1/*
2 * DHCP snooping for Proxy ARP
3 * Copyright (c) 2014, Qualcomm Atheros, Inc.
4 *
5 * This software may be distributed under the terms of the BSD license.
6 * See README for more details.
7 */
8
9#include "utils/includes.h"
10
11#include "utils/common.h"
12#include "common/dhcp.h"
13#include "l2_packet/l2_packet.h"
14#include "hostapd.h"
15#include "sta_info.h"
16#include "ap_drv_ops.h"
17#include "x_snoop.h"
18#include "dhcp_snoop.h"
19
20
21static const char * ipaddr_str(u32 addr)
22{
23	static char buf[17];
24
25	os_snprintf(buf, sizeof(buf), "%u.%u.%u.%u",
26		    (addr >> 24) & 0xff, (addr >> 16) & 0xff,
27		    (addr >> 8) & 0xff, addr & 0xff);
28	return buf;
29}
30
31
32static void handle_dhcp(void *ctx, const u8 *src_addr, const u8 *buf,
33			size_t len)
34{
35	struct hostapd_data *hapd = ctx;
36	const struct bootp_pkt *b;
37	struct sta_info *sta;
38	int exten_len;
39	const u8 *end, *pos;
40	int res, msgtype = 0, prefixlen = 32;
41	u32 subnet_mask = 0;
42	u16 tot_len;
43
44	exten_len = len - ETH_HLEN - (sizeof(*b) - sizeof(b->exten));
45	if (exten_len < 4)
46		return;
47
48	b = (const struct bootp_pkt *) &buf[ETH_HLEN];
49	tot_len = ntohs(b->iph.tot_len);
50	if (tot_len > (unsigned int) (len - ETH_HLEN))
51		return;
52
53	if (WPA_GET_BE32(b->exten) != DHCP_MAGIC)
54		return;
55
56	/* Parse DHCP options */
57	end = (const u8 *) b + tot_len;
58	pos = &b->exten[4];
59	while (pos < end && *pos != DHCP_OPT_END) {
60		const u8 *opt = pos++;
61
62		if (*opt == DHCP_OPT_PAD)
63			continue;
64
65		if (pos >= end || 1 + *pos > end - pos)
66			break;
67		pos += *pos + 1;
68		if (pos >= end)
69			break;
70
71		switch (*opt) {
72		case DHCP_OPT_SUBNET_MASK:
73			if (opt[1] == 4)
74				subnet_mask = WPA_GET_BE32(&opt[2]);
75			if (subnet_mask == 0)
76				return;
77			while (!(subnet_mask & 0x1)) {
78				subnet_mask >>= 1;
79				prefixlen--;
80			}
81			break;
82		case DHCP_OPT_MSG_TYPE:
83			if (opt[1])
84				msgtype = opt[2];
85			break;
86		default:
87			break;
88		}
89	}
90
91	if (hapd->conf->disable_dgaf && is_broadcast_ether_addr(buf)) {
92		for (sta = hapd->sta_list; sta; sta = sta->next) {
93			if (!(sta->flags & WLAN_STA_AUTHORIZED))
94				continue;
95			x_snoop_mcast_to_ucast_convert_send(hapd, sta,
96							    (u8 *) buf, len);
97		}
98	}
99
100	if (msgtype == DHCPACK) {
101		if (b->your_ip == 0)
102			return;
103
104		/* DHCPACK for DHCPREQUEST */
105		sta = ap_get_sta(hapd, b->hw_addr);
106		if (!sta)
107			return;
108
109		wpa_printf(MSG_DEBUG, "dhcp_snoop: Found DHCPACK for " MACSTR
110			   " @ IPv4 address %s/%d",
111			   MAC2STR(sta->addr),
112			   ipaddr_str(be_to_host32(b->your_ip)),
113			   prefixlen);
114
115		if (sta->ipaddr == b->your_ip)
116			return;
117
118		if (sta->ipaddr != 0) {
119			wpa_printf(MSG_DEBUG,
120				   "dhcp_snoop: Removing IPv4 address %s from the ip neigh table",
121				   ipaddr_str(be_to_host32(sta->ipaddr)));
122			hostapd_drv_br_delete_ip_neigh(hapd, 4,
123						       (u8 *) &sta->ipaddr);
124		}
125
126		res = hostapd_drv_br_add_ip_neigh(hapd, 4, (u8 *) &b->your_ip,
127						  prefixlen, sta->addr);
128		if (res) {
129			wpa_printf(MSG_DEBUG,
130				   "dhcp_snoop: Adding ip neigh table failed: %d",
131				   res);
132			return;
133		}
134		sta->ipaddr = b->your_ip;
135	}
136}
137
138
139int dhcp_snoop_init(struct hostapd_data *hapd)
140{
141	hapd->sock_dhcp = x_snoop_get_l2_packet(hapd, handle_dhcp,
142						L2_PACKET_FILTER_DHCP);
143	if (hapd->sock_dhcp == NULL) {
144		wpa_printf(MSG_DEBUG,
145			   "dhcp_snoop: Failed to initialize L2 packet processing for DHCP packet: %s",
146			   strerror(errno));
147		return -1;
148	}
149
150	return 0;
151}
152
153
154void dhcp_snoop_deinit(struct hostapd_data *hapd)
155{
156	l2_packet_deinit(hapd->sock_dhcp);
157	hapd->sock_dhcp = NULL;
158}
159