989 lines
28 KiB
Groff
989 lines
28 KiB
Groff
.\" -*- 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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.\" granted, provided that both the above copyright notice and this
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.\" permission notice appear in all copies, that both the above
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.\" copyright notice and this permission notice appear in all
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.\" supporting documentation, and that the name of M.I.T. not be used
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.\" in advertising or publicity pertaining to distribution of the
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.\" software without specific, written prior permission. M.I.T. makes
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.\" no representations about the suitability of this software for any
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.\" purpose. It is provided "as is" without express or implied
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.\" warranty.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''. M.I.T. DISCLAIMS
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.\" ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
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.\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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.\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
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.\" SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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.\" LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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.\" USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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.\" ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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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 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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.Nm ifaddr ,
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.Nm ifqueue ,
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.Nm if_data
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.Nd kernel interfaces for manipulating network interfaces
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.Sh SYNOPSIS
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.Fd #include <sys/types.h>
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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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.Ft void
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.Fn if_attach "struct ifnet *ifp"
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.Ft void
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.Fn if_down "struct ifnet *ifp"
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.Ft int
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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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.Fn if_up "struct ifnet *ifp"
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.\"
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.Ss "Interface address functions"
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.Ft "struct ifaddr *"
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.Fn ifa_ifwithaddr "struct sockaddr *addr"
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.Ft "struct ifaddr *"
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.Fn ifa_ifwithdstaddr "struct sockaddr *addr"
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.Ft "struct ifaddr *"
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.Fn ifa_ifwithnet "struct sockaddr *addr"
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.Ft "struct ifaddr *"
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.Fn ifaof_ifpforaddr "struct sockaddr *addr" "struct ifnet *ifp"
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.Ft void
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.Fn ifafree "struct ifaddr *ifa"
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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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.Ft void \"macro
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.Fn IF_DEQUEUE "struct ifqueue *ifq" "struct mbuf *m"
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.\"
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.Ss "struct ifnet member functions"
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.Ft int
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.Fn (*if_output) "struct ifnet *ifp" "struct mbuf *m" "struct sockaddr *dst" "struct rtentry *rt"
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.Ft void
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.Fn (*if_start) "struct ifnet *ifp"
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.Ft int
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.Fn (*if_dont) "struct ifnet *ifp"
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.Ft int
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.Fn (*if_ioctl) "struct ifnet *ifp" "int cmd" "caddr_t data"
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.Ft void
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.Fn (*if_watchdog) "struct ifnet *ifp"
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.Ft int
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.Fn (*if_poll_recv) "struct ifnet *ifp" "int *quotap"
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.Ft int
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.Fn (*if_poll_xmit) "struct ifnet *ifp" "int *quotap"
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.Ft void
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.Fn (*if_poll_inttrn) "struct ifnet *ifp"
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.Ft void
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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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.Ss "Global variables"
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.Fd extern struct ifnethead ifnet;
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.Fd extern struct ifaddr \&**ifnet_addrs;
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.Fd extern int if_index;
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.Fd extern int ifqmaxlen;
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.Sh DATA STRUCTURES
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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 ifmultiaddr
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structures in
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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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.Xr queue 3 ;
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this list is headed by a
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.Li "struct ifnethead"
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called
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.Li ifnet .
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The elements of this list are of type
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.Li "struct ifnet" ,
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and most kernel routines which manipulate interface as such accept or
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return pointers to these structures. Each interface structure
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contains an
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.Li if_data
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structure, which contains statistics and identifying information used
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by management programs, and which is exported to user programs by way
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of the
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.Xr ifmib 4
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branch of the
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.Xr sysctl 3
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MIB.
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Each interface also has a
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.Li TAILQ
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of interface addresses, described by
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.Li ifaddr
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structures; the head of the queue is always an
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.Dv AF_LINK
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address
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(see
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.Xr link_addr 3 )
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describing the link layer implemented by the interface (if any).
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(Some trivial interfaces do not provide any link layer addresses;
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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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process of sending another. The current implementation implements a
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drop-tail queuing discipline, but in the future a Random Early Drop
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discipline is expected to be used. For this reason, kernel code
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should not depend on the internals of the queue structure; in
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particular, only the
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.Fn IF_ENQ_DROP
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and
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.Fn IF_DEQUEUE
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macros will be supported in future implementations.
