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1.1 root 1: .TH IP 4
2: .CT 2 comm_mach
3: .SH NAME
4: ip, ip_ld \- DARPA internet protocol
5: .SH SYNOPSIS
6: .B #include <sys/inio.h>
7: .br
8: .B #include <sys/inet/in.h>
9: .br
10: .B #include <sys/inet/ip_var.h>
11: .SH DESCRIPTION
12: .PP
13: The
14: .I ip_ld
15: line discipline and the
16: .F /dev/ip*
17: files together implement the DARPA IP datagram protocol.
18: They are used by
19: the programs described in
20: .IR ipconfig (8)
21: and
22: .IR route (8).
23: .PP
24: Each Ethernet device,
25: Datakit channel,
26: or other stream
27: that is to send and receive IP packets
28: must be registered as an
29: `IP interface'
30: by pushing
31: .I ip_ld
32: and setting local and remote addresses
33: with
34: .I ioctl
35: calls.
36: Thereafter,
37: data received from the network
38: are assumed to be IP packets,
39: and are intercepted by the line discipline.
40: Packets destined for the local address of an active IP interface
41: are routed for reading on one of the
42: .I ip
43: device files.
44: Other packets are routed to the IP interface
45: with a matching remote address
46: and retransmitted.
47: .PP
48: Data written on
49: .I ip
50: devices
51: are taken to be IP packets,
52: are handed to the IP interface
53: with a matching address,
54: and are sent.
55: Packets destined for unreachable places
56: are quietly dropped.
57: .PP
58: A packet consists of a single stream record,
59: followed by a delimiter:
60: at most one packet is returned by a
61: .I read
62: call;
63: an entire packet must be presented in a single
64: .IR write .
65: A packet includes the IP header.
66: Numbers in the header are in host byte order.
67: .PP
68: Different
69: .I ip
70: devices handle different protocols atop IP.
71: The minor device is the protocol number in the IP header;
72: e.g. 6 for TCP or 17 for UDP.
73: While an
74: .I ip
75: device is open,
76: it may not be opened again.
77: IP packets are often processed by pushing a line discipline
78: such as
79: .IR tcp_ld
80: on an
81: .I ip
82: device,
83: rather than by explicit
84: .I read
85: and
86: .I write
87: calls;
88: see
89: .IR tcp (4).
90: .PP
91: The following
92: .IR ioctl (2)
93: calls, defined in
94: .BR <sys/inio.h> ,
95: apply to an IP interface.
96: .B IPIOLOCAL
97: and either
98: .B IPIOHOST
99: or
100: .B IPIONET
101: must be called on each interface
102: before packets will be routed correctly.
103: Type
104: .BR in_addr ,
105: defined in
106: .BR <sys/inet/in.h> ,
107: is a 32-bit integer
108: representing an IP address
109: in host byte order.
110: .nr Pw \w'\f5IPIORESOLVE 'u
111: .TP \n(Pwu
112: .B IPIOLOCAL
113: The third argument points to an
114: .BR in_addr :
115: the local IP address for this interface.
116: .TP
117: .B IPIOHOST
118: The third argument points to an
119: .BR in_addr :
120: the remote IP address of the single host
121: reachable through this interface.
122: .TP
123: .B IPIONET
124: The third argument
125: points to an
126: .BR in_addr :
127: the remote IP address of the network of many hosts
128: reachable through this interface.
129: IP addresses are matched to the network address
130: by applying an internal bit-mask:
131: any IP address for which
132: .BI ( address & mask )== net-address
133: is part of the network.
134: The default mask depends on
135: the IP address class;
136: see the IP protocol standard for details.
137: .TP
138: .B IPIOMASK
139: The third argument points to an
140: .B in_addr
141: containing a new network mask for this interface.
142: .TP
143: .B IPIOMTU
144: The third argument points to an integer number of bytes.
145: IP packets larger than this size (1500 by default)
146: will be split into smaller ones
147: before being sent through this interface.
148: .TP
149: .B IPIOARP
150: The network device for this interface
151: is an Ethernet.
152: Discard the Ethernet header from each incoming packet.
153: When sending a packet,
154: prefix an Ethernet header
155: containing protocol type
156: .B 0x8
157: and a destination address
158: obtained by looking up the IP destination address
159: in a table.
160: If the IP address is not in the table,
161: discard the packet,
162: and make an
163: .B in_addr
164: containing the offending address
165: available for reading
166: on this file descriptor
167: (the one on which
168: .I ip_ld
169: was pushed).
170: .TP
171: .B IPIORESOLVE
172: The third argument points to a structure:
173: .EX
174: struct {
175: in_addr inaddr;
176: unsigned char enaddr[6];
177: };
178: .EE
179: Add an entry to the table consulted after
180: .BR IPIOARP ,
181: mapping IP address
182: .B inaddr
183: to Ethernet address
184: .BR enaddr .
185: .LP
186: The following
187: .I ioctl
188: calls, define in
189: .BR <sys/inio.h> ,
190: apply to the entire IP subsystem;
191: they may be used on any file with
192: .I ip_ld
193: pushed.
194: .TP \n(Pwu
195: .B IPIOROUTE
196: The third argument points to a structure:
197: .EX
198: struct route {
199: in_addr dst;
200: in_addr gate;
201: };
202: .EE
203: Arrange that henceforth,
204: any IP packet destined for address
205: .B dst
206: will be routed as if destined for
207: .BR gate .
208: .TP
209: .B IPIOGETIFS
210: The third argument points to a union as follows.
211: The structure is defined in
212: .BR <sys/inet/ip_var.h> .
213: .EX
214: union {
215: int index;
216: struct ipif {
217: struct queue *queue;
218: int flags;
219: int mtu;
220: in_addr thishost;
221: in_addr that;
222: in_addr mask;
223: in_addr broadcast;
224: int ipackets, ierrors;
225: int opackets, oerrors;
226: int arp;
227: int dev;
228: } ipif;
229: };
230: .EE
231: Before the call,
232: .B index
233: should contain an integer
234: naming an entry in the system's table
235: of active interfaces.
236: Interfaces are numbered in a continuous sequence starting at 0.
237: Out-of-range numbers return an error.
238: After the call,
239: .B ipif
240: is filled in with various numbers
241: about that interface.
242: .SH FILES
243: .B /dev/ip*
244: .SH SEE ALSO
245: .IR ioctl (2),
246: .IR internet (3),
247: .IR ipconfig (8),
248: .IR route (8)
249: .br
250: DARPA standards RFC 791, RFC 1122
251: .SH BUGS
252: The ARP mechanism should be generalized
253: to deal with networks other than Ethernet.
254: There is only one ARP table for the entire system;
255: there should be one for each interface.
256: .br
257: The structures used by
258: .B IPIOROUTE
259: and
260: .B IPIORESOLVE
261: should appear in a header file somewhere.
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