src/libsystemd-network/lldp-network.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <linux/filter.h>
   4 #include <netinet/if_ether.h>
   5
   6 #include "fd-util.h"
   7 #include "lldp-network.h"
   8 #include "missing_network.h"
   9 #include "socket-util.h"
  10
  11 int lldp_network_bind_raw_socket(int ifindex) {
  12
  13         static const struct sock_filter filter[] = {
  14                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct ethhdr, h_dest)),      /* A <- 4 bytes of destination MAC */
  15                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x0180c200, 1, 0),                    /* A != 01:80:c2:00 */
  16                 BPF_STMT(BPF_RET + BPF_K, 0),                                             /* drop packet */
  17                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ethhdr, h_dest) + 4),  /* A <- remaining 2 bytes of destination MAC */
  18                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x0000, 3, 0),                        /* A != 00:00 */
  19                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x0003, 2, 0),                        /* A != 00:03 */
  20                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x000e, 1, 0),                        /* A != 00:0e */
  21                 BPF_STMT(BPF_RET + BPF_K, 0),                                             /* drop packet */
  22                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ethhdr, h_proto)),     /* A <- protocol */
  23                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_LLDP, 1, 0),                /* A != ETHERTYPE_LLDP */
  24                 BPF_STMT(BPF_RET + BPF_K, 0),                                             /* drop packet */
  25                 BPF_STMT(BPF_RET + BPF_K, (uint32_t) -1),                                 /* accept packet */
  26         };
  27
  28         static const struct sock_fprog fprog = {
  29                 .len = ELEMENTSOF(filter),
  30                 .filter = (struct sock_filter*) filter,
  31         };
  32
  33         struct packet_mreq mreq = {
  34                 .mr_ifindex = ifindex,
  35                 .mr_type = PACKET_MR_MULTICAST,
  36                 .mr_alen = ETH_ALEN,
  37                 .mr_address = { 0x01, 0x80, 0xC2, 0x00, 0x00, 0x00 }
  38         };
  39
  40         union sockaddr_union saddrll = {
  41                 .ll.sll_family = AF_PACKET,
  42                 .ll.sll_ifindex = ifindex,
  43         };
  44
  45         _cleanup_close_ int fd = -1;
  46         int r;
  47
  48         assert(ifindex > 0);
  49
  50         fd = socket(AF_PACKET, SOCK_RAW|SOCK_CLOEXEC|SOCK_NONBLOCK,
  51                     htobe16(ETHERTYPE_LLDP));
  52         if (fd < 0)
  53                 return -errno;
  54
  55         r = setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &fprog, sizeof(fprog));
  56         if (r < 0)
  57                 return -errno;
  58
  59         r = setsockopt(fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
  60         if (r < 0)
  61                 return -errno;
  62
  63         mreq.mr_address[ETH_ALEN - 1] = 0x03;
  64         r = setsockopt(fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
  65         if (r < 0)
  66                 return -errno;
  67
  68         mreq.mr_address[ETH_ALEN - 1] = 0x0E;
  69         r = setsockopt(fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
  70         if (r < 0)
  71                 return -errno;
  72
  73         r = bind(fd, &saddrll.sa, sizeof(saddrll.ll));
  74         if (r < 0)
  75                 return -errno;
  76
  77         return TAKE_FD(fd);
  78 }