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man pages section 4: Device and Network Interfaces

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Updated: Thursday, June 13, 2019
 
 

if (4P)

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(4P).

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(4I)). The SIOCSLIFNAME ioctl(2) is issued to specify the name of the interface and to indicate whether it is IPv4 or IPv6. This can 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, Ethernets using arp(4P)), 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.

You cannot create IPMP IP interfaces using the procedure described above. Instead, use ipadm(8) or ifconfig(8).

Ioctls

The following ioctl() calls can be used to manipulate IP network interfaces. Unless specified otherwise, the request takes an lifreq structure as its parameter. This structure is defined in <net/if.h> and has the form:


/*
 * Structure required for ioctl SIOCCLIFFLAGS
 */
struct lif_cflags_req {
     uint64_t lcr_modflags;  /* flags to be modified on if */
     uint64_t lcr_modmask;   /* mask of valid flags in lcr_modflags */
     uint64_t lcr_origflags; /* expected initial flag values */
     uint64_t lcr_origmask;  /* mask of valid flags in lcr_origflags */
};

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;     /* [GS]LIFZONE */
         struct lif_cflags_req lifru_cflags_req; /*SIOCCLIFFLAGS*/
   } 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_ip_muxid  lifr_lifru.lif_muxid[0]
#define lifr_arp_muxid lifr_lifru.lif_muxid[1]
#define lifr_nd        lifr_lifru.lifru_nd_req     /* LIF*ND */
#define lifr_ifinfo    lifr_lifru.lifru_ifinfo_req /* [GS]LIFLNKINFO */
#define lifr_zone      lifr_lifru.lifru_zone       /* [GS]LIFZONE */
#define lifr_cflags    lifr_lifru.lifru_cflags_req
};
SIOCSLIFADDR

Set interface address.

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.

SIOCCLIFFLAGS

Change the given flags on the interface. The caller needs to fill in the fields lcr_modflags and lcr_modmask in struct lif_cflags_req and optionally set lcr_origflags and lcr_origmask to fail the ioctl if any of the flags in lcr_origflags that are of interest to the caller do not match the current flags before applying the changes. This ioctl is preferred over SIOCSLIFFLAGS since the set and clear of the flags is done atomically unlike using SIOCGLIFFLAGS followed by SIOCSLIFFLAGS.

SIOCGLIFCONF

Get interface configuration list. This request takes a 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_len field should be set to the size of the buffer pointed to by lifc_buf.

The lifc_flags field should usually be set to zero, but callers that need low-level knowledge of the underlying IP interfaces that comprise an IPMP group can set it to LIFC_UNDER_IPMP to request that those interfaces be included in the result. Upon success, lifc_len contains 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 are valid.

SIOCGLIFNUM

Get number of interfaces. This request returns an integer which is the number of interface descriptions (struct lifreq) returned by the SIOCGLIFCONF ioctl (in other words, indicates how large lifc_len must be).

This request takes a struct lifnum (see below) as a value-result parameter. The lifn_family field can be set to AF_UNSPEC to count both AF_INET and AF_INET6 interfaces. The lifn_flags field should usually be set to zero, but callers that need low-level knowledge of the underlying IP interfaces that comprise an IPMP group can set it to LIFC_UNDER_IPMP to request that those interfaces be included in the count.

SIOCSLIFMTU

Set the maximum transmission unit (MTU) size for interface. Place the request in the 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.

SIOCSLIFMETRIC

Set the metric associated with the interface. The metric is used by routing daemons such as in.routed(8).

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 interface number.

SIOCLIFREMOVEIF

Remove a logical interface by specifying its IP address or logical interface name.

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.

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 ipadm(8) 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 ipadm(8) 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 ipadm(8) for examples of the usesrc option.

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 contains a non-zero value if the address is onlink.

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 contains a non-zero value if the address is assigned to this node.

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 contains a non-zero value if the address is in the same site.

SIOCGLIFHWADDR

Retrieve the hardware address. For PF_INET and PF_INET6 sockets, the name must refer to a network interface that is visible with ipadm(8). This ioctl can also be against PF_PACKET sockets for which the name must match an existing datalink reported by dladm(8). A sockaddr_dl structure is filled out and returned in lifr_addr.

The structure used by SIOCGLIFCONF has the form:


struct lifconf {
   sa_family_t     lifc_family;
   int             lifc_flags;       /* request 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 */
};

The structure used by SIOCGLIFNUM has the form:


struct lifnum {
   sa_family_t     lifn_family;
   int             lifn_flags;   /* req. specf. interfaces */
   int             lifn_count;   /* Result */
};

The structure used by SIOCTONLINK, SIOCTMYADDR and SIOCTMYSITE has the form:


struct sioc_addrreq {
   struct sockaddr_storage sa_addr; /* Address to test */
   int                     sa_res;  /* Result - 0/1 */
};

The structure used by SIOCGLIFSRCOF has the form:


 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 */  
};

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:


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.

