src/libsystemd-network/dhcp-network.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2 /***
   3   Copyright © 2013 Intel Corporation. All rights reserved.
   4 ***/
   5
   6 /* Make sure the net/if.h header is included before any linux/ one */
   7 #include <net/if.h>
   8 #include <errno.h>
   9 #include <linux/filter.h>
  10 #include <linux/if_infiniband.h>
  11 #include <linux/if_packet.h>
  12 #include <net/ethernet.h>
  13 #include <net/if_arp.h>
  14 #include <stdio.h>
  15 #include <string.h>
  16
  17 #include "dhcp-network.h"
  18 #include "dhcp-protocol.h"
  19 #include "fd-util.h"
  20 #include "unaligned.h"
  21
  22 static int _bind_raw_socket(
  23                 int ifindex,
  24                 union sockaddr_union *link,
  25                 uint32_t xid,
  26                 const struct hw_addr_data *hw_addr,
  27                 const struct hw_addr_data *bcast_addr,
  28                 uint16_t arp_type,
  29                 uint16_t port,
  30                 bool so_priority_set,
  31                 int so_priority) {
  32
  33         assert(ifindex > 0);
  34         assert(link);
  35         assert(hw_addr);
  36         assert(bcast_addr);
  37         assert(IN_SET(arp_type, ARPHRD_ETHER, ARPHRD_INFINIBAND));
  38
  39         switch (arp_type) {
  40         case ARPHRD_ETHER:
  41                 assert(hw_addr->length == ETH_ALEN);
  42                 assert(bcast_addr->length == ETH_ALEN);
  43                 break;
  44         case ARPHRD_INFINIBAND:
  45                 assert(hw_addr->length == 0);
  46                 assert(bcast_addr->length == INFINIBAND_ALEN);
  47                 break;
  48         default:
  49                 assert_not_reached();
  50         }
  51
  52         struct sock_filter filter[] = {
  53                 BPF_STMT(BPF_LD + BPF_W + BPF_LEN, 0),                                 /* A <- packet length */
  54                 BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, sizeof(DHCPPacket), 1, 0),         /* packet >= DHCPPacket ? */
  55                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  56                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, ip.protocol)), /* A <- IP protocol */
  57                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 1, 0),                /* IP protocol == UDP ? */
  58                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  59                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, ip.frag_off)), /* A <- Flags */
  60                 BPF_STMT(BPF_ALU + BPF_AND + BPF_K, 0x20),                             /* A <- A & 0x20 (More Fragments bit) */
  61                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                          /* A == 0 ? */
  62                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  63                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, ip.frag_off)), /* A <- Flags + Fragment offset */
  64                 BPF_STMT(BPF_ALU + BPF_AND + BPF_K, 0x1fff),                           /* A <- A & 0x1fff (Fragment offset) */
  65                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                          /* A == 0 ? */
  66                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  67                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, udp.dest)),    /* A <- UDP destination port */
  68                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, port, 1, 0),                       /* UDP destination port == DHCP client port ? */
  69                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  70                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.op)),     /* A <- DHCP op */
  71                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, BOOTREPLY, 1, 0),                  /* op == BOOTREPLY ? */
  72                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  73                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.htype)),  /* A <- DHCP header type */
  74                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, arp_type, 1, 0),                   /* header type == arp_type ? */
  75                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  76                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.xid)),    /* A <- client identifier */
  77                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, xid, 1, 0),                        /* client identifier == xid ? */
