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Хостинг:
networking - introduction to networking facilities
All network protocols are associated with a specific protocol family 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 socket(2) 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 socket(2). 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 SOCK_STREAM 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 config(8) program. The DIAGNOSTICS section lists messages which may appear on the console and/or in the system error log, /var/log/messages (see syslogd(8)), due to errors in device operation.
struct sockaddr {
u_char sa_len;
u_char sa_family;
char sa_data[14];
};
The field sa_len contains the total length of the structure, which may exceed 16 bytes. The following address values for sa_family 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 */
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 ioctl(2) used in earlier releases.
This facility is described in route(4).
The following
ioctl(2)
calls may be used to manipulate network interfaces.
The
ioctl ();
is made on a socket (typically of type
SOCK_DGRAM
in the desired domain.
Most of the requests supported in earlier releases
take an
Vt ifreq
structure as its parameter.
This structure has the form
struct ifreq {
#define IFNAMSIZ 16
char ifr_name[IFNAMSIZ]; /* if name, e.g. "en0" */
union {
struct sockaddr ifru_addr;
struct sockaddr ifru_dstaddr;
struct sockaddr ifru_broadaddr;
short ifru_flags[2];
short ifru_index;
int ifru_metric;
int ifru_mtu;
int ifru_phys;
int ifru_media;
caddr_t ifru_data;
int ifru_cap[2];
} 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[0] /* flags (low 16 bits) */
#define ifr_flagshigh ifr_ifru.ifru_flags[1] /* flags (high 16 bits) */
#define ifr_metric ifr_ifru.ifru_metric /* metric */
#define ifr_mtu ifr_ifru.ifru_mtu /* mtu */
#define ifr_phys ifr_ifru.ifru_phys /* physical wire */
#define ifr_media ifr_ifru.ifru_media /* physical media */
#define ifr_data ifr_ifru.ifru_data /* for use by interface */
#define ifr_reqcap ifr_ifru.ifru_cap[0] /* requested capabilities */
#define ifr_curcap ifr_ifru.ifru_cap[1] /* current capabilities */
#define ifr_index ifr_ifru.ifru_index /* interface index */
};
Calls which are now deprecated are:
Ioctl ();
requests to obtain addresses and requests both to set and
retrieve other data are still fully supported
and use the
Vt ifreq
structure:
There are two requests that make use of a new structure:
/*
* 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 */
};
/* Structure used in SIOCIFGCLONERS request. */
struct if_clonereq {
int ifcr_total; /* total cloners (out) */
int ifcr_count; /* room for this many in user buffer */
char *ifcr_buffer; /* buffer for cloner names */
};
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