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.\" The old structure will probably be retained for compatibility
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.\" under a different name.
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.Pp
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.Ss The ifnet structure
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The fields of
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.Li "struct ifnet"
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are as follows:
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.Pp
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.Bl -tag -width "if_poll_slowq" -offset indent
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.It Li "if_softc"
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.Pq Li "void *"
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A pointer to the driver's private state block. (Initialized by
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driver.)
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.It Li if_name
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.Pq Li "char *"
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The name of the interface, not including the unit number
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(e.g.,
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.Dq Li de
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or
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.Dq Li lo ) .
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(Initialized by driver.)
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.It Li if_link
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.Pq Li "TAILQ_ENTRY(ifnet)"
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.Xr queue 3
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macro glue.
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.It Li if_addrhead
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.Pq Li "struct ifaddrhead"
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The head of the
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.Xr queue 3
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.Li TAILQ
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containing the list of addresses assigned to this interface.
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.It Li if_pcount
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.Pq Li "int"
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A count of promiscuous listeners on this interface, used to
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reference-count the
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.Dv IFF_PROMISC
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flag.
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.It Li "if_bpf"
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.Pq Li "struct bpf_if *"
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Opaque per-interface data for the packet filter,
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.Xr bpf 4 .
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(Initialized by
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.Fn bpf_attach . )
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.It Li "if_index"
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.Pq Li "u_short"
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A unique number assigned to each interface in sequence as it is
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attached. This number can be used in a
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.Li "struct sockaddr_dl"
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to refer to a particular interface by index
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(see
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.Xr link_addr 3 ) .
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.It Li "if_unit"
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.Pq Li "short"
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A unique number assigned to each interface managed by a particular
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driver, usually related to the unit number of a physical device in the
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kernel configuration file
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(see
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.Xr config 8 ) .
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(Initialized by driver.)
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.It Li "if_timer"
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.Pq Li "short"
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Number of seconds until the watchdog timer
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.Fn if_watchdog
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is called, or zero if the timer is disabled. (Set by driver,
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decremented by generic watchdog code.)
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.It Li "if_flags"
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.Pq Li "short"
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Flags describing operational parameters of this interface (see below).
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(Manipulated by both driver and generic code.)
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.\" .It Li "if_ipending"
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.\" Interrupt-pending bits for polled operation:
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.\" .Dv IFI_XMIT
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.\" (transmit complete interrupt)
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.\" and
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.\" .Dv IFI_RECV
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.\" (received packet ready interrupt). See the
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.\" .Sx Polling
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.\" section, below. (Manipulated by driver.)
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.It Li "if_linkmib"
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.Pq Li "void *"
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A pointer to an interface-specific MIB structure exported by
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.Xr ifmib 4 .
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(Initialized by driver.)
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.It Li "if_linkmiblen"
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.Pq Li "size_t"
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The size of said structure. (Initialized by driver.)
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.It Li "if_data"
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.Pq Li "struct if_data"
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More statistics and information; see
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.Dq Sx "The if_data structure" ,
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below. (Initialized by driver, manipulated by both driver and generic
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code.)
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.It Li "if_snd"
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.Pq Li "struct ifqueue"
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The output queue. (Manipulated by driver.)
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.\".It Li "if_poll_slowq"
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.\".Pq Li "struct ifqueue *"
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.\"A pointer to the input queue for devices which do not support polling
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.\"well. See the
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.\".Sx Polling
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.\"section, below. (Initialized by driver.)
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.El
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.Pp
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There are in addition a number of function pointers which the driver
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must initialize to complete its interface with the generic interface
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layer:
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.Bl -ohang -offset indent
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.It Fn if_output
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Output a packet on interface
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.Ar ifp ,
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or queue it on the output queue if the interface is already active.
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.It Fn if_start
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Start queued output on an interface. This function is exposed in
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order to provide for some interface classes to share a
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.Fn if_output
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among all drivers.
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.Fn if_start
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may only be called when the
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.Dv IFF_OACTIVE
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flag is not set. (Thus,
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.Dv IFF_OACTIVE
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does not literally mean that output is active, but rather that the
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device's internal output queue is full.)
