hostapd/src/ap/dhcp_snoop.c
Jouni Malinen b98933eafc HS 2.0: DHCP broadcast-to-unicast conversion before address learning
handle_dhcp() was first trying to learn the IP address of an associated
STA before doing broadcast-to-unicast conversion. This could result in
not converting some DHCPACK messages since the address learning part
aborts processing by returning from the function in various cases.

Reorder these operations to allow broadcast-to-unicast conversion to
happen even if an associated STA entry is not updated based on a
DHCPACK.

Signed-off-by: Jouni Malinen <j@w1.fi>
2018-12-30 01:05:18 +02:00

158 lines
3.4 KiB
C

/*
* 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 "utils/common.h"
#include "common/dhcp.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"
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 (WPA_GET_BE32(b->exten) != DHCP_MAGIC)
return;
/* Parse DHCP options */
end = (const u8 *) b + tot_len;
pos = &b->exten[4];
while (pos < end && *pos != DHCP_OPT_END) {
const u8 *opt = pos++;
if (*opt == DHCP_OPT_PAD)
continue;
if (pos >= end || 1 + *pos > end - pos)
break;
pos += *pos + 1;
if (pos >= end)
break;
switch (*opt) {
case DHCP_OPT_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 DHCP_OPT_MSG_TYPE:
if (opt[1])
msgtype = opt[2];
break;
default:
break;
}
}
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);
}
}
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;
}
}
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);
hapd->sock_dhcp = NULL;
}