src/libsystemd-network/dhcp-network.c

   1 /***
   2   This file is part of systemd.
   3
   4   Copyright (C) 2013 Intel Corporation. All rights reserved.
   5
   6   systemd is free software; you can redistribute it and/or modify it
   7   under the terms of the GNU Lesser General Public License as published by
   8   the Free Software Foundation; either version 2.1 of the License, or
   9   (at your option) any later version.
  10
  11   systemd is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   Lesser General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public License
  17   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  18 ***/
  19
  20 #include <errno.h>
  21 #include <net/ethernet.h>
  22 #include <net/if.h>
  23 #include <net/if_arp.h>
  24 #include <stdio.h>
  25 #include <string.h>
  26 #include <sys/socket.h>
  27 #include <linux/filter.h>
  28 #include <linux/if_infiniband.h>
  29 #include <linux/if_packet.h>
  30
  31 #include "dhcp-internal.h"
  32 #include "fd-util.h"
  33 #include "socket-util.h"
  34
  35 static int _bind_raw_socket(int ifindex, union sockaddr_union *link,
  36                             uint32_t xid, const uint8_t *mac_addr,
  37                             size_t mac_addr_len,
  38                             const uint8_t *bcast_addr,
  39                             const struct ether_addr *eth_mac,
  40                             uint16_t arp_type, uint8_t dhcp_hlen,
  41                             uint16_t port) {
  42         struct sock_filter filter[] = {
  43                 BPF_STMT(BPF_LD + BPF_W + BPF_LEN, 0),                                 /* A <- packet length */
  44                 BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, sizeof(DHCPPacket), 1, 0),         /* packet >= DHCPPacket ? */
  45                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  46                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, ip.protocol)), /* A <- IP protocol */
  47                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 1, 0),                /* IP protocol == UDP ? */
  48                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  49                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, ip.frag_off)), /* A <- Flags */
  50                 BPF_STMT(BPF_ALU + BPF_AND + BPF_K, 0x20),                             /* A <- A & 0x20 (More Fragments bit) */
  51                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                          /* A == 0 ? */
  52                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  53                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, ip.frag_off)), /* A <- Flags + Fragment offset */
  54                 BPF_STMT(BPF_ALU + BPF_AND + BPF_K, 0x1fff),                           /* A <- A & 0x1fff (Fragment offset) */
  55                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                          /* A == 0 ? */
  56                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  57                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, udp.dest)),    /* A <- UDP destination port */
  58                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, port, 1, 0),                       /* UDP destination port == DHCP client port ? */
  59                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  60                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.op)),     /* A <- DHCP op */
  61                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, BOOTREPLY, 1, 0),                  /* op == BOOTREPLY ? */
  62                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  63                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.htype)),  /* A <- DHCP header type */
  64                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, arp_type, 1, 0),                   /* header type == arp_type ? */
  65                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  66                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.hlen)),   /* A <- MAC address length */
  67                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, dhcp_hlen, 1, 0),                  /* address length == dhcp_hlen ? */
  68                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  69                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.xid)),    /* A <- client identifier */
  70                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, xid, 1, 0),                        /* client identifier == xid ? */
  71                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  72                 BPF_STMT(BPF_LD + BPF_IMM, htobe32(*((unsigned int *) eth_mac))),                     /* A <- 4 bytes of client's MAC */
  73                 BPF_STMT(BPF_MISC + BPF_TAX, 0),                                                       /* X <- A */
  74                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr)),                 /* A <- 4 bytes of MAC from dhcp.chaddr */
  75                 BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0),                                                /* A xor X */
  76                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                                          /* A == 0 ? */
  77                 BPF_STMT(BPF_RET + BPF_K, 0),                                                          /* ignore */
  78                 BPF_STMT(BPF_LD + BPF_IMM, htobe16(*((unsigned short *) (((char *) eth_mac) + 4)))),   /* A <- remainder of client's MAC */
  79                 BPF_STMT(BPF_MISC + BPF_TAX, 0),                                                       /* X <- A */
  80                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr) + 4),             /* A <- remainder of MAC from dhcp.chaddr */
  81                 BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0),                                                /* A xor X */
  82                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                                          /* A == 0 ? */
  83                 BPF_STMT(BPF_RET + BPF_K, 0),                                                          /* ignore */
