man pages section 7: Device and Network Interfaces

if(7P)

Name

if_tcp, if– general properties of Internet Protocol network interfaces

Description

A network interface is a device for sending and receiving packets on a network. It is usually a hardware device, although it can be implemented in software. Network interfaces used by the Internet Protocol (IPv4 or IPv6) must be STREAMS devices conforming to the Data Link Provider Interface (DLPI). See dlpi(7P).

APPLICATION PROGRAMMING INTERFACE

An interface becomes available to IP when it is opened and the IP module is pushed onto the stream with the I_PUSH ioctl(2) command. (See streamio(7I)). The SIOCSLIFNAME ioctl(2) is issued to specify the name of the interface and to indicate whether it is IPv4 or IPv6. This may be initiated by the kernel at boot time or by a user program after the system is running. Each interface must be assigned an IP address with the SIOCSLIFADDR ioctl() before it can be used. On interfaces where the network-to-link layer address mapping is static, only the network number is taken from the ioctl() request; the remainder is found in a hardware specific manner. On interfaces which provide dynamic network-to-link layer address mapping facilities (for example, 10Mb/s Ethernets using arp(7P)), the entire address specified in the ioctl() is used. A routing table entry for destinations on the network of the interface is installed automatically when an interface's address is set.

ioctls

The following ioctl() calls may be used to manipulate IP network interfaces. Unless specified otherwise, the request takes an lifreq structure as its parameter. This structure has the form:

/* Interface request struct. used for socket ioctls.  All   */
/* interface ioctls must have parameter definitions which    */
/* begin with lifr_name. The remainder may be interface specific. */
struct lifreq {
#define LIFNAMSIZ	32
   char    lifr_name[LIFNAMSIZ];        /* if name, e.g. "le1" */
   union {
      int    lifru_addrlen;            /* for subnet/token etc */
      uint_t lifru_ppa;                /* SIOCSLIFNAME */
   } lifr_lifru1;
   union {
      struct sockaddr_storage lifru_addr;
      struct sockaddr_storage lifru_dstaddr;
      struct sockaddr_storage lifru_broadaddr;
      struct sockaddr_storage lifru_token;    /* With lifr_addrlen */
      struct sockaddr_storage lifru_subnet;   /* With lifr_addrlen */
      int                     lifru_index;    /* interface index */
      uint64_t                lifru_flags;    /* SIOC?LIFFLAGS */
      int                     lifru_metric;
      uint_t                  lifru_mtu;
      int                     lif_muxid[2];   /* mux id's for arp & ip */
      struct lif_nd_req       lifru_nd_req;
      struct lif_ifinfo_req   lifru_ifinfo_req;
      zoneid_t                lifru_zone;     /* SIOC[GS]LIFZONE */
   } lifr_lifru;

#define lifr_addrlen   lifr_lifru1.lifru_addrlen
#define lifr_ppa       lifr_lifru1.lifru_ppa       /* Driver's ppa */
#define lifr_addr      lifr_lifru.lifru_addr       /* address */
#define lifr_dstaddr   lifr_lifru.lifru_dstaddr    
#define lifr_broadaddr lifr_lifru.lifru_broadaddr  /* broadcast addr. */
#define lifr_token     lifr_lifru.lifru_token      /* address token */
#define lifr_subnet    lifr_lifru.lifru_subnet     /* subnet prefix */
#define lifr_index     lifr_lifru.lifru_index      /* interface index */
#define lifr_flags     lifr_lifru.lifru_flags      /* flags */
#define lifr_metric    lifr_lifru.lifru_metric     /* metric */
#define lifr_mtu       lifr_lifru.lifru_mtu        /* mtu */
#define lifr_index     lifr_lifru.lifru_index      /* interface index  */
#define lifr_ip_muxid  lifr_lifru.lif_muxid[0]
#define lifr_arp_muxid lifr_lifru.lif_muxid[1]
#define lifr_nd        lifr_lifru.lifru_nd_req     /* SIOCLIF*ND */
#define lifr_ifinfo    lifr_lifru.lifru_ifinfo_req /* SIOC[GS]LIFLNKINFO */
#define lifr_zone      lifr_lifru.lifru_zone       /* SIOC[GS]LIFZONE */
};

SIOCSLIFADDR

Set interface address. Following the address assignment, the “initialization” routine for the interface is called.