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.It Fn if_done
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Not used. We're not even sure what it was ever for.
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.It Fn if_ioctl
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Process interface-related
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.Xr ioctl 2
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requests
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(defined in
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.Aq Pa sys/sockio.h ) .
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Preliminary processing is done by the generic routine
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.Fn ifioctl
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to check for appropriate privileges, locate the interface being
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manipulated, and perform certain generic operations like twiddling
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flags and flushing queues. See the description of
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.Fn ifioctl
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below for more information.
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.It Fn if_watchdog
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Routine called by the generic code when the watchdog timer,
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.Li if_timer ,
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expires. Usually this will reset the interface.
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.\" .It Fn if_poll_recv
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.\" .It Fn if_poll_xmit
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.\" .It Fn if_poll_slowinput
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.\" .It Fn if_poll_intren
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.\" See the
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.\" .Sx Polling
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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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flags simply indicate information about the type of interface and its
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capabilities; others are dynamically manipulated to reflect the
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current state of the interface. Flags of the former kind are marked
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.Aq S
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in this table; the latter are marked
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.Aq D .
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.Pp
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.Bl -tag -width "IFF_POINTOPOINT" -compact -offset indent
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.It Dv IFF_UP
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.Aq D
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The interface has been configured up by the user-level code.
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.It Dv IFF_BROADCAST
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.Aq S*
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The interface supports broadcast.
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.It Dv IFF_DEBUG
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.Aq D
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Used to enable/disable driver debugging code.
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.It Dv IFF_LOOPBACK
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.Aq S
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The interface is a loopback device.
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.It Dv IFF_POINTOPOINT
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.Aq S*
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The interface is point-to-point;
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.Dq broadcast
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addresses are actually the address of the other end.
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.It Dv IFF_RUNNING
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.Aq D*
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The interface has been configured and dynamic resources were
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successfully allocated. Probably only useful internal to the
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interface.
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.It Dv IFF_NOARP
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.Aq D
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Disable network address resolution on this interface.
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.It Dv IFF_PROMISC
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.Aq D
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This interface is in promiscuous mode.
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.It Dv IFF_ALLMULTI
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.Aq D*
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This interface is in all-multicasts mode (used by multicast routers).
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.It Dv IFF_OACTIVE
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.Aq D*
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The interface's hardware output queue (if any) is full; output packets
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are to be queued.
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.It Dv IFF_SIMPLEX
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.Aq S*
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The interface cannot hear its own transmissions.
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.It Dv IFF_LINK0
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.It Dv IFF_LINK1
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.It Dv IFF_LINK2
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.Aq D
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Control flags for the link layer. (Currently abused to select among
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multiple physical layers on some devices.)
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.It Dv IFF_MULTICAST
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.Aq S*
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This interface supports multicast.
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.El
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.Pp
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The macro
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.Dv IFF_CANTCHANGE
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defines the bits which cannot be set by a user program using the
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.Dv SIOCSIFFLAGS
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command to
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.Xr ioctl 2 ;
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these are indicated by an asterisk in the listing above.
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.Ss The if_data structure
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In
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.Bx 4.4 ,
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a subset of the interface information believed to be of interest to
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management stations was segregated from the
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.Li ifnet
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structure and moved into its own
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.Li if_data
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structure to facilitate its use by user programs. The following
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elements of the
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.Li if_data
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structure are initialized by the interface and are not expected to change
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significantly over the course of normal operation:
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.Bl -tag -width "ifi_lastchange" -offset indent
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.It Li ifi_type
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.Pq Li u_char
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The type of the interface, as defined in
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.Aq Pa net/if_types.h
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and described below in the
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.Dq Sx "Interface types"
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section.
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.It Li ifi_physical
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.Pq Li u_char
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Intended to represent a selection of physical layers on devices which
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support more than one; never implemented.
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.It Li ifi_addrlen
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.Pq Li u_char
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Length of a link-layer address on this device, or zero if there are
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none. Used to initialized the address length field in
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.Li "sockaddr_dl"
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structures referring to this interface.
