Dmitry Shmidt | fb45fd5 | 2015-01-05 13:08:17 -0800 | [diff] [blame] | 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 | #include <netinet/ip.h> |
| 11 | #include <netinet/udp.h> |
| 12 | |
| 13 | #include "utils/common.h" |
| 14 | #include "l2_packet/l2_packet.h" |
| 15 | #include "hostapd.h" |
| 16 | #include "sta_info.h" |
| 17 | #include "ap_drv_ops.h" |
| 18 | #include "x_snoop.h" |
| 19 | #include "dhcp_snoop.h" |
| 20 | |
| 21 | struct bootp_pkt { |
| 22 | struct iphdr iph; |
| 23 | struct udphdr udph; |
| 24 | u8 op; |
| 25 | u8 htype; |
| 26 | u8 hlen; |
| 27 | u8 hops; |
| 28 | be32 xid; |
| 29 | be16 secs; |
| 30 | be16 flags; |
| 31 | be32 client_ip; |
| 32 | be32 your_ip; |
| 33 | be32 server_ip; |
| 34 | be32 relay_ip; |
| 35 | u8 hw_addr[16]; |
| 36 | u8 serv_name[64]; |
| 37 | u8 boot_file[128]; |
| 38 | u8 exten[312]; |
| 39 | } STRUCT_PACKED; |
| 40 | |
| 41 | #define DHCPACK 5 |
| 42 | static const u8 ic_bootp_cookie[] = { 99, 130, 83, 99 }; |
| 43 | |
| 44 | |
Dmitry Shmidt | aff761d | 2015-02-06 10:50:36 -0800 | [diff] [blame^] | 45 | static const char * ipaddr_str(u32 addr) |
| 46 | { |
| 47 | static char buf[17]; |
| 48 | |
| 49 | os_snprintf(buf, sizeof(buf), "%u.%u.%u.%u", |
| 50 | (addr >> 24) & 0xff, (addr >> 16) & 0xff, |
| 51 | (addr >> 8) & 0xff, addr & 0xff); |
| 52 | return buf; |
| 53 | } |
| 54 | |
| 55 | |
Dmitry Shmidt | fb45fd5 | 2015-01-05 13:08:17 -0800 | [diff] [blame] | 56 | static void handle_dhcp(void *ctx, const u8 *src_addr, const u8 *buf, |
| 57 | size_t len) |
| 58 | { |
| 59 | struct hostapd_data *hapd = ctx; |
| 60 | const struct bootp_pkt *b; |
| 61 | struct sta_info *sta; |
| 62 | int exten_len; |
| 63 | const u8 *end, *pos; |
| 64 | int res, msgtype = 0, prefixlen = 32; |
| 65 | u32 subnet_mask = 0; |
| 66 | u16 tot_len; |
| 67 | |
| 68 | exten_len = len - ETH_HLEN - (sizeof(*b) - sizeof(b->exten)); |
| 69 | if (exten_len < 4) |
| 70 | return; |
| 71 | |
| 72 | b = (const struct bootp_pkt *) &buf[ETH_HLEN]; |
| 73 | tot_len = ntohs(b->iph.tot_len); |
| 74 | if (tot_len > (unsigned int) (len - ETH_HLEN)) |
| 75 | return; |
| 76 | |
| 77 | if (os_memcmp(b->exten, ic_bootp_cookie, ARRAY_SIZE(ic_bootp_cookie))) |
| 78 | return; |
| 79 | |
| 80 | /* Parse DHCP options */ |
| 81 | end = (const u8 *) b + tot_len; |
| 82 | pos = &b->exten[4]; |
| 83 | while (pos < end && *pos != 0xff) { |
| 84 | const u8 *opt = pos++; |
| 85 | |
| 86 | if (*opt == 0) /* padding */ |
| 87 | continue; |
| 88 | |
| 89 | pos += *pos + 1; |
| 90 | if (pos >= end) |
| 91 | break; |
| 92 | |
| 93 | switch (*opt) { |
| 94 | case 1: /* subnet mask */ |
| 95 | if (opt[1] == 4) |
| 96 | subnet_mask = WPA_GET_BE32(&opt[2]); |
