Document Monday's changes in the interface structure.
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@ -1,5 +1,5 @@
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.\"
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.\" Copyright 1996 Massachusetts Institute of Technology
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.\" -*- Nroff -*-
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.\" Copyright 1996, 1997 Massachusetts Institute of Technology
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.\"
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.\" Permission to use, copy, modify, and distribute this software and
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.\" its documentation for any purpose and without fee is hereby
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@ -26,9 +26,9 @@
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.\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.Dd December 16, 1996
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.Os FreeBSD 2.2
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.\" $Id: ifnet.9,v 1.3 1996/12/26 16:16:37 wosch Exp $
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.Dd January 15, 1997
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.Os FreeBSD 3.0
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.Dt IFNET 9
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.Sh NAME
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.Nm ifnet ,
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@ -41,6 +41,7 @@
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.Fd #include <sys/time.h>
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.Fd #include <sys/socket.h>
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.Fd #include <net/if.h>
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.Fd #include <net/if_var.h>
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.Fd #include <net/if_types.h>
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.\"
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.Ss "Interface manipulation functions"
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@ -52,6 +53,8 @@
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.Fn ifioctl "struct socket *so" "int cmd" "caddr_t data" "struct proc *p"
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.Ft int
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.Fn ifpromisc "struct ifnet *ifp" "int pswitch"
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.Ft int
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.Fn if_allmulti "struct ifnet *ifp" "int amswitch"
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.Ft "struct ifnet *"
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.Fn ifunit "char *name"
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.Ft void
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@ -71,6 +74,13 @@
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.Ft void \"macro
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.Fn IFAFREE "struct ifaddr *ifa"
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.\"
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.Ss "Interface multicast address functions"
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.Ft int
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.Fn if_addmulti "struct ifnet *ifp" "struct sockaddr *sa" "struct ifmultiaddr **ifmap"
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.Ft int
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.Fn if_delmulti "struct ifnet *ifp" "struct sockaddr *sa"
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.Ft "struct ifmultiaddr *"
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.Fn ifmaof_ifpforaddr "struct sockaddr *addr" "struct ifnet *ifp"
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.Ss "Output queue macros"
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.Ft void \"macro
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.Fn IF_ENQ_DROP "struct ifqueue *ifq" "struct mbuf *m"
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@ -98,6 +108,8 @@
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.Fn (*if_poll_slowinput) "struct ifnet *ifp" "struct mbuf *m"
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.Ft void
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.Fn (*if_init) "void *wtf_is_this"
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.Ft int
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.Fn (*if_resolvemulti) "struct ifnet *ifp" "struct sockaddr **retsa" "struct sockaddr *addr"
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.Ss "struct ifaddr member function"
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.Ft void
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.Fn (*ifa_rtrequest) "int cmd" "struct rtentry *rt" "struct sockaddr *dst"
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@ -111,12 +123,40 @@ The kernel mechanisms for handling network interfaces reside primarily
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in the
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.Li ifnet ,
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.Li if_data ,
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.Li ifaddr ,
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and
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.Li ifaddr
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.Li ifmultiaddr
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structures in
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.Aq Pa net/if.h ,
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.Aq Pa net/if.h
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and
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.Aq Pa net/if_var.h
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and the functions named above and defined in
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.Pa /sys/net/if.c .
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Those interfaces which are intended to be used by user programs
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are defined in
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.Aq Pa net/if.h ;
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these include the interface flags, the
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.Li if_data
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structure, and the structures defining the appearance of
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interface-related messages on the
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.Xr route 4
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routing socket and in
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.Xr sysctl 3 .
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The header file
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.Aq Pa net/if_var.h
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defines the kernel-internal interfaces, including the
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.Li ifnet ,
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.Li ifaddr ,
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and
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.Li ifmultiaddr
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structures and the functions which manipulate them.
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(A few user programs will need
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.Aq Pa net/if_var.h
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because it is the prerequisite of some other header file like
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.Aq Pa netinet/if_ether.h .
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Most references to those two files in particular can be replaced by
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.Aq Pa net/ethernet.h . )
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.Pp
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The system keeps a linked list of interfaces using the
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.Li TAILQ
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macros defined in
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@ -152,6 +192,13 @@ describing the link layer implemented by the interface (if any).
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this structure, while still present, serves only to identify the
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interface name and index.)
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.Pp
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Finally, those interfaces supporting reception of multicast datagrams
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have a
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.Li LIST
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of multicast group memberships, described by
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.Li ifmultiaddr
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structures. These memberships are reference-counted.
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.Pp
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Interfaces are also associated with an output queue, defined as a
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.Li "struct ifqueue" ;
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this structure is used to hold packets while the interface is in the
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@ -315,6 +362,13 @@ expires. Usually this will reset the interface.
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.\" section, below.
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.It Fn if_init
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XXX fill me in
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.It Fn if_resolvemulti
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Check the requested multicast group membership,
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.Ar addr ,
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for validity, and if necessary compute a link-layer group which
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corresponds to that address which is returned in
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.Ar \&*retsa .
