![[BACK]](/cvsweb/icons/back.gif){kind=icon}
Return to b.t CVS log ![[TXT]](/cvsweb/icons/text.gif){kind=icon}
![[DIR]](/cvsweb/icons/dir.gif){kind=icon}
Up to [CSRG BSD Unix] / 43BSDReno / share / doc / smm / 15.net|
Return to b.t CVS log | Up to [CSRG BSD Unix] / 43BSDReno / share / doc / smm / 15.net |
1.1 root 1: .\" Copyright (c) 1983, 1986 The Regents of the University of California.
2: .\" All rights reserved.
3: .\"
4: .\" Redistribution and use in source and binary forms are permitted
5: .\" provided that the above copyright notice and this paragraph are
6: .\" duplicated in all such forms and that any documentation,
7: .\" advertising materials, and other materials related to such
8: .\" distribution and use acknowledge that the software was developed
9: .\" by the University of California, Berkeley. The name of the
10: .\" University may not be used to endorse or promote products derived
11: .\" from this software without specific prior written permission.
12: .\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
13: .\" IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
14: .\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
15: .\"
16: .\" @(#)b.t 6.4 (Berkeley) 3/7/89
17: .\"
18: .nr H2 1
19: .\".ds RH "Raw sockets
20: .br
21: .ne 2i
22: .NH
23: \s+2Raw sockets\s0
24: .PP
25: A raw socket is an object which allows users direct access
26: to a lower-level protocol. Raw sockets are intended for knowledgeable
27: processes which wish to take advantage of some protocol
28: feature not directly accessible through the normal interface, or
29: for the development of new protocols built atop existing lower level
30: protocols. For example, a new version of TCP might be developed at the
31: user level by utilizing a raw IP socket for delivery of packets.
32: The raw IP socket interface attempts to provide an identical interface
33: to the one a protocol would have if it were resident in the kernel.
34: .PP
35: The raw socket support is built around a generic raw socket interface,
36: (possibly) augmented by protocol-specific processing routines.
37: This section will describe the core of the raw socket interface.
38: .NH 2
39: Control blocks
40: .PP
41: Every raw socket has a protocol control block of the following form:
42: .DS
43: .ta \w'struct 'u +\w'caddr_t 'u +\w'sockproto rcb_proto; 'u
44: struct rawcb {
45: struct rawcb *rcb_next; /* doubly linked list */
46: struct rawcb *rcb_prev;
47: struct socket *rcb_socket; /* back pointer to socket */
48: struct sockaddr rcb_faddr; /* destination address */
49: struct sockaddr rcb_laddr; /* socket's address */
50: struct sockproto rcb_proto; /* protocol family, protocol */
51: caddr_t rcb_pcb; /* protocol specific stuff */
52: struct mbuf *rcb_options; /* protocol specific options */
53: struct route rcb_route; /* routing information */
54: short rcb_flags;
55: };
56: .DE
57: All the control blocks are kept on a doubly linked list for
58: performing lookups during packet dispatch. Associations may
59: be recorded in the control block and used by the output routine
60: in preparing packets for transmission.
61: The \fIrcb_proto\fP structure contains the protocol family and protocol
62: number with which the raw socket is associated.
63: The protocol, family and addresses are
64: used to filter packets on input; this will be described in more
65: detail shortly. If any protocol-specific information is required,
66: it may be attached to the control block using the \fIrcb_pcb\fP
67: field.
68: Protocol-specific options for transmission in outgoing packets
69: may be stored in \fIrcb_options\fP.
70: .PP
71: A raw socket interface is datagram oriented. That is, each send
72: or receive on the socket requires a destination address. This
73: address may be supplied by the user or stored in the control block
74: and automatically installed in the outgoing packet by the output
75: routine. Since it is not possible to determine whether an address
76: is present or not in the control block, two flags, RAW_LADDR and
77: RAW_FADDR, indicate if a local and foreign address are present.
78: Routing is expected to be performed by the underlying protocol
79: if necessary.
80: .NH 2
81: Input processing
82: .PP
83: Input packets are ``assigned'' to raw sockets based on a simple
84: pattern matching scheme. Each network interface or protocol
85: gives unassigned packets
86: to the raw input routine with the call:
87: .DS
88: raw_input(m, proto, src, dst)
89: struct mbuf *m; struct sockproto *proto, struct sockaddr *src, *dst;
90: .DE
91: The data packet then has a generic header prepended to it of the
92: form
93: .DS
94: ._f
95: struct raw_header {
96: struct sockproto raw_proto;
97: struct sockaddr raw_dst;
98: struct sockaddr raw_src;
99: };
100: .DE
101: and it is placed in a packet queue for the ``raw input protocol'' module.
102: Packets taken from this queue are copied into any raw sockets that
103: match the header according to the following rules,
104: .IP 1)
105: The protocol family of the socket and header agree.
106: .IP 2)
107: If the protocol number in the socket is non-zero, then it agrees
108: with that found in the packet header.
109: .IP 3)
110: If a local address is defined for the socket, the address format
111: of the local address is the same as the destination address's and
112: the two addresses agree bit for bit.
113: .IP 4)
114: The rules of 3) are applied to the socket's foreign address and the packet's
115: source address.
116: .LP
117: A basic assumption is that addresses present in the
118: control block and packet header (as constructed by the network
119: interface and any raw input protocol module) are in a canonical
120: form which may be ``block compared''.
121: .NH 2
122: Output processing
123: .PP
124: On output the raw \fIpr_usrreq\fP routine
125: passes the packet and a pointer to the raw control block to the
126: raw protocol output routine for any processing required before
127: it is delivered to the appropriate network interface. The
128: output routine is normally the only code required to implement
129: a raw socket interface.
This archive runs on limited infrastructure. Preserving old code on modern bandwidth. Automated agents are requested to crawl responsibly.