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_W + BPF_ABS, offsetof(DHCPPacket, dhcp.xid)),    /* A <- client identifier */
  54                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, xid, 1, 0),                        /* client identifier == xid ? */
  55                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  56                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.hlen)),   /* A <- MAC address length */
  57                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, dhcp_hlen, 1, 0),                  /* address length == dhcp_hlen ? */
  58                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  59
  60                 /* We only support MAC address length to be either 0 or 6 (ETH_ALEN). Optionally
  61                  * compare chaddr for ETH_ALEN bytes. */
  62                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETH_ALEN, 0, 12),                                  /* A (the MAC address length) == ETH_ALEN ? */
  63                 BPF_STMT(BPF_LD + BPF_IMM, unaligned_read_be32(&eth_mac->ether_addr_octet[0])),        /* A <- 4 bytes of client's MAC */
  64                 BPF_STMT(BPF_MISC + BPF_TAX, 0),                                                       /* X <- A */
  65                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr)),                 /* A <- 4 bytes of MAC from dhcp.chaddr */
  66                 BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0),                                                /* A xor X */
  67                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                                          /* A == 0 ? */
  68                 BPF_STMT(BPF_RET + BPF_K, 0),                                                          /* ignore */
  69                 BPF_STMT(BPF_LD + BPF_IMM, unaligned_read_be16(&eth_mac->ether_addr_octet[4])),        /* A <- remainder of client's MAC */
  70                 BPF_STMT(BPF_MISC + BPF_TAX, 0),                                                       /* X <- A */
  71                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr) + 4),             /* A <- remainder of MAC from dhcp.chaddr */
  72                 BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0),                                                /* A xor X */
  73                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                                          /* A == 0 ? */
  74                 BPF_STMT(BPF_RET + BPF_K, 0),                                                          /* ignore */
  75
  76                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.magic)),  /* A <- DHCP magic cookie */
  77                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DHCP_MAGIC_COOKIE, 1, 0),          /* cookie == DHCP magic cookie ? */
  78                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  79                 BPF_STMT(BPF_RET + BPF_K, 65535),                                      /* return all */
  80         };
  81         struct sock_fprog fprog = {
  82                 .len = ELEMENTSOF(filter),
  83                 .filter = filter
  84         };
  85         _cleanup_close_ int s = -1;
  86         int r;
  87
  88         assert(ifindex > 0);
  89         assert(link);
  90
  91         s = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
  92         if (s < 0)
  93                 return -errno;
  94
  95         r = setsockopt_int(s, SOL_PACKET, PACKET_AUXDATA, true);
  96         if (r < 0)
  97                 return r;
  98
  99         r = setsockopt(s, SOL_SOCKET, SO_ATTACH_FILTER, &fprog, sizeof(fprog));
 100         if (r < 0)
 101                 return -errno;
 102
 103         link->ll = (struct sockaddr_ll) {
 104                 .sll_family = AF_PACKET,
 105                 .sll_protocol = htobe16(ETH_P_IP),
 106                 .sll_ifindex = ifindex,
 107                 .sll_hatype = htobe16(arp_type),
 108                 .sll_halen = mac_addr_len,
 109         };
 110         memcpy(link->ll.sll_addr, bcast_addr, mac_addr_len);
 111
 112         r = bind(s, &link->sa, SOCKADDR_LL_LEN(link->ll));
 113         if (r < 0)
 114                 return -errno;
 115
 116         return TAKE_FD(s);
 117 }
 118
 119 int dhcp_network_bind_raw_socket(int ifindex, union sockaddr_union *link,
 120                                  uint32_t xid, const uint8_t *mac_addr,
 121                                  size_t mac_addr_len, uint16_t arp_type,
 122                                  uint16_t port) {
 123         static const uint8_t eth_bcast[] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
 124         /* Default broadcast address for IPoIB */
 125         static const uint8_t ib_bcast[] = {
 126                 0x00, 0xff, 0xff, 0xff, 0xff, 0x12, 0x40, 0x1b,
 127                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 128                 0xff, 0xff, 0xff, 0xff
 129           };
 130         struct ether_addr eth_mac = { { 0, 0, 0, 0, 0, 0 } };
 131         const uint8_t *bcast_addr = NULL;
 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                 bcast_addr = eth_bcast;
 138                 dhcp_hlen = ETH_ALEN;
 139         } else if (arp_type == ARPHRD_INFINIBAND) {
 140                 assert_return(mac_addr_len == INFINIBAND_ALEN, -EINVAL);
 141                 bcast_addr = ib_bcast;
 142         } else
 143                 return -EINVAL;
 144
 145         return _bind_raw_socket(ifindex, link, xid, mac_addr, mac_addr_len,
 146                                 bcast_addr, &eth_mac, arp_type, dhcp_hlen, port);
 147 }
 148
 149 int dhcp_network_bind_udp_socket(int ifindex, be32_t address, uint16_t port) {
 150         union sockaddr_union src = {
 151                 .in.sin_family = AF_INET,
 152                 .in.sin_port = htobe16(port),
 153                 .in.sin_addr.s_addr = address,
 154         };
 155         _cleanup_close_ int s = -1;
 156         int r;
 157
 158         s = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
 159         if (s < 0)
 160                 return -errno;
 161
 162         r = setsockopt_int(s, IPPROTO_IP, IP_TOS, IPTOS_CLASS_CS6);
 163         if (r < 0)
 164                 return r;
 165
 166         r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 167         if (r < 0)
 168                 return r;
 169
 170         if (ifindex > 0) {
 171                 r = socket_bind_to_ifindex(s, ifindex);
 172                 if (r < 0)
 173                         return r;
 174         }
 175
 176         if (address == INADDR_ANY) {
 177                 r = setsockopt_int(s, IPPROTO_IP, IP_PKTINFO, true);
 178                 if (r < 0)
 179                         return r;
 180
 181                 r = setsockopt_int(s, SOL_SOCKET, SO_BROADCAST, true);
 182                 if (r < 0)
 183                         return r;
 184
 185         } else {
 186                 r = setsockopt_int(s, IPPROTO_IP, IP_FREEBIND, true);
 187                 if (r < 0)
 188                         return r;
 189         }
 190
 191         r = bind(s, &src.sa, sizeof(src.in));
 192         if (r < 0)
 193                 return -errno;
 194
 195         return TAKE_FD(s);
 196 }
 197
 198 int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link,
 199                                  const void *packet, size_t len) {
 200         int r;
 201
 202         assert(link);
 203         assert(packet);
 204         assert(len);
 205
 206         r = sendto(s, packet, len, 0, &link->sa, SOCKADDR_LL_LEN(link->ll));
 207         if (r < 0)
 208                 return -errno;
 209
 210         return 0;
 211 }
 212
 213 int dhcp_network_send_udp_socket(int s, be32_t address, uint16_t port,
 214                                  const void *packet, size_t len) {
 215         union sockaddr_union dest = {
 216                 .in.sin_family = AF_INET,
 217                 .in.sin_port = htobe16(port),
 218                 .in.sin_addr.s_addr = address,
 219         };
 220         int r;
 221
 222         assert(s >= 0);
 223         assert(packet);
 224         assert(len);
 225
 226         r = sendto(s, packet, len, 0, &dest.sa, sizeof(dest.in));
 227         if (r < 0)
 228                 return -errno;
 229
 230         return 0;
 231 }