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-rw-r--r--src/libsystemd-network/arp-util.c153
1 files changed, 153 insertions, 0 deletions
diff --git a/src/libsystemd-network/arp-util.c b/src/libsystemd-network/arp-util.c
new file mode 100644
index 0000000000..2f5b9b3731
--- /dev/null
+++ b/src/libsystemd-network/arp-util.c
@@ -0,0 +1,153 @@
+/***
+ 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 "util.h"
+#include "arp-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 = htons(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 = htons(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 = htons(ARPHRD_ETHER), /* HTYPE */
+ .ea_hdr.ar_pro = htons(ETHERTYPE_IP), /* PTYPE */
+ .ea_hdr.ar_hln = ETH_ALEN, /* HLEN */
+ .ea_hdr.ar_pln = sizeof(be32_t), /* PLEN */
+ .ea_hdr.ar_op = htons(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);
+}
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