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.It Li ifi_hdrlen
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.Pq Li u_char
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Maximum length of any link-layer header which might be prepended by
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the driver to a packet before transmission. The generic code computes
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the maximum over all interfaces and uses that value to influence the
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placement of data in
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.Li mbuf Ns s
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to attempt to ensure that there is always
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sufficient space to prepend a link-layer header without allocating an
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additional
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.Li mbuf .
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.\" (See
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.\" .Xr mbuf 9 . )
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.\" .It Li ifi_recvquota
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.\" .Pq Li u_char
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.\" Number of packets the interface is permitted to receive at one time
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.\" when in polled mode.
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.\" .It Li ifi_xmitquota
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.\" .Pq Li u_char
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.\" Number of packets the interface is permitted to queue for transmission
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.\" at one time when in polled mode. There is some controversy over
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.\" whether such a restriction makes any sense at all.
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.It Li ifi_mtu
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|
.Pq Li u_long
|
|
The maximum transmission unit of the medium, exclusive of any
|
|
link-layer overhead.
|
|
.It Li ifi_metric
|
|
.Pq Li u_long
|
|
A dimensionless metric interpreted by a user-mode routing process.
|
|
.It Li ifi_baudrate
|
|
.Pq Li u_long
|
|
The line rate of the interface, in bits per second.
|
|
.El
|
|
.Pp
|
|
The structure additionally contains generic statistics applicable to a
|
|
variety of different interface types (except as noted, all members are
|
|
of type
|
|
.Li u_long ) :
|
|
.Bl -tag -width "ifi_lastchange" -offset indent
|
|
.It Li ifi_ipackets
|
|
Number of packets received.
|
|
.It Li ifi_ierrors
|
|
Number of receive errors detected (e.g., FCS errors, DMA overruns,
|
|
etc.). More detailed breakdowns can often be had by way of a
|
|
link-specific MIB.
|
|
.It Li ifi_opackets
|
|
Number of packets transmitted.
|
|
.It Li ifi_oerrors
|
|
Number of output errors detected (e.g., late collisions, DMA overruns,
|
|
etc.). More detailed breakdowns can often be had by way of a
|
|
link-specific MIB.
|
|
.It Li ifi_collisions
|
|
Total number of collisions detected on output for CSMA interfaces.
|
|
(This member is sometimes [ab]used by other types of interfaces for
|
|
other output error counts.)
|
|
.It Li ifi_ibytes
|
|
Total traffic received, in bytes.
|
|
.It Li ifi_obytes
|
|
Total traffic transmitted, in bytes.
|
|
.It Li ifi_imcasts
|
|
Number of packets received which were sent by link-layer multicast.
|
|
.It Li ifi_omcasts
|
|
Number of packets sent by link-layer multicast.
|
|
.It Li ifi_iqdrops
|
|
Number of packets dropped on input. Rarely implemented.
|
|
.It Li ifi_noproto
|
|
Number of packets received for unknown network-layer protocol.
|
|
.\" .It Li ifi_recvtiming
|
|
.\" Amount of time, in microseconds, spent to receive an average packet on
|
|
.\" this interface. See the
|
|
.\" .Sx Polling
|
|
.\" section, below.
|
|
.\" .It Li ifi_xmittiming
|
|
.\" Amount of time, in microseconds, spent to service a transmit-complete
|
|
.\" interrupt on this interface. See the
|
|
.\" .Sx Polling
|
|
.\" section, below.
|
|
.It Li ifi_lastchange
|
|
.Pq Li "struct timeval"
|
|
The time of the last administrative change to the interface (as required
|
|
for
|
|
.Tn SNMP ) .
|
|
.El
|
|
.Ss Interface types
|
|
The header file
|
|
.Aq Pa net/if_types.h
|
|
defines symbolic constants for a number of different types of
|
|
interfaces. The most common are:
|
|
.Pp
|
|
.Bl -tag -compact -offset indent -width IFT_PROPVIRTUAL
|
|
.It Dv IFT_OTHER
|
|
none of the following
|
|
.It Dv IFT_ETHER
|
|
Ethernet
|
|
.It Dv IFT_ISO88023
|
|
ISO 8802-3 CSMA/CD
|
|
.It Dv IFT_ISO88024
|
|
ISO 8802-4 Token Bus
|
|
.It Dv IFT_ISO88025
|
|
ISO 8802-5 Token Ring
|
|
.It Dv IFT_ISO88026
|
|
ISO 8802-6 DQDB MAN
|
|
.It Dv IFT_FDDI
|
|
FDDI
|
|
.It Dv IFT_PPP
|
|
Internet Point-to-Point Protocol
|
|
.Pq Xr ppp 8
|
|
.It Dv IFT_LOOP
|
|
The loopback
|
|
.Pq Xr lo 4
|
|
interface.
