release/src/router/busybox/networking/udhcp/packet.c

   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 int minpkt = 0; // zzz
  16
  17 void FAST_FUNC udhcp_init_header(struct dhcp_packet *packet, char type)
  18 {
  19         memset(packet, 0, sizeof(*packet));
  20         packet->op = BOOTREQUEST; /* if client to a server */
  21         switch (type) {
  22         case DHCPOFFER:
  23         case DHCPACK:
  24         case DHCPNAK:
  25                 packet->op = BOOTREPLY; /* if server to client */
  26         }
  27         packet->htype = 1; /* ethernet */
  28         packet->hlen = 6;
  29         packet->cookie = htonl(DHCP_MAGIC);
  30         if (DHCP_END != 0)
  31                 packet->options[0] = DHCP_END;
  32         udhcp_add_simple_option(packet, DHCP_MESSAGE_TYPE, type);
  33 }
  34
  35 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 2
  36 void FAST_FUNC udhcp_dump_packet(struct dhcp_packet *packet)
  37 {
  38         char buf[sizeof(packet->chaddr)*2 + 1];
  39
  40         if (dhcp_verbose < 2)
  41                 return;
  42
  43         bb_info_msg(
  44                 //" op %x"
  45                 //" htype %x"
  46                 " hlen %x"
  47                 //" hops %x"
  48                 " xid %x"
  49                 //" secs %x"
  50                 //" flags %x"
  51                 " ciaddr %x"
  52                 " yiaddr %x"
  53                 " siaddr %x"
  54                 " giaddr %x"
  55                 //" chaddr %s"
  56                 //" sname %s"
  57                 //" file %s"
  58                 //" cookie %x"
  59                 //" options %s"
  60                 //, packet->op
  61                 //, packet->htype
  62                 , packet->hlen
  63                 //, packet->hops
  64                 , packet->xid
  65                 //, packet->secs
  66                 //, packet->flags
  67                 , packet->ciaddr
  68                 , packet->yiaddr
  69                 , packet->siaddr_nip
  70                 , packet->gateway_nip
  71                 //, packet->chaddr[16]
  72                 //, packet->sname[64]
  73                 //, packet->file[128]
  74                 //, packet->cookie
  75                 //, packet->options[]
  76         );
  77         *bin2hex(buf, (void *) packet->chaddr, sizeof(packet->chaddr)) = '\0';
  78         bb_info_msg(" chaddr %s", buf);
  79 }
  80 #endif
  81
  82 /* Read a packet from socket fd, return -1 on read error, -2 on packet error */
  83 int FAST_FUNC udhcp_recv_kernel_packet(struct dhcp_packet *packet, int fd)
  84 {
  85         int bytes;
  86
  87         memset(packet, 0, sizeof(*packet));
  88         bytes = safe_read(fd, packet, sizeof(*packet));
  89         if (bytes < 0) {
  90                 log1("Packet read error, ignoring");
  91                 return bytes; /* returns -1 */
  92         }
  93
  94         if (bytes < offsetof(struct dhcp_packet, options)
  95          || packet->cookie != htonl(DHCP_MAGIC)
  96         ) {
  97                 bb_info_msg("Packet with bad magic, ignoring");
  98                 return -2;
  99         }
 100         log1("Received a packet");
 101         udhcp_dump_packet(packet);
 102
 103         return bytes;
 104 }
 105
 106 /* Construct a ip/udp header for a packet, send packet */
 107 int FAST_FUNC udhcp_send_raw_packet(struct dhcp_packet *dhcp_pkt,
 108                 uint32_t source_nip, int source_port,
 109                 uint32_t dest_nip, int dest_port, const uint8_t *dest_arp,
 110                 int ifindex)
 111 {
 112         struct sockaddr_ll dest_sll;
 113         struct ip_udp_dhcp_packet packet;
 114         unsigned padding;
 115         int fd;
 116         int result = -1;
 117         const char *msg;
 118
 119         fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
 120         if (fd < 0) {
 121                 msg = "socket(%s)";
 122                 goto ret_msg;
 123         }
 124
 125         memset(&dest_sll, 0, sizeof(dest_sll));
 126         memset(&packet, 0, offsetof(struct ip_udp_dhcp_packet, data));
 127         packet.data = *dhcp_pkt; /* struct copy */
 128
 129         dest_sll.sll_family = AF_PACKET;
 130         dest_sll.sll_protocol = htons(ETH_P_IP);
 131         dest_sll.sll_ifindex = ifindex;
 132         dest_sll.sll_halen = 6;
 133         memcpy(dest_sll.sll_addr, dest_arp, 6);
 134
 135         if (bind(fd, (struct sockaddr *)&dest_sll, sizeof(dest_sll)) < 0) {
 136                 msg = "bind(%s)";
 137                 goto ret_close;
 138         }
 139
 140         /* We were sending full-sized DHCP packets (zero padded),
 141          * but some badly configured servers were seen dropping them.
