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
ipaddr_str(u32 addr)21 static 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
handle_dhcp(void * ctx,const u8 * src_addr,const u8 * buf,size_t len)32 static 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
dhcp_snoop_init(struct hostapd_data * hapd)139 int 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
dhcp_snoop_deinit(struct hostapd_data * hapd)154 void dhcp_snoop_deinit(struct hostapd_data *hapd)
155 {
156 l2_packet_deinit(hapd->sock_dhcp);
157 hapd->sock_dhcp = NULL;
158 }
159