|
|
.It Dv IFT_SLIP
|
|
Serial Line IP
|
|
.It Dv IFT_PARA
|
|
Parallel-port IP
|
|
.Pq Dq Tn PLIP
|
|
.It Dv IFT_ATM
|
|
Asynchronous Transfer Mode
|
|
.El
|
|
.Ss The ifaddr structure
|
|
Every interface is associated with a list
|
|
(or, rather, a
|
|
.Dv TAILQ )
|
|
of addresses, rooted at the interface structure's
|
|
.Li if_addrlist
|
|
member. The first element in this list is always an
|
|
.Dv AF_LINK
|
|
address representing the interface itself; multi-access network
|
|
drivers should complete this structure by filling in their link-layer
|
|
addresses after calling
|
|
.Fn if_attach .
|
|
Other members of the structure represent network-layer addresses which
|
|
have been configured by means of the
|
|
.Dv SIOCAIFADDR
|
|
command to
|
|
.Xr ioctl 2 ,
|
|
called on a socket of the appropriate protocol family.
|
|
The elements of this list consist of
|
|
.Li ifaddr
|
|
structures. Most protocols will declare their own protocol-specific
|
|
interface address structures, but all begin with a
|
|
.Li "struct ifaddr"
|
|
which provides the most-commonly-needed functionality across all
|
|
protocols. Interface addresses are reference-counted.
|
|
.Pp
|
|
The members of
|
|
.Li "struct ifaddr"
|
|
are as follows:
|
|
.Bl -tag -width ifa_rtrequest -offset indent
|
|
.It Li ifa_addr
|
|
.Pq Li "struct sockaddr *"
|
|
The local address of the interface.
|
|
.It Li ifa_dstaddr
|
|
.Pq Li "struct sockaddr *"
|
|
The remote address of point-to-point interfaces, and the broadcast
|
|
address of broadcast interfaces.
|
|
.Po
|
|
.Li ifa_broadaddr
|
|
is a macro for
|
|
.Li ifa_dstaddr .
|
|
.Pc
|
|
.It Li ifa_netmask
|
|
.Pq Li "struct sockaddr *"
|
|
The network mask for multi-access interfaces, and the confusion
|
|
generator for point-to-point interfaces.
|
|
.It Li ifa_ifp
|
|
.Pq Li "struct ifnet *"
|
|
A link back to the interface structure.
|
|
.It Li ifa_link
|
|
.Pq Li TAILQ_ENTRY(ifaddr)
|
|
.Xr queue 3
|
|
glue for list of addresses on each interface.
|
|
.It Li ifa_rtrequest
|
|
See below.
|
|
.It Li ifa_flags
|
|
.Pq Li u_short
|
|
Some of the flags which would be used for a route representing this
|
|
address in the route table.
|
|
.It Li ifa_refcnt
|
|
.Pq Li short
|
|
The reference count.
|
|
.It Li ifa_metric
|
|
.Pq Li int
|
|
A metric associated with this interface address, for the use of some
|
|
external routing protocol.
|
|
.El
|
|
.Pp
|
|
References to
|
|
.Li ifaddr
|
|
structures are gained manually, by incrementing the
|
|
.Li ifa_refcnt
|
|
member. References are released by calling either the
|
|
.Fn ifafree
|
|
function or the
|
|
.Fn IFAFREE
|
|
macro.
|
|
.Pp
|
|
.Fn ifa_rtrequest
|
|
is a pointer to a function which receives callouts from the routing
|
|
code
|
|
.Pq Fn rtrequest
|
|
to perform link-layer-specific actions upon requests to add, resolve,
|
|
or delete routes. The
|
|
.Ar cmd
|
|
argument indicates the request in question:
|
|
.Dv RTM_ADD ,
|
|
.Dv RTM_RESOLVE ,
|
|
or
|
|
.Dv RTM_DELETE .
