src/libsystemd-network/lldp-network.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2
   3 #include <linux/filter.h>
   4
   5 #include "fd-util.h"
   6 #include "lldp-network.h"
   7 #include "socket-util.h"
   8
   9 int lldp_network_bind_raw_socket(int ifindex) {
  10         static const struct sock_filter filter[] = {
  11                 BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct ethhdr, h_dest)),      /* A <- 4 bytes of destination MAC */
  12                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x0180c200, 1, 0),                    /* A != 01:80:c2:00 */
  13                 BPF_STMT(BPF_RET + BPF_K, 0),                                             /* drop packet */
  14                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ethhdr, h_dest) + 4),  /* A <- remaining 2 bytes of destination MAC */
  15                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x0000, 3, 0),                        /* A != 00:00 */
  16                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x0003, 2, 0),                        /* A != 00:03 */
  17                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x000e, 1, 0),                        /* A != 00:0e */
  18                 BPF_STMT(BPF_RET + BPF_K, 0),                                             /* drop packet */
  19                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ethhdr, h_proto)),     /* A <- protocol */
  20                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETH_P_LLDP, 1, 0),                    /* A != ETH_P_LLDP */
  21                 BPF_STMT(BPF_RET + BPF_K, 0),                                             /* drop packet */
  22                 BPF_STMT(BPF_RET + BPF_K, UINT32_MAX),                                    /* accept packet */
  23         };
  24         static const struct sock_fprog fprog = {
  25                 .len = ELEMENTSOF(filter),
  26                 .filter = (struct sock_filter*) filter,
  27         };
  28         struct packet_mreq mreq = {
  29                 .mr_ifindex = ifindex,
  30                 .mr_type = PACKET_MR_MULTICAST,
  31                 .mr_alen = ETH_ALEN,
  32                 .mr_address = { 0x01, 0x80, 0xC2, 0x00, 0x00, 0x00 }
  33         };
  34         union sockaddr_union saddrll = {
  35                 .ll.sll_family = AF_PACKET,
  36                 .ll.sll_ifindex = ifindex,
  37         };
  38         _cleanup_close_ int fd = -EBADF;
  39
  40         assert(ifindex > 0);
  41
  42         fd = socket(AF_PACKET, SOCK_RAW|SOCK_CLOEXEC|SOCK_NONBLOCK,
  43                     htobe16(ETH_P_LLDP));
  44         if (fd < 0)
  45                 return -errno;
  46
  47         if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &fprog, sizeof(fprog)) < 0)
  48                 return -errno;
  49
  50         /* customer bridge */
  51         if (setsockopt(fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0)
  52                 return -errno;
  53
  54         /* non TPMR bridge */
  55         mreq.mr_address[ETH_ALEN - 1] = 0x03;
  56         if (setsockopt(fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0)
  57                 return -errno;
  58
  59         /* nearest bridge */
  60         mreq.mr_address[ETH_ALEN - 1] = 0x0E;
  61         if (setsockopt(fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0)
  62                 return -errno;
  63
  64         if (bind(fd, &saddrll.sa, sizeof(saddrll.ll)) < 0)
  65                 return -errno;
  66
  67         return TAKE_FD(fd);
  68 }