| 97 | if (subnet_mask == 0) |
| 98 | return; |
| 99 | while (!(subnet_mask & 0x1)) { |
| 100 | subnet_mask >>= 1; |
| 101 | prefixlen--; |
| 102 | } |
| 103 | break; |
| 104 | case 53: /* message type */ |
| 105 | if (opt[1]) |
| 106 | msgtype = opt[2]; |
| 107 | break; |
| 108 | default: |
| 109 | break; |
| 110 | } |
| 111 | } |
| 112 | |
| 113 | if (msgtype == DHCPACK) { |
| 114 | if (b->your_ip == 0) |
| 115 | return; |
| 116 | |
| 117 | /* DHCPACK for DHCPREQUEST */ |
| 118 | sta = ap_get_sta(hapd, b->hw_addr); |
| 119 | if (!sta) |
| 120 | return; |
| 121 | |
| 122 | wpa_printf(MSG_DEBUG, "dhcp_snoop: Found DHCPACK for " MACSTR |
Dmitry Shmidt | aff761d | 2015-02-06 10:50:36 -0800 | [diff] [blame^] | 123 | " @ IPv4 address %s/%d", |
| 124 | MAC2STR(sta->addr), ipaddr_str(ntohl(b->your_ip)), |
| 125 | prefixlen); |
Dmitry Shmidt | fb45fd5 | 2015-01-05 13:08:17 -0800 | [diff] [blame] | 126 | |
| 127 | if (sta->ipaddr == b->your_ip) |
| 128 | return; |
| 129 | |
| 130 | if (sta->ipaddr != 0) { |
| 131 | wpa_printf(MSG_DEBUG, |
Dmitry Shmidt | aff761d | 2015-02-06 10:50:36 -0800 | [diff] [blame^] | 132 | "dhcp_snoop: Removing IPv4 address %s from the ip neigh table", |
| 133 | ipaddr_str(be_to_host32(sta->ipaddr))); |
Dmitry Shmidt | fb45fd5 | 2015-01-05 13:08:17 -0800 | [diff] [blame] | 134 | hostapd_drv_br_delete_ip_neigh(hapd, 4, |
| 135 | (u8 *) &sta->ipaddr); |
| 136 | } |
| 137 | |
| 138 | res = hostapd_drv_br_add_ip_neigh(hapd, 4, (u8 *) &b->your_ip, |
| 139 | prefixlen, sta->addr); |
| 140 | if (res) { |
| 141 | wpa_printf(MSG_DEBUG, |
| 142 | "dhcp_snoop: Adding ip neigh table failed: %d", |
| 143 | res); |
| 144 | return; |
| 145 | } |
| 146 | sta->ipaddr = b->your_ip; |
| 147 | } |
| 148 | |
| 149 | if (hapd->conf->disable_dgaf && is_broadcast_ether_addr(buf)) { |
| 150 | for (sta = hapd->sta_list; sta; sta = sta->next) { |
| 151 | if (!(sta->flags & WLAN_STA_AUTHORIZED)) |
| 152 | continue; |
| 153 | x_snoop_mcast_to_ucast_convert_send(hapd, sta, |
| 154 | (u8 *) buf, len); |
| 155 | } |
| 156 | } |
| 157 | } |
| 158 | |
| 159 | |
| 160 | int dhcp_snoop_init(struct hostapd_data *hapd) |
| 161 | { |
| 162 | hapd->sock_dhcp = x_snoop_get_l2_packet(hapd, handle_dhcp, |
| 163 | L2_PACKET_FILTER_DHCP); |
| 164 | if (hapd->sock_dhcp == NULL) { |
| 165 | wpa_printf(MSG_DEBUG, |
| 166 | "dhcp_snoop: Failed to initialize L2 packet processing for DHCP packet: %s", |
| 167 | strerror(errno)); |
| 168 | return -1; |
| 169 | } |
| 170 | |
| 171 | return 0; |
| 172 | } |
| 173 | |
| 174 | |
| 175 | void dhcp_snoop_deinit(struct hostapd_data *hapd) |
| 176 | { |
| 177 | l2_packet_deinit(hapd->sock_dhcp); |
| 178 | } |