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IFNET(9) Kernel Developer's Manual IFNET(9) NAME if_t, 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 if_t if_alloc(u_char type); if_t if_alloc_dev(u_char type, device_t dev); if_t if_alloc_domain(u_char type, int numa_domain); void if_attach(if_t ifp); void if_detach(if_t ifp); void if_free(if_t ifp); void if_free_type(if_t ifp, u_char type); void if_down(if_t ifp); int ifioctl(struct socket *so, u_long cmd, caddr_t data, struct thread *td); int ifpromisc(if_t ifp, int pswitch); int if_allmulti(if_t ifp, int amswitch); if_t ifunit(const char *name); if_t ifunit_ref(const char *name); void if_up(if_t ifp); Interface Address Functions 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, if_t ifp); void ifa_ref(struct ifaddr *ifa); void ifa_free(struct ifaddr *ifa); Interface Multicast Address Functions int if_addmulti(if_t ifp, struct sockaddr *sa, struct ifmultiaddr **ifmap); int if_delmulti(if_t ifp, struct sockaddr *sa); struct ifmultiaddr * if_findmulti(if_t ifp, struct sockaddr *sa); Output queue accessors if_dequeue(if_t ifp, struct mbuf *m); Output queue macros IF_DEQUEUE(struct ifqueue *ifq, struct mbuf *m); if_t accesors uint64_t if_setbaudrate(if_t ifp, uint64_t baudrate); uint64_t if_getbaudrate(const if_t ifp); int if_setcapabilities(if_t ifp, int capabilities); int if_setcapabilitiesbit(if_t ifp, int setbit, int clearbit); int if_getcapabilities(const if_t ifp); int if_togglecapenable(if_t ifp, int togglecap); int if_setcapenable(if_t ifp, int capenable); int if_setcapenablebit(if_t ifp, int setcap, int clearcap); int if_getcapenable(const if_t ifp); int if_setcapabilities2(if_t ifp, int capabilities); int if_setcapabilities2bit(if_t ifp, int setbit, int clearbit); int if_getcapabilities2(const if_t ifp); int if_togglecapenable2(if_t ifp, int togglecap); int if_setcapenable2(if_t ifp, int capenable); int if_setcapenable2bit(if_t ifp, int setcap, int clearcap); int if_getcapenable2(const if_t ifp); int if_getdunit(const if_t ifp); int if_getindex(const if_t ifp); int if_getidxgen(const if_t ifp); const char * if_getdname(const if_t ifp); void if_setdname(if_t ifp, const char *name); const char * if_name(if_t ifp); int if_setname(if_t ifp, const char *name); void if_setdescr(if_t ifp, char *descrbuf); char * if_allocdescr(size_t sz, int malloc_flag); void if_freedescr(char *descrbuf); int if_getalloctype(const if_t ifp); int if_gettype(const if_t ifp); int if_setdev(if_t ifp, void *dev); int if_setdrvflagbits(if_t ifp, int if_setflags, int clear_flags); int if_getdrvflags(const if_t ifp); int if_setdrvflags(if_t ifp, int flags); int if_getlinkstate(if_t ifp); int if_clearhwassist(if_t ifp); int if_sethwassistbits(if_t ifp, int toset, int toclear); int if_sethwassist(if_t ifp, int hwassist_bit); int if_gethwassist(const if_t ifp); int if_togglehwassist(if_t ifp, int toggle_bits); int if_setsoftc(if_t ifp, void *softc); void * if_getsoftc(if_t ifp); void if_setllsoftc(if_t ifp, void *softc); void * if_getllsoftc(if_t ifp); u_int if_getfib(if_t ifp); uint8_t if_getaddrlen(if_t ifp); int if_gethwaddr(const if_t ifp, struct ifreq *); const uint8_t * if_getbroadcastaddr(const if_t ifp); void if_setbroadcastaddr(if_t ifp, const uint8_t *); int if_setmtu(if_t ifp, int mtu); int if_getmtu(const if_t ifp); int if_getmtu_family(const if_t ifp, int family); void if_notifymtu(if_t ifp); int if_setflagbits(if_t ifp, int set, int clear); int if_setflags(if_t ifp, int flags); int if_getflags(const if_t ifp); int if_getnumadomain(if_t ifp); int if_sendq_empty(if_t ifp); int if_setsendqready(if_t ifp); int if_setsendqlen(if_t ifp, int tx_desc_count); int if_sethwtsomax(if_t ifp, u_int if_hw_tsomax); int if_sethwtsomaxsegcount(if_t ifp, u_int if_hw_tsomaxsegcount); int if_sethwtsomaxsegsize(if_t ifp, u_int if_hw_tsomaxsegsize); u_int if_gethwtsomax(const if_t ifp); u_int if_gethwtsomaxsegcount(const if_t ifp); u_int if_gethwtsomaxsegsize(const if_t ifp); void if_setnetmapadapter(if_t ifp, struct netmap_adapter *na); struct netmap_adapter * if_getnetmapadapter(if_t ifp); void if_input(if_t ifp, struct mbuf* sendmp); int if_sendq_prepend(if_t ifp, struct mbuf *m); struct mbuf * if_dequeue(if_t ifp); int if_setifheaderlen(if_t ifp, int len); void if_setrcvif(struct mbuf *m, if_t ifp); void if_setvtag(struct mbuf *m, u_int16_t tag); u_int16_t if_getvtag(struct mbuf *m); int if_vlantrunkinuse(if_t ifp); caddr_t if_getlladdr(const if_t ifp); struct vnet * if_getvnet(const if_t ifp); void * if_gethandle(u_char); void