|
|
The
|
|
.Ar rt
|
|
argument is the route in question; the
|
|
.Ar sa
|
|
argument is the specific destination being manipulated
|
|
for
|
|
.Dv RTM_RESOLVE ,
|
|
or a null pointer otherwise.
|
|
.Sh FUNCTIONS
|
|
The functions provided by the generic interface code can be divided
|
|
into two groups: those which manipulate interfaces, and those which
|
|
manipulate interface addresses. In addition to these functions, there
|
|
may also be link-layer support routines which are used by a number of
|
|
drivers implementing a specific link layer over different hardware;
|
|
see the documentation for that link layer for more details.
|
|
.Ss The ifmultiaddr structure
|
|
Every multicast-capable interface is associated with a list of
|
|
multicast group memberships, which indicate at a low level which
|
|
link-layer multicast addresses (if any) should be accepted, and at a
|
|
high level, in which network-layer multicast groups a user process has
|
|
expressed interest.
|
|
.Pp
|
|
The elements of the structure are as follows:
|
|
.Bl -tag -width ifma_refcount -offset indent
|
|
.It Li ifma_link
|
|
.Pq Li LIST_ENTRY(ifmultiaddr)
|
|
.Xr queue 3
|
|
macro glue.
|
|
.It Li ifma_addr
|
|
.Pq Li "struct sockaddr *"
|
|
A pointer to the address which this record represents. The
|
|
memberships for various address families are stored in arbitrary
|
|
order.
|
|
.It Li ifma_lladdr
|
|
.Pq Li "struct sockaddr *"
|
|
A pointer to the link-layer multicast address, if any, to which the
|
|
network-layer multicast address in
|
|
.Li ifma_addr
|
|
is mapped, else a null pointer. If this element is non-nil, this
|
|
membership also holds an invisible reference to another membership for
|
|
that link-layer address.
|
|
.It Li ifma_refcount
|
|
.Pq Li u_int
|
|
A reference count of requests for this particular membership.
|
|
.El
|
|
.Ss Interface manipulation functions
|
|
.Bl -ohang -offset indent
|
|
.It Fn if_attach
|
|
Link the specified interface
|
|
.Ar ifp
|
|
into the list of network interfaces. Also initialize the list of
|
|
addresses on that interface, and create a link-layer
|
|
.Li ifaddr
|
|
structure to be the first element in that list. (A pointer to
|
|
this address structure is saved in the global array
|
|
.Li ifnet_addrs . )
|
|
.It Fn if_down
|
|
Mark the interface
|
|
.Ar ifp
|
|
as down (i.e.,
|
|
.Dv IFF_UP
|
|
is not set),
|
|
flush its output queue, notify protocols of the transition,
|
|
and generate a message from the
|
|
.Xr route 4
|
|
routing socket.
|
|
.It Fn if_up
|
|
Mark the interface
|
|
.Ar ifp
|
|
as up, notify protocols of the transition,
|
|
and generate a message from the
|
|
.Xr route 4
|
|
routing socket.
|
|
.It Fn ifpromisc
|
|
Add or remove a promiscuous reference to
|
|
.Ar ifp .
|
|
If
|
|
.Ar pswitch
|
|
is true, add a reference;
|
|
if it is false, remove a reference. On reference count transitions
|
|
from zero to one and one to zero, set the
|
|
.Dv IFF_PROMISC
|
|
flag appropriately and call
|
|
.Fn if_ioctl
|
|
to set up the interface in the desired mode.
|
|
.It Fn if_allmulti
|
|
As
|
|
.Fn ifpromisc ,
|
|
but for the all-multicasts
|
|
.Pq Dv IFF_ALLMULTI
|
|
flag instead of the promiscuous flag.
|
|
.It Fn ifunit
|
|
Return an
|
|
.Li ifnet
|
|
pointer for the interface named
|
|
.Ar name .
