface flags. Caller must have
appropriate privilege. If a change to the
IFF_UP flag is requested, if_up() or
if_down() is called as appropriate. Flags
listed in IFF_CANTCHANGE are masked off, and
the field if_flags in the interface structure
is updated. Finally, the driver if_ioctl()
routine is called to perform any setup
requested.
SIOCSIFMETRIC
SIOCSIFPHYS Change interface metric or medium. Caller
must have appropriate privilege.
SIOCSIFMTU Change interface MTU. Caller must have
appropriate privilege. MTU values less than
72 or greater than 65535 are considered
invalid. The driver if_ioctl() routine is
called to implement the change; it is
responsible for any additional sanity
checking and for actually modifying the MTU
in the interface structure.
SIOCADDMULTI
SIOCDELMULTI Add or delete permanent multicast group
memberships on the interface. Caller must
have appropriate privilege. The
if_addmulti() or if_delmulti() function is
called to perform the operation; qq.v.
SIOCAIFADDR
SIOCDIFADDR The socket's protocol control routine is
called to implement the requested action.
Interface Address Functions
Several functions exist to look up an interface address structure given
an address. ifa_ifwithaddr() returns an interface address with either a
local address or a broadcast address precisely matching the parameter
addr. ifa_ifwithdstaddr() returns an interface address for a point-to-
point interface whose remote ("destination") address is addr and a fib is
fib. If fib is RT_ALL_FIBS, then the first interface address matching
addr will be returned.
ifa_ifwithnet() returns the most specific interface address which matches
the specified address, addr, subject to its configured netmask, or a
point-to-point interface address whose remote address is addr if one is
found. If ignore_ptp is true, skip point-to-point interface addresses.
The fib parameter is handled the same way as by ifa_ifwithdstaddr().
ifaof_ifpforaddr() returns the most specific address configured on
interface ifp which matches address addr, subject to its configured
netmask. If the interface is point-to-point, only an interface address
Interface Multicast Address Functions
The if_addmulti(), if_delmulti(), and if_findmulti() functions provide
support for requesting and relinquishing multicast group memberships, and
for querying an interface's membership list, respectively. The
if_addmulti() function takes a pointer to an interface, ifp, and a
generic address, sa. It also takes a pointer to a struct ifmultiaddr *
which is filled in on successful return with the address of the group
membership control block. The if_addmulti() function performs the
following four-step process:
1. Call the interface's if_resolvemulti() entry point to
determine the link-layer address, if any, corresponding to
this membership request, and also to give the link layer an
opportunity to veto this membership request should it so
desire.
2. Check the interface's group membership list for a pre-existing
membership for this group. If one is not found, allocate a
new one; if one is, increment its reference count.
3. If the if_resolvemulti() routine returned a link-layer address
corresponding to the group, repeat the previous step for that
address as well.
4. If the interface's multicast address filter needs to be
changed because a new membership was added, call the
interface's if_ioctl() routine (with a cmd argument of
SIOCADDMULTI) to request that it do so.
The if_delmulti() function, given an interface ifp and an address, sa,
reverses this process. Both functions return zero on success, or a
standard error number on failure.
The if_findmulti() function examines the membership list of interface ifp
for an address matching sa, and returns a pointer to that struct
ifmultiaddr if one is found, else it returns a null pointer.
SEE ALSO
ioctl(2), link_addr(3), queue(3), sysctl(3), bpf(4), ifmib(4), lo(4),
netintro(4), polling(4), config(8), ppp(8), mbuf(9), rtentry(9)
Gary R. Wright and W. Richard Stevens, TCP/IP Illustrated, Vol. 2,
Addison-Wesley, ISBN 0-201-63354-X.
AUTHORS
This manual page was written by Garrett A. Wollman.
FreeBSD 14.0-RELEASE-p11 May 24, 2022 FreeBSD 14.0-RELEASE-p11