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 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 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 } 137 138 139 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 } 152 153 154 void dhcp_snoop_deinit(struct hostapd_data *hapd) 155 { 156 l2_packet_deinit(hapd->sock_dhcp); 157 hapd->sock_dhcp = NULL; 158 } 159