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_B + BPF_ABS, offsetof(DHCPPacket, ip.frag_off)), /* A <- Flags */
  45             BPF_STMT(BPF_ALU + BPF_AND + BPF_K, 0x20),                             /* A <- A & 0x20 (More Fragments bit) */
  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, ip.frag_off)), /* A <- Flags + Fragment offset */
  49             BPF_STMT(BPF_ALU + BPF_AND + BPF_K, 0x1fff),                           /* A <- A & 0x1fff (Fragment offset) */
  50             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                          /* A == 0 ? */
  51             BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  52             BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, udp.dest)),    /* A <- UDP destination port */
  53             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DHCP_PORT_CLIENT, 1, 0),           /* UDP destination port == DHCP client port ? */
  54             BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  55             BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.op)),     /* A <- DHCP op */
  56             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, BOOTREPLY, 1, 0),                  /* op == BOOTREPLY ? */
  57             BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  58             BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.htype)),  /* A <- DHCP header type */
  59             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPHRD_ETHER, 1, 0),               /* header type == ARPHRD_ETHER ? */
  60             BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  61             BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.hlen)),   /* A <- mac address length */
  62             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHER_ADDR_LEN, 1, 0),             /* address length == ETHER_ADDR_LEN ? */
  63             BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  64             BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.xid)),    /* A <- client identifier */
  65             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, xid, 1, 0),                        /* client identifier == xid ? */
  66             BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  67             BPF_STMT(BPF_LD + BPF_IMM, htobe32(*((unsigned int *) &mac_addr))),                    /* A <- 4 bytes of client's MAC */
  68             BPF_STMT(BPF_MISC + BPF_TAX, 0),                                                       /* X <- A */
  69             BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr)),                 /* A <- 4 bytes 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_IMM, htobe16(*((unsigned short *) (((char *) &mac_addr) + 4)))), /* A <- remainder of client's MAC */
  74             BPF_STMT(BPF_MISC + BPF_TAX, 0),                                                       /* X <- A */
  75             BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr) + 4),             /* A <- remainder of MAC from dhcp.chaddr */
  76             BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0),                                                /* A xor X */
  77             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                                          /* A == 0 ? */
  78             BPF_STMT(BPF_RET + BPF_K, 0),                                                          /* ignore */
  79             BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.magic)),  /* A <- DHCP magic cookie */
  80             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DHCP_MAGIC_COOKIE, 1, 0),          /* cookie == DHCP magic cookie ? */
  81             BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
  82             BPF_STMT(BPF_RET + BPF_K, 65535),                                      /* return all */
  83         };
  84         struct sock_fprog fprog = {
  85             .len = ELEMENTSOF(filter),
  86             .filter = filter
  87         };
  88         _cleanup_close_ int s = -1;
  89         int r, on = 1;
  90
  91         assert(index > 0);
  92         assert(link);
  93
  94         s = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
  95         if (s < 0)
  96                 return -errno;
  97
  98         r = setsockopt (s, SOL_PACKET, PACKET_AUXDATA, &on, sizeof(on));
  99         if (r < 0)
 100                 return -errno;
 101
 102         r = setsockopt(s, SOL_SOCKET, SO_ATTACH_FILTER, &fprog, sizeof(fprog));
 103         if (r < 0)
 104                 return -errno;
 105
 106         link->ll.sll_family = AF_PACKET;
 107         link->ll.sll_protocol = htons(ETH_P_IP);
 108         link->ll.sll_ifindex =  index;
 109         link->ll.sll_halen = ETH_ALEN;
 110         memset(link->ll.sll_addr, 0xff, ETH_ALEN);
 111
 112         r = bind(s, &link->sa, sizeof(link->ll));
 113         if (r < 0)
 114                 return -errno;
 115
 116         r = s;
 117         s = -1;
 118
 119         return r;
 120 }
 121
 122 int dhcp_network_bind_udp_socket(be32_t address, uint16_t port) {
 123         union sockaddr_union src = {
 124                 .in.sin_family = AF_INET,
 125                 .in.sin_port = htobe16(port),
 126                 .in.sin_addr.s_addr = address,
 127         };
 128         _cleanup_close_ int s = -1;
 129         int r, tos = IPTOS_CLASS_CS6;
 130
 131         s = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
 132         if (s < 0)
 133                 return -errno;
 134
 135         r = setsockopt(s, IPPROTO_IP, IP_TOS, &tos, sizeof(tos));
 136         if (r < 0)
 137                 return -errno;
 138
 139         if (address == INADDR_ANY) {
 140                 int on = 1;
 141
 142                 r = setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
 143                 if (r < 0)
 144                         return -errno;
 145
 146                 r = setsockopt(s, IPPROTO_IP, IP_PKTINFO, &on, sizeof(on));
 147                 if (r < 0)
 148                         return -errno;
 149
 150                 r = setsockopt(s, SOL_SOCKET, SO_BROADCAST, &on, sizeof(on));
 151                 if (r < 0)
 152                         return -errno;
 153         }
 154
 155         r = bind(s, &src.sa, sizeof(src.in));
 156         if (r < 0)
 157                 return -errno;
 158
 159         r = s;
 160         s = -1;
 161
 162         return r;
 163 }
 164
 165 int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link,
 166                                  const void *packet, size_t len) {
 167         int r;
 168
 169         assert(link);
 170         assert(packet);
 171         assert(len);
 172
 173         r = sendto(s, packet, len, 0, &link->sa, sizeof(link->ll));
 174         if (r < 0)
 175                 return -errno;
 176
 177         return 0;
 178 }
 179
 180 int dhcp_network_send_udp_socket(int s, be32_t address, uint16_t port,
 181                                  const void *packet, size_t len) {
 182         union sockaddr_union dest = {
 183                 .in.sin_family = AF_INET,
 184                 .in.sin_port = htobe16(port),
 185                 .in.sin_addr.s_addr = address,
 186         };
 187         int r;
 188
 189         assert(s >= 0);
 190         assert(packet);
 191         assert(len);
 192
 193         r = sendto(s, packet, len, 0, &dest.sa, sizeof(dest.in));
 194         if (r < 0)
 195                 return -errno;
 196
 197         return 0;
 198 }