src/libsystemd-network/dhcp-network.c

   1 /***
   2   This file is part of systemd.
   3
   4   Copyright (C) 2013 Intel Corporation. All rights reserved.
   5
   6   systemd is free software; you can redistribute it and/or modify it
   7   under the terms of the GNU Lesser General Public License as published by
   8   the Free Software Foundation; either version 2.1 of the License, or
   9   (at your option) any later version.
  10
  11   systemd is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   Lesser General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public License
  17   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  18 ***/
  19
  20 #include <errno.h>
  21 #include <sys/types.h>
  22 #include <sys/socket.h>
  23 #include <string.h>
  24 #include <linux/if_packet.h>
  25 #include <net/ethernet.h>
  26 #include <net/if_arp.h>
  27 #include <stdio.h>
  28 #include <unistd.h>
  29 #include <linux/filter.h>
  30
  31 #include "socket-util.h"
  32
  33 #include "dhcp-internal.h"
  34
  35 int dhcp_network_bind_raw_socket(int ifindex, union sockaddr_union *link,
  36                                  uint32_t xid, struct ether_addr mac_addr) {
  37
  38         struct sock_filter filter[] = {
  39                 BPF_STMT(BPF_LD + BPF_W + BPF_LEN, 0),                                 /* A <- packet length */
  40                 BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, sizeof(DHCPPacket), 1, 0),         /* packet >= DHCPPacket ? */
  41                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  42                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, ip.protocol)), /* A <- IP protocol */
  43                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 1, 0),                /* IP protocol == UDP ? */
  44                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  45                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, ip.frag_off)), /* A <- Flags */
  46                 BPF_STMT(BPF_ALU + BPF_AND + BPF_K, 0x20),                             /* A <- A & 0x20 (More Fragments bit) */
  47                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                          /* A == 0 ? */
  48                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  49                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, ip.frag_off)), /* A <- Flags + Fragment offset */
  50                 BPF_STMT(BPF_ALU + BPF_AND + BPF_K, 0x1fff),                           /* A <- A & 0x1fff (Fragment offset) */
  51                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                          /* A == 0 ? */
  52                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  53                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, udp.dest)),    /* A <- UDP destination port */
  54                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DHCP_PORT_CLIENT, 1, 0),           /* UDP destination port == DHCP client port ? */
  55                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  56                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.op)),     /* A <- DHCP op */
  57                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, BOOTREPLY, 1, 0),                  /* op == BOOTREPLY ? */
  58                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  59                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.htype)),  /* A <- DHCP header type */
  60                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPHRD_ETHER, 1, 0),               /* header type == ARPHRD_ETHER ? */
  61                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  62                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.hlen)),   /* A <- mac address length */
  63                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHER_ADDR_LEN, 1, 0),             /* address length == ETHER_ADDR_LEN ? */
  64                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  65                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.xid)),    /* A <- client identifier */
  66                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, xid, 1, 0),                        /* client identifier == xid ? */
  67                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  68                 BPF_STMT(BPF_LD + BPF_IMM, htobe32(*((unsigned int *) &mac_addr))),                    /* A <- 4 bytes of client's MAC */
  69                 BPF_STMT(BPF_MISC + BPF_TAX, 0),                                                       /* X <- A */
  70                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr)),                 /* A <- 4 bytes 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                 BPF_STMT(BPF_LD + BPF_IMM, htobe16(*((unsigned short *) (((char *) &mac_addr) + 4)))), /* A <- remainder of client's MAC */