if_bpfmtap(if_t ifp, struct mbuf *m); void if_etherbpfmtap(if_t ifp, struct mbuf *m); void if_vlancap(if_t ifp); int if_transmit(if_t ifp, struct mbuf *m); void if_init(if_t ifp, void *ctx); int if_resolvemulti(if_t ifp, struct sockaddr **, struct sockaddr *); uint64_t if_getcounter(if_t ifp, ift_counter counter); struct label * if_getmaclabel(if_t ifp); void if_setmaclabel(if_t ifp, struct label *label); struct bpf_if * if_getbpf(if_t ifp); uint8_t if_getpcp(if_t ifp); void * if_getl2com(if_t ifp); struct ifvlantrunk * if_getvlantrunk(if_t ifp); bool if_altq_is_enabled(if_t ifp); struct ifnet Member Functions void (*if_input)(if_t ifp, struct mbuf *m); int (*if_output)(if_t ifp, struct mbuf *m, const struct sockaddr *dst, struct route *ro); void (*if_start)(if_t ifp); int (*if_transmit)(if_t ifp, struct mbuf *m); void (*if_qflush)(if_t ifp); int (*if_ioctl)(if_t ifp, u_long cmd, caddr_t data); void (*if_init)(void *if_softc); int (*if_resolvemulti)(if_t 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 prerequi- site 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 inter- face 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 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 struc- tures. 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 accessors The accessors for if_t are as follows: if_getbaudrate() if_setbaudrate() (u_long) The line rate of the interface, in bits per second. if_setcapabilities() if_setcapabilitiesbit() if_getcapabilities() (int) Flags describing the capabilities the interface sup- ports (see below). if_getcapenable() if_setcapenable() if_setcapenablebit() if_toggle- capenable() (int) Flags describing the enabled capabilities of the inter- face (see below). if_getcapabilities2() if_setcapabilities2() if_setcapabilities2bit() if_getcapenable2() if_setcapenable2() if_setcapenable2bit() if_tog- glecapenable2() if_getdunit() (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 de- vice. (Initialized by driver, usually via if_initname().) if_getindex() (u_short) Return the unique number assigned to the device when attached. This number can be used in a struct sock- addr_dl to refer to a particular interface by index (see link_addr(3)). This is initialized by if_alloc(). if_getidxgen() if_getdname() if_setdname() (const char *) The name of the driver. This is initialized by driver (usually via if_initname()). if_name() if_setname() (char *) The name of the interface, (e.g., `fxp0' or "lo0"). This is initialized by driver, usually via if_initname(). if_getalloctype() (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_gettype() if_setdev() if_getdrvflags() if_setdrvflags() if_setdrvflagbits() if_getlinkstate() if_clearhwassist() if_sethwassistbits() if_gethwassist() if_sethwassist() if_togglehwassist() (u_long) A detailed interpretation of the capabilities to of- fload computational tasks for outgoing packets. The inter- face driver must keep this field in accord with the current value of if_capenable. if_getsoftc() if_setsoftc() (void *) A pointer to the driver's private state block. This is initialized by driver at attach. if_setllsoftc() if_getllsoftc() if_getfib() if_getaddrlen() if_gethwaddr() if_getbroadcastaddr() if_setbroadcastaddr() Access the interface broadcast address. if_setmtu() if_getmtu() Access the interface MTU. if_setflags() if_getflags() if_setflagbits() (int) Flags describing operational parameters of this inter- face (see below). These flags are manipulated by generic code. if_getnumadomain() (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_al- loc_domain(). if_sendq_empty() if_setsendqready() if_setsendqlen() if_sethwtsomax() if_gethwtsomax() if_sethwtsomaxsegcount() if_gethwtsomaxsegcount() if_sethwtsomaxsegsize() if_gethwtsomaxsegsize() if_setnetmapadapter() if_getnetmapadapter() if_setifheaderlen() if_setrcvif() if_setvtag() if_getvtag() if_vlantrunkinuse() if_getlladdr() if_getvnet() (struct vnet *) A pointer to the virtual network stack in- stance. This is initialized by if_attach(). if_gethandle() if_vlancap() if_getcounter() if_getmaclabel() if_setmaclabel() if_getbpf() (struct bpf_if *) Opaque per-interface data for the packet filter, bpf(4). This is initialized by bpf_attach(). if_getpcp() if_getl2com() A pointer to the common data for the interface's layer 2 pro- tocol. This is initialized by if_alloc(). if_getvlantrunk(if_t ifp) (struct ifvlantrunk *) A pointer to 802.1Q trunk structure, vlan(4). This is initialized by the driver-specific if_ioctl() routine. if_getdrvflags() if_setdrvflags() if_setdrvflagbits() (int) Flags describing operational status of this interface (see below). These flags are manipulated by driver. if_addmulti() if_delmulti() if_findmulti() Add, remove, and find multicast addresses assigned to this interface. if_getifaddr() (struct ifaddr *) Get a pointer to the interface's link-level address. if_getbroadcastaddr() if_setbroadcastaddr() (const u_int8_t *) A link-level broadcast bytestring for pro- tocols with variable address length. if_getafdata() (void *) An address family dependent data region. if_addgroup() if_delgroup() Add and delete groups from the interface. 