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 #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 <linux/filter.h>
  13 #include <linux/if_infiniband.h>
  14 #include <linux/if_packet.h>
  15
  16 #include "dhcp-internal.h"
  17 #include "fd-util.h"
  18 #include "socket-util.h"
  19 #include "unaligned.h"
  20
  21 static int _bind_raw_socket(int ifindex, union sockaddr_union *link,
  22                             uint32_t xid,
  23                             const uint8_t *bcast_addr,
  24                             size_t bcast_addr_len,
  25                             const struct ether_addr *eth_mac,
  26                             uint16_t arp_type, uint8_t dhcp_hlen,
  27                             uint16_t port) {
  28         struct sock_filter filter[] = {
  29                 BPF_STMT(BPF_LD + BPF_W + BPF_LEN, 0),                                 /* A <- packet length */
  30                 BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, sizeof(DHCPPacket), 1, 0),         /* packet >= DHCPPacket ? */
  31                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  32                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, ip.protocol)), /* A <- IP protocol */
  33                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 1, 0),                /* IP protocol == UDP ? */
  34                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  35                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, ip.frag_off)), /* A <- Flags */
  36                 BPF_STMT(BPF_ALU + BPF_AND + BPF_K, 0x20),                             /* A <- A & 0x20 (More Fragments bit) */
  37                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                          /* A == 0 ? */
  38                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  39                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, ip.frag_off)), /* A <- Flags + Fragment offset */
  40                 BPF_STMT(BPF_ALU + BPF_AND + BPF_K, 0x1fff),                           /* A <- A & 0x1fff (Fragment offset) */
  41                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                          /* A == 0 ? */
  42                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  43                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, udp.dest)),    /* A <- UDP destination port */
  44                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, port, 1, 0),                       /* UDP destination port == DHCP client port ? */
  45                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  46                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.op)),     /* A <- DHCP op */
  47                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, BOOTREPLY, 1, 0),                  /* op == BOOTREPLY ? */
  48                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  49                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.htype)),  /* A <- DHCP header type */
  50                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, arp_type, 1, 0),                   /* header type == arp_type ? */
  51                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  52                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.xid)),    /* A <- client identifier */
  53                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, xid, 1, 0),                        /* client identifier == xid ? */
  54                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  55                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.hlen)),   /* A <- MAC address length */
  56                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, dhcp_hlen, 1, 0),                  /* address length == dhcp_hlen ? */
  57                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  58
  59                 /* We only support MAC address length to be either 0 or 6 (ETH_ALEN). Optionally
  60                  * compare chaddr for ETH_ALEN bytes. */
  61                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETH_ALEN, 0, 12),                                  /* A (the MAC address length) == ETH_ALEN ? */
  62                 BPF_STMT(BPF_LD + BPF_IMM, unaligned_read_be32(&eth_mac->ether_addr_octet[0])),        /* A <- 4 bytes of client's MAC */
  63                 BPF_STMT(BPF_MISC + BPF_TAX, 0),                                                       /* X <- A */
  64                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr)),                 /* A <- 4 bytes of MAC from dhcp.chaddr */
  65                 BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0),                                                /* A xor X */
  66                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                                          /* A == 0 ? */
  67                 BPF_STMT(BPF_RET + BPF_K, 0),                                                          /* ignore */
  68                 BPF_STMT(BPF_LD + BPF_IMM, unaligned_read_be16(&eth_mac->ether_addr_octet[4])),        /* A <- remainder of client's MAC */
  69                 BPF_STMT(BPF_MISC + BPF_TAX, 0),                                                       /* X <- A */
  70                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr) + 4),             /* A <- remainder of MAC from dhcp.chaddr */
  71                 BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0),                                                /* A xor X */
  72                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                                          /* A == 0 ? */
  73                 BPF_STMT(BPF_RET + BPF_K, 0),                                                          /* ignore */
  74
  75                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.magic)),  /* A <- DHCP magic cookie */
  76                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DHCP_MAGIC_COOKIE, 1, 0),          /* cookie == DHCP magic cookie ? */
  77                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  78                 BPF_STMT(BPF_RET + BPF_K, 65535),                                      /* return all */
  79         };
  80         struct sock_fprog fprog = {
  81                 .len = ELEMENTSOF(filter),
