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1.1 root 1: /*
2: * Copyright (C) 2006 Michael Brown <[email protected]>.
3: *
4: * This program is free software; you can redistribute it and/or
5: * modify it under the terms of the GNU General Public License as
6: * published by the Free Software Foundation; either version 2 of the
7: * License, or any later version.
8: *
9: * This program is distributed in the hope that it will be useful, but
10: * WITHOUT ANY WARRANTY; without even the implied warranty of
11: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12: * General Public License for more details.
13: *
14: * You should have received a copy of the GNU General Public License
15: * along with this program; if not, write to the Free Software
16: * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
17: */
18:
19: FILE_LICENCE ( GPL2_OR_LATER );
20:
21: #include <stdint.h>
22: #include <string.h>
23: #include <byteswap.h>
24: #include <errno.h>
25: #include <ipxe/if_ether.h>
26: #include <ipxe/if_arp.h>
27: #include <ipxe/iobuf.h>
28: #include <ipxe/netdevice.h>
29: #include <ipxe/arp.h>
30:
31: /** @file
32: *
33: * Address Resolution Protocol
34: *
35: * This file implements the address resolution protocol as defined in
36: * RFC826. The implementation is media-independent and
37: * protocol-independent; it is not limited to Ethernet or to IPv4.
38: *
39: */
40:
41: /** An ARP cache entry */
42: struct arp_entry {
43: /** Network-layer protocol */
44: struct net_protocol *net_protocol;
45: /** Link-layer protocol */
46: struct ll_protocol *ll_protocol;
47: /** Network-layer address */
48: uint8_t net_addr[MAX_NET_ADDR_LEN];
49: /** Link-layer address */
50: uint8_t ll_addr[MAX_LL_ADDR_LEN];
51: };
52:
53: /** Number of entries in the ARP cache
54: *
55: * This is a global cache, covering all network interfaces,
56: * network-layer protocols and link-layer protocols.
57: */
58: #define NUM_ARP_ENTRIES 4
59:
60: /** The ARP cache */
61: static struct arp_entry arp_table[NUM_ARP_ENTRIES];
62: #define arp_table_end &arp_table[NUM_ARP_ENTRIES]
63:
64: static unsigned int next_new_arp_entry = 0;
65:
66: struct net_protocol arp_protocol __net_protocol;
67:
68: /**
69: * Find entry in the ARP cache
70: *
71: * @v ll_protocol Link-layer protocol
72: * @v net_protocol Network-layer protocol
73: * @v net_addr Network-layer address
74: * @ret arp ARP cache entry, or NULL if not found
75: *
76: */
77: static struct arp_entry *
78: arp_find_entry ( struct ll_protocol *ll_protocol,
79: struct net_protocol *net_protocol,
80: const void *net_addr ) {
81: struct arp_entry *arp;
82:
83: for ( arp = arp_table ; arp < arp_table_end ; arp++ ) {
84: if ( ( arp->ll_protocol == ll_protocol ) &&
85: ( arp->net_protocol == net_protocol ) &&
86: ( memcmp ( arp->net_addr, net_addr,
87: net_protocol->net_addr_len ) == 0 ) )
88: return arp;
89: }
90: return NULL;
91: }
92:
93: /**
94: * Look up media-specific link-layer address in the ARP cache
95: *
96: * @v netdev Network device
97: * @v net_protocol Network-layer protocol
98: * @v dest_net_addr Destination network-layer address
99: * @v source_net_addr Source network-layer address
100: * @ret dest_ll_addr Destination link layer address
101: * @ret rc Return status code
102: *
103: * This function will use the ARP cache to look up the link-layer
104: * address for the link-layer protocol associated with the network
105: * device and the given network-layer protocol and addresses. If
106: * found, the destination link-layer address will be filled in in @c
107: * dest_ll_addr.
108: *
109: * If no address is found in the ARP cache, an ARP request will be
110: * transmitted on the specified network device and -ENOENT will be
111: * returned.
