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diff --git a/share/doc/smm/18.net/b.t b/share/doc/smm/18.net/b.t new file mode 100644 index 0000000..2e39a8a --- /dev/null +++ b/share/doc/smm/18.net/b.t @@ -0,0 +1,145 @@ +.\" Copyright (c) 1983, 1986, 1993 +.\" The Regents of the University of California. All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" 3. All advertising materials mentioning features or use of this software +.\" must display the following acknowledgement: +.\" This product includes software developed by the University of +.\" California, Berkeley and its contributors. +.\" 4. Neither the name of the University nor the names of its contributors +.\" may be used to endorse or promote products derived from this software +.\" without specific prior written permission. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" @(#)b.t 8.1 (Berkeley) 6/8/93 +.\" +.nr H2 1 +.\".ds RH "Raw sockets +.br +.ne 2i +.NH +\s+2Raw sockets\s0 +.PP +A raw socket is an object which allows users direct access +to a lower-level protocol. Raw sockets are intended for knowledgeable +processes which wish to take advantage of some protocol +feature not directly accessible through the normal interface, or +for the development of new protocols built atop existing lower level +protocols. For example, a new version of TCP might be developed at the +user level by utilizing a raw IP socket for delivery of packets. +The raw IP socket interface attempts to provide an identical interface +to the one a protocol would have if it were resident in the kernel. +.PP +The raw socket support is built around a generic raw socket interface, +(possibly) augmented by protocol-specific processing routines. +This section will describe the core of the raw socket interface. +.NH 2 +Control blocks +.PP +Every raw socket has a protocol control block of the following form: +.DS +.ta \w'struct 'u +\w'caddr_t 'u +\w'sockproto rcb_proto; 'u +struct rawcb { + struct rawcb *rcb_next; /* doubly linked list */ + struct rawcb *rcb_prev; + struct socket *rcb_socket; /* back pointer to socket */ + struct sockaddr rcb_faddr; /* destination address */ + struct sockaddr rcb_laddr; /* socket's address */ + struct sockproto rcb_proto; /* protocol family, protocol */ + caddr_t rcb_pcb; /* protocol specific stuff */ + struct mbuf *rcb_options; /* protocol specific options */ + struct route rcb_route; /* routing information */ + short rcb_flags; +}; +.DE +All the control blocks are kept on a doubly linked list for +performing lookups during packet dispatch. Associations may +be recorded in the control block and used by the output routine +in preparing packets for transmission. +The \fIrcb_proto\fP structure contains the protocol family and protocol +number with which the raw socket is associated. +The protocol, family and addresses are +used to filter packets on input; this will be described in more +detail shortly. If any protocol-specific information is required, +it may be attached to the control block using the \fIrcb_pcb\fP +field. +Protocol-specific options for transmission in outgoing packets +may be stored in \fIrcb_options\fP. +.PP +A raw socket interface is datagram oriented. That is, each send +or receive on the socket requires a destination address. This +address may be supplied by the user or stored in the control block +and automatically installed in the outgoing packet by the output +routine. Since it is not possible to determine whether an address +is present or not in the control block, two flags, RAW_LADDR and +RAW_FADDR, indicate if a local and foreign address are present. +Routing is expected to be performed by the underlying protocol +if necessary. +.NH 2 +Input processing +.PP +Input packets are ``assigned'' to raw sockets based on a simple +pattern matching scheme. Each network interface or protocol +gives unassigned packets +to the raw input routine with the call: +.DS +raw_input(m, proto, src, dst) +struct mbuf *m; struct sockproto *proto, struct sockaddr *src, *dst; +.DE +The data packet then has a generic header prepended to it of the +form +.DS +._f +struct raw_header { + struct sockproto raw_proto; + struct sockaddr raw_dst; + struct sockaddr raw_src; +}; +.DE +and it is placed in a packet queue for the ``raw input protocol'' module. +Packets taken from this queue are copied into any raw sockets that +match the header according to the following rules, +.IP 1) +The protocol family of the socket and header agree. +.IP 2) +If the protocol number in the socket is non-zero, then it agrees +with that found in the packet header. +.IP 3) +If a local address is defined for the socket, the address format +of the local address is the same as the destination address's and +the two addresses agree bit for bit. +.IP 4) +The rules of 3) are applied to the socket's foreign address and the packet's +source address. +.LP +A basic assumption is that addresses present in the +control block and packet header (as constructed by the network +interface and any raw input protocol module) are in a canonical +form which may be ``block compared''. +.NH 2 +Output processing +.PP +On output the raw \fIpr_usrreq\fP routine +passes the packet and a pointer to the raw control block to the +raw protocol output routine for any processing required before +it is delivered to the appropriate network interface. The +output routine is normally the only code required to implement +a raw socket interface. |
