hostap/src/ap/dhcp_snoop.c

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/*
* DHCP snooping for Proxy ARP
* Copyright (c) 2014, Qualcomm Atheros, Inc.
*
* This software may be distributed under the terms of the BSD license.
* See README for more details.
*/
#include "utils/includes.h"
#include <netinet/ip.h>
#include <netinet/udp.h>
#include "utils/common.h"
#include "l2_packet/l2_packet.h"
#include "hostapd.h"
#include "sta_info.h"
#include "ap_drv_ops.h"
#include "x_snoop.h"
#include "dhcp_snoop.h"
struct bootp_pkt {
struct iphdr iph;
struct udphdr udph;
u8 op;
u8 htype;
u8 hlen;
u8 hops;
be32 xid;
be16 secs;
be16 flags;
be32 client_ip;
be32 your_ip;
be32 server_ip;
be32 relay_ip;
u8 hw_addr[16];
u8 serv_name[64];
u8 boot_file[128];
u8 exten[312];
} STRUCT_PACKED;
#define DHCPACK 5
static const u8 ic_bootp_cookie[] = { 99, 130, 83, 99 };
static const char * ipaddr_str(u32 addr)
{
static char buf[17];
os_snprintf(buf, sizeof(buf), "%u.%u.%u.%u",
(addr >> 24) & 0xff, (addr >> 16) & 0xff,
(addr >> 8) & 0xff, addr & 0xff);
return buf;
}
static void handle_dhcp(void *ctx, const u8 *src_addr, const u8 *buf,
size_t len)
{
struct hostapd_data *hapd = ctx;
const struct bootp_pkt *b;
struct sta_info *sta;
int exten_len;
const u8 *end, *pos;
int res, msgtype = 0, prefixlen = 32;
u32 subnet_mask = 0;
u16 tot_len;
exten_len = len - ETH_HLEN - (sizeof(*b) - sizeof(b->exten));
if (exten_len < 4)
return;
b = (const struct bootp_pkt *) &buf[ETH_HLEN];
tot_len = ntohs(b->iph.tot_len);
if (tot_len > (unsigned int) (len - ETH_HLEN))
return;
if (os_memcmp(b->exten, ic_bootp_cookie, ARRAY_SIZE(ic_bootp_cookie)))
return;
/* Parse DHCP options */
end = (const u8 *) b + tot_len;
pos = &b->exten[4];
while (pos < end && *pos != 0xff) {
const u8 *opt = pos++;
if (*opt == 0) /* padding */
continue;
pos += *pos + 1;
if (pos >= end)
break;
switch (*opt) {
case 1: /* subnet mask */
if (opt[1] == 4)
subnet_mask = WPA_GET_BE32(&opt[2]);
if (subnet_mask == 0)
return;
while (!(subnet_mask & 0x1)) {
subnet_mask >>= 1;
prefixlen--;
}
break;
case 53: /* message type */
if (opt[1])
msgtype = opt[2];
break;
default:
break;
}
}
if (msgtype == DHCPACK) {
if (b->your_ip == 0)
return;
/* DHCPACK for DHCPREQUEST */
sta = ap_get_sta(hapd, b->hw_addr);
if (!sta)
return;
wpa_printf(MSG_DEBUG, "dhcp_snoop: Found DHCPACK for " MACSTR
" @ IPv4 address %s/%d",
MAC2STR(sta->addr),
ipaddr_str(be_to_host32(b->your_ip)),
prefixlen);
if (sta->ipaddr == b->your_ip)
return;
if (sta->ipaddr != 0) {
wpa_printf(MSG_DEBUG,
"dhcp_snoop: Removing IPv4 address %s from the ip neigh table",
ipaddr_str(be_to_host32(sta->ipaddr)));
hostapd_drv_br_delete_ip_neigh(hapd, 4,
(u8 *) &sta->ipaddr);
}
res = hostapd_drv_br_add_ip_neigh(hapd, 4, (u8 *) &b->your_ip,
prefixlen, sta->addr);
if (res) {
wpa_printf(MSG_DEBUG,
"dhcp_snoop: Adding ip neigh table failed: %d",
res);
return;
}
sta->ipaddr = b->your_ip;
}
if (hapd->conf->disable_dgaf && is_broadcast_ether_addr(buf)) {
for (sta = hapd->sta_list; sta; sta = sta->next) {
if (!(sta->flags & WLAN_STA_AUTHORIZED))
continue;
x_snoop_mcast_to_ucast_convert_send(hapd, sta,
(u8 *) buf, len);
}
}
}
int dhcp_snoop_init(struct hostapd_data *hapd)
{
hapd->sock_dhcp = x_snoop_get_l2_packet(hapd, handle_dhcp,
L2_PACKET_FILTER_DHCP);
if (hapd->sock_dhcp == NULL) {
wpa_printf(MSG_DEBUG,
"dhcp_snoop: Failed to initialize L2 packet processing for DHCP packet: %s",
strerror(errno));
return -1;
}
return 0;
}
void dhcp_snoop_deinit(struct hostapd_data *hapd)
{
l2_packet_deinit(hapd->sock_dhcp);
}