  78                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  79                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.hlen)),   /* A <- MAC address length */
  80                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, (uint8_t) hw_addr->length, 1, 0),  /* address length == hw_addr->length ? */
  81                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  82
  83                 /* We only support MAC address length to be either 0 or 6 (ETH_ALEN). Optionally
  84                  * compare chaddr for ETH_ALEN bytes. */
  85                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETH_ALEN, 0, 8),                        /* A (the MAC address length) == ETH_ALEN ? */
  86                 BPF_STMT(BPF_LDX + BPF_IMM, unaligned_read_be32(hw_addr->bytes)),           /* X <- 4 bytes of client's MAC */
  87                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr)),      /* A <- 4 bytes of MAC from dhcp.chaddr */
  88                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_X, 0, 1, 0),                               /* A == X ? */
  89                 BPF_STMT(BPF_RET + BPF_K, 0),                                               /* ignore */
  90                 BPF_STMT(BPF_LDX + BPF_IMM, unaligned_read_be16(hw_addr->bytes + 4)),       /* X <- remainder of client's MAC */
  91                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr) + 4),  /* A <- remainder of MAC from dhcp.chaddr */
  92                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_X, 0, 1, 0),                               /* A == X ? */
  93                 BPF_STMT(BPF_RET + BPF_K, 0),                                               /* ignore */
  94
  95                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.magic)),  /* A <- DHCP magic cookie */
  96                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DHCP_MAGIC_COOKIE, 1, 0),          /* cookie == DHCP magic cookie ? */
  97                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  98                 BPF_STMT(BPF_RET + BPF_K, UINT32_MAX),                                 /* accept */
  99         };
 100         struct sock_fprog fprog = {
 101                 .len = ELEMENTSOF(filter),
 102                 .filter = filter
 103         };
 104         _cleanup_close_ int s = -EBADF;
 105         int r;
 106
 107         s = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
 108         if (s < 0)
 109                 return -errno;
 110
 111         r = setsockopt_int(s, SOL_PACKET, PACKET_AUXDATA, true);
 112         if (r < 0)
 113                 return r;
 114
 115         r = setsockopt(s, SOL_SOCKET, SO_ATTACH_FILTER, &fprog, sizeof(fprog));
 116         if (r < 0)
 117                 return -errno;
 118
 119         r = setsockopt_int(s, SOL_SOCKET, SO_TIMESTAMP, true);
 120         if (r < 0)
 121                 return r;
 122
 123         if (so_priority_set) {
 124                 r = setsockopt_int(s, SOL_SOCKET, SO_PRIORITY, so_priority);
 125                 if (r < 0)
 126                         return r;
 127         }
 128
 129         link->ll = (struct sockaddr_ll) {
 130                 .sll_family = AF_PACKET,
 131                 .sll_protocol = htobe16(ETH_P_IP),
 132                 .sll_ifindex = ifindex,
 133                 .sll_hatype = htobe16(arp_type),
 134                 .sll_halen = bcast_addr->length,
 135         };
 136         /* We may overflow link->ll. link->ll_buffer ensures we have enough space. */
 137         memcpy(link->ll.sll_addr, bcast_addr->bytes, bcast_addr->length);
 138
 139         r = bind(s, &link->sa, SOCKADDR_LL_LEN(link->ll));
 140         if (r < 0)
 141                 return -errno;
 142
 143         return TAKE_FD(s);
 144 }
 145
 146 int dhcp_network_bind_raw_socket(
 147                 int ifindex,
 148                 union sockaddr_union *link,
 149                 uint32_t xid,
 150                 const struct hw_addr_data *hw_addr,
 151                 const struct hw_addr_data *bcast_addr,
 152                 uint16_t arp_type,
 153                 uint16_t port,
 154                 bool so_priority_set,
 155                 int so_priority) {
 156
 157         static struct hw_addr_data default_eth_bcast = {
 158                 .length = ETH_ALEN,
 159                 .ether = {{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff }},
 160         }, default_ib_bcast = {
 161                 .length = INFINIBAND_ALEN,
 162                 .infiniband = {
 163                         0x00, 0xff, 0xff, 0xff, 0xff, 0x12, 0x40, 0x1b,