|
|
.It Fn ifioctl
|
|
Process the ioctl request
|
|
.Ar cmd ,
|
|
issued on socket
|
|
.Ar so
|
|
by process
|
|
.Ar p ,
|
|
with data parameter
|
|
.Ar data .
|
|
This is the main routine for handling all interface configuration
|
|
requests from user mode.
|
|
It is ordinarily only called from the socket-layer
|
|
.Xr ioctl 2
|
|
handler, and only for commands with class
|
|
.Sq Li i .
|
|
Any unrecognized commands will be passed down to socket
|
|
.Ar so Ns 's
|
|
protocol for
|
|
further interpretation. The following commands are handled by
|
|
.Fn ifioctl :
|
|
.Pp
|
|
.Bl -tag -width OSIOCGIFNETMASK -compact -offset indent
|
|
.It Dv SIOCGIFCONF
|
|
.It Dv OSIOCGIFCONF
|
|
Get interface configuration. (No call-down to driver.)
|
|
.It Dv SIOCGIFFLAGS
|
|
.It Dv SIOCGIFMETRIC
|
|
.It Dv SIOCGIFMTU
|
|
.It Dv SIOCGIFPHYS
|
|
Get interface flags, metric, MTU, medium selection. (No call-down to
|
|
driver.)
|
|
.Pp
|
|
.It Dv SIOCSIFFLAGS
|
|
Change interface flags. Caller must have appropriate privilege. If
|
|
requested a change to the IFF_UP flag is requested,
|
|
.Fn if_up
|
|
or
|
|
.Fn if_down
|
|
is called as appropriate. Flags listed in
|
|
.Dv IFF_CANTCHANGE
|
|
are masked off, and the driver
|
|
.Fn if_ioctl
|
|
routine is called to perform any setup
|
|
requested.
|
|
.It Dv SIOCSIFMETRIC
|
|
.It Dv SIOCSIFPHYS
|
|
Change interface metric or medium. Caller must have appropriate privilege.
|
|
.Pp
|
|
.It Dv SIOCSIFMTU
|
|
Change interface MTU. Caller must have appropriate privilege. MTU
|
|
values less than 72 or greater than 65535 are considered invalid. The
|
|
driver
|
|
.Fn if_ioctl
|
|
routine is called to implement the change; it is responsible for any
|
|
additional sanity checking and for actually modifying the MTU in the
|
|
interface structure.
|
|
.It Dv SIOCADDMULTI
|
|
.It Dv SIOCDELMULTI
|
|
Add or delete permanent multicast group memberships on the interface.
|
|
Caller must have appropriate privilege. The
|
|
.Fn if_addmulti
|
|
or
|
|
.Fn if_delmulti
|
|
function is called to perform the operation; qq.v.
|
|
.It Dv SIOCSIFDSTADDR
|
|
.It Dv SIOCSIFADDR
|
|
.It Dv SIOCSIFBRDADDR
|
|
.It Dv SIOCSIFNETMASK
|
|
The socket's protocol control routine is called to implement the
|
|
requested action.
|
|
.It Dv OSIOGIFADDR
|
|
.It Dv OSIOCGIFDSTADDR
|
|
.It Dv OSIOCGIFBRDADDR
|
|
.It Dv OSIOCGIFNETMASK
|
|
The socket's protocol control routine is called to implement the
|
|
requested action. On return,
|
|
.Li sockaddr
|
|
structures are converted into old-style (no
|
|
.Li sa_len
|
|
member).
|
|
.El
|
|
.Pp
|
|
.Fn if_down ,
|
|
.Fn ifioctl ,
|
|
.Fn ifpromisc ,
|
|
and
|
|
.Fn if_up
|
|
must be called at
|
|
.Fn splnet
|
|
or higher.
|
|
.Ss "Interface address functions"
|
|
Several functions exist to look up an interface address structure
|
|
given an address.
|
|
.Fn ifa_ifwithaddr
|
|
returns an interface address with either a local address or a
|
|
broadcast address precisely matching the parameter
|
|
.Ar addr .
|
|
.Fn ifa_ifwithdstaddr
|
|
returns an interface address for a point-to-point interface whose
|
|
remote (``destination'') address is
|
|
.Ar addr .
