Table of Contents
This
section is a general introduction to the networking facilities available
in the system. Documentation in this part of section 4 is broken up into
three areas: (domains), and All network protocols are associated with
a specific A protocol family provides basic services to the protocol implementation
to allow it to function within a specific network environment. These services
may include packet fragmentation and reassembly, routing, addressing,
and basic transport. A protocol family may support multiple methods of
addressing, though the current protocol implementations do not. A protocol
family is normally comprised of a number of protocols, one per type. It
is not required that a protocol family support all socket types. A protocol
family may contain multiple protocols supporting the same socket abstraction.
A protocol supports one of the socket abstractions detailed in A specific
protocol may be accessed either by creating a socket of the appropriate
type and protocol family, or by requesting the protocol explicitly when
creating a socket. Protocols normally accept only one type of address format,
usually determined by the addressing structure inherent in the design of
the protocol family/network architecture. Certain semantics of the basic
socket abstractions are protocol specific. All protocols are expected to
support the basic model for their particular socket type, but may, in addition,
provide non-standard facilities or extensions to a mechanism. For example,
a protocol supporting the abstraction may allow more than one byte of
out-of-band data to be transmitted per out-of-band message. A network interface
is similar to a device interface. Network interfaces comprise the lowest
layer of the networking subsystem, interacting with the actual transport
hardware. An interface may support one or more protocol families and/or
address formats. The SYNOPSIS section of each network interface entry gives
a sample specification of the related drivers for use in providing a system
description to the program. The DIAGNOSTICS section lists messages which
may appear on the console and/or in the system error log, (see due to
errors in device operation.
The system currently supports the Internet
protocols, the Xerox Network Systems(tm) protocols, and some of the protocols.
Raw socket interfaces are provided to the protocol layer of the Internet,
and to the protocol of Xerox Consult the appropriate manual pages in
this section for more information regarding the support for each protocol
family.
Associated with each protocol family is an address format.
All network address adhere to a general structure, called a sockaddr,
described below. However, each protocol imposes finer and more specific
structure, generally renaming the variant, which is discussed in the protocol
family manual page alluded to above. struct sockaddr {
u_char sa_len;
u_char sa_family;
char sa_data[14];
}; The field contains the total length of the of the structure, which
may exceed 16 bytes. The following address values for are known to the
system (and additional formats are defined for possible future implementation):
#define AF_UNIX 1 /* local to host (pipes, portals) */ #define
AF_INET 2 /* internetwork: UDP, TCP, etc. */ #define AF_NS
6 /* Xerox NS protocols */ #define AF_CCITT 10 /* CCITT
protocols, X.25 etc */ #define AF_HYLINK 15 /* NSC Hyperchannel
*/ #define AF_ISO 18 /* ISO protocols */
provides some
packet routing facilities. The kernel maintains a routing information database,
which is used in selecting the appropriate network interface when transmitting
packets. A user process (or possibly multiple co-operating processes) maintains
this database by sending messages over a special kind of socket. This supplants
fixed size used in earlier releases. This facility is described in
Each
network interface in a system corresponds to a path through which messages
may be sent and received. A network interface usually has a hardware device
associated with it, though certain interfaces such as the loopback interface,
do not. The following calls may be used to manipulate network interfaces.
The is made on a socket (typically of type in the desired domain. Most
of the requests supported in earlier releases take an structure as its
parameter. This structure has the form struct ifreq { #define IFNAMSIZ
16 char ifr_name[IFNAMSIZE]; /* if name, e.g. "en0" */
union {
struct sockaddr ifru_addr;
struct sockaddr ifru_dstaddr;
struct sockaddr ifru_broadaddr;
short ifru_flags;
int ifru_metric;
caddr_t ifru_data;
} 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_metric ifr_ifru.ifru_metric /* metric */ #define
ifr_data ifr_ifru.ifru_data /* for use by interface */ }; Calls
which are now deprecated are: Set interface address for protocol family.
Following the address assignment, the ‘‘initialization’’ routine for the interface
is called. Set point to point address for protocol family and interface.
Set broadcast address for protocol family and interface. requests to
obtain addresses and requests both to set and retrieve other data are still
fully supported and use the structure: Get interface address for protocol
family. Get point to point address for protocol family and interface. Get
broadcast address for protocol family and interface. Set interface flags
field. If the interface is marked down, any processes currently routing
packets through the interface are notified; some interfaces may be reset
so that incoming packets are no longer received. When marked up again, the
interface is reinitialized. Get interface flags. Set interface routing
metric. The metric is used only by user-level routers. Get interface metric.
There are two requests that make use of a new structure: An interface
may have more than one address associated with it in some protocols. This
request provides a means to add additional addresses (or modify characteristics
of the primary address if the default address for the address family is
specified). Rather than making separate calls to set destination or broadcast
addresses, or network masks (now an integral feature of multiple protocols)
a separate structure is used to specify all three facets simultaneously
(see below). One would use a slightly tailored version of this struct specific
to each family (replacing each sockaddr by one of the family-specific type).
Where the sockaddr itself is larger than the default size, one needs to
modify the identifier itself to include the total size, as described in
This requests deletes the specified address from the list associated
with an interface. It also uses the structure to allow for the possibility
of protocols allowing multiple masks or destination addresses, and also
adopts the convention that specification of the default address means to
delete the first address for the interface belonging to the address family
in which the original socket was opened. Get interface configuration list.
This request takes an structure (see below) as a value-result parameter.
The field should be initially set to the size of the buffer pointed
to by On return it will contain the length, in bytes, of the configuration
list. /* * Structure used in SIOCAIFCONF request. */ struct ifaliasreq
{ char ifra_name[IFNAMSIZ]; /* if name, e.g. "en0" */
struct sockaddr ifra_addr;
struct sockaddr ifra_broadaddr;
struct sockaddr ifra_mask;
}; /* * 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 */ };
The
manual appeared in
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