 142          * Apparently they drop all DHCP packets >576 *ethernet* octets big,
 143          * whereas they may only drop packets >576 *IP* octets big
 144          * (which for typical Ethernet II means 590 octets: 6+6+2 + 576).
 145          *
 146          * In order to work with those buggy servers,
 147          * we truncate packets after end option byte.
 148          */
 149         padding = minpkt ? DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(packet.data.options) : 0;
 150
 151         packet.ip.protocol = IPPROTO_UDP;
 152         packet.ip.saddr = source_nip;
 153         packet.ip.daddr = dest_nip;
 154         packet.udp.source = htons(source_port);
 155         packet.udp.dest = htons(dest_port);
 156         /* size, excluding IP header: */
 157         packet.udp.len = htons(UDP_DHCP_SIZE - padding);
 158         /* for UDP checksumming, ip.len is set to UDP packet len */
 159         packet.ip.tot_len = packet.udp.len;
 160         packet.udp.check = inet_cksum((uint16_t *)&packet,
 161                         IP_UDP_DHCP_SIZE - padding);
 162         /* but for sending, it is set to IP packet len */
 163         packet.ip.tot_len = htons(IP_UDP_DHCP_SIZE - padding);
 164         packet.ip.ihl = sizeof(packet.ip) >> 2;
 165         packet.ip.version = IPVERSION;
 166         packet.ip.ttl = IPDEFTTL * 2;
 167         packet.ip.check = inet_cksum((uint16_t *)&packet.ip, sizeof(packet.ip));
 168
 169         udhcp_dump_packet(dhcp_pkt);
 170         result = sendto(fd, &packet, IP_UDP_DHCP_SIZE - padding, /*flags:*/ 0,
 171                         (struct sockaddr *) &dest_sll, sizeof(dest_sll));
 172         msg = "sendto";
 173  ret_close:
 174         close(fd);
 175         if (result < 0) {
 176  ret_msg:
 177                 bb_perror_msg(msg, "PACKET");
 178         }
 179         return result;
 180 }
 181
 182 /* Let the kernel do all the work for packet generation */
 183 int FAST_FUNC udhcp_send_kernel_packet(struct dhcp_packet *dhcp_pkt,
 184                 uint32_t source_nip, int source_port,
 185                 uint32_t dest_nip, int dest_port)
 186 {
 187         struct sockaddr_in sa;
 188         unsigned padding;
 189         int fd;
 190         int result = -1;
 191         const char *msg;
 192
 193         fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
 194         if (fd < 0) {
 195                 msg = "socket(%s)";
 196                 goto ret_msg;
 197         }
 198         setsockopt_reuseaddr(fd);
 199
 200         memset(&sa, 0, sizeof(sa));
 201         sa.sin_family = AF_INET;
 202         sa.sin_port = htons(source_port);
 203         sa.sin_addr.s_addr = source_nip;
 204         if (bind(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
 205                 msg = "bind(%s)";
 206                 goto ret_close;
 207         }
 208
 209         memset(&sa, 0, sizeof(sa));
 210         sa.sin_family = AF_INET;
 211         sa.sin_port = htons(dest_port);
 212         sa.sin_addr.s_addr = dest_nip;
 213         if (connect(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
 214                 msg = "connect";
 215                 goto ret_close;
 216         }
 217
 218         udhcp_dump_packet(dhcp_pkt);
 219
 220         padding = minpkt ? DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(dhcp_pkt->options) : 0;
 221         result = safe_write(fd, dhcp_pkt, DHCP_SIZE - padding);
 222         msg = "write";
 223  ret_close:
 224         close(fd);
 225         if (result < 0) {
 226  ret_msg:
 227                 bb_perror_msg(msg, "UDP");
 228         }
 229         return result;
 230 }