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/***
This file is part of systemd.
Copyright (C) 2014 Tom Gundersen
Copyright (C) 2014 Susant Sahani
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <linux/filter.h>
#include <netinet/if_ether.h>
#include "fd-util.h"
#include "lldp-network.h"
#include "socket-util.h"
int lldp_network_bind_raw_socket(int ifindex) {
static const struct sock_filter filter[] = {
BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct ethhdr, h_dest)), /* A <- 4 bytes of destination MAC */
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x0180c200, 1, 0), /* A != 01:80:c2:00 */
BPF_STMT(BPF_RET + BPF_K, 0), /* drop packet */
BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ethhdr, h_dest) + 4), /* A <- remaining 2 bytes of destination MAC */
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x0000, 3, 0), /* A != 00:00 */
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x0003, 2, 0), /* A != 00:03 */
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x000e, 1, 0), /* A != 00:0e */
BPF_STMT(BPF_RET + BPF_K, 0), /* drop packet */
BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ethhdr, h_proto)), /* A <- protocol */
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_LLDP, 1, 0), /* A != ETHERTYPE_LLDP */
BPF_STMT(BPF_RET + BPF_K, 0), /* drop packet */
BPF_STMT(BPF_RET + BPF_K, (uint32_t) -1), /* accept packet */
};
static const struct sock_fprog fprog = {
.len = ELEMENTSOF(filter),
.filter = (struct sock_filter*) filter,
};
union sockaddr_union saddrll = {
.ll.sll_family = AF_PACKET,
.ll.sll_ifindex = ifindex,
};
_cleanup_close_ int fd = -1;
int r;
assert(ifindex > 0);
fd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
if (fd < 0)
return -errno;
r = setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &fprog, sizeof(fprog));
if (r < 0)
return -errno;
r = bind(fd, &saddrll.sa, sizeof(saddrll.ll));
if (r < 0)
return -errno;
r = fd;
fd = -1;
return r;
}
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