112: */
113: int arp_resolve ( struct net_device *netdev, struct net_protocol *net_protocol,
114: const void *dest_net_addr, const void *source_net_addr,
115: void *dest_ll_addr ) {
116: struct ll_protocol *ll_protocol = netdev->ll_protocol;
117: const struct arp_entry *arp;
118: struct io_buffer *iobuf;
119: struct arphdr *arphdr;
120: int rc;
121:
122: /* Look for existing entry in ARP table */
123: arp = arp_find_entry ( ll_protocol, net_protocol, dest_net_addr );
124: if ( arp ) {
125: DBG ( "ARP cache hit: %s %s => %s %s\n",
126: net_protocol->name, net_protocol->ntoa ( arp->net_addr ),
127: ll_protocol->name, ll_protocol->ntoa ( arp->ll_addr ) );
128: memcpy ( dest_ll_addr, arp->ll_addr, ll_protocol->ll_addr_len);
129: return 0;
130: }
131: DBG ( "ARP cache miss: %s %s\n", net_protocol->name,
132: net_protocol->ntoa ( dest_net_addr ) );
133:
134: /* Allocate ARP packet */
135: iobuf = alloc_iob ( MAX_LL_HEADER_LEN + sizeof ( *arphdr ) +
136: 2 * ( MAX_LL_ADDR_LEN + MAX_NET_ADDR_LEN ) );
137: if ( ! iobuf )
138: return -ENOMEM;
139: iob_reserve ( iobuf, MAX_LL_HEADER_LEN );
140:
141: /* Build up ARP request */
142: arphdr = iob_put ( iobuf, sizeof ( *arphdr ) );
143: arphdr->ar_hrd = ll_protocol->ll_proto;
144: arphdr->ar_hln = ll_protocol->ll_addr_len;
145: arphdr->ar_pro = net_protocol->net_proto;
146: arphdr->ar_pln = net_protocol->net_addr_len;
147: arphdr->ar_op = htons ( ARPOP_REQUEST );
148: memcpy ( iob_put ( iobuf, ll_protocol->ll_addr_len ),
149: netdev->ll_addr, ll_protocol->ll_addr_len );
150: memcpy ( iob_put ( iobuf, net_protocol->net_addr_len ),
151: source_net_addr, net_protocol->net_addr_len );
152: memset ( iob_put ( iobuf, ll_protocol->ll_addr_len ),
153: 0, ll_protocol->ll_addr_len );
154: memcpy ( iob_put ( iobuf, net_protocol->net_addr_len ),
155: dest_net_addr, net_protocol->net_addr_len );
156:
157: /* Transmit ARP request */
158: if ( ( rc = net_tx ( iobuf, netdev, &arp_protocol,
159: netdev->ll_broadcast, netdev->ll_addr ) ) != 0 )
160: return rc;
161:
162: return -ENOENT;
163: }
164:
165: /**
166: * Identify ARP protocol
167: *
168: * @v net_proto Network-layer protocol, in network-endian order
169: * @ret arp_net_protocol ARP protocol, or NULL
170: *
171: */
172: static struct arp_net_protocol * arp_find_protocol ( uint16_t net_proto ) {
173: struct arp_net_protocol *arp_net_protocol;
174:
175: for_each_table_entry ( arp_net_protocol, ARP_NET_PROTOCOLS ) {
176: if ( arp_net_protocol->net_protocol->net_proto == net_proto ) {
177: return arp_net_protocol;
178: }
179: }
180: return NULL;
181: }
182:
183: /**
184: * Process incoming ARP packets
185: *
186: * @v iobuf I/O buffer
187: * @v netdev Network device
188: * @v ll_source Link-layer source address
189: * @ret rc Return status code
190: *
191: * This handles ARP requests and responses as detailed in RFC826. The
192: * method detailed within the RFC is pretty optimised, handling
193: * requests and responses with basically a single code path and
194: * avoiding the need for extraneous ARP requests; read the RFC for
195: * details.
