blob: 148f52551a129e179ea8fe031ddb36a81eaa09a2
1 | /* vi: set sw=4 ts=4: */ |
2 | /* |
3 | * Packet ops |
4 | * |
5 | * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001 |
6 | * |
7 | * Licensed under GPLv2, see file LICENSE in this source tree. |
8 | */ |
9 | #include "common.h" |
10 | #include "dhcpd.h" |
11 | #include <netinet/in.h> |
12 | #include <netinet/if_ether.h> |
13 | #include <netpacket/packet.h> |
14 | |
15 | void FAST_FUNC udhcp_init_header(struct dhcp_packet *packet, char type) |
16 | { |
17 | memset(packet, 0, sizeof(*packet)); |
18 | packet->op = BOOTREQUEST; /* if client to a server */ |
19 | switch (type) { |
20 | case DHCPOFFER: |
21 | case DHCPACK: |
22 | case DHCPNAK: |
23 | packet->op = BOOTREPLY; /* if server to client */ |
24 | } |
25 | packet->htype = 1; /* ethernet */ |
26 | packet->hlen = 6; |
27 | packet->cookie = htonl(DHCP_MAGIC); |
28 | if (DHCP_END != 0) |
29 | packet->options[0] = DHCP_END; |
30 | udhcp_add_simple_option(packet, DHCP_MESSAGE_TYPE, type); |
31 | } |
32 | |
33 | #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 2 |
34 | void FAST_FUNC udhcp_dump_packet(struct dhcp_packet *packet) |
35 | { |
36 | char buf[sizeof(packet->chaddr)*2 + 1]; |
37 | |
38 | if (dhcp_verbose < 2) |
39 | return; |
40 | |
41 | bb_info_msg( |
42 | //" op %x" |
43 | //" htype %x" |
44 | " hlen %x" |
45 | //" hops %x" |
46 | " xid %x" |
47 | //" secs %x" |
48 | //" flags %x" |
49 | " ciaddr %x" |
50 | " yiaddr %x" |
51 | " siaddr %x" |
52 | " giaddr %x" |
53 | //" chaddr %s" |
54 | //" sname %s" |
55 | //" file %s" |
56 | //" cookie %x" |
57 | //" options %s" |
58 | //, packet->op |
59 | //, packet->htype |
60 | , packet->hlen |
61 | //, packet->hops |
62 | , packet->xid |
63 | //, packet->secs |
64 | //, packet->flags |
65 | , packet->ciaddr |
66 | , packet->yiaddr |
67 | , packet->siaddr_nip |
68 | , packet->gateway_nip |
69 | //, packet->chaddr[16] |
70 | //, packet->sname[64] |
71 | //, packet->file[128] |
72 | //, packet->cookie |
73 | //, packet->options[] |
74 | ); |
75 | *bin2hex(buf, (void *) packet->chaddr, sizeof(packet->chaddr)) = '\0'; |
76 | bb_info_msg(" chaddr %s", buf); |
77 | } |
78 | #endif |
79 | |
80 | /* Read a packet from socket fd, return -1 on read error, -2 on packet error */ |
81 | int FAST_FUNC udhcp_recv_kernel_packet(struct dhcp_packet *packet, int fd) |
82 | { |
83 | int bytes; |
84 | |
85 | memset(packet, 0, sizeof(*packet)); |
86 | bytes = safe_read(fd, packet, sizeof(*packet)); |
87 | if (bytes < 0) { |
88 | log1("Packet read error, ignoring"); |
89 | return bytes; /* returns -1 */ |
90 | } |
91 | |
92 | if (bytes < offsetof(struct dhcp_packet, options) |
93 | || packet->cookie != htonl(DHCP_MAGIC) |
94 | ) { |
95 | bb_info_msg("Packet with bad magic, ignoring"); |
96 | return -2; |
97 | } |
98 | log1("Received a packet"); |
99 | udhcp_dump_packet(packet); |
100 | |
101 | return bytes; |
102 | } |
103 | |
104 | /* Construct a ip/udp header for a packet, send packet */ |
105 | int FAST_FUNC udhcp_send_raw_packet(struct dhcp_packet *dhcp_pkt, |
106 | uint32_t source_nip, int source_port, |
107 | uint32_t dest_nip, int dest_port, const uint8_t *dest_arp, |
108 | int ifindex) |
109 | { |
110 | struct sockaddr_ll dest_sll; |
111 | struct ip_udp_dhcp_packet packet; |
112 | unsigned padding; |
113 | int fd; |
114 | int result = -1; |
115 | const char *msg; |
116 | |
117 | fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP)); |
118 | if (fd < 0) { |
119 | msg = "socket(%s)"; |
120 | goto ret_msg; |
121 | } |
122 | |
123 | memset(&dest_sll, 0, sizeof(dest_sll)); |
124 | memset(&packet, 0, offsetof(struct ip_udp_dhcp_packet, data)); |
125 | packet.data = *dhcp_pkt; /* struct copy */ |
126 | |
127 | dest_sll.sll_family = AF_PACKET; |
128 | dest_sll.sll_protocol = htons(ETH_P_IP); |
129 | dest_sll.sll_ifindex = ifindex; |
130 | dest_sll.sll_halen = 6; |
131 | memcpy(dest_sll.sll_addr, dest_arp, 6); |
132 | |