  82                 .filter = filter
  83         };
  84         _cleanup_close_ int s = -1;
  85         int r;
  86
  87         assert(ifindex > 0);
  88         assert(link);
  89
  90         s = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
  91         if (s < 0)
  92                 return -errno;
  93
  94         r = setsockopt_int(s, SOL_PACKET, PACKET_AUXDATA, true);
  95         if (r < 0)
  96                 return r;
  97
  98         r = setsockopt(s, SOL_SOCKET, SO_ATTACH_FILTER, &fprog, sizeof(fprog));
  99         if (r < 0)
 100                 return -errno;
 101
 102         link->ll = (struct sockaddr_ll) {
 103                 .sll_family = AF_PACKET,
 104                 .sll_protocol = htobe16(ETH_P_IP),
 105                 .sll_ifindex = ifindex,
 106                 .sll_hatype = htobe16(arp_type),
 107                 .sll_halen = bcast_addr_len,
 108         };
 109         memcpy(link->ll.sll_addr, bcast_addr, bcast_addr_len); /* We may overflow link->ll. link->ll_buffer ensures we have enough space. */
 110
 111         r = bind(s, &link->sa, SOCKADDR_LL_LEN(link->ll));
 112         if (r < 0)
 113                 return -errno;
 114
 115         return TAKE_FD(s);
 116 }
 117
 118 int dhcp_network_bind_raw_socket(int ifindex, union sockaddr_union *link, uint32_t xid,
 119                                  const uint8_t *mac_addr, size_t mac_addr_len,
 120                                  const uint8_t *bcast_addr, size_t bcast_addr_len,
 121                                  uint16_t arp_type, uint16_t port) {
 122         static const uint8_t eth_bcast[] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
 123         /* Default broadcast address for IPoIB */
 124         static const uint8_t ib_bcast[] = {
 125                 0x00, 0xff, 0xff, 0xff, 0xff, 0x12, 0x40, 0x1b,
 126                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 127                 0xff, 0xff, 0xff, 0xff
 128         };
 129         struct ether_addr eth_mac = { { 0, 0, 0, 0, 0, 0 } };
 130         const uint8_t *default_bcast_addr;
 131         size_t expected_bcast_addr_len;
 132         uint8_t dhcp_hlen = 0;
 133
 134         if (arp_type == ARPHRD_ETHER) {
 135                 assert_return(mac_addr_len == ETH_ALEN, -EINVAL);
 136                 memcpy(&eth_mac, mac_addr, ETH_ALEN);
 137                 dhcp_hlen = ETH_ALEN;
 138
 139                 default_bcast_addr = eth_bcast;
 140                 expected_bcast_addr_len = ETH_ALEN;
 141         } else if (arp_type == ARPHRD_INFINIBAND) {
 142                 default_bcast_addr = ib_bcast;
 143                 expected_bcast_addr_len = INFINIBAND_ALEN;
 144         } else
 145                 return -EINVAL;
 146
 147         if (bcast_addr && bcast_addr_len > 0)
 148                 assert_return(bcast_addr_len == expected_bcast_addr_len, -EINVAL);
 149         else {
 150                 bcast_addr = default_bcast_addr;
 151                 bcast_addr_len = expected_bcast_addr_len;
 152         }
 153
 154         return _bind_raw_socket(ifindex, link, xid, bcast_addr, bcast_addr_len,
 155                                 &eth_mac, arp_type, dhcp_hlen, port);
 156 }
 157
 158 int dhcp_network_bind_udp_socket(int ifindex, be32_t address, uint16_t port, int ip_service_type) {
 159         union sockaddr_union src = {
 160                 .in.sin_family = AF_INET,
 161                 .in.sin_port = htobe16(port),
 162                 .in.sin_addr.s_addr = address,
 163         };
 164         _cleanup_close_ int s = -1;
 165         int r;
 166
 167         s = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
 168         if (s < 0)
 169                 return -errno;
 170
 171         if (ip_service_type >= 0)
 172                 r = setsockopt_int(s, IPPROTO_IP, IP_TOS, ip_service_type);
 173         else
 174                 r = setsockopt_int(s, IPPROTO_IP, IP_TOS, IPTOS_CLASS_CS6);
 175
 176         if (r < 0)
 177                 return r;
 178
 179         r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 180         if (r < 0)
 181                 return r;
 182
 183         if (ifindex > 0) {
 184                 r = socket_bind_to_ifindex(s, ifindex);
 185                 if (r < 0)
 186                         return r;
 187         }
 188
 189         if (port == DHCP_PORT_SERVER) {
 190                 r = setsockopt_int(s, SOL_SOCKET, SO_BROADCAST, true);
 191                 if (r < 0)
 192                         return r;
 193                 if (address == INADDR_ANY) {
 194                         /* IP_PKTINFO filter should not be applied when packets are
 195                            allowed to enter/leave through the interface other than
 196                            DHCP server sits on(BindToInterface option). */
 197                         r = setsockopt_int(s, IPPROTO_IP, IP_PKTINFO, true);
 198                         if (r < 0)
 199                                 return r;
 200                 }
 201         } else {
 202                 r = setsockopt_int(s, IPPROTO_IP, IP_FREEBIND, true);
 203                 if (r < 0)
 204                         return r;
 205         }
 206
 207         r = bind(s, &src.sa, sizeof(src.in));
 208         if (r < 0)
 209                 return -errno;
 210
 211         return TAKE_FD(s);
 212 }
 213
 214 int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link,
 215                                  const void *packet, size_t len) {
 216         int r;
 217
 218         assert(link);
 219         assert(packet);
 220         assert(len);
 221
 222         r = sendto(s, packet, len, 0, &link->sa, SOCKADDR_LL_LEN(link->ll));
 223         if (r < 0)
 224                 return -errno;
 225
 226         return 0;
 227 }
 228
 229 int dhcp_network_send_udp_socket(int s, be32_t address, uint16_t port,
 230                                  const void *packet, size_t len) {
 231         union sockaddr_union dest = {
 232                 .in.sin_family = AF_INET,
 233                 .in.sin_port = htobe16(port),
 234                 .in.sin_addr.s_addr = address,
 235         };
 236         int r;
 237
 238         assert(s >= 0);
 239         assert(packet);
 240         assert(len);
 241
 242         r = sendto(s, packet, len, 0, &dest.sa, sizeof(dest.in));
 243         if (r < 0)
 244                 return -errno;
 245
 246         return 0;
 247 }