/* SPDX-License-Identifier: LGPL-2.1-or-later */ /*** Copyright © 2014 Axis Communications AB. All rights reserved. ***/ #include #include #include #include "arp-util.h" #include "fd-util.h" #include "unaligned.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, unaligned_read_be32(ð_mac->ether_addr_octet[0])),/* 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, unaligned_read_be16(ð_mac->ether_addr_octet[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(AF_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; return TAKE_FD(s); } 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); }