Intro(7tcp)

Synopsis

#include  <sys/socket.h> 

 
#include  <netinet/in.h> 

 
#include  <net/if.h> 

 
#include  <netinet/ip_str.h> 

 
#include  <net/strioc.h> 

 
#include  <net/sockio.h> 

Description

Protocol family entries

A protocol supports one of the socket abstractions detailed in socket(3sock). A specific protocol may be accessed by creating a socket of the appropriate type and protocol family, by requesting the protocol explicitly when creating a socket, by executing the appropriate TLI/XTI primitives, or by opening the associated STREAMS device.

Protocol entries

Addressing

       struct sockaddr { 
           u_char  sa_len; 
           u_char  sa_family; 
           char    sa_data[14]; 
       }; 

The following address values for sa_family are known to the system:

   #define    AF_UNIX      1    /* UNIX domain */ 
   #define    AF_INET      2    /* internetwork: UDP, TCP, etc. */ 
   #define    AF_LINK     18    /* data-link layer (ARP) */ 
   #define    AF_INET6    27    /* internetwork: UDP, TCP, etc. */ 

Routing

A user process (or possibly multiple co-operating processes) maintains this database by sending messages over a special kind of stream. This supplants fixed size ioctl(2) used in earlier releases.

This facility is described in route(7tcp).

Socket ioctls

   ioctl(file_descriptor,code,arg) 

SIOCSPGRP

Set the process group for a socket to enable signaling (SIGUSR1) of that process group when out-of-band data arrives. The argument, arg, is a pointer to an int and, if positive, is treated as a process ID; otherwise, (if negative) is treated as a process group ID.

SIOCGPGRP

Get the process group ID associated with a particular socket. If the value returned to the int location pointed to by arg is negative, it should be interpreted as a process group ID; otherwise, it should be interpreted as a process ID.

SIOCCATMARK

Used to ascertain whether or not the socket read pointer is currently at the point (mark) in the data stream where out-of-band data was sent. If a 1 is returned to the int location pointed to by arg, the next read will return data after the mark. Otherwise (assuming out-of-band data has arrived), the next read will provide data sent by the client prior to transmission of the out-of-band signal.

FIONREAD

Returns (to the int location pointed to by arg) the number of bytes currently waiting to be read on the socket.

FIONBIO

Toggles the socket into blocking/non-blocking mode. If the int location pointed to by arg contains a non-zero value, subsequent socket operations that would cause the process to block waiting on a specific event will return abnormally with errno set to EWOULDBLOCK; otherwise, the process will block.

Queue ioctls

   struct iocqp { 
           ushort iqp_type; 
           ushort iqp_value; 
   }; 

iqp_value specifies the value for the queue parameter according to iqp_type, which may be one of: IQP_RQ (read queue), IQP_WQ (write queue), IQP_MUXRQ (mux read queue), IQP_MUXWQ (mux write queue), or IQP_HDRQ (stream head queue), each OR'ed with either IQP_LOWAT (value is for low water mark of queue), or IQP_HIWAT (value is for high water mark of queue).

Interface ioctls

The following ioctl calls may be used to manipulate network interfaces. The ioctl is made on a socket (typically of type SOCK_DGRAM) in the desired ``communications domain'' (see protocols(4tcp)). 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];   /* name of interface, e.g. net0 */ 
        union { 
                struct  sockaddr ifru_addr; 
                struct  sockaddr ifru_dstaddr; 
                struct  sockaddr ifru_broadaddr; 
                short   ifru_flags; 
                int     ifru_metric; 
                caddr_t ifru_data; 
                char    ifru_enaddr[6]; 
                struct  onepacket ifru_onepacket; 
                struct  ifperf ifru_perf; 
        } 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	/* routing metric */ 
#define ifr_nif		ifr_ifru.ifru_metric	/* # of interfaces */ 
#define ifr_naddr	ifr_ifru.ifru_metric	/* # of addresses */ 
#define ifr_data	ifr_ifru_ifru_data	/* for use by interface */ 
#define ifr_enaddr	ifr_ifru_ifru_enaddr	/* ethernet address */ 
#define ifr_onepacket 	ifr_ifru.ifru_onepacket	/* one-packet mode params */ 
#define ifr_perf      	ifr_ifru.ifru_onepacket	/* performance tuning */ 
}; 

SIOCSIFADDR

Set interface address for protocol family. Following the address assignment, the ``initialization'' routine for the interface is called.

SIOCGIFADDR

Get interface address for protocol family.

SIOCSIFNETMASK

Set interface network mask. The network mask defines the network part of the address; if it contains more of the address than the address type would indicate, then subnets are in use.

SIOCGIFNETMASK

Get interface network mask.

SIOCSIFBRDADDR

Set broadcast address for protocol family and interface.

SIOCGIFBRDADDR

Get broadcast address for protocol family and interface.

SIOCSIFDSTADDR

Set destination address for protocol family of point-to-point interfaces.

SIOCGIFDSTADDR

Get destination address for protocol family of point-to-point interfaces.

SIOCSIFFLAGS

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.

SIOCGIFFLAGS

Get interface flags.

SIOCSIFMETRIC

Set interface routing metric. The metric is used only by user-level routers.

SIOCGIFMETRIC

Get interface metric.

SIOCSIFMTU

Sets the maximum-transmission-unit size of the interface. This value indicates the largest atomic data-unit (including all protocol headers) that can be transmitted via this interface. The ifr_metric field is used to contain the MTU value.