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. 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 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 / de- queue 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 al- low 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 or- der 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 rou- tine ifioctl() to check for appropriate privileges, locate the inter- face 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 capabili- ties; 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 dynamic resources were successfully allocated. Probably only useful internal to the interface. IFF_NOARP <D> Disable network address resolution on this in- terface. 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_PALLMULTI <D> This interface is in the permanently all-multi- casts mode (implies IFF_ALLMULTI). 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. (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 meaning- ful 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 in- terface. IFF_DYING <D*> Set when the ifnet structure of this interface is being released and still has if_refcount refer- ences. 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 en- abled, 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 con- trol over itself (e.g., depend on another capability's state.) Such pecu- liarities 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). 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 hard- coded 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 inter- face in software tagging mode without having to decrease MTU on vlan(4) interfaces below 1500 bytes. This implies the ability of this inter- face 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 in- put. IFCAP_JUMBO_MTU This Ethernet interface can transmit and re- ceive 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 Segmenta- tion offloading. IFCAP_TSO6 This Ethernet interface supports TCP6 Segmenta- tion 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_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 of- floading 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. There- fore a separate field associated with an interface (see ifnet.if_data.ifi_hwassist below) keeps a detailed description of its en- abled capabilities specific to TCP/IP processing. The TCP/IP module con- sults 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 per- formed 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 inter- face. 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 ac- tual 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 physi- cal layers on devices which support more than one; never implemented. ifi_addrlen (u_char) Length of a link-layer address on this de- vice, or zero if there are none. Used to initialized 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 ad- ditional 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_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 interface of the same index have returned results for the same interface. The structure additionally contains generic statistics applicable to a va- riety 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 inter- faces. 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 colli- sions, 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_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 imple- mented. 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 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 inter- face 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 con- sist 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 inter- face. ifa_dstaddr (struct sockaddr *) The remote address of point-to- point interfaces, and the broadcast address of broad- cast interfaces. (ifa_broadaddr is a macro for ifa_dstaddr.) ifa_netmask (struct sockaddr *) The network mask for multi-access interfaces, and the confusion generator for point-to- point interfaces. ifa_ifp (if_t) A link back to the interface structure. ifa_link (TAILQ_ENTRY(ifaddr)) queue(3) glue for list of ad- dresses 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() func- tion 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 re- quests 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 ques- tion; the info argument contains the specific destination being manipu- lated. 