  75                 BPF_STMT(BPF_MISC + BPF_TAX, 0),                                                       /* X <- A */
  76                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr) + 4),             /* A <- remainder of MAC from dhcp.chaddr */
  77                 BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0),                                                /* A xor X */
  78                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                                          /* A == 0 ? */
  79                 BPF_STMT(BPF_RET + BPF_K, 0),                                                          /* ignore */
  80                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.magic)),  /* A <- DHCP magic cookie */
  81                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DHCP_MAGIC_COOKIE, 1, 0),          /* cookie == DHCP magic cookie ? */
  82                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  83                 BPF_STMT(BPF_RET + BPF_K, 65535),                                      /* return all */
  84         };
  85         struct sock_fprog fprog = {
  86                 .len = ELEMENTSOF(filter),
  87                 .filter = filter
  88         };
  89         _cleanup_close_ int s = -1;
  90         int r, on = 1;
  91
  92         assert(ifindex > 0);
  93         assert(link);
  94
  95         s = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
  96         if (s < 0)
  97                 return -errno;
  98
  99         r = setsockopt(s, SOL_PACKET, PACKET_AUXDATA, &on, sizeof(on));
 100         if (r < 0)
 101                 return -errno;
 102
 103         r = setsockopt(s, SOL_SOCKET, SO_ATTACH_FILTER, &fprog, sizeof(fprog));
 104         if (r < 0)
 105                 return -errno;
 106
 107         link->ll.sll_family = AF_PACKET;
 108         link->ll.sll_protocol = htons(ETH_P_IP);
 109         link->ll.sll_ifindex = ifindex;
 110         link->ll.sll_halen = ETH_ALEN;
 111         memset(link->ll.sll_addr, 0xff, ETH_ALEN);
 112
 113         r = bind(s, &link->sa, sizeof(link->ll));
 114         if (r < 0)
 115                 return -errno;
 116
 117         r = s;
 118         s = -1;
 119
 120         return r;
 121 }
 122
 123 int dhcp_network_bind_udp_socket(be32_t address, uint16_t port) {
 124         union sockaddr_union src = {
 125                 .in.sin_family = AF_INET,
 126                 .in.sin_port = htobe16(port),
 127                 .in.sin_addr.s_addr = address,
 128         };
 129         _cleanup_close_ int s = -1;
 130         int r, on = 1, tos = IPTOS_CLASS_CS6;
 131
 132         s = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
 133         if (s < 0)
 134                 return -errno;
 135
 136         r = setsockopt(s, IPPROTO_IP, IP_TOS, &tos, sizeof(tos));
 137         if (r < 0)
 138                 return -errno;
 139
 140         r = setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
 141         if (r < 0)
 142                 return -errno;
 143
 144         if (address == INADDR_ANY) {
 145                 r = setsockopt(s, IPPROTO_IP, IP_PKTINFO, &on, sizeof(on));
 146                 if (r < 0)
 147                         return -errno;
 148
 149                 r = setsockopt(s, SOL_SOCKET, SO_BROADCAST, &on, sizeof(on));
 150                 if (r < 0)
 151                         return -errno;
 152         } else {
 153                 r = setsockopt(s, IPPROTO_IP, IP_FREEBIND, &on, sizeof(on));
 154                 if (r < 0)
 155                         return -errno;
 156         }
 157
 158         r = bind(s, &src.sa, sizeof(src.in));
 159         if (r < 0)
 160                 return -errno;
 161
 162         r = s;
 163         s = -1;
 164
 165         return r;
 166 }
 167
 168 int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link,
 169                                  const void *packet, size_t len) {
 170         int r;
 171
 172         assert(link);
 173         assert(packet);
 174         assert(len);
 175
 176         r = sendto(s, packet, len, 0, &link->sa, sizeof(link->ll));
 177         if (r < 0)
 178                 return -errno;
 179
 180         return 0;
 181 }
 182
 183 int dhcp_network_send_udp_socket(int s, be32_t address, uint16_t port,
 184                                  const void *packet, size_t len) {
 185         union sockaddr_union dest = {
 186                 .in.sin_family = AF_INET,
 187                 .in.sin_port = htobe16(port),
 188                 .in.sin_addr.s_addr = address,
 189         };
 190         int r;
 191
 192         assert(s >= 0);
 193         assert(packet);
 194         assert(len);
 195
 196         r = sendto(s, packet, len, 0, &dest.sa, sizeof(dest.in));
 197         if (r < 0)
 198                 return -errno;
 199
 200         return 0;
 201 }