src/libsystemd-network/dhcp-network.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   This file is part of systemd.
   4
   5   Copyright (C) 2013 Intel Corporation. All rights reserved.
   6 ***/
   7
   8 #include <errno.h>
   9 #include <net/ethernet.h>
  10 #include <net/if.h>
  11 #include <net/if_arp.h>
  12 #include <stdio.h>
  13 #include <string.h>
  14 #include <sys/socket.h>
  15 #include <linux/filter.h>
  16 #include <linux/if_infiniband.h>
  17 #include <linux/if_packet.h>
  18
  19 #include "dhcp-internal.h"
  20 #include "fd-util.h"
  21 #include "socket-util.h"
  22 #include "unaligned.h"
  23
  24 static int _bind_raw_socket(int ifindex, union sockaddr_union *link,
  25                             uint32_t xid, const uint8_t *mac_addr,
  26                             size_t mac_addr_len,
  27                             const uint8_t *bcast_addr,
  28                             const struct ether_addr *eth_mac,
  29                             uint16_t arp_type, uint8_t dhcp_hlen,
  30                             uint16_t port) {
  31         struct sock_filter filter[] = {
  32                 BPF_STMT(BPF_LD + BPF_W + BPF_LEN, 0),                                 /* A <- packet length */
  33                 BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, sizeof(DHCPPacket), 1, 0),         /* packet >= DHCPPacket ? */
  34                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  35                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, ip.protocol)), /* A <- IP protocol */
  36                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 1, 0),                /* IP protocol == UDP ? */
  37                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  38                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, ip.frag_off)), /* A <- Flags */
  39                 BPF_STMT(BPF_ALU + BPF_AND + BPF_K, 0x20),                             /* A <- A & 0x20 (More Fragments bit) */
  40                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                          /* A == 0 ? */
  41                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  42                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, ip.frag_off)), /* A <- Flags + Fragment offset */
  43                 BPF_STMT(BPF_ALU + BPF_AND + BPF_K, 0x1fff),                           /* A <- A & 0x1fff (Fragment offset) */
  44                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                          /* A == 0 ? */
  45                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  46                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, udp.dest)),    /* A <- UDP destination port */
  47                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, port, 1, 0),                       /* UDP destination port == DHCP client port ? */
  48                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  49                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.op)),     /* A <- DHCP op */
  50                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, BOOTREPLY, 1, 0),                  /* op == BOOTREPLY ? */
  51                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  52                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.htype)),  /* A <- DHCP header type */
  53                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, arp_type, 1, 0),                   /* header type == arp_type ? */
  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                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.xid)),    /* A <- client identifier */
  59                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, xid, 1, 0),                        /* client identifier == xid ? */
  60                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  61                 BPF_STMT(BPF_LD + BPF_IMM, unaligned_read_be32(&eth_mac->ether_addr_octet[0])),        /* A <- 4 bytes of client's MAC */
  62                 BPF_STMT(BPF_MISC + BPF_TAX, 0),                                                       /* X <- A */
  63                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr)),                 /* A <- 4 bytes of MAC from dhcp.chaddr */
  64                 BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0),                                                /* A xor X */
  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_IMM, unaligned_read_be16(&eth_mac->ether_addr_octet[4])),        /* A <- remainder of client's MAC */
  68                 BPF_STMT(BPF_MISC + BPF_TAX, 0),                                                       /* X <- A */
  69                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr) + 4),             /* A <- remainder of MAC from dhcp.chaddr */
  70                 BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0),                                                /* A xor X */
  71                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                                          /* A == 0 ? */
  72                 BPF_STMT(BPF_RET + BPF_K, 0),                                                          /* ignore */
  73                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.magic)),  /* A <- DHCP magic cookie */
  74                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DHCP_MAGIC_COOKIE, 1, 0),          /* cookie == DHCP magic cookie ? */
  75                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  76                 BPF_STMT(BPF_RET + BPF_K, 65535),                                      /* return all */
  77         };
  78         struct sock_fprog fprog = {
