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 index, union sockaddr_union *link,
  36                                  uint32_t xid, struct ether_addr mac_addr) {
  37         struct sock_filter filter[] = {
  38             BPF_STMT(BPF_LD + BPF_W + BPF_LEN, 0),                                 /* A <- packet length */
  39             BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, sizeof(DHCPPacket), 1, 0),         /* packet >= DHCPPacket ? */
  40             BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  41             BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, ip.protocol)), /* A <- IP protocol */
  42             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 1, 0),                /* IP protocol == UDP ? */
  43             BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  44             BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, ip.frag_off)), /* A <- Flags + Fragment offset */
  45             BPF_STMT(BPF_ALU + BPF_AND + BPF_K, 0x1fff),                           /* A <- A & 0x1fff */
  46             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                          /* A == 0 ? */
  47             BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  48             BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, udp.dest)),    /* A <- UDP destination port */
  49             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DHCP_PORT_CLIENT, 1, 0),           /* UDP destination port == DHCP client port ? */
  50             BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  51             BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.op)),     /* A <- DHCP op */
  52             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, BOOTREPLY, 1, 0),                  /* op == BOOTREPLY ? */
  53             BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  54             BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.htype)),  /* A <- DHCP header type */
  55             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPHRD_ETHER, 1, 0),               /* header type == ARPHRD_ETHER ? */
  56             BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  57             BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.hlen)),   /* A <- mac address length */
  58             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHER_ADDR_LEN, 1, 0),             /* address length == ETHER_ADDR_LEN ? */
  59             BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  60             BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.xid)),    /* A <- client identifier */
  61             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, xid, 1, 0),                        /* client identifier == xid ? */
  62             BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  63             BPF_STMT(BPF_LD + BPF_IMM, htobe32(*((unsigned int *) &mac_addr))),                    /* 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, htobe16(*((unsigned short *) (((char *) &mac_addr) + 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             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, on = 1;
  86
  87         assert(index > 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 (s, SOL_PACKET, PACKET_AUXDATA, &on, sizeof(on));
  95         if (r < 0)
  96                 return -errno;
  97
  98         r = setsockopt(s, SOL_SOCKET, SO_ATTACH_FILTER, &fprog, sizeof(fprog));
  99         if (r < 0)
 100                 return -errno;
 101
 102         link->ll.sll_family = AF_PACKET;
 103         link->ll.sll_protocol = htons(ETH_P_IP);
 104         link->ll.sll_ifindex =  index;
 105         link->ll.sll_halen = ETH_ALEN;
 106         memset(link->ll.sll_addr, 0xff, ETH_ALEN);
 107
 108         r = bind(s, &link->sa, sizeof(link->ll));
 109         if (r < 0)
 110                 return -errno;
 111
 112         r = s;
 113         s = -1;
 114
 115         return r;
 116 }
 117
 118 int dhcp_network_bind_udp_socket(be32_t address, uint16_t port) {
 119         union sockaddr_union src = {
 120                 .in.sin_family = AF_INET,
 121                 .in.sin_port = htobe16(port),
 122                 .in.sin_addr.s_addr = address,
 123         };
 124         _cleanup_close_ int s = -1;
 125         int r, tos = IPTOS_CLASS_CS6;
 126
 127         s = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
 128         if (s < 0)
 129                 return -errno;
 130
 131         r = setsockopt(s, IPPROTO_IP, IP_TOS, &tos, sizeof(tos));
 132         if (r < 0)
 133                 return -errno;
 134
 135         if (address == INADDR_ANY) {
 136                 int on = 1;
 137
 138                 r = setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
 139                 if (r < 0)
 140                         return -errno;
 141
 142                 r = setsockopt(s, IPPROTO_IP, IP_PKTINFO, &on, sizeof(on));
 143                 if (r < 0)
 144                         return -errno;
 145
 146                 r = setsockopt(s, SOL_SOCKET, SO_BROADCAST, &on, sizeof(on));
 147                 if (r < 0)
 148                         return -errno;
 149         }
 150
 151         r = bind(s, &src.sa, sizeof(src.in));
 152         if (r < 0)
 153                 return -errno;
 154
 155         r = s;
 156         s = -1;
 157
 158         return r;
 159 }
 160
 161 int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link,
 162                                  const void *packet, size_t len) {
 163         int r;
 164
 165         assert(link);
 166         assert(packet);
 167         assert(len);
 168
 169         r = sendto(s, packet, len, 0, &link->sa, sizeof(link->ll));
 170         if (r < 0)
 171                 return -errno;
 172
 173         return 0;
 174 }
 175
 176 int dhcp_network_send_udp_socket(int s, be32_t address, uint16_t port,
 177                                  const void *packet, size_t len) {
 178         union sockaddr_union dest = {
 179                 .in.sin_family = AF_INET,
 180                 .in.sin_port = htobe16(port),
 181                 .in.sin_addr.s_addr = address,
 182         };
 183         int r;
 184
 185         assert(s >= 0);
 186         assert(packet);
 187         assert(len);
 188
 189         r = sendto(s, packet, len, 0, &dest.sa, sizeof(dest.in));
 190         if (r < 0)
 191                 return -errno;
 192
 193         return 0;
 194 }