SIOCGIFMTU

Retrieves the maximum-transmission-unit size associated with the interface. The MTU value is returned in the ifr_metric field.

SIOCSIFDEBUG

Sets the debugging level of the interface. The ifr_metric field is used to contain the MTU value.

SIOCGIFDEBUG

Retrieves the current debugging level associated with the interface. The level is returned in the ifr_metric field.

SIOCSIFTYPE

Sets the interface type to the value specified in the ifr_metric field. Valid interface types are specified in <sys/net/if_types.h>. This is performed by the system when appropriate and should never normally be issued by an application.

SIOCGIFTYPE

Retrieves the interface type of the specified interface. The value is returned in the ifr_metric field.

SIOCSIFONEP

Set one-packet mode parameters. The ifr_onepacket field of the ifreq structure is used for this request. This structure is defined as follows:

struct onepacket { 
        int     spsize;         /* small packet size */ 
        int     spthresh;       /* small packet threshold */ 
}; 

One-packet mode is enabled by setting the IFF_ONEPACKET flag (see SIOCSIFFLAGS above). See tcp(7tcp) for an explanation of one-packet mode.

SIOCGIFONEP

Get one-packet mode parameters.

SIOCSIFPERF

Set performance tuning parameters. The ifr_perf field of the ifreq structure is used for this request. This structure is defined as follows:

struct ifperf { 
        u_short     ip_recvspace;      /* recv buffering */ 
        u_short     ip_sendspace;      /* send buffering */ 
        u_short     ip_fullsize;       /* use full-size segments */ 
}; 

These values control interface-specific information that TCP will use to determine optimal window and segment sizes. They can be configured on a per-interface basis so that systems with multiple different types of interfaces do not have to be configured in such a way as to penalize faster hardware.

SIOCGIFPERF

Get performance tuning parameters.

SIOCAIFADDR

An interface may have more than one address associated with it in the Internet protocol. 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 the protocol), 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 types, for example, sockaddr_in).

SIOCDIFADDR

This request deletes the specified address from the list associated with an interface. It also uses the if_aliasreq 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.

The following structure is used with SIOCAIFADDR, SIOCGIFALIAS, and SIOCDIFADDR:

/* 
 * Structure used in SIOCAIFADDR/SIOCGIFALIAS/SIOCDIFADDR requests. 
 */ 
struct ifaliasreq { 
        char    ifra_name[IFNAMSIZ];   /* if name, e.g. net0 */ 
        struct  sockaddr        ifra_addr; 
        struct  sockaddr        ifra_broadaddr; 
        struct  sockaddr        ifra_mask; 
}; 

SIOCGIFALIAS

Get interface alias. This request takes an ifaliasreq structure as an argument. The alias about which information is desired is identified by the combination of the ifra_name and ifra_addr fields. For example, to retrieve information about the alias ``127.0.0.2'' on interface ``lo0'', ifra_name should contain the string ``lo0'' and ifra_addr should be initialized to a sockaddr_in structure whose sin_addr field contains 0x7f000002 in network-byte order. The remaining fields will be returned by the kernel.

SIOCGIFNUM

This returns the current number of interfaces in ifr_nif. No values need be set in the passed ifreq structure.

SIOCGIFANUM

This returns the current number of non-multicast interface addresses in ifr_naddr. No values need be set in the passed ifreq structure.

This is useful for sizing buffers to be used with the SIOCGIFCONF ioctl, since that ioctl will return a struct ifreq for every interface address.

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. If the SIOCGIFANUM ioctl is used to size the buffer, the size should be equal to the number returned via the SIOCGIFANUM ioctl multiplied by the size of an ifreq structure. On return it will contain the length, in bytes, of the configuration list.

/* Structure used in SIOCGIFCONF request. 
 * Used to retrieve interface configuration 
 * for machine (useful for programs which 
 * must know all networks accessible 
 * or all local addresses). 
 */ 
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 */ 
}; 

Streams ioctl interface

In all cases, the ic_len field should be set to the appropriate size.

TLI/XTI options management

If the value of the environment variable XTI_OPTMGMT is set to 1 and exported (XTI option management), options may be set and retrieved using a struct t_opthdr header (as defined in X/Open CAE Specification, Networking Services, Issue 4, 1994):

   struct t_opthdr { 
   	unsigned long length;	/* total length of option          */ 
   				/* sizeof (struct t_opthdr) plus   */ 
   				/* length of option value in bytes */ 
   	unsigned long level;	/* protocol level affected */ 
   	unsigned long name;	/* option to modify */ 
   	unsigned long status;	/* status value */ 
   } 
   /* option value */ 

   struct opthdr { 
           long level;     /* protocol level affected */ 
           long name;      /* option to modify */ 
           long len;       /* length of option value in bytes */ 
   }; 
   /* option value */ 

To get the values of options, set the flags field of the t_optmgmt structure to T_CHECK. Set the length or len fields to 0 and make the option headers adjacent. A new options buffer will be formatted and returned to the user. Note that T_CHECK may have failed even if t_optmgmt returns zero. You must check the flags field of the returned t_optmgmt structure. If this field contains T_FAILURE, one or more of the options were invalid.

To set options, set the flags field of the t_optmgmt structure to T_NEGOTIATE.

To retrieve the default values of all options, set the flags field of the t_optmgmt structure to T_DEFAULT. For this operation, no input buffer should be specified.

Obtaining RFCs

References

``Obtaining RFCs from the Internet''

RFC 1180, RFC 1500