1 /* vi: set sw=4 ts=4: */
2 /*
3  * Copyright (C) 2011 Denys Vlasenko.
4  *
5  * Licensed under GPLv2, see file LICENSE in this source tree.
6  */
7 #include "common.h"
8 #include "d6_common.h"
9 #include "dhcpd.h"
10 #include <netinet/in.h>
11 #include <netinet/if_ether.h>
12 #include <netpacket/packet.h>
13 
14 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 2
d6_dump_packet(struct d6_packet * packet)15 void FAST_FUNC d6_dump_packet(struct d6_packet *packet)
16 {
17 	if (dhcp_verbose < 2)
18 		return;
19 
20 	bb_error_msg(
21 		"xid %x"
22 		, packet->d6_xid32
23 	);
24 	//*bin2hex(buf, (void *) packet->chaddr, sizeof(packet->chaddr)) = '\0';
25 	//bb_error_msg(" chaddr %s", buf);
26 }
27 #endif
28 
d6_recv_kernel_packet(struct in6_addr * peer_ipv6 UNUSED_PARAM,struct d6_packet * packet,int fd)29 int FAST_FUNC d6_recv_kernel_packet(struct in6_addr *peer_ipv6
30 	UNUSED_PARAM
31 	, struct d6_packet *packet, int fd)
32 {
33 	int bytes;
34 
35 	memset(packet, 0, sizeof(*packet));
36 	bytes = safe_read(fd, packet, sizeof(*packet));
37 	if (bytes < 0) {
38 		log1("packet read error, ignoring");
39 		return bytes; /* returns -1 */
40 	}
41 
42 	if (bytes < offsetof(struct d6_packet, d6_options)) {
43 		bb_error_msg("packet with bad magic, ignoring");
44 		return -2;
45 	}
46 	log1("received %s", "a packet");
47 	d6_dump_packet(packet);
48 
49 	return bytes;
50 }
51 
52 /* Construct a ipv6+udp header for a packet, send packet */
d6_send_raw_packet(struct d6_packet * d6_pkt,unsigned d6_pkt_size,struct in6_addr * src_ipv6,int source_port,struct in6_addr * dst_ipv6,int dest_port,const uint8_t * dest_arp,int ifindex)53 int FAST_FUNC d6_send_raw_packet(
54 		struct d6_packet *d6_pkt, unsigned d6_pkt_size,
55 		struct in6_addr *src_ipv6, int source_port,
56 		struct in6_addr *dst_ipv6, int dest_port, const uint8_t *dest_arp,
57 		int ifindex)
58 {
59 	struct sockaddr_ll dest_sll;
60 	struct ip6_udp_d6_packet packet;
61 	int fd;
62 	int result = -1;
63 	const char *msg;
64 
65 	fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IPV6));
66 	if (fd < 0) {
67 		msg = "socket(%s)";
68 		goto ret_msg;
69 	}
70 
71 	memset(&dest_sll, 0, sizeof(dest_sll));
72 	memset(&packet, 0, offsetof(struct ip6_udp_d6_packet, data));
73 	packet.data = *d6_pkt; /* struct copy */
74 
75 	dest_sll.sll_family = AF_PACKET;
76 	dest_sll.sll_protocol = htons(ETH_P_IPV6);
77 	dest_sll.sll_ifindex = ifindex;
78 	dest_sll.sll_halen = 6;
79 	memcpy(dest_sll.sll_addr, dest_arp, 6);
80 
81 	if (bind(fd, (struct sockaddr *)&dest_sll, sizeof(dest_sll)) < 0) {
82 		msg = "bind(%s)";
83 		goto ret_close;
84 	}
85 
86 	packet.ip6.ip6_vfc = (6 << 4); /* 4 bits version, top 4 bits of tclass */
87 	if (src_ipv6)
88 		packet.ip6.ip6_src = *src_ipv6; /* struct copy */
89 	packet.ip6.ip6_dst = *dst_ipv6; /* struct copy */
90 	packet.udp.source = htons(source_port);
91 	packet.udp.dest = htons(dest_port);
92 	/* size, excluding IP header: */
93 	packet.udp.len = htons(sizeof(struct udphdr) + d6_pkt_size);
94 	packet.ip6.ip6_plen = packet.udp.len;
95 	/*
96 	 * Someone was smoking weed (at least) while inventing UDP checksumming:
97 	 * UDP checksum skips first four bytes of IPv6 header.
98 	 * 'next header' field should be summed as if it is one more byte
99 	 * to the right, therefore we write its value (IPPROTO_UDP)
100 	 * into ip6_hlim, and its 'real' location remains zero-filled for now.
101 	 */
102 	packet.ip6.ip6_hlim = IPPROTO_UDP;
103 	packet.udp.check = inet_cksum(
104 				(uint16_t *)&packet + 2,
105 				offsetof(struct ip6_udp_d6_packet, data) - 4 + d6_pkt_size
106 	);
107 	/* fix 'hop limit' and 'next header' after UDP checksumming */
108 	packet.ip6.ip6_hlim = 1; /* observed Windows machines to use hlim=1 */
109 	packet.ip6.ip6_nxt = IPPROTO_UDP;
110 
111 	d6_dump_packet(d6_pkt);
112 	result = sendto(fd, &packet, offsetof(struct ip6_udp_d6_packet, data) + d6_pkt_size,
113 			/*flags:*/ 0,
114 			(struct sockaddr *) &dest_sll, sizeof(dest_sll)
115 	);
116 	msg = "sendto";
117  ret_close:
118 	close(fd);
119 	if (result < 0) {
120  ret_msg:
121 		bb_perror_msg(msg, "PACKET");
122 	}
123 	return result;
124 }
125 
126 /* Let the kernel do all the work for packet generation */
d6_send_kernel_packet(struct d6_packet * d6_pkt,unsigned d6_pkt_size,struct in6_addr * src_ipv6,int source_port,struct in6_addr * dst_ipv6,int dest_port)127 int FAST_FUNC d6_send_kernel_packet(
128 		struct d6_packet *d6_pkt, unsigned d6_pkt_size,
129 		struct in6_addr *src_ipv6, int source_port,
130 		struct in6_addr *dst_ipv6, int dest_port)
131 {
132 	struct sockaddr_in6 sa;
133 	int fd;
134 	int result = -1;
135 	const char *msg;
136 
137 	fd = socket(PF_INET6, SOCK_DGRAM, IPPROTO_UDP);
138 	if (fd < 0) {
139 		msg = "socket(%s)";
140 		goto ret_msg;
141 	}
142 	setsockopt_reuseaddr(fd);
143 
144 	memset(&sa, 0, sizeof(sa));
145 	sa.sin6_family = AF_INET6;
146 	sa.sin6_port = htons(source_port);
147 	sa.sin6_addr = *src_ipv6; /* struct copy */
148 	if (bind(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
149 		msg = "bind(%s)";
150 		goto ret_close;
151 	}
152 
153 	memset(&sa, 0, sizeof(sa));
154 	sa.sin6_family = AF_INET6;
155 	sa.sin6_port = htons(dest_port);
156 	sa.sin6_addr = *dst_ipv6; /* struct copy */
157 	if (connect(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
158 		msg = "connect";
159 		goto ret_close;
160 	}
161 
162 	d6_dump_packet(d6_pkt);
163 	result = safe_write(fd, d6_pkt, d6_pkt_size);
164 	msg = "write";
165  ret_close:
166 	close(fd);
167 	if (result < 0) {
168  ret_msg:
169 		bb_perror_msg(msg, "UDP");
170 	}
171 	return result;
172 }
173