src/libsystemd-network/lldp-network.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   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         static const struct sock_filter filter[] = {
  13                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct ethhdr, h_dest)),      /* A <- 4 bytes of destination MAC */
  14                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x0180c200, 1, 0),                    /* A != 01:80:c2:00 */
  15                 BPF_STMT(BPF_RET + BPF_K, 0),                                             /* drop packet */
  16                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ethhdr, h_dest) + 4),  /* A <- remaining 2 bytes of destination MAC */
  17                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x0000, 3, 0),                        /* A != 00:00 */
  18                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x0003, 2, 0),                        /* A != 00:03 */
  19                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x000e, 1, 0),                        /* A != 00:0e */
  20                 BPF_STMT(BPF_RET + BPF_K, 0),                                             /* drop packet */
  21                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ethhdr, h_proto)),     /* A <- protocol */
  22                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_LLDP, 1, 0),                /* A != ETHERTYPE_LLDP */
  23                 BPF_STMT(BPF_RET + BPF_K, 0),                                             /* drop packet */
  24                 BPF_STMT(BPF_RET + BPF_K, UINT32_MAX),                                    /* accept packet */
  25         };
  26         static const struct sock_fprog fprog = {
  27                 .len = ELEMENTSOF(filter),
  28                 .filter = (struct sock_filter*) filter,
  29         };
  30         struct packet_mreq mreq = {
  31                 .mr_ifindex = ifindex,
  32                 .mr_type = PACKET_MR_MULTICAST,
  33                 .mr_alen = ETH_ALEN,
  34                 .mr_address = { 0x01, 0x80, 0xC2, 0x00, 0x00, 0x00 }
  35         };
  36         union sockaddr_union saddrll = {
  37                 .ll.sll_family = AF_PACKET,
  38                 .ll.sll_ifindex = ifindex,
  39         };
  40         _cleanup_close_ int fd = -EBADF;
  41
  42         assert(ifindex > 0);
  43
  44         fd = socket(AF_PACKET, SOCK_RAW|SOCK_CLOEXEC|SOCK_NONBLOCK,
  45                     htobe16(ETHERTYPE_LLDP));
  46         if (fd < 0)
  47                 return -errno;
  48
  49         if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &fprog, sizeof(fprog)) < 0)
  50                 return -errno;
  51
  52         /* customer bridge */
  53         if (setsockopt(fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0)
  54                 return -errno;
  55
  56         /* non TPMR bridge */
  57         mreq.mr_address[ETH_ALEN - 1] = 0x03;
  58         if (setsockopt(fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0)
  59                 return -errno;
  60
  61         /* nearest bridge */
  62         mreq.mr_address[ETH_ALEN - 1] = 0x0E;
  63         if (setsockopt(fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0)
  64                 return -errno;
  65
  66         if (bind(fd, &saddrll.sa, sizeof(saddrll.ll)) < 0)
  67                 return -errno;
  68
  69         return TAKE_FD(fd);
  70 }