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 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 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 123 " @ IPv4 address %s/%d", 124 MAC2STR(sta->addr), ipaddr_str(ntohl(b->your_ip)), 125 prefixlen); 126 127 if (sta->ipaddr == b->your_ip) 128 return; 129 130 if (sta->ipaddr != 0) { 131 wpa_printf(MSG_DEBUG, 132 "dhcp_snoop: Removing IPv4 address %s from the ip neigh table", 133 ipaddr_str(be_to_host32(sta->ipaddr))); 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 } 179