 164                         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 165                         0xff, 0xff, 0xff, 0xff
 166                 },
 167         };
 168
 169         assert(ifindex > 0);
 170         assert(link);
 171         assert(hw_addr);
 172
 173         switch (arp_type) {
 174         case ARPHRD_ETHER:
 175                 return _bind_raw_socket(ifindex, link, xid,
 176                                         hw_addr,
 177                                         (bcast_addr && !hw_addr_is_null(bcast_addr)) ? bcast_addr : &default_eth_bcast,
 178                                         arp_type, port, so_priority_set, so_priority);
 179
 180         case ARPHRD_INFINIBAND:
 181                 return _bind_raw_socket(ifindex, link, xid,
 182                                         &HW_ADDR_NULL,
 183                                         (bcast_addr && !hw_addr_is_null(bcast_addr)) ? bcast_addr : &default_ib_bcast,
 184                                         arp_type, port, so_priority_set, so_priority);
 185         default:
 186                 return -EINVAL;
 187         }
 188 }
 189
 190 int dhcp_network_bind_udp_socket(int ifindex, be32_t address, uint16_t port, int ip_service_type) {
 191         union sockaddr_union src = {
 192                 .in.sin_family = AF_INET,
 193                 .in.sin_port = htobe16(port),
 194                 .in.sin_addr.s_addr = address,
 195         };
 196         _cleanup_close_ int s = -EBADF;
 197         int r;
 198
 199         s = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
 200         if (s < 0)
 201                 return -errno;
 202
 203         if (ip_service_type >= 0)
 204                 r = setsockopt_int(s, IPPROTO_IP, IP_TOS, ip_service_type);
 205         else
 206                 r = setsockopt_int(s, IPPROTO_IP, IP_TOS, IPTOS_CLASS_CS6);
 207         if (r < 0)
 208                 return r;
 209
 210         r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 211         if (r < 0)
 212                 return r;
 213
 214         r = setsockopt_int(s, SOL_SOCKET, SO_TIMESTAMP, true);
 215         if (r < 0)
 216                 return r;
 217
 218         if (ifindex > 0) {
 219                 r = socket_bind_to_ifindex(s, ifindex);
 220                 if (r < 0)
 221                         return r;
 222         }
 223
 224         if (port == DHCP_PORT_SERVER) {
 225                 r = setsockopt_int(s, SOL_SOCKET, SO_BROADCAST, true);
 226                 if (r < 0)
 227                         return r;
 228                 if (address == INADDR_ANY) {
 229                         /* IP_PKTINFO filter should not be applied when packets are
 230                            allowed to enter/leave through the interface other than
 231                            DHCP server sits on(BindToInterface option). */
 232                         r = setsockopt_int(s, IPPROTO_IP, IP_PKTINFO, true);
 233                         if (r < 0)
 234                                 return r;
 235                 }
 236         } else {
 237                 r = setsockopt_int(s, IPPROTO_IP, IP_FREEBIND, true);
 238                 if (r < 0)
 239                         return r;
 240         }
 241
 242         if (bind(s, &src.sa, sizeof(src.in)) < 0)
 243                 return -errno;
 244
 245         return TAKE_FD(s);
 246 }
 247
 248 int dhcp_network_send_raw_socket(
 249                 int s,
 250                 const union sockaddr_union *link,
 251                 const void *packet,
 252                 size_t len) {
 253
 254         /* Do not add assert(s >= 0) here, as this is called in fuzz-dhcp-server, and in that case this
 255          * function should fail with negative errno. */
 256
 257         assert(link);
 258         assert(packet);
 259         assert(len > 0);
 260
 261         if (sendto(s, packet, len, 0, &link->sa, SOCKADDR_LL_LEN(link->ll)) < 0)
 262                 return -errno;
 263
 264         return 0;
 265 }
 266
 267 int dhcp_network_send_udp_socket(
 268                 int s,
 269                 be32_t address,
 270                 uint16_t port,
 271                 const void *packet,
 272                 size_t len) {
 273
 274         union sockaddr_union dest = {
 275                 .in.sin_family = AF_INET,
 276                 .in.sin_port = htobe16(port),
 277                 .in.sin_addr.s_addr = address,
 278         };
 279
 280         assert(s >= 0);
 281         assert(packet);
 282         assert(len > 0);
 283
 284         if (sendto(s, packet, len, 0, &dest.sa, sizeof(dest.in)) < 0)
 285                 return -errno;
 286
 287         return 0;
 288 }