Line data Source code
1 : /* SPDX-License-Identifier: LGPL-2.1+ */
2 : /***
3 : Copyright © 2014 Axis Communications AB. All rights reserved.
4 : ***/
5 :
6 : #include <arpa/inet.h>
7 : #include <linux/filter.h>
8 : #include <netinet/if_ether.h>
9 :
10 : #include "arp-util.h"
11 : #include "fd-util.h"
12 : #include "unaligned.h"
13 : #include "util.h"
14 :
15 0 : int arp_network_bind_raw_socket(int ifindex, be32_t address, const struct ether_addr *eth_mac) {
16 0 : struct sock_filter filter[] = {
17 : BPF_STMT(BPF_LD + BPF_W + BPF_LEN, 0), /* A <- packet length */
18 : BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, sizeof(struct ether_arp), 1, 0), /* packet >= arp packet ? */
19 : BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
20 : BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_hrd)), /* A <- header */
21 : BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPHRD_ETHER, 1, 0), /* header == ethernet ? */
22 : BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
23 : BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_pro)), /* A <- protocol */
24 : BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 1, 0), /* protocol == IP ? */
25 : BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
26 : BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_hln)), /* A <- hardware address length */
27 : BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, sizeof(struct ether_addr), 1, 0), /* length == sizeof(ether_addr)? */
28 : BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
29 : BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_pln)), /* A <- protocol address length */
30 : BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, sizeof(struct in_addr), 1, 0), /* length == sizeof(in_addr) ? */
31 : BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
32 : BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_op)), /* A <- operation */
33 : BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPOP_REQUEST, 2, 0), /* protocol == request ? */
34 : BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPOP_REPLY, 1, 0), /* protocol == reply ? */
35 : BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
36 : /* Sender Hardware Address must be different from our own */
37 0 : BPF_STMT(BPF_LD + BPF_IMM, unaligned_read_be32(ð_mac->ether_addr_octet[0])),/* A <- 4 bytes of client's MAC */
38 : BPF_STMT(BPF_MISC + BPF_TAX, 0), /* X <- A */
39 : BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct ether_arp, arp_sha)), /* A <- 4 bytes of SHA */
40 : BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0), /* A xor X */
41 : BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 0, 6), /* A == 0 ? */
42 0 : BPF_STMT(BPF_LD + BPF_IMM, unaligned_read_be16(ð_mac->ether_addr_octet[4])),/* A <- remainder of client's MAC */
43 : BPF_STMT(BPF_MISC + BPF_TAX, 0), /* X <- A */
44 : BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ether_arp, arp_sha) + 4), /* A <- remainder of SHA */
45 : BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0), /* A xor X */
46 : BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 0, 1), /* A == 0 ? */
47 : BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
48 : /* Sender Protocol Address or Target Protocol Address must be equal to the one we care about */
49 0 : BPF_STMT(BPF_LD + BPF_IMM, htobe32(address)), /* A <- clients IP */
50 : BPF_STMT(BPF_MISC + BPF_TAX, 0), /* X <- A */
51 : BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct ether_arp, arp_spa)), /* A <- SPA */
52 : BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0), /* X xor A */
53 : BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 0, 1), /* A == 0 ? */
54 : BPF_STMT(BPF_RET + BPF_K, 65535), /* return all */
55 0 : BPF_STMT(BPF_LD + BPF_IMM, htobe32(address)), /* A <- clients IP */
56 : BPF_STMT(BPF_MISC + BPF_TAX, 0), /* X <- A */
57 : BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct ether_arp, arp_tpa)), /* A <- TPA */
58 : BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0), /* X xor A */
59 : BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 0, 1), /* A == 0 ? */
60 : BPF_STMT(BPF_RET + BPF_K, 65535), /* return all */
61 : BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
62 : };
63 0 : struct sock_fprog fprog = {
64 : .len = ELEMENTSOF(filter),
65 : .filter = (struct sock_filter*) filter
66 : };
67 0 : union sockaddr_union link = {
68 : .ll.sll_family = AF_PACKET,
69 0 : .ll.sll_protocol = htobe16(ETH_P_ARP),
70 : .ll.sll_ifindex = ifindex,
71 : .ll.sll_halen = ETH_ALEN,
72 : .ll.sll_addr = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff },
73 : };
74 0 : _cleanup_close_ int s = -1;
75 : int r;
76 :
77 0 : assert(ifindex > 0);
78 :
79 0 : s = socket(PF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
80 0 : if (s < 0)
81 0 : return -errno;
82 :
83 0 : r = setsockopt(s, SOL_SOCKET, SO_ATTACH_FILTER, &fprog, sizeof(fprog));
84 0 : if (r < 0)
85 0 : return -errno;
86 :
87 0 : r = bind(s, &link.sa, sizeof(link.ll));
88 0 : if (r < 0)
89 0 : return -errno;
90 :
91 0 : return TAKE_FD(s);
92 : }
93 :
94 0 : static int arp_send_packet(int fd, int ifindex,
95 : be32_t pa, const struct ether_addr *ha,
96 : bool announce) {
97 0 : union sockaddr_union link = {
98 : .ll.sll_family = AF_PACKET,
99 0 : .ll.sll_protocol = htobe16(ETH_P_ARP),
100 : .ll.sll_ifindex = ifindex,
101 : .ll.sll_halen = ETH_ALEN,
102 : .ll.sll_addr = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff },
103 : };
104 0 : struct ether_arp arp = {
105 0 : .ea_hdr.ar_hrd = htobe16(ARPHRD_ETHER), /* HTYPE */
106 0 : .ea_hdr.ar_pro = htobe16(ETHERTYPE_IP), /* PTYPE */
107 : .ea_hdr.ar_hln = ETH_ALEN, /* HLEN */
108 : .ea_hdr.ar_pln = sizeof(be32_t), /* PLEN */
109 0 : .ea_hdr.ar_op = htobe16(ARPOP_REQUEST), /* REQUEST */
110 : };
111 : int r;
112 :
113 0 : assert(fd >= 0);
114 0 : assert(pa != 0);
115 0 : assert(ha);
116 :
117 0 : memcpy(&arp.arp_sha, ha, ETH_ALEN);
118 0 : memcpy(&arp.arp_tpa, &pa, sizeof(pa));
119 :
120 0 : if (announce)
121 0 : memcpy(&arp.arp_spa, &pa, sizeof(pa));
122 :
123 0 : r = sendto(fd, &arp, sizeof(struct ether_arp), 0, &link.sa, sizeof(link.ll));
124 0 : if (r < 0)
125 0 : return -errno;
126 :
127 0 : return 0;
128 : }
129 :
130 0 : int arp_send_probe(int fd, int ifindex,
131 : be32_t pa, const struct ether_addr *ha) {
132 0 : return arp_send_packet(fd, ifindex, pa, ha, false);
133 : }
134 :
135 0 : int arp_send_announcement(int fd, int ifindex,
136 : be32_t pa, const struct ether_addr *ha) {
137 0 : return arp_send_packet(fd, ifindex, pa, ha, true);
138 : }
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