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IFNET(9) 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 * ifaddr_byindex(u_short idx); struct ifaddr * ifa_ifwithaddr(struct sockaddr *addr); struct ifaddr * ifa_ifwithdstaddr(struct sockaddr *addr, int fib); 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 extern struct ifnethead ifnet; extern int if_index; extern int ifqmaxlen; DATA STRUCTURES The kernel mechanisms for handling network interfaces reside primarily in the ifnet, if_data, ifaddr, and ifmultiaddr structures in <net/if.h> and <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 par- ticular can be replaced by <net/ethernet.h>.) The system keeps a linked list of interfaces using the TAILQ macros de- fined 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 struc- tures. 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 inter- faces 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 inter- face 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 origi- nates 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 (usu- ally via if_initname()).) if_dname (const char *) The name of the driver. (Ini- tialized by driver (usually via if_initname()).) if_dunit (int) A unique number assigned to each interface managed by a particular driver. Drivers may choose to set this to IF_DUNIT_NONE if a unit number is not associated with the device. (Ini- tialized 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 inter- face 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 in- terface 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 in- terface 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. (Initial- ized by driver.) if_data (struct if_data) More statistics and informa- tion; see "The if_data structure", below. (Ini- tialized 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_amcount (int) A number of multicast requests on this in- terface, used to reference-count the IFF_ALLMULTI flag. if_addr (struct ifaddr *) A pointer to the link-level interface address. (Initialized by if_alloc().) 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 re- gion. 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 pro- tect 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 pro- tect 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 in- terface 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() func- tion 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. There are in addition a number of function pointers which the driver must initialize to complete its interface with the generic interface layer: if_input() Pass a packet to an appropriate upper layer as determined from the link-layer header of the packet. This routine is to be called from 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 soft- ware and hardware queues are both full. This function must be installed after if_attach() to override the default implementa- tion. This function is exposed in order to allow drivers to man- age their own queues and to reduce the latency caused by a fre- quently 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 re- duce the latency caused by a frequently gratuitous enqueue / de- queue pair to ifq. The suggested internal software queuing mech- anism 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 opera- tions like twiddling flags and flushing queues. See the descrip- tion 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 valid- ity, and if necessary compute a link-layer group which corre- sponds 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 capabilities; others are dynamically manipulated to reflect the current state of the interface. Flags of the former kind are marked <S> in this table; the latter are marked <D>. Flags which begin with "IFF_DRV_" are stored in if_drv_flags; all other flags are stored in if_flags. The macro IFF_CANTCHANGE defines the bits which cannot be set by a user program using the SIOCSIFFLAGS command to ioctl(2); these are indicated 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 dy- namic 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 promis- cuous 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 transmis- sions. IFF_LINK0 IFF_LINK1 IFF_LINK2 <D> Control flags for the link layer. (Cur- rently 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 pack- ets and discards incoming packets after BPF pro- cessing. 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 inter- face 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. Conse- quently, 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). The following capabilities are currently supported by the system: IFCAP_RXCSUM This interface can do checksum validation on receiving data. Some interfaces do not have sufficient buffer storage to store frames above a certain MTU-size completely. The 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) inter- faces 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 out- put 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 Seg- mentation offloading. IFCAP_TSO6 This Ethernet interface supports TCP6 Seg- mentation offloading. IFCAP_TSO A shorthand for (IFCAP_TSO4 | IFCAP_TSO6). IFCAP_TOE4 This Ethernet interface supports TCP4 Of- fload Engine. IFCAP_TOE6 This Ethernet interface supports TCP6 Of- fload 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_WOL A shorthand for (IFCAP_WOL_UCAST | IFCAP_WOL_MCAST | IFCAP_WOL_MAGIC). IFCAP_VLAN_HWFILTER This interface supports frame filtering in hardware on vlan(4) interfaces. 