167 lines
7.2 KiB
Perl
167 lines
7.2 KiB
Perl
.\" Copyright (c) 1983, 1986, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT 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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.\" @(#)8.t 8.1 (Berkeley) 6/8/93
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.\"
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.nr H2 1
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.\".ds RH "Protocol/protocol interface
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.br
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.ne 2i
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.NH
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\s+2Protocol/protocol interface\s0
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.PP
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The interface between protocol modules is through the \fIpr_usrreq\fP,
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\fIpr_input\fP, \fIpr_output\fP, \fIpr_ctlinput\fP, and
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\fIpr_ctloutput\fP routines. The calling conventions for all
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but the \fIpr_usrreq\fP routine are expected to be specific to
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the protocol
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modules and are not guaranteed to be consistent across protocol
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families. We
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will examine the conventions used for some of the Internet
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protocols in this section as an example.
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.NH 2
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pr_output
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.PP
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The Internet protocol UDP uses the convention,
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.DS
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error = udp_output(inp, m);
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int error; struct inpcb *inp; struct mbuf *m;
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.DE
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where the \fIinp\fP, ``\fIin\fP\^ternet
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\fIp\fP\^rotocol \fIc\fP\^ontrol \fIb\fP\^lock'',
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passed between modules conveys per connection state information, and
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the mbuf chain contains the data to be sent. UDP
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performs consistency checks, appends its header, calculates a
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checksum, etc. before passing the packet on.
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UDP is based on the Internet Protocol, IP [Postel81a], as its transport.
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UDP passes a packet to the IP module for output as follows:
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.DS
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error = ip_output(m, opt, ro, flags);
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int error; struct mbuf *m, *opt; struct route *ro; int flags;
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.DE
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.PP
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The call to IP's output routine is more complicated than that for
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UDP, as befits the additional work the IP module must do.
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The \fIm\fP parameter is the data to be sent, and the \fIopt\fP
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parameter is an optional list of IP options which should
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be placed in the IP packet header. The \fIro\fP parameter is
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is used in making routing decisions (and passing them back to the
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caller for use in subsequent calls). The
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final parameter, \fIflags\fP contains flags indicating whether the
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user is allowed to transmit a broadcast packet
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and if routing is to be performed. The broadcast flag may
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be inconsequential if the underlying hardware does not support the
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notion of broadcasting.
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.PP
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All output routines return 0 on success and a UNIX error number
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if a failure occurred which could be detected immediately
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(no buffer space available, no route to destination, etc.).
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.NH 2
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pr_input
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.PP
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Both UDP and TCP use the following calling convention,
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.DS
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(void) (*protosw[].pr_input)(m, ifp);
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struct mbuf *m; struct ifnet *ifp;
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.DE
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Each mbuf list passed is a single packet to be processed by
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the protocol module.
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The interface from which the packet was received is passed as the second
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parameter.
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.PP
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The IP input routine is a VAX software interrupt level routine,
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and so is not called with any parameters. It instead communicates
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with network interfaces through a queue, \fIipintrq\fP, which is
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identical in structure to the queues used by the network interfaces
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for storing packets awaiting transmission.
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The software interrupt is enabled by the network interfaces
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when they place input data on the input queue.
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.NH 2
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pr_ctlinput
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.PP
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This routine is used to convey ``control'' information to a
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protocol module (i.e. information which might be passed to the
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user, but is not data).
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.PP
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The common calling convention for this routine is,
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.DS
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(void) (*protosw[].pr_ctlinput)(req, addr);
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int req; struct sockaddr *addr;
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.DE
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The \fIreq\fP parameter is one of the following,
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.DS
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.ta \w'#define 'u +\w'PRC_UNREACH_NEEDFRAG 'u +8n
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#define PRC_IFDOWN 0 /* interface transition */
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#define PRC_ROUTEDEAD 1 /* select new route if possible */
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#define PRC_QUENCH 4 /* some said to slow down */
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#define PRC_MSGSIZE 5 /* message size forced drop */
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#define PRC_HOSTDEAD 6 /* normally from IMP */
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#define PRC_HOSTUNREACH 7 /* ditto */
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#define PRC_UNREACH_NET 8 /* no route to network */
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#define PRC_UNREACH_HOST 9 /* no route to host */
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#define PRC_UNREACH_PROTOCOL 10 /* dst says bad protocol */
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#define PRC_UNREACH_PORT 11 /* bad port # */
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#define PRC_UNREACH_NEEDFRAG 12 /* IP_DF caused drop */
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#define PRC_UNREACH_SRCFAIL 13 /* source route failed */
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#define PRC_REDIRECT_NET 14 /* net routing redirect */
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#define PRC_REDIRECT_HOST 15 /* host routing redirect */
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#define PRC_REDIRECT_TOSNET 14 /* redirect for type of service & net */
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#define PRC_REDIRECT_TOSHOST 15 /* redirect for tos & host */
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#define PRC_TIMXCEED_INTRANS 18 /* packet lifetime expired in transit */
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#define PRC_TIMXCEED_REASS 19 /* lifetime expired on reass q */
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#define PRC_PARAMPROB 20 /* header incorrect */
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.DE
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while the \fIaddr\fP parameter is the address to which the condition applies.
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Many of the requests have obviously been
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derived from ICMP (the Internet Control Message Protocol [Postel81c]),
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and from error messages defined in the 1822 host/IMP convention
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[BBN78]. Mapping tables exist to convert
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control requests to UNIX error codes which are delivered
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to a user.
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.NH 2
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pr_ctloutput
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.PP
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This is the routine that implements per-socket options at the protocol
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level for \fIgetsockopt\fP and \fIsetsockopt\fP.
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The calling convention is,
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.DS
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error = (*protosw[].pr_ctloutput)(op, so, level, optname, mp);
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int op; struct socket *so; int level, optname; struct mbuf **mp;
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.DE
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where \fIop\fP is one of PRCO_SETOPT or PRCO_GETOPT,
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\fIso\fP is the socket from whence the call originated,
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and \fIlevel\fP and \fIoptname\fP are the protocol level and option name
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supplied by the user.
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The results of a PRCO_GETOPT call are returned in an mbuf whose address
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is placed in \fImp\fP before return.
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On a PRCO_SETOPT call, \fImp\fP contains the address of an mbuf
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containing the option data; the mbuf should be freed before return.
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