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Returns zero on success, or an error code on failure.
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.El
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.Ss "Interface flags"
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Interface flags are used for a number of different purposes. Some
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@ -637,6 +691,36 @@ manipulate interface addresses. In addition to these functions, there
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may also be link-layer support routines which are used by a number of
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drivers implementing a specific link layer over different hardware;
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see the documentation for that link layer for more details.
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.Ss The ifmultiaddr structure
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Every multicast-capable interface is associated with a list of
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multicast group memberships, which indicate at a low level which
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link-layer multicast addresses (if any) should be accepted, and at a
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high level, in which network-layer multicast groups a user process has
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expressed interest.
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.Pp
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The elements of the structure are as follows:
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.Bl -tag -width ifma_refcount -offset indent
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.It Li ifma_link
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.Pq Li LIST_ENTRY(ifmultiaddr)
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.Xr queue 3
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macro glue.
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.It Li ifma_addr
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.Pq Li "struct sockaddr *"
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A pointer to the address which this record represents. The
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memberships for various address families are stored in arbitrary
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order.
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.It Li ifma_lladdr
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.Pq Li "struct sockaddr *"
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A pointer to the link-layer multicast address, if any, to which the
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network-layter multicast address in
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.Li ifma_addr
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is mapped, else a null pointer. If this element is non-nil, this
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membership also holds an invisible reference to another membership for
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that link-layer address.
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.It Li ifma_refcount
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.Pq Li u_int
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A reference count of requests for this particular membership.
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.El
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.Ss Interface manipulation functions
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.Bl -ohang -offset indent
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.It Fn if_attach
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@ -675,6 +759,12 @@ from zero to one and one to zero, set the
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flag appropriately and call
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.Fn if_ioctl
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to set up the interface in the desired mode.
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.It Fn if_allmulti
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As
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.Fn ifpromisc ,
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but for the all-multicasts
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.Pq Dv IFF_ALLMULTI
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flag instead of the promiscuous flag.
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.It Fn ifunit
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Return an
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.Li ifnet
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@ -739,9 +829,11 @@ interface structure.
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.It Dv SIOCADDMULTI
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.It Dv SIOCDELMULTI
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Add or delete permanent multicast group memberships on the interface.
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Caller must have appropriate privilege. The driver
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.Fn if_ioctl
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routine is called to perform the requested action.
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Caller must have appropriate privilege. The
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.Fn if_addmulti
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or
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.Fn if_delmulti
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function is called to perform the operation; qq.v.
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.It Dv SIOCSIFDSTADDR
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.It Dv SIOCSIFADDR
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.It Dv SIOCSIFBRDADDR
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@ -802,6 +894,72 @@ will be returned.
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.Pp
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All of these functions return a null pointer if no such address can be
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found.
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.Ss "Interface multicast address functions"
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The
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.Fn if_addmulti ,
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.Fn if_delmulti ,
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and
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.Fn ifmaof_ifpforaddr
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functions provide support for requesting and relinquishing multicast
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group memberships, and for querying an interface's membership list,
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respectively. The
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.Fn if_addmulti
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function takes a pointer to an interface,
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.Ar ifp ,
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and a generic address,
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.Ar sa .
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It also takes a pointer to a
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.Sq Li "struct ifmultiaddr *"
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which is filled in on successful return with the address of the
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group membership control block. The
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.Fn if_addmulti
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function performs the following four-step process:
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.Bl -enum -offset indent
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.It
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Call the interface's
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.Fn if_resolvemulti
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entry point to determine the link-layer address, if any, corresponding
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to this membership request, and also to give the link layer an
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opportunity to veto this membership request should it so desire.
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.It
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Check the interface's group membership list for a pre-existing
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membership for this group. If one is not found, allocate a new one;
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if one is, increment its reference count.
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.It
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If the
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.Fn if_resolvemulti
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routine returned a link-layer address corresponding to the group,
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repeat the previous step for that address as well.
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.It
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If the interface's multicast address filter needs to be changed
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because a new membership was added, call the interface's
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.Fn if_ioctl
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routine
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(with a
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.Ar cmd
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argument of
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.Dv SIOCADDMULTI )
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to request that it do so.
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.El
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.Pp
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The
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.Fn if_delmulti
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function, given an interface
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.Ar ifp
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and an address,
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.Ar sa ,
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reverses this process. Both functions return zero on success, or a
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standard error number on failure.
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.Pp
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The
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.Fn ifmaof_ifpforaddr
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function examines the membership list of interface
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.Ar ifp
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for an address matching
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.Ar addr ,
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and returns a pointer to that
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.Li "struct ifmultiaddr"
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if one is found, else it returns a null pointer.
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.\" .Sh POLLING
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.\" XXX write me!
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.Sh SEE ALSO
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@ -824,4 +982,4 @@ found.
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.%O Addison-Wesley, ISBN 0-201-63354-X
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.Re
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.Sh AUTHOR
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This manual page was written by Garrett A. Wollman
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This manual page was written by Garrett A. Wollman.
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