133 | if (bind(fd, (struct sockaddr *)&dest_sll, sizeof(dest_sll)) < 0) { |
134 | msg = "bind(%s)"; |
135 | goto ret_close; |
136 | } |
137 | |
138 | /* We were sending full-sized DHCP packets (zero padded), |
139 | * but some badly configured servers were seen dropping them. |
140 | * Apparently they drop all DHCP packets >576 *ethernet* octets big, |
141 | * whereas they may only drop packets >576 *IP* octets big |
142 | * (which for typical Ethernet II means 590 octets: 6+6+2 + 576). |
143 | * |
144 | * In order to work with those buggy servers, |
145 | * we truncate packets after end option byte. |
146 | * |
147 | * However, RFC 1542 says "The IP Total Length and UDP Length |
148 | * must be large enough to contain the minimal BOOTP header of 300 octets". |
149 | * Thus, we retain enough padding to not go below 300 BOOTP bytes. |
150 | * Some devices have filters which drop DHCP packets shorter than that. |
151 | */ |
152 | padding = DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(packet.data.options); |
153 | if (padding > DHCP_SIZE - 300) |
154 | padding = DHCP_SIZE - 300; |
155 | |
156 | packet.ip.protocol = IPPROTO_UDP; |
157 | packet.ip.saddr = source_nip; |
158 | packet.ip.daddr = dest_nip; |
159 | packet.udp.source = htons(source_port); |
160 | packet.udp.dest = htons(dest_port); |
161 | /* size, excluding IP header: */ |
162 | packet.udp.len = htons(UDP_DHCP_SIZE - padding); |
163 | /* for UDP checksumming, ip.len is set to UDP packet len */ |
164 | packet.ip.tot_len = packet.udp.len; |
165 | packet.udp.check = inet_cksum((uint16_t *)&packet, |
166 | IP_UDP_DHCP_SIZE - padding); |
167 | /* but for sending, it is set to IP packet len */ |
168 | packet.ip.tot_len = htons(IP_UDP_DHCP_SIZE - padding); |
169 | packet.ip.ihl = sizeof(packet.ip) >> 2; |
170 | packet.ip.version = IPVERSION; |
171 | packet.ip.ttl = IPDEFTTL; |
172 | packet.ip.check = inet_cksum((uint16_t *)&packet.ip, sizeof(packet.ip)); |
173 | |
174 | udhcp_dump_packet(dhcp_pkt); |
175 | result = sendto(fd, &packet, IP_UDP_DHCP_SIZE - padding, /*flags:*/ 0, |
176 | (struct sockaddr *) &dest_sll, sizeof(dest_sll)); |
177 | msg = "sendto"; |
178 | ret_close: |
179 | close(fd); |
180 | if (result < 0) { |
181 | ret_msg: |
182 | bb_perror_msg(msg, "PACKET"); |
183 | } |
184 | return result; |
185 | } |
186 | |
187 | /* Let the kernel do all the work for packet generation */ |
188 | int FAST_FUNC udhcp_send_kernel_packet(struct dhcp_packet *dhcp_pkt, |
189 | uint32_t source_nip, int source_port, |
190 | uint32_t dest_nip, int dest_port) |
191 | { |
192 | struct sockaddr_in sa; |
193 | unsigned padding; |
194 | int fd; |
195 | int result = -1; |
196 | const char *msg; |
197 | |
198 | fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP); |
199 | if (fd < 0) { |
200 | msg = "socket(%s)"; |
201 | goto ret_msg; |
202 | } |
203 | setsockopt_reuseaddr(fd); |
204 | |
205 | memset(&sa, 0, sizeof(sa)); |
206 | sa.sin_family = AF_INET; |
207 | sa.sin_port = htons(source_port); |
208 | sa.sin_addr.s_addr = source_nip; |
209 | if (bind(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) { |
210 | msg = "bind(%s)"; |
211 | goto ret_close; |
212 | } |
213 | |
214 | memset(&sa, 0, sizeof(sa)); |
215 | sa.sin_family = AF_INET; |
216 | sa.sin_port = htons(dest_port); |
217 | sa.sin_addr.s_addr = dest_nip; |
218 | if (connect(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) { |
219 | msg = "connect"; |
220 | goto ret_close; |
221 | } |
222 | |
223 | udhcp_dump_packet(dhcp_pkt); |
224 | padding = DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(dhcp_pkt->options); |
225 | if (padding > DHCP_SIZE - 300) |
226 | padding = DHCP_SIZE - 300; |
227 | result = safe_write(fd, dhcp_pkt, DHCP_SIZE - padding); |
228 | msg = "write"; |
229 | ret_close: |
230 | close(fd); |
231 | if (result < 0) { |
232 | ret_msg: |
233 | bb_perror_msg(msg, "UDP"); |
234 | } |
235 | return result; |
236 | } |
237 |