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 imple- menting a specific link layer over different hardware; see the documenta- tion 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 net- work-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 multi- cast address, if any, to which the network-layer mul- ticast 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 member- ship for that link-layer address. ifma_refcount (u_int) A reference count of requests for this partic- ular membership. Interface Manipulation Functions if_alloc() Allocate and initialize struct ifnet. Initialization includes the allocation of an interface index and may include the allocation of a type specific structure in if_l2com. if_alloc_dev() Allocate and initialize struct ifnet as if_alloc() does, with the ad- dition 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 ad- dition 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.) 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 mes- sage 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 in- terface in the desired mode. if_allmulti() As ifpromisc(), but for the all-multicasts (IFF_ALLMULTI) flag in- stead 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 in- terface 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 in- terface configuration requests from user mode. It is ordinarily 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 interpretation. The following com- mands are handled by ifioctl(): SIOCGIFCONF Get interface configuration. (No call-down to driver.) SIOCSIFNAME Set the interface name. RTM_IFANNOUNCE depar- ture 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() rou- tine, the requested mask for enabled capabili- ties is checked against the mask of capabili- ties supported by the interface, if_capabilities. Requesting to enable an un- supported capability is invalid. The rest is supposed to be done by the driver, which in- cludes 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 seri- alized 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 ca- pabilities are boolean, identified by names. Presence of the boolean element means that cor- responding capability is supported by the in- terface. Element's value describes the current configured state: true means that the capabil- ity 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 se- rialized nvlist of length bytes. Each element of nvlist describes a requested update of one capability, 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 appropri- ate privilege. FIB values start at 0 and val- ues greater or equals than net.fibs are consid- ered invalid. SIOCSIFFLAGS Change interface flags. Caller must have ap- propriate 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 appro- priate privilege. MTU values less than 72 or greater than 65535 are considered invalid. The driver if_ioctl() routine is called to imple- ment the change; it is responsible for any ad- ditional sanity checking and for actually modi- fying the MTU in the interface structure. SIOCADDMULTI SIOCDELMULTI Add or delete permanent multicast group member- ships on the interface. Caller must have ap- propriate 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 in- terface 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 inter- face ifp which matches address addr, subject to its configured netmask. If the interface is point-to-point, only an interface address whose remote ad- dress is precisely addr will be returned. 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 sup- port 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 re- quest that it do so. The if_delmulti() function, given an interface ifp and an address, sa, re- verses 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 ifmulti- addr 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), net- intro(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 ports 15.quarterly December 10, 2024 IFNET(9)
NAME | SYNOPSIS | DATA STRUCTURES | FUNCTIONS | SEE ALSO | AUTHORS
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