SIOCGLIFADDR

Get interface address.

SIOCSLIFDSTADDR

Set point to point address for interface.

SIOCGLIFDSTADDR

Get point to point address for interface.

SIOCSLIFFLAGS

Set interface flags field. If the interface is marked down, any processes currently routing packets through the interface are notified.

SIOCGLIFFLAGS

Get interface flags.

SIOCGLIFCONF

Get interface configuration list. This request takes an lifconf structure (see below) as a value-result parameter. The lifc_family field can be set to AF_UNSPEC to retrieve both AF_INET and AF_INET6 interfaces. The lifc_flags field should be set to zero. The lifc_len field should be set to the size of the buffer pointed to by lifc_buf. Upon success, lifc_len will contain the length, in bytes, of the array of lifreq structures pointed to by lifc_req. For each lifreq structure, the lifr_name and lifr_addr fields will be valid.

SIOCGLIFNUM

Get number of interfaces. This request returns an integer which is the number of interface descriptions (struct lifreq) that will be returned by the SIOCGLIFCONF ioctl; that is, it gives an indication of how large lifc_len has to be. This request takes an lifnum structure (see below) as a value-result parameter. The lifn_family field should be set to AF_UNSPEC to count both AF_INET and AF_INET6 interfaces. The lifn_flags field should be initially set to zero.

SIOCSLIFMTU

Set the maximum transmission unit (MTU) size for interface. Place the result of this request in lifru_mtu field. The MTU can not exceed the physical MTU limitation (which is reported in the DLPI DL_INFO_ACK message).

SIOCGLIFMTU

Get the maximum transmission unit size for interface. Place the result of this request in ifru_mtu field.

SIOCSLIFMETRIC

Set the metric associated with the interface. The metric is used by routing daemons such as in.routed(1M).

SIOCGLIFMETRIC

Get the metric associated with the interface.

SIOCGLIFMUXID

Get the ip and arp muxid associated with the interface.

SIOCSLIFMUXID

Set the ip and arp muxid associated with the interface.

SIOCGLIFINDEX

Get the interface index associated with the interface.

SIOCSLIFINDEX

Set the interface index associated with the interface.

SIOCGLIFZONE

Get the zone associated with the interface.

SIOCSLIFZONE

Set the zone associated with the interface. Only applies for zones that use the shared-IP instance.

SIOCLIFADDIF

Add a new logical interface on a physical interface using an unused logical unit number. If the physical interface is part of an IP multipathing group, the logical interface may be added to a different physical interface in the same group. Upon return, the lifr_name field contains the name of the actual logical interface created.

SIOCLIFREMOVEIF

Remove a logical interface by specifying its IP address or logical interface name. When the IP address is specified and the interface is part of an IP multipathing group, the logical interface is removed from the physical interface in the group which holds the IP address.

SIOCSLIFTOKEN

Set the address token used to form IPv6 link-local addresses and for stateless address autoconfiguration.

SIOCGLIFTOKEN

Get the address token used to form IPv6 link-local addresses and for stateless address autoconfiguration.

SIOCSLIFSUBNET

Set the subnet prefix associated with the interface.

SIOCGLIFSUBNET

Get the subnet prefix associated with the interface.

SIOCSLIFLNKINFO

Set link specific parameters for the interface.

SIOCGLIFLNKINFO

Get link specific parameters for the interface.

SIOCLIFDELND

Delete a neighbor cache entry for IPv6.

SIOCLIFGETND

Get a neighbor cache entry for IPv6.

SIOCLIFSETND

Set a neighbor cache entry for IPv6.

