if_tcp(7P) manual page
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if_tcp, if - general properties of Internet Protocol network interfaces
A network interface is a device for sending and receiving
packets on a network. A network interface is usually a hardware device,
although one may be implemented in software. Network interfaces used by
the Internet Protocol (IP
) must be STREAMS
devices conforming to the Datalink
Provider Interface (DLPI
). See dlpi(7P)
.
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)
).
This may be initiated by the kernel at boot time or by a user program
some time after the system is running. Each interface must be assigned an
IP
address with the SIOCSIFADDR
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.
The following ioctl() calls may
be used to manipulate IP
network interfaces. 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 ifr_name. The remainder may be interface specific. */
struct ifreq {
#define IFNAMSIZ 16
char ifr_name[IFNAMSIZ]; /* if name, for example */
/* "emd1" */
union {
struct sockaddr ifru_addr;
struct sockaddr ifru_dstaddr;
char ifru_oname[IFNAMSIZ]; /* other if name */
struct sockaddr ifru_broadaddr;
short ifru_flags;
int ifru_metric;
char ifru_data[1]; /* interface dependent data */
char ifru_enaddr[6];
int if_muxid[2]; /* mux id’s for arp and ip */
} 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_oname ifr_ifru.ifru_oname /* other if name */
#define ifr_broadaddr ifr_ifru.ifru_broadaddr /* broadcast address */
#define ifr_flags ifr_ifru.ifru_flags
/* flags */
#define ifr_metric ifr_ifru.ifru_metric /* metric */
#define ifr_data ifr_ifru.ifru_data /* for use by interface */
#define ifr_enaddr ifr_ifru.ifru_enaddr /* ethernet address */
};
- 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 initially set to the size of the buffer pointed to by ifc_buf.
On return it will contain the length, in bytes, of the configuration list.
- SIOGIFNUM
- 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.
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 associated 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 structures returned */
};
- EPERM
- The effective user id of the calling process in not superuser.
- ENXIO
- The ifr_name member of the ifreq structure contains an invalid
value.
- EBADADDR
- Wrong address family or malformed address.
- EBUSY
- For SIOCSIFFLAGS
,
this error is returned when the order of bringing the primary/physical
interface (e.g. le0) and a secondary/logical interface associated with the
same physical interface (e.g. le0:1) up or down is violated. The physical
interface must be configured up first and cannot be configured down until
all the corresponding logical interfaces have been configured down.
- EINVAL
- For SIOCGIFCONF
, this error is returned when the size of the buffer pointed
to by the ifc_buf member of the ifconf structure is too small.
- For
- SIOCSIFMTU
,
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.
ifconfig(1M)
, in.routed(1M)
, ioctl(2)
,
arp(7P)
, dlpi(7P)
, ip(7P)
, streamio(7I)
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