196: */
197: static int arp_rx ( struct io_buffer *iobuf, struct net_device *netdev,
198: const void *ll_dest __unused,
199: const void *ll_source __unused ) {
200: struct arphdr *arphdr = iobuf->data;
201: struct arp_net_protocol *arp_net_protocol;
202: struct net_protocol *net_protocol;
203: struct ll_protocol *ll_protocol;
204: struct arp_entry *arp;
205: int merge = 0;
206:
207: /* Identify network-layer and link-layer protocols */
208: arp_net_protocol = arp_find_protocol ( arphdr->ar_pro );
209: if ( ! arp_net_protocol )
210: goto done;
211: net_protocol = arp_net_protocol->net_protocol;
212: ll_protocol = netdev->ll_protocol;
213:
214: /* Sanity checks */
215: if ( ( arphdr->ar_hrd != ll_protocol->ll_proto ) ||
216: ( arphdr->ar_hln != ll_protocol->ll_addr_len ) ||
217: ( arphdr->ar_pln != net_protocol->net_addr_len ) )
218: goto done;
219:
220: /* See if we have an entry for this sender, and update it if so */
221: arp = arp_find_entry ( ll_protocol, net_protocol,
222: arp_sender_pa ( arphdr ) );
223: if ( arp ) {
224: memcpy ( arp->ll_addr, arp_sender_ha ( arphdr ),
225: arphdr->ar_hln );
226: merge = 1;
227: DBG ( "ARP cache update: %s %s => %s %s\n",
228: net_protocol->name, net_protocol->ntoa ( arp->net_addr ),
229: ll_protocol->name, ll_protocol->ntoa ( arp->ll_addr ) );
230: }
231:
232: /* See if we own the target protocol address */
233: if ( arp_net_protocol->check ( netdev, arp_target_pa ( arphdr ) ) != 0)
234: goto done;
235:
236: /* Create new ARP table entry if necessary */
237: if ( ! merge ) {
238: arp = &arp_table[next_new_arp_entry++ % NUM_ARP_ENTRIES];
239: arp->ll_protocol = ll_protocol;
240: arp->net_protocol = net_protocol;
241: memcpy ( arp->ll_addr, arp_sender_ha ( arphdr ),
242: arphdr->ar_hln );
243: memcpy ( arp->net_addr, arp_sender_pa ( arphdr ),
244: arphdr->ar_pln);
245: DBG ( "ARP cache add: %s %s => %s %s\n",
246: net_protocol->name, net_protocol->ntoa ( arp->net_addr ),
247: ll_protocol->name, ll_protocol->ntoa ( arp->ll_addr ) );
248: }
249:
250: /* If it's not a request, there's nothing more to do */
251: if ( arphdr->ar_op != htons ( ARPOP_REQUEST ) )
252: goto done;
253:
254: /* Change request to a reply */
255: DBG ( "ARP reply: %s %s => %s %s\n", net_protocol->name,
256: net_protocol->ntoa ( arp_target_pa ( arphdr ) ),
257: ll_protocol->name, ll_protocol->ntoa ( netdev->ll_addr ) );
258: arphdr->ar_op = htons ( ARPOP_REPLY );
259: memswap ( arp_sender_ha ( arphdr ), arp_target_ha ( arphdr ),
260: arphdr->ar_hln + arphdr->ar_pln );
261: memcpy ( arp_sender_ha ( arphdr ), netdev->ll_addr, arphdr->ar_hln );
262:
263: /* Send reply */
264: net_tx ( iob_disown ( iobuf ), netdev, &arp_protocol,
265: arp_target_ha ( arphdr ), netdev->ll_addr );
266:
267: done:
268: free_iob ( iobuf );
269: return 0;
270: }
271:
272: /**
273: * Transcribe ARP address
274: *
275: * @v net_addr ARP address
276: * @ret string "<ARP>"
277: *
278: * This operation is meaningless for the ARP protocol.
279: */
280: static const char * arp_ntoa ( const void *net_addr __unused ) {
281: return "<ARP>";
282: }
283:
284: /** ARP protocol */
285: struct net_protocol arp_protocol __net_protocol = {
286: .name = "ARP",
287: .net_proto = htons ( ETH_P_ARP ),
288: .rx = arp_rx,
289: .ntoa = arp_ntoa,
290: };
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