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 contains 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 are valid. Though IPMP IP interfaces are included in the array, underlying IP interfaces that comprise those IPMP groups are not.

SIOCGIFNUM

Get number of interfaces. This request returns an integer which is the number of interface descriptions (struct ifreq) returned by the SIOCGIFCONF ioctl (in other words, indicates how large ifc_len must be). Though IPMP IP interfaces are included in the array, underlying IP interfaces that comprise those IPMP groups are not.

SIOCSIFMTU

Set the maximum transmission unit (MTU) size for interface. Place the request in the ifr_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. Upon success, the request is placed in the ifr_metric field.

SIOCSIFMETRIC

Set the metric associated with the interface. The metric is used by routine daemons such as in.routed(8).

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.

SIOCGIFHWADDR

Return the hardware address associated with the interface. See SIOCGLIFHWADDR for details on associations between names and sockets. This ioctl returns a sockaddr structure inside ifr_addr and should behave in a manner compatible with Linux.

The ifconf structure has the form:


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

You can use the ipadm command to display the IFF_ flags listed below (with the leading IFF_ prefix removed). See the ipadm(8) manual page for a definition of each flag.


#define IFF_UP          0x0000000001  /* Address is up */
#define IFF_BROADCAST   0x0000000002  /* Broadcast address valid */
#define IFF_DEBUG       0x0000000004  /* Turn on debugging */
#define IFF_LOOPBACK    0x0000000008  /* Loopback net */

#define IFF_POINTOPOINT 0x0000000010  /* Interface is p-to-p */
#define IFF_NOTRAILERS  0x0000000020  /* Avoid use of trailers */
#define IFF_RUNNING     0x0000000040  /* Resources allocated */
#define IFF_NOARP       0x0000000080  /* No address res. protocol */

#define IFF_PROMISC     0x0000000100  /* Receive all packets */
#define IFF_ALLMULTI    0x0000000200  /* Receive all multicast pkts */
#define IFF_INTELLIGENT 0x0000000400  /* Protocol code on board */
#define IFF_MULTICAST   0x0000000800  /* Supports multicast */

#define IFF_MULTI_BCAST 0x0000001000  /* Multicast using broadcst. add*/
#define IFF_UNNUMBERED  0x0000002000  /* Non-unique address */
#define IFF_DHCPRUNNING 0x0000004000  /* DHCP controls interface */
#define IFF_PRIVATE     0x0000008000  /* Do not advertise */

#define IFF_NOXMIT      0x0000010000  /* Do not transmit pkts */
#define IFF_NOLOCAL     0x0000020000  /*No address;just on-link subnet*/
#define IFF_DEPRECATED  0x0000040000  /* Address is deprecated */
#define IFF_ADDRCONF    0x0000080000  /* Addr. from stateless addrconf*/

#define IFF_ROUTER      0x0000100000  /* Router on interface */
#define IFF_NONUD       0x0000200000  /* No NUD on interface */
#define IFF_ANYCAST     0x0000400000  /* Anycast address */
#define IFF_NORTEXCH    0x0000800000  /* Don't xchange rout. info */

#define IFF_IPV4        0x0001000000  /* IPv4 interface */
#define IFF_IPV6        0x0002000000  /* IPv6 interface */
#define IFF_NOFAILOVER  0x0008000000  /* in.mpathd test address */
#define IFF_FAILED      0x0010000000  /* Interface has failed */

#define IFF_STANDBY     0x0020000000  /* Interface is a hot-spare */
#define IFF_INACTIVE    0x0040000000  /* Functioning but not used */
#define IFF_OFFLINE     0x0080000000  /* Interface is offline */
#define IFF_COS_ENABLED 0x0200000000  /* If CoS marking is supported

#define IFF_COS_ENABLED 0x0200000000  /* If CoS marking is supported */
#define IFF_PREFERRED   0x0400000000  /* Prefer as source address */
#define IFF_TEMPORARY   0x0800000000  /* 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 */
#define IFF_IPMP        0x8000000000  /* IPMP IP interface */
#define IFF_PHYSRUNNING 0x10000000000 /* physical connectivity to */
																		/* an external network */
#define IFF_VNI         0x200000000000ll /* VNI interface */

Errors

EPERM

Calling process has insufficient privileges.

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 1280 (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 returned if the lifr_name member in the lifreq structure corresponds to an interface that already has the PPA specified by lifr_ppa plumbed.

See Also

ioctl(2), streamio(4I), arp(4P), dlpi(4P), ip(4P), ip6(4P), dladm(8), ifconfig(8), in.routed(8), ipadm(8), ipadm(8)