  84                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.magic)),  /* A <- DHCP magic cookie */
  85                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DHCP_MAGIC_COOKIE, 1, 0),          /* cookie == DHCP magic cookie ? */
  86                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  87                 BPF_STMT(BPF_RET + BPF_K, 65535),                                      /* return all */
  88         };
  89         struct sock_fprog fprog = {
  90                 .len = ELEMENTSOF(filter),
  91                 .filter = filter
  92         };
  93         _cleanup_close_ int s = -1;
  94         int r, on = 1;
  95
  96         assert(ifindex > 0);
  97         assert(link);
  98
  99         s = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
 100         if (s < 0)
 101                 return -errno;
 102
 103         r = setsockopt(s, SOL_PACKET, PACKET_AUXDATA, &on, sizeof(on));
 104         if (r < 0)
 105                 return -errno;
 106
 107         r = setsockopt(s, SOL_SOCKET, SO_ATTACH_FILTER, &fprog, sizeof(fprog));
 108         if (r < 0)
 109                 return -errno;
 110
 111         link->ll = (struct sockaddr_ll) {
 112                 .sll_family = AF_PACKET,
 113                 .sll_protocol = htobe16(ETH_P_IP),
 114                 .sll_ifindex = ifindex,
 115                 .sll_hatype = htobe16(arp_type),
 116                 .sll_halen = mac_addr_len,
 117         };
 118         memcpy(link->ll.sll_addr, bcast_addr, mac_addr_len);
 119
 120         r = bind(s, &link->sa, SOCKADDR_LL_LEN(link->ll));
 121         if (r < 0)
 122                 return -errno;
 123
 124         r = s;
 125         s = -1;
 126
 127         return r;
 128 }
 129
 130 int dhcp_network_bind_raw_socket(int ifindex, union sockaddr_union *link,
 131                                  uint32_t xid, const uint8_t *mac_addr,
 132                                  size_t mac_addr_len, uint16_t arp_type,
 133                                  uint16_t port) {
 134         static const uint8_t eth_bcast[] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
 135         /* Default broadcast address for IPoIB */
 136         static const uint8_t ib_bcast[] = {
 137                 0x00, 0xff, 0xff, 0xff, 0xff, 0x12, 0x40, 0x1b,
 138                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 139                 0xff, 0xff, 0xff, 0xff
 140           };
 141         struct ether_addr eth_mac = { { 0, 0, 0, 0, 0, 0 } };
 142         const uint8_t *bcast_addr = NULL;
 143         uint8_t dhcp_hlen = 0;
 144
 145         assert_return(mac_addr_len > 0, -EINVAL);
 146
 147         if (arp_type == ARPHRD_ETHER) {
 148                 assert_return(mac_addr_len == ETH_ALEN, -EINVAL);
 149                 memcpy(&eth_mac, mac_addr, ETH_ALEN);
 150                 bcast_addr = eth_bcast;
 151                 dhcp_hlen = ETH_ALEN;
 152         } else if (arp_type == ARPHRD_INFINIBAND) {
 153                 assert_return(mac_addr_len == INFINIBAND_ALEN, -EINVAL);
 154                 bcast_addr = ib_bcast;
 155         } else
 156                 return -EINVAL;
 157
 158         return _bind_raw_socket(ifindex, link, xid, mac_addr, mac_addr_len,
 159                                 bcast_addr, &eth_mac, arp_type, dhcp_hlen, port);
 160 }
 161
 162 int dhcp_network_bind_udp_socket(int ifindex, be32_t address, uint16_t port) {
 163         union sockaddr_union src = {
 164                 .in.sin_family = AF_INET,
 165                 .in.sin_port = htobe16(port),
 166                 .in.sin_addr.s_addr = address,
 167         };
 168         _cleanup_close_ int s = -1;
 169         char ifname[IF_NAMESIZE] = "";
 170         int r, on = 1, tos = IPTOS_CLASS_CS6;
 171
 172         s = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
 173         if (s < 0)
 174                 return -errno;
 175
 176         r = setsockopt(s, IPPROTO_IP, IP_TOS, &tos, sizeof(tos));
 177         if (r < 0)
 178                 return -errno;
 179
 180         r = setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
 181         if (r < 0)
 182                 return -errno;
 183
 184         if (ifindex > 0) {
 185                 if (if_indextoname(ifindex, ifname) == 0)
 186                         return -errno;
 187
 188                 r = setsockopt(s, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname));
 189                 if (r < 0)
 190                         return -errno;
 191         }
 192
 193         if (address == INADDR_ANY) {
 194                 r = setsockopt(s, IPPROTO_IP, IP_PKTINFO, &on, sizeof(on));
 195                 if (r < 0)
 196                         return -errno;
 197
 198                 r = setsockopt(s, SOL_SOCKET, SO_BROADCAST, &on, sizeof(on));
 199                 if (r < 0)
 200                         return -errno;
 201
 202         } else {
 203                 r = setsockopt(s, IPPROTO_IP, IP_FREEBIND, &on, sizeof(on));
 204                 if (r < 0)
 205                         return -errno;
 206         }
 207
 208         r = bind(s, &src.sa, sizeof(src.in));
 209         if (r < 0)
 210                 return -errno;
 211
 212         r = s;
 213         s = -1;
 214
 215         return r;
 216 }
 217
 218 int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link,
 219                                  const void *packet, size_t len) {
 220         int r;
 221
 222         assert(link);
 223         assert(packet);
 224         assert(len);
 225
 226         r = sendto(s, packet, len, 0, &link->sa, SOCKADDR_LL_LEN(link->ll));
 227         if (r < 0)
 228                 return -errno;
 229
 230         return 0;
 231 }
 232
 233 int dhcp_network_send_udp_socket(int s, be32_t address, uint16_t port,
 234                                  const void *packet, size_t len) {
 235         union sockaddr_union dest = {
 236                 .in.sin_family = AF_INET,
 237                 .in.sin_port = htobe16(port),
 238                 .in.sin_addr.s_addr = address,
 239         };
 240         int r;
 241
 242         assert(s >= 0);
 243         assert(packet);
 244         assert(len);
 245
 246         r = sendto(s, packet, len, 0, &dest.sa, sizeof(dest.in));
 247         if (r < 0)
 248                 return -errno;
 249
 250         return 0;
 251 }