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, 8),                                   /* A (the MAC address length) == ETH_ALEN ? */
  62                 BPF_STMT(BPF_LDX + BPF_IMM, unaligned_read_be32(&eth_mac->ether_addr_octet[0])),       /* X <- 4 bytes of client's MAC */
  63                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr)),                 /* A <- 4 bytes of MAC from dhcp.chaddr */
  64                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_X, 0, 1, 0),                                          /* A == X ? */
  65                 BPF_STMT(BPF_RET + BPF_K, 0),                                                          /* ignore */
  66                 BPF_STMT(BPF_LDX + BPF_IMM, unaligned_read_be16(&eth_mac->ether_addr_octet[4])),       /* X <- remainder of client's MAC */
  67                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr) + 4),             /* A <- remainder of MAC from dhcp.chaddr */
  68                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_X, 0, 1, 0),                                          /* A == X ? */
  69                 BPF_STMT(BPF_RET + BPF_K, 0),                                                          /* ignore */
  70
  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, UINT32_MAX),                                 /* accept */
  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 = bcast_addr_len,
 104         };
 105         memcpy(link->ll.sll_addr, bcast_addr, bcast_addr_len); /* We may overflow link->ll. link->ll_buffer ensures we have enough space. */
 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(
 115                 int ifindex,
 116                 union sockaddr_union *link,
 117                 uint32_t xid,
 118                 const uint8_t *mac_addr,
 119                 size_t mac_addr_len,
 120                 const uint8_t *bcast_addr,
 121                 size_t bcast_addr_len,
 122                 uint16_t arp_type,
 123                 uint16_t port) {
 124
 125         static const uint8_t eth_bcast[] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
 126         /* Default broadcast address for IPoIB */
 127         static const uint8_t ib_bcast[] = {
 128                 0x00, 0xff, 0xff, 0xff, 0xff, 0x12, 0x40, 0x1b,
 129                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 130                 0xff, 0xff, 0xff, 0xff
 131         };
 132         struct ether_addr eth_mac = { { 0, 0, 0, 0, 0, 0 } };
 133         const uint8_t *default_bcast_addr;
 134         size_t expected_bcast_addr_len;
 135         uint8_t dhcp_hlen = 0;
 136
 137         if (arp_type == ARPHRD_ETHER) {
 138                 assert_return(mac_addr_len == ETH_ALEN, -EINVAL);
 139                 memcpy(&eth_mac, mac_addr, ETH_ALEN);
 140                 dhcp_hlen = ETH_ALEN;
 141
 142                 default_bcast_addr = eth_bcast;
 143                 expected_bcast_addr_len = ETH_ALEN;
 144         } else if (arp_type == ARPHRD_INFINIBAND) {
 145                 default_bcast_addr = ib_bcast;
 146                 expected_bcast_addr_len = INFINIBAND_ALEN;
 147         } else
 148                 return -EINVAL;
 149
 150         if (bcast_addr && bcast_addr_len > 0)
 151                 assert_return(bcast_addr_len == expected_bcast_addr_len, -EINVAL);
 152         else {
 153                 bcast_addr = default_bcast_addr;
 154                 bcast_addr_len = expected_bcast_addr_len;
 155         }
 156
 157         return _bind_raw_socket(ifindex, link, xid, bcast_addr, bcast_addr_len,
 158                                 &eth_mac, arp_type, dhcp_hlen, port);
 159 }
 160
 161 int dhcp_network_bind_udp_socket(int ifindex, be32_t address, uint16_t port, int ip_service_type) {
 162         union sockaddr_union src = {
 163                 .in.sin_family = AF_INET,
 164                 .in.sin_port = htobe16(port),
 165                 .in.sin_addr.s_addr = address,
 166         };
 167         _cleanup_close_ int s = -1;
 168         int r;
 169
 170         s = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
 171         if (s < 0)
 172                 return -errno;
 173
 174         if (ip_service_type >= 0)
 175                 r = setsockopt_int(s, IPPROTO_IP, IP_TOS, ip_service_type);
 176         else
 177                 r = setsockopt_int(s, IPPROTO_IP, IP_TOS, IPTOS_CLASS_CS6);
 178         if (r < 0)
 179                 return r;
 180
 181         r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
 182         if (r < 0)
 183                 return r;
 184
 185         if (ifindex > 0) {
 186                 r = socket_bind_to_ifindex(s, ifindex);
 187                 if (r < 0)
 188                         return r;
 189         }
 190
 191         if (port == DHCP_PORT_SERVER) {
 192                 r = setsockopt_int(s, SOL_SOCKET, SO_BROADCAST, true);
 193                 if (r < 0)
 194                         return r;
 195                 if (address == INADDR_ANY) {
 196                         /* IP_PKTINFO filter should not be applied when packets are
 197                            allowed to enter/leave through the interface other than
 198                            DHCP server sits on(BindToInterface option). */
 199                         r = setsockopt_int(s, IPPROTO_IP, IP_PKTINFO, true);
 200                         if (r < 0)
 201                                 return r;
 202                 }
 203         } else {
 204                 r = setsockopt_int(s, IPPROTO_IP, IP_FREEBIND, true);
 205                 if (r < 0)
 206                         return r;
 207         }
 208
 209         if (bind(s, &src.sa, sizeof(src.in)) < 0)
 210                 return -errno;
 211
 212         return TAKE_FD(s);
 213 }
 214
 215 int dhcp_network_send_raw_socket(
 216                 int s,
 217                 const union sockaddr_union *link,
 218                 const void *packet,
 219                 size_t len) {
 220
 221         /* Do not add assert(s >= 0) here, as this is called in fuzz-dhcp-server, and in that case this
 222          * function should fail with negative errno. */
 223
 224         assert(link);
 225         assert(packet);
 226         assert(len > 0);
 227
 228         if (sendto(s, packet, len, 0, &link->sa, SOCKADDR_LL_LEN(link->ll)) < 0)
 229                 return -errno;
 230
 231         return 0;
 232 }
 233
 234 int dhcp_network_send_udp_socket(
 235                 int s,
 236                 be32_t address,
 237                 uint16_t port,
 238                 const void *packet,
 239                 size_t len) {
 240
 241         union sockaddr_union dest = {
 242                 .in.sin_family = AF_INET,
 243                 .in.sin_port = htobe16(port),
 244                 .in.sin_addr.s_addr = address,
 245         };
 246
 247         assert(s >= 0);
 248         assert(packet);
 249         assert(len > 0);
 250
 251         if (sendto(s, packet, len, 0, &dest.sa, sizeof(dest.in)) < 0)
 252                 return -errno;
 253
 254         return 0;
 255 }