| /* SPDX-License-Identifier: LGPL-2.1+ */ |
| /*** |
| This file is part of systemd. |
| |
| Copyright (C) 2014 Axis Communications AB. All rights reserved. |
| Copyright (C) 2015 Tom Gundersen |
| |
| 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 <arpa/inet.h> |
| |
| #include "arp-util.h" |
| #include "fd-util.h" |
| #include "util.h" |
| |
| int arp_network_bind_raw_socket(int ifindex, be32_t address, const struct ether_addr *eth_mac) { |
| struct sock_filter filter[] = { |
| BPF_STMT(BPF_LD + BPF_W + BPF_LEN, 0), /* A <- packet length */ |
| BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, sizeof(struct ether_arp), 1, 0), /* packet >= arp packet ? */ |
| BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */ |
| BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_hrd)), /* A <- header */ |
| BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPHRD_ETHER, 1, 0), /* header == ethernet ? */ |
| BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */ |
| BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_pro)), /* A <- protocol */ |
| BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 1, 0), /* protocol == IP ? */ |
| BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */ |
| BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_hln)), /* A <- hardware address length */ |
| BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, sizeof(struct ether_addr), 1, 0), /* length == sizeof(ether_addr)? */ |
| BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */ |
| BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_pln)), /* A <- protocol address length */ |
| BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, sizeof(struct in_addr), 1, 0), /* length == sizeof(in_addr) ? */ |
| BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */ |
| BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_op)), /* A <- operation */ |
| BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPOP_REQUEST, 2, 0), /* protocol == request ? */ |
| BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPOP_REPLY, 1, 0), /* protocol == reply ? */ |
| BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */ |
| /* Sender Hardware Address must be different from our own */ |
| BPF_STMT(BPF_LD + BPF_IMM, htobe32(*((uint32_t *) eth_mac))), /* A <- 4 bytes of client's MAC */ |
| BPF_STMT(BPF_MISC + BPF_TAX, 0), /* X <- A */ |
| BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct ether_arp, arp_sha)), /* A <- 4 bytes of SHA */ |
| BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0), /* A xor X */ |
| BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 0, 6), /* A == 0 ? */ |
| BPF_STMT(BPF_LD + BPF_IMM, htobe16(*((uint16_t *) (((char *) eth_mac) + 4)))), /* A <- remainder of client's MAC */ |
| BPF_STMT(BPF_MISC + BPF_TAX, 0), /* X <- A */ |
| BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ether_arp, arp_sha) + 4), /* A <- remainder of SHA */ |
| BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0), /* A xor X */ |
| BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 0, 1), /* A == 0 ? */ |
| BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */ |
| /* Sender Protocol Address or Target Protocol Address must be equal to the one we care about */ |
| BPF_STMT(BPF_LD + BPF_IMM, htobe32(address)), /* A <- clients IP */ |
| BPF_STMT(BPF_MISC + BPF_TAX, 0), /* X <- A */ |
| BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct ether_arp, arp_spa)), /* A <- SPA */ |
| BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0), /* X xor A */ |
| BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 0, 1), /* A == 0 ? */ |
| BPF_STMT(BPF_RET + BPF_K, 65535), /* return all */ |
| BPF_STMT(BPF_LD + BPF_IMM, htobe32(address)), /* A <- clients IP */ |
| BPF_STMT(BPF_MISC + BPF_TAX, 0), /* X <- A */ |
| BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct ether_arp, arp_tpa)), /* A <- TPA */ |
| BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0), /* X xor A */ |
| BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 0, 1), /* A == 0 ? */ |
| BPF_STMT(BPF_RET + BPF_K, 65535), /* return all */ |
| BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */ |
| }; |
| struct sock_fprog fprog = { |
| .len = ELEMENTSOF(filter), |
| .filter = (struct sock_filter*) filter |
| }; |
| union sockaddr_union link = { |
| .ll.sll_family = AF_PACKET, |
| .ll.sll_protocol = htobe16(ETH_P_ARP), |
| .ll.sll_ifindex = ifindex, |
| .ll.sll_halen = ETH_ALEN, |
| .ll.sll_addr = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff }, |
| }; |
| _cleanup_close_ int s = -1; |
| int r; |
| |
| assert(ifindex > 0); |
| |
| s = socket(PF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0); |
| if (s < 0) |
| return -errno; |
| |
| r = setsockopt(s, SOL_SOCKET, SO_ATTACH_FILTER, &fprog, sizeof(fprog)); |
| if (r < 0) |
| return -errno; |
| |
| r = bind(s, &link.sa, sizeof(link.ll)); |
| if (r < 0) |
| return -errno; |
| |
| r = s; |
| s = -1; |
| |
| return r; |
| } |
| |
| static int arp_send_packet(int fd, int ifindex, |
| be32_t pa, const struct ether_addr *ha, |
| bool announce) { |
| union sockaddr_union link = { |
| .ll.sll_family = AF_PACKET, |
| .ll.sll_protocol = htobe16(ETH_P_ARP), |
| .ll.sll_ifindex = ifindex, |
| .ll.sll_halen = ETH_ALEN, |
| .ll.sll_addr = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff }, |
| }; |
| struct ether_arp arp = { |
| .ea_hdr.ar_hrd = htobe16(ARPHRD_ETHER), /* HTYPE */ |
| .ea_hdr.ar_pro = htobe16(ETHERTYPE_IP), /* PTYPE */ |
| .ea_hdr.ar_hln = ETH_ALEN, /* HLEN */ |
| .ea_hdr.ar_pln = sizeof(be32_t), /* PLEN */ |
| .ea_hdr.ar_op = htobe16(ARPOP_REQUEST), /* REQUEST */ |
| }; |
| int r; |
| |
| assert(fd >= 0); |
| assert(pa != 0); |
| assert(ha); |
| |
| memcpy(&arp.arp_sha, ha, ETH_ALEN); |
| memcpy(&arp.arp_tpa, &pa, sizeof(pa)); |
| |
| if (announce) |
| memcpy(&arp.arp_spa, &pa, sizeof(pa)); |
| |
| r = sendto(fd, &arp, sizeof(struct ether_arp), 0, &link.sa, sizeof(link.ll)); |
| if (r < 0) |
| return -errno; |
| |
| return 0; |
| } |
| |
| int arp_send_probe(int fd, int ifindex, |
| be32_t pa, const struct ether_addr *ha) { |
| return arp_send_packet(fd, ifindex, pa, ha, false); |
| } |
| |
| int arp_send_announcement(int fd, int ifindex, |
| be32_t pa, const struct ether_addr *ha) { |
| return arp_send_packet(fd, ifindex, pa, ha, true); |
| } |