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 computa- tional 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 in- volves 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 in- terface. If set in if_capabilities, the same flag can be marked or cleared in the interface's if_capenable within ifioctl(), thus initiat- ing switch of the interface to polling(4) mode or interrupt mode, re- spectively. The actual mode change is managed by the driver-specific if_ioctl() routine. The polling(4) handler returns the number of pack- ets 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 ele- ments of the if_data structure are initialized by the interface and are not expected to change significantly over the course of normal opera- tion: 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 ini- tialized the address length field in sockaddr_dl structures referring to this interface. ifi_hdrlen (u_char) Maximum length of any link-layer header which might be prepended by the driver to a packet before transmission. The generic code computes the maximum over all interfaces and uses that value to influence the placement of data in mbufs to attempt to ensure that there is always sufficient space to 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 capa- bilities 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 at- tached 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 in- terface 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 in- terfaces. See the "Interface Link States" sec- tion for possible values. ifi_ipackets Number of packets received. ifi_ierrors Number of receive errors detected (e.g., FCS er- rors, DMA overruns, etc.). More detailed break- downs 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 col- lisions, DMA overruns, etc.). More detailed breakdowns can often be had by way of a link-spe- cific 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_obytes Total traffic transmitted, in bytes. ifi_imcasts Number of packets received which were sent by link-layer multicast. ifi_omcasts Number of packets sent by link-layer multicast. ifi_iqdrops Number of packets dropped on input. Rarely im- plemented. 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 administra- tive change to the interface (as required for SNMP). Interface Types The header file <net/if_types.h> defines symbolic constants for a num- ber 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 ad- dresses, 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 com- mand to ioctl(2), called on a socket of the appropriate protocol fam- ily. 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 ad- dresses are reference-counted. The members of struct ifaddr are as follows: ifa_addr (struct sockaddr *) The local address of the in- terface. ifa_dstaddr (struct sockaddr *) The remote address of point- to-point interfaces, and the broadcast address of broadcast interfaces. (ifa_broadaddr is a macro for ifa_dstaddr.) ifa_netmask (struct sockaddr *) The network mask for multi-ac- cess interfaces, and the confusion generator for point-to-point interfaces. 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 ma- nipulate 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 multi- cast 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 vari- ous address families are stored in arbitrary or- der. 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() Allocate and initialize struct ifnet. Initialization includes the allocation of an interface index and may include the alloca- tion of a type specific structure in if_l2com. if_alloc_dev() Allocate and initialize struct ifnet as if_alloc() does, with the addition that the ifnet can be tagged with the appropriate NUMA 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 inter- faces. 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() func- tion.) 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 gener- ate 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, with data parameter data. This is the main routine for handling all interface configuration requests from user mode. It is ordi- narily only called from the socket-layer ioctl(2) handler, and only for commands with class `i'. Any unrecognized commands will be passed down to socket so's protocol for further interpreta- tion. The following commands are handled by ifioctl(): SIOCGIFCONF Get interface configuration. (No call-down to driver.) SIOCSIFNAME Set the interface name. RTM_IFANNOUNCE de- parture and arrival messages are sent so that routing code that relies on the inter- face 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 in- terface, if_capabilities. Requesting to enable an unsupported capability is in- valid. The rest is supposed to be done by the driver, which includes updating if_capenable and if_data.ifi_hwassist ap- propriately. 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 mini- mal required length, and error EFBIG is re- turned. Elements of the returned nvlist for simple capabilities are boolean, identified by names. Presence of the boolean element means that corresponding capability is sup- ported 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 points to serialized nvlist of length bytes. Each element of nvlist de- scribes a requested update of one capabil- ity, identified by the element name. For simple capabilities, the element must be boolean. Its true value means that the caller asks to enable the capability, and false value to disable. Only capabilities listed in the nvlist are affected by the call. SIOCSIFFIB Sets interface FIB. Caller must have ap- propriate 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 ap- propriate privilege. MTU values less than 72 or greater than 65535 are considered in- valid. The driver if_ioctl() routine is called to implement the change; it is re- sponsible for any additional sanity check- ing 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 match- ing 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 ad- dresses. The fib parameter is handled the same way as by ifa_ifwithdstaddr(). ifaof_ifpforaddr() returns the most specific address configured on in- terface ifp which matches address addr, subject to its configured net- mask. If the interface is point-to-point, only an interface address whose remote address is precisely addr will be returned. ifaddr_byindex() returns the link-level address of the interface with the given index idx. All of these functions return a null pointer if no such address can be found. 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 fol- lowing four-step process: 1. Call the interface's if_resolvemulti() entry point to deter- mine the link-layer address, if any, corresponding to this membership request, and also to give the link layer an op- portunity to veto this membership request should it so de- sire. 2. Check the interface's group membership list for a pre-exist- ing membership for this group. If one is not found, allo- cate a new one; if one is, increment its reference count. 3. If the if_resolvemulti() routine returned a link-layer ad- dress 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 inter- face'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 13.2 May 24, 2022 IFNET(9)
NAME | SYNOPSIS | DATA STRUCTURES | FUNCTIONS | SEE ALSO | AUTHORS
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