src/libsystemd-network/dhcp-network.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   Copyright © 2013 Intel Corporation. All rights reserved.
   4 ***/
   5
   6 #include <errno.h>
   7 #include <net/ethernet.h>
   8 #include <net/if.h>
   9 #include <net/if_arp.h>
  10 #include <stdio.h>
  11 #include <string.h>
  12 #include <sys/socket.h>
  13 #include <linux/filter.h>
  14 #include <linux/if_infiniband.h>
  15 #include <linux/if_packet.h>
  16
  17 #include "dhcp-internal.h"
  18 #include "fd-util.h"
  19 #include "socket-util.h"
  20 #include "unaligned.h"
  21
  22 static int _bind_raw_socket(int ifindex, union sockaddr_union *link,
  23                             uint32_t xid, const uint8_t *mac_addr,
  24                             size_t mac_addr_len,
  25                             const uint8_t *bcast_addr,
  26                             const struct ether_addr *eth_mac,
  27                             uint16_t arp_type, uint8_t dhcp_hlen,
  28                             uint16_t port) {
  29         struct sock_filter filter[] = {
  30                 BPF_STMT(BPF_LD + BPF_W + BPF_LEN, 0),                                 /* A <- packet length */
  31                 BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, sizeof(DHCPPacket), 1, 0),         /* packet >= DHCPPacket ? */
  32                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  33                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, ip.protocol)), /* A <- IP protocol */
  34                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 1, 0),                /* IP protocol == UDP ? */
  35                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  36                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, ip.frag_off)), /* A <- Flags */
  37                 BPF_STMT(BPF_ALU + BPF_AND + BPF_K, 0x20),                             /* A <- A & 0x20 (More Fragments bit) */
  38                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                          /* A == 0 ? */
  39                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  40                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, ip.frag_off)), /* A <- Flags + Fragment offset */
  41                 BPF_STMT(BPF_ALU + BPF_AND + BPF_K, 0x1fff),                           /* A <- A & 0x1fff (Fragment offset) */
  42                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                          /* A == 0 ? */
  43                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  44                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, udp.dest)),    /* A <- UDP destination port */
  45                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, port, 1, 0),                       /* UDP destination port == DHCP client port ? */
  46                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  47                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.op)),     /* A <- DHCP op */
  48                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, BOOTREPLY, 1, 0),                  /* op == BOOTREPLY ? */
  49                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  50                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.htype)),  /* A <- DHCP header type */
  51                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, arp_type, 1, 0),                   /* header type == arp_type ? */
  52                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  53                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.hlen)),   /* A <- MAC address length */
  54                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, dhcp_hlen, 1, 0),                  /* address length == dhcp_hlen ? */
  55                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  56                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.xid)),    /* A <- client identifier */
  57                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, xid, 1, 0),                        /* client identifier == xid ? */
  58                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  59                 BPF_STMT(BPF_LD + BPF_IMM, unaligned_read_be32(&eth_mac->ether_addr_octet[0])),        /* A <- 4 bytes of client's MAC */
  60                 BPF_STMT(BPF_MISC + BPF_TAX, 0),                                                       /* X <- A */
  61                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr)),                 /* A <- 4 bytes of MAC from dhcp.chaddr */
  62                 BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0),                                                /* A xor X */
  63                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                                          /* A == 0 ? */
  64                 BPF_STMT(BPF_RET + BPF_K, 0),                                                          /* ignore */
  65                 BPF_STMT(BPF_LD + BPF_IMM, unaligned_read_be16(&eth_mac->ether_addr_octet[4])),        /* A <- remainder of client's MAC */
  66                 BPF_STMT(BPF_MISC + BPF_TAX, 0),                                                       /* X <- A */
  67                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr) + 4),             /* A <- remainder of MAC from dhcp.chaddr */
  68                 BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0),                                                /* A xor X */
  69                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                                          /* A == 0 ? */
  70                 BPF_STMT(BPF_RET + BPF_K, 0),                                                          /* ignore */
  71                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.magic)),  /* A <- DHCP magic cookie */