|
|
.Pp
|
|
.Fn ifa_ifwithnet
|
|
returns the most specific interface address which matches the
|
|
specified address,
|
|
.Ar addr ,
|
|
subject to its configured netmask, or a point-to-point interface
|
|
address whose remote address is
|
|
.Ar addr
|
|
if one is found.
|
|
.Pp
|
|
.Fn ifaof_ifpforaddr
|
|
returns the most specific address configured on interface
|
|
.Ar ifp
|
|
which matches address
|
|
.Ar addr ,
|
|
subject to its configured netmask. If the interface is
|
|
point-to-point, only an interface address whose remote address is
|
|
precisely
|
|
.Ar addr
|
|
will be returned.
|
|
.Pp
|
|
All of these functions return a null pointer if no such address can be
|
|
found.
|
|
.Ss "Interface multicast address functions"
|
|
The
|
|
.Fn if_addmulti ,
|
|
.Fn if_delmulti ,
|
|
and
|
|
.Fn ifmaof_ifpforaddr
|
|
functions provide support for requesting and relinquishing multicast
|
|
group memberships, and for querying an interface's membership list,
|
|
respectively. The
|
|
.Fn if_addmulti
|
|
function takes a pointer to an interface,
|
|
.Ar ifp ,
|
|
and a generic address,
|
|
.Ar sa .
|
|
It also takes a pointer to a
|
|
.Sq Li "struct ifmultiaddr *"
|
|
which is filled in on successful return with the address of the
|
|
group membership control block. The
|
|
.Fn if_addmulti
|
|
function performs the following four-step process:
|
|
.Bl -enum -offset indent
|
|
.It
|
|
Call the interface's
|
|
.Fn if_resolvemulti
|
|
entry point to determine the link-layer address, if any, corresponding
|
|
to this membership request, and also to give the link layer an
|
|
opportunity to veto this membership request should it so desire.
|
|
.It
|
|
Check the interface's group membership list for a pre-existing
|
|
membership for this group. If one is not found, allocate a new one;
|
|
if one is, increment its reference count.
|
|
.It
|
|
If the
|
|
.Fn if_resolvemulti
|
|
routine returned a link-layer address corresponding to the group,
|
|
repeat the previous step for that address as well.
|
|
.It
|
|
If the interface's multicast address filter needs to be changed
|
|
because a new membership was added, call the interface's
|
|
.Fn if_ioctl
|
|
routine
|
|
(with a
|
|
.Ar cmd
|
|
argument of
|
|
.Dv SIOCADDMULTI )
|
|
to request that it do so.
|
|
.El
|
|
.Pp
|
|
The
|
|
.Fn if_delmulti
|
|
function, given an interface
|
|
.Ar ifp
|
|
and an address,
|
|
.Ar sa ,
|
|
reverses this process. Both functions return zero on success, or a
|
|
standard error number on failure.
|
|
.Pp
|
|
The
|
|
.Fn ifmaof_ifpforaddr
|
|
function examines the membership list of interface
|
|
.Ar ifp
|
|
for an address matching
|
|
.Ar addr ,
|
|
and returns a pointer to that
|
|
.Li "struct ifmultiaddr"
|
|
if one is found, else it returns a null pointer.
|
|
.\" .Sh POLLING
|
|
.\" XXX write me!
|
|
.Sh SEE ALSO
|
|
.Xr ioctl 2 ,
|
|
.Xr link_addr 3 ,
|
|
.Xr queue 3 ,
|
|
.Xr sysctl 3 ,
|
|
.Xr bpf 4 ,
|
|
.Xr ifmib 4 ,
|
|
.Xr lo 4 ,
|
|
.Xr netintro 4 ,
|
|
.Xr config 8 ,
|
|
.Xr ppp 8 ,
|
|
.Xr rtentry 9
|
|
.\" .Xr mbuf 9 ,
|
|
.Rs
|
|
.%A Gary R. Wright and W. Richard Stevens
|
|
.%B TCP/IP Illustrated
|
|
.%V vol. 2
|
|
.%O Addison-Wesley, ISBN 0-201-63354-X
|
|
.Re
|
|
.Sh AUTHORS
|
|
This manual page was written by
|
|
.An Garrett A. Wollman .
|