  79                 .len = ELEMENTSOF(filter),
  80                 .filter = filter
  81         };
  82         _cleanup_close_ int s = -1;
  83         int r, on = 1;
  84
  85         assert(ifindex > 0);
  86         assert(link);
  87
  88         s = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
  89         if (s < 0)
  90                 return -errno;
  91
  92         r = setsockopt(s, SOL_PACKET, PACKET_AUXDATA, &on, sizeof(on));
  93         if (r < 0)
  94                 return -errno;
  95
  96         r = setsockopt(s, SOL_SOCKET, SO_ATTACH_FILTER, &fprog, sizeof(fprog));
  97         if (r < 0)
  98                 return -errno;
  99
 100         link->ll = (struct sockaddr_ll) {
 101                 .sll_family = AF_PACKET,
 102                 .sll_protocol = htobe16(ETH_P_IP),
 103                 .sll_ifindex = ifindex,
 104                 .sll_hatype = htobe16(arp_type),
 105                 .sll_halen = mac_addr_len,
 106         };
 107         memcpy(link->ll.sll_addr, bcast_addr, mac_addr_len);
 108
 109         r = bind(s, &link->sa, SOCKADDR_LL_LEN(link->ll));
 110         if (r < 0)
 111                 return -errno;
 112
 113         return TAKE_FD(s);
 114 }
 115
 116 int dhcp_network_bind_raw_socket(int ifindex, union sockaddr_union *link,
 117                                  uint32_t xid, const uint8_t *mac_addr,
 118                                  size_t mac_addr_len, uint16_t arp_type,
 119                                  uint16_t port) {
 120         static const uint8_t eth_bcast[] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
 121         /* Default broadcast address for IPoIB */
 122         static const uint8_t ib_bcast[] = {
 123                 0x00, 0xff, 0xff, 0xff, 0xff, 0x12, 0x40, 0x1b,
 124                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 125                 0xff, 0xff, 0xff, 0xff
 126           };
 127         struct ether_addr eth_mac = { { 0, 0, 0, 0, 0, 0 } };
 128         const uint8_t *bcast_addr = NULL;
 129         uint8_t dhcp_hlen = 0;
 130
 131         assert_return(mac_addr_len > 0, -EINVAL);
 132
 133         if (arp_type == ARPHRD_ETHER) {
 134                 assert_return(mac_addr_len == ETH_ALEN, -EINVAL);
 135                 memcpy(&eth_mac, mac_addr, ETH_ALEN);
 136                 bcast_addr = eth_bcast;
 137                 dhcp_hlen = ETH_ALEN;
 138         } else if (arp_type == ARPHRD_INFINIBAND) {
 139                 assert_return(mac_addr_len == INFINIBAND_ALEN, -EINVAL);
 140                 bcast_addr = ib_bcast;
 141         } else
 142                 return -EINVAL;
 143
 144         return _bind_raw_socket(ifindex, link, xid, mac_addr, mac_addr_len,
 145                                 bcast_addr, &eth_mac, arp_type, dhcp_hlen, port);
 146 }
 147
 148 int dhcp_network_bind_udp_socket(int ifindex, be32_t address, uint16_t port) {
 149         union sockaddr_union src = {
 150                 .in.sin_family = AF_INET,
 151                 .in.sin_port = htobe16(port),
 152                 .in.sin_addr.s_addr = address,
 153         };
 154         _cleanup_close_ int s = -1;
 155         char ifname[IF_NAMESIZE] = "";
 156         int r, on = 1, tos = IPTOS_CLASS_CS6;
 157
 158         s = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
 159         if (s < 0)
 160                 return -errno;
 161
 162         r = setsockopt(s, IPPROTO_IP, IP_TOS, &tos, sizeof(tos));
 163         if (r < 0)
 164                 return -errno;
 165
 166         r = setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
 167         if (r < 0)
 168                 return -errno;
 169
 170         if (ifindex > 0) {
 171                 if (if_indextoname(ifindex, ifname) == 0)
 172                         return -errno;
 173
 174                 r = setsockopt(s, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname));
 175                 if (r < 0)
 176                         return -errno;
 177         }
 178
 179         if (address == INADDR_ANY) {
 180                 r = setsockopt(s, IPPROTO_IP, IP_PKTINFO, &on, sizeof(on));
 181                 if (r < 0)
 182                         return -errno;
 183
 184                 r = setsockopt(s, SOL_SOCKET, SO_BROADCAST, &on, sizeof(on));
 185                 if (r < 0)
 186                         return -errno;
 187
 188         } else {
 189                 r = setsockopt(s, IPPROTO_IP, IP_FREEBIND, &on, sizeof(on));
 190                 if (r < 0)
 191                         return -errno;
 192         }
 193
 194         r = bind(s, &src.sa, sizeof(src.in));
 195         if (r < 0)
 196                 return -errno;
 197
 198         return TAKE_FD(s);
 199 }
 200
 201 int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link,
 202                                  const void *packet, size_t len) {
 203         int r;
 204
 205         assert(link);
 206         assert(packet);
 207         assert(len);
 208
 209         r = sendto(s, packet, len, 0, &link->sa, SOCKADDR_LL_LEN(link->ll));
 210         if (r < 0)
 211                 return -errno;
 212
 213         return 0;
 214 }
 215
 216 int dhcp_network_send_udp_socket(int s, be32_t address, uint16_t port,
 217                                  const void *packet, size_t len) {
 218         union sockaddr_union dest = {
 219                 .in.sin_family = AF_INET,
 220                 .in.sin_port = htobe16(port),
 221                 .in.sin_addr.s_addr = address,
 222         };
 223         int r;
 224
 225         assert(s >= 0);
 226         assert(packet);
 227         assert(len);
 228
 229         r = sendto(s, packet, len, 0, &dest.sa, sizeof(dest.in));
 230         if (r < 0)
 231                 return -errno;
 232
 233         return 0;
 234 }