openbsd-manpages-netintro.sgml

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     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 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;
                     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_media     ifr_ifru.ifru_metric  /* media options (overload) */
     #define ifr_data      ifr_ifru.ifru_data    /* for use by interface */
     };

     Calls which are now deprecated are:

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

     SIOCSIFDSTADDR  Set point to point address for protocol family and inter-
                     face.

     SIOCSIFBRDADDR  Set broadcast address for protocol family and interface.

     ioctl requests to obtain addresses and requests both to set and retrieve
     other data are still fully supported and use the ifreq structure:

     SIOCGIFADDR     Get interface address for protocol family.

     SIOCGIFDSTADDR  Get point to point address for protocol family and inter-
                     face.

     SIOCGIFBRDADDR  Get broadcast address for protocol family and interface.

     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.

     SIOCSIFMEDIA    Set interface media.  See ifmedia(4) for possible values.

     SIOCGIFMEDIA    Get interface media.  See ifmedia(4) for interpreting
                     this value.

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

     SIOCGIFMETRIC   Get interface metric.

     There are two requests that make use of a new structure:

     SIOCAIFADDR     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 ad-
                     dress family is specified).  Rather than making separate
                     calls to set destination or broadcast addresses, or net-
                     work masks (now an integral feature of multiple proto-
                     cols) 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-spe-
                     cific type).  Where the sockaddr itself is larger than
                     the default size, one needs to modify the ioctl(2) iden-
                     tifier itself to include the total size, as described in
                     ioctl(2).

     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 address-
                     es, 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.

     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 con-
                     tain the length, in bytes, of the configuration list.
                     Alternately, if the ifc_len passed in is set to 0,
                     SIOCGIFCONF will set ifc_len to the size that ifc_buf
                     needs to be to fit the entire configuration list and not
                     fill in the other parameters.  This is useful for deter-
                     mining the exact size that ifc_buf needs to be in ad-
                     vance.  Note, however, that this is an extension that not
                     all operating systems support.

     /*
     * Structure used in SIOCAIFADDR 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 */
     };

SEE ALSO
     <link linkend="openbsd-manpages-bridge">bridge</link>, <link linkend="openbsd-manpages-stp">spanning-tree</link>

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