SIOCTMYADDR

Test if the address is assigned to this node. This request takes an sioc_addrreq structure (see below) as a value-result parameter. The sa_addr field should be set to the address to test. The sa_res field will contain a non-zero value if the address is assigned to this node.

SIOCSLIFUSESRC

Set the interface from which to choose a source address. The lifr_index field has the interface index corresponding to the interface whose address is to be used as the source address for packets going out on the interface whose name is provided by lifr_name. If the lifr_index field is set to zero, the previous setting is cleared. See ifconfig(1M) for examples of the 'usesrc' option.

SIOCGLIFUSESRC

Get the interface index of the interface whose address is used as the source address for packets going out on the interface provided by lifr_name field. The value is retrieved in the lifr_index field. See ifconfig(1M) for examples of the 'usesrc' option.

SIOCGLIFSRCOF

Get the interface configuration list for interfaces that use an address hosted on the interface provided by the lifs_ifindex field in the lifsrcof struct (see below), as a source address. The application sets lifs_maxlen to the size (in bytes) of the buffer it has allocated for the data. On return, the kernel sets lifs_len to the actual size required. Note, the application could set lifs_maxlen to zero to query the kernel of the required buffer size instead of estimating a buffer size. The application tests 'lifs_len <= lifs_maxlen' -- if that's true, the buffer was big enough and the application has an accurate list. If it is false, it needs to allocate a bigger buffer and try again, and lifs_len provides a hint of how big to make the next trial. See ifconfig(1M) for examples of the 'usesrc' option.

The lifsrcof structure has the form:

/*
  * Structure used in SIOCGLIFSRCOF to get interface
  * configuration list for interfaces that use an 
  * address hosted on the interface (set in lifs_ifindex),
  * as the source address.
  */
struct lifsrcof {
  uint_t  lifs_ifindex;  /* addr on this interface*/ 
                         /*  used as the src addr */
  size_t  lifs_maxlen;    /* size of buffer: input */
  size_t  lifs_len;       /* size of buffer: output */
        union {
          caddr_t lifsu_buf;
          struct  lifreq *lifsu_req;
  } lifs_lifsu;
#define lifs_buf lifs_lifsu.lifsu_buf /* buffer addr. */
#define lifs_req lifs_lifsu.lifsu_req /* array returned */  
};

SIOCTONLINK

Test if the address is directly reachable, for example, that it can be reached without going through a router. This request takes an sioc_addrreq structure (see below) as a value-result parameter. The sa_addr field should be set to the address to test. The sa_res field will contain a non-zero value if the address is onlink.

SIOCTMYSITE

Test if the address is part of the same site as this node. This request takes an sioc_addrreq structure (see below) as a value-result parameter. The sa_addr field should be set to the address to test. The sa_res field will contain a non-zero value if the address is in the same site.

The lifconf structure has the form:

/*
 /* Structure used in SIOCGLIFCONF request. */

struct lifconf {
   sa_family_t     lifc_family;
   int             lifc_flags;          /* req. specific interfaces */
   int             lifc_len;            /* size of assoc. buffer */
   union {
      caddr_t      lifcu_buf;
      struct lifreq *lifcu_req;
   } lifc_lifcu;

#define lifc_buf lifc_lifcu.lifcu_buf   /* buffer address */
#define lifc_req lifc_lifcu.lifcu_req   /* array of structs returned */
};

/* Structure used in SIOCGLIFNUM request. */
struct lifnum {
   sa_family_t     lifn_family;
   int             lifn_flags;   /* req. specific interfaces */
   int             lifn_count;   /* Result */
};
The sioc_addrreq structure has the form:
/*
 * Argument structure for SIOCT* address testing ioctls.
 */
struct sioc_addrreq {
   struct sockaddr_storage sa_addr; /* Address to test */
   int                     sa_res;  /* Result - 0/1 */
};

The following ioctl() calls are maintained for compatibility but only apply to IPv4 network interfaces, since the data structures are too small to hold an IPv6 address. Unless specified otherwise, the request takes an ifreq structure as its parameter. This structure has the form:

/* Interface request structure used for socket ioctls.  All */
/* interface ioctls must have parameter definitions which */
/* begin with lifr_name.  The remainder may be interface specific. */
struct ifreq {
#define IFNAMSIZ	16
	char	ifr_name[IFNAMSIZ];	              /* interface name - e.g. "hme0" */
	union {
		struct sockaddr	ifru_addr;
		struct sockaddr	ifru_dstaddr;
		struct sockaddr	ifru_broadaddr;
		short	ifru_flags;
		int	ifru_metric;
		int	if_muxid[2];                     /* mux id's for arp and ip */
		int	ifru_index;	                      /* interface index */
	} ifr_ifru;

#define ifr_addr	ifr_ifru.ifru_addr      /* address */
#define ifr_dstaddr	ifr_ifru.ifru_dstaddr /* other end of p-to-p link */
#define ifr_broadaddr	ifr_ifru.ifru_broadaddr	/* broadcast address */
#define ifr_flags	ifr_ifru.ifru_flags     /* flags */
#define ifr_index 	ifr_ifru.ifru_index	  /* interface index  */
#define ifr_metric	ifr_ifru.ifru_metric  /* metric */
};

SIOCSIFADDR: Set interface address. Following the address assignment, the “initialization” routine for the interface is called.
SIOCGIFADDR: Get interface address.
SIOCSIFDSTADDR: Set point to point address for interface.
SIOCGIFDSTADDR: Get point to point address for interface.
SIOCSIFFLAGS: Set interface flags field. If the interface is marked down, any processes currently routing packets through the interface are notified.
SIOCGIFFLAGS: Get interface flags.
SIOCGIFCONF: Get interface configuration list. This request takes an ifconf structure (see below) as a value-result parameter. The ifc_len field should be set to the size of the buffer pointed to by ifc_buf. Upon success, ifc_len will contain the length, in bytes, of the array of ifreq structures pointed to by ifc_req. For each ifreq structure, the ifr_name and ifr_addr fields will be valid.
SIOCGIFNUM: Get number of interfaces. This request returns an integer which is the number of interface descriptions (struct ifreq) that will be returned by the SIOCGIFCONF ioctl; that is, it gives an indication of how large ifc_len has to be.
SIOCSIFMTU: Set the maximum transmission unit (MTU) size for interface. Place the result of this request in ifru_metric field. The MTU has to be smaller than physical MTU limitation (which is reported in the DLPI DL_INFO_ACK message).
SIOCGIFMTU: Get the maximum transmission unit size for interface. Place the result of this request in ifru_metric field.
SIOCSIFMETRIC: Set the metric associated with the interface. The metric is used by routine daemons such as in.routed(1M).
SIOCGIFMETRIC: Get the metric associated with the interface.
SIOCGIFMUXID: Get the ip and arp muxid associated with the interface.
SIOCSIFMUXID: Set the ip and arp muxid associated with the interface.
SIOCGIFINDEX: Get the interface index associated with the interface.
SIOCSIFINDEX: Set the interface index associated with the interface.

The ifconf structure has the form:

/*
 * Structure used in SIOCGIFCONF request.
 * Used to retrieve interface configuration
 * for machine (useful for programs which
 * must know all networks accessible).
 */
struct ifconf {
	int	ifc_len;		               /* size of assoc. buffer */
	union {
		caddr_t	ifcu_buf;
		struct ifreq	*ifcu_req;
	} ifc_ifcu;

#define ifc_buf	ifc_ifcu.ifcu_buf	/* buffer address */
#define ifc_req	ifc_ifcu.ifcu_req	/* array of structs returned */
};

IFF_ Flags

To display addressing information for each interface, enter ifconfig -a. IFF_ flags are defined in /usr/include/net/if.h. The flags are:

#define IFF_UP          0x00000001      /* Interface is up */
#define IFF_BROADCAST   0x00000002      /* Broadcast address valid */
#define IFF_DEBUG       0x00000004      /* Turn on debugging */
#define IFF_LOOPBACK    0x00000008      /* Loopback net */
#define IFF_POINTOPOINT 0x00000010      /* Interface is point-to-point link */
#define IFF_NOTRAILERS  0x00000020      /* Avoid use of trailers */
#define IFF_RUNNING     0x00000040      /* Resources allocated */
#define IFF_NOARP       0x00000080      /* No address res. protocol */
#define IFF_PROMISC     0x00000100      /* Receive all packets */
#define IFF_ALLMULTI    0x00000200      /* Receive all multicast pkts */
#define IFF_INTELLIGENT 0x00000400      /* Protocol code on board */
#define IFF_MULTICAST   0x00000800      /* Supports multicast */
#define IFF_MULTI_BCAST 0x00001000      /* Multicast using broadcast add. */
#define IFF_UNNUMBERED  0x00002000      /* Non-unique address */
#define IFF_DHCPRUNNING 0x00004000      /* DHCP controls interface */
#define IFF_PRIVATE     0x00008000      /* Do not advertise */

#define IFF_NOXMIT      0x00010000      /* Do not transmit pkts */
#define IFF_NOLOCAL     0x00020000      /* No address - just on-link subnet */
#define IFF_DEPRECATED  0x00040000      /* Interface addr. deprecated */
#define IFF_ADDRCONF    0x00080000      /* Addr. from stateless addrconf */

#define IFF_ROUTER      0x00100000      /* Router on interface */
#define IFF_NONUD       0x00200000      /* No NUD on interface */
#define IFF_ANYCAST     0x00400000      /* Anycast address */
#define IFF_NORTEXCH    0x00800000      /* Don't exchange routing info */

#define IFF_IPV4        0x01000000      /* IPv4 interface */
#define IFF_IPV6        0x02000000      /* IPv6 interface */
#define IFF_MIPRUNNING  0x04000000      /* Mobile IP controls interface */

#define	IFF_NOFAILOVER 0x008000000	 /* Don't failover on NIC failure */

#define	IFF_FAILED	0x010000000	 /* NIC has failed */
#define	IFF_STANDBY	0x020000000	 /* Standby NIC-use on failures */
#define	IFF_INACTIVE	0x040000000	 /* Standby active or not? */
#define	IFF_OFFLINE	0x080000000	 /* NIC offlined */

#define	IFF_XRESOLV	0x100000000	  /* IPv6 external resolver */
#define	IFF_COS_ENABLED 0x200000000	 /* If CoS marking is supported */
#define IFF_PREFERRED   0x400000000      /* Prefer as source address */
#define IFF_TEMPORARY   0x800000000      /* RFC3041 */

#define IFF_FIXEDMTU    0x1000000000     /* MTU set with SIOCSLIFMTU */
#define IFF_VIRTUAL     0x2000000000     /* Cannot send/receive pkts */
#define IFF_DUPLICATE   0x4000000000     /* Local address in use */

For more information on IFF_ flags, see ifconfig(1M).

Errors

EPERM

The effective user id of the calling process in not superuser.

ENXIO

The lifr_name member of the lifreq structure contains an invalid value.

For SIOCGLIFSRCOF, the lifs_ifindex member of the lifsrcof structure contains an invalid value.

For SIOCSLIFUSESRC, this error is returned if the lifr_index is set to an invalid value.

EBADADDR

Wrong address family or malformed address.

EINVAL

For SIOCSLIFMTU, this error is returned when the requested MTU size is invalid. This error indicates the MTU size is greater than the MTU size supported by the DLPI provider or less than 68 (for IPv4 ) or less than 1200 (for IPv6 ). ]

For SIOCSLIFUSESRC, this error is returned if either the lifr_index or lifr_name identify interfaces that are already part of an existing IPMP group.

EEXIST

For SIOCLIFADDIF, this error is rifeturned if the lifr_name member in the lifreq structure corresponds to an interface that already has the PPA specified by lifru_ppa plumbed.