src/libsystemd-network/ipv4ll-network.c

   1 /***
   2   This file is part of systemd.
   3
   4   Copyright (C) 2014 Axis Communications AB. 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 <linux/filter.h>
  21
  22 #include "util.h"
  23 #include "ipv4ll-internal.h"
  24
  25 int arp_network_send_raw_socket(int fd, const union sockaddr_union *link,
  26                                         const struct ether_arp *arp) {
  27         int r;
  28
  29         assert(arp);
  30         assert(link);
  31         assert(fd >= 0);
  32
  33         r = sendto(fd, arp, sizeof(struct ether_arp), 0, &link->sa, sizeof(link->ll));
  34         if (r < 0)
  35                 return -errno;
  36
  37         return 0;
  38 }
  39
  40 int arp_network_bind_raw_socket(int index, union sockaddr_union *link) {
  41         struct sock_filter filter[] = {
  42             BPF_STMT(BPF_LD + BPF_W + BPF_LEN, 0),                                         /* A <- packet length */
  43             BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, sizeof(struct ether_arp), 1, 0),           /* packet >= arp packet ? */
  44             BPF_STMT(BPF_RET + BPF_K, 0),                                                  /* ignore */
  45             BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_hrd)), /* A <- header */
  46             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPHRD_ETHER, 1, 0),                       /* header == ethernet ? */
  47             BPF_STMT(BPF_RET + BPF_K, 0),                                                  /* ignore */
  48             BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_pro)), /* A <- protocol */
  49             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 1, 0),                       /* protocol == IP ? */
  50             BPF_STMT(BPF_RET + BPF_K, 0),                                                  /* ignore */
  51             BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_op)),  /* A <- operation */
  52             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPOP_REQUEST, 0, 1),                      /* protocol == request ? */
  53             BPF_STMT(BPF_RET + BPF_K, 65535),                                              /* return all */
  54             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPOP_REPLY, 0, 1),                        /* protocol == reply ? */
  55             BPF_STMT(BPF_RET + BPF_K, 65535),                                              /* return all */
  56             BPF_STMT(BPF_RET + BPF_K, 0),                                                  /* ignore */
  57         };
  58         struct sock_fprog fprog = {
  59             .len = ELEMENTSOF(filter),
  60             .filter = filter
  61         };
  62         _cleanup_close_ int s = -1;
  63         int r;
  64
  65         assert(index > 0);
  66         assert(link);
  67
  68         s = socket(PF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
  69         if (s < 0)
  70                 return -errno;
  71
  72         r = setsockopt(s, SOL_SOCKET, SO_ATTACH_FILTER, &fprog, sizeof(fprog));
  73         if (r < 0)
  74                 return -errno;
  75
  76         link->ll.sll_family = AF_PACKET;
  77         link->ll.sll_protocol = htons(ETH_P_ARP);
  78         link->ll.sll_ifindex = index;
  79         link->ll.sll_halen = ETH_ALEN;
  80         memset(link->ll.sll_addr, 0xff, ETH_ALEN);
  81
  82         r = bind(s, &link->sa, sizeof(link->ll));
  83         if (r < 0)
  84                 return -errno;
  85
  86         r = s;
  87         s = -1;
  88
  89         return r;
  90 }