  72                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DHCP_MAGIC_COOKIE, 1, 0),          /* cookie == DHCP magic cookie ? */
  73                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  74                 BPF_STMT(BPF_RET + BPF_K, 65535),                                      /* return all */
  75         };
  76         struct sock_fprog fprog = {
  77                 .len = ELEMENTSOF(filter),
  78                 .filter = filter
  79         };
  80         _cleanup_close_ int s = -1;
  81         int r;
  82
  83         assert(ifindex > 0);
  84         assert(link);
  85
  86         s = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
  87         if (s < 0)
  88                 return -errno;
  89
  90         r = setsockopt_int(s, SOL_PACKET, PACKET_AUXDATA, true);
  91         if (r < 0)
  92                 return r;
  93
  94         r = setsockopt(s, SOL_SOCKET, SO_ATTACH_FILTER, &fprog, sizeof(fprog));
  95         if (r < 0)
  96                 return -errno;
  97
  98         link->ll = (struct sockaddr_ll) {
  99                 .sll_family = AF_PACKET,
 100                 .sll_protocol = htobe16(ETH_P_IP),
 101                 .sll_ifindex = ifindex,
 102                 .sll_hatype = htobe16(arp_type),
 103                 .sll_halen = mac_addr_len,
 104         };
 105         memcpy(link->ll.sll_addr, bcast_addr, mac_addr_len);
 106
 107         r = bind(s, &link->sa, SOCKADDR_LL_LEN(link->ll));
 108         if (r < 0)
 109                 return -errno;
 110
 111         return TAKE_FD(s);
 112 }
 113
 114 int dhcp_network_bind_raw_socket(int ifindex, union sockaddr_union *link,
 115                                  uint32_t xid, const uint8_t *mac_addr,
 116                                  size_t mac_addr_len, uint16_t arp_type,
 117                                  uint16_t port) {
 118         static const uint8_t eth_bcast[] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
 119         /* Default broadcast address for IPoIB */
 120         static const uint8_t ib_bcast[] = {
 121                 0x00, 0xff, 0xff, 0xff, 0xff, 0x12, 0x40, 0x1b,
 122                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 123                 0xff, 0xff, 0xff, 0xff
 124           };
 125         struct ether_addr eth_mac = { { 0, 0, 0, 0, 0, 0 } };
 126         const uint8_t *bcast_addr = NULL;
 127         uint8_t dhcp_hlen = 0;
 128
 129         if (arp_type == ARPHRD_ETHER) {
 130                 assert_return(mac_addr_len == ETH_ALEN, -EINVAL);
 131                 memcpy(&eth_mac, mac_addr, ETH_ALEN);
 132                 bcast_addr = eth_bcast;
 133                 dhcp_hlen = ETH_ALEN;
 134         } else if (arp_type == ARPHRD_INFINIBAND) {
 135                 assert_return(mac_addr_len == INFINIBAND_ALEN, -EINVAL);
 136                 bcast_addr = ib_bcast;
 137         } else
 138                 return -EINVAL;
 139
 140         return _bind_raw_socket(ifindex, link, xid, mac_addr, mac_addr_len,
 141                                 bcast_addr, &eth_mac, arp_type, dhcp_hlen, port);
 142 }
 143
 144 int dhcp_network_bind_udp_socket(int ifindex, be32_t address, uint16_t port) {
 145         union sockaddr_union src = {
 146                 .in.sin_family = AF_INET,
 147                 .in.sin_port = htobe16(port),
 148                 .in.sin_addr.s_addr = address,
 149         };
 150         _cleanup_close_ int s = -1;
 151         char ifname[IF_NAMESIZE] = "";
 152         int r;
 153
 154         s = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
 155         if (s < 0)
 156                 return -errno;
 157
 158         r = setsockopt_int(s, IPPROTO_IP, IP_TOS, IPTOS_CLASS_CS6);
 159         if (r < 0)
 160                 return r;
 161
 162         r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 163         if (r < 0)
 164                 return r;
 165
 166         if (ifindex > 0) {
 167                 if (if_indextoname(ifindex, ifname) == 0)
 168                         return -errno;
 169
 170                 r = setsockopt(s, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname));
 171                 if (r < 0)
 172                         return -errno;
 173         }
 174
 175         if (address == INADDR_ANY) {
 176                 r = setsockopt_int(s, IPPROTO_IP, IP_PKTINFO, true);
 177                 if (r < 0)
 178                         return r;
 179
 180                 r = setsockopt_int(s, SOL_SOCKET, SO_BROADCAST, true);
 181                 if (r < 0)
 182                         return r;
 183
 184         } else {
 185                 r = setsockopt_int(s, IPPROTO_IP, IP_FREEBIND, true);
 186                 if (r < 0)
 187                         return r;
 188         }
 189
 190         r = bind(s, &src.sa, sizeof(src.in));
 191         if (r < 0)
 192                 return -errno;
 193
 194         return TAKE_FD(s);
 195 }
 196
 197 int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link,
 198                                  const void *packet, size_t len) {
 199         int r;
 200
 201         assert(link);
 202         assert(packet);
 203         assert(len);
 204
 205         r = sendto(s, packet, len, 0, &link->sa, SOCKADDR_LL_LEN(link->ll));
 206         if (r < 0)
 207                 return -errno;
 208
 209         return 0;
 210 }
 211
 212 int dhcp_network_send_udp_socket(int s, be32_t address, uint16_t port,
 213                                  const void *packet, size_t len) {
 214         union sockaddr_union dest = {
 215                 .in.sin_family = AF_INET,
 216                 .in.sin_port = htobe16(port),
 217                 .in.sin_addr.s_addr = address,
 218         };
 219         int r;
 220
 221         assert(s >= 0);
 222         assert(packet);
 223         assert(len);
 224
 225         r = sendto(s, packet, len, 0, &dest.sa, sizeof(dest.in));
 226         if (r < 0)
 227                